1This is coreutils.info, produced by makeinfo version 6.6 from 2coreutils.texi. 3 4This manual documents version 8.32 of the GNU core utilities, including 5the standard programs for text and file manipulation. 6 7 Copyright © 1994-2020 Free Software Foundation, Inc. 8 9 Permission is granted to copy, distribute and/or modify this 10 document under the terms of the GNU Free Documentation License, 11 Version 1.3 or any later version published by the Free Software 12 Foundation; with no Invariant Sections, with no Front-Cover Texts, 13 and with no Back-Cover Texts. A copy of the license is included in 14 the section entitled “GNU Free Documentation License”. 15INFO-DIR-SECTION Basics 16START-INFO-DIR-ENTRY 17* Coreutils: (coreutils). Core GNU (file, text, shell) utilities. 18* Common options: (coreutils)Common options. 19* File permissions: (coreutils)File permissions. Access modes. 20* Date input formats: (coreutils)Date input formats. 21END-INFO-DIR-ENTRY 22 23INFO-DIR-SECTION Individual utilities 24START-INFO-DIR-ENTRY 25* arch: (coreutils)arch invocation. Print machine hardware name. 26* b2sum: (coreutils)b2sum invocation. Print or check BLAKE2 digests. 27* base32: (coreutils)base32 invocation. Base32 encode/decode data. 28* base64: (coreutils)base64 invocation. Base64 encode/decode data. 29* basename: (coreutils)basename invocation. Strip directory and suffix. 30* basenc: (coreutils)basenc invocation. Encoding/decoding of data. 31* cat: (coreutils)cat invocation. Concatenate and write files. 32* chcon: (coreutils)chcon invocation. Change SELinux CTX of files. 33* chgrp: (coreutils)chgrp invocation. Change file groups. 34* chmod: (coreutils)chmod invocation. Change access permissions. 35* chown: (coreutils)chown invocation. Change file owners and groups. 36* chroot: (coreutils)chroot invocation. Specify the root directory. 37* cksum: (coreutils)cksum invocation. Print POSIX CRC checksum. 38* comm: (coreutils)comm invocation. Compare sorted files by line. 39* cp: (coreutils)cp invocation. Copy files. 40* csplit: (coreutils)csplit invocation. Split by context. 41* cut: (coreutils)cut invocation. Print selected parts of lines. 42* date: (coreutils)date invocation. Print/set system date and time. 43* dd: (coreutils)dd invocation. Copy and convert a file. 44* df: (coreutils)df invocation. Report file system disk usage. 45* dir: (coreutils)dir invocation. List directories briefly. 46* dircolors: (coreutils)dircolors invocation. Color setup for ls. 47* dirname: (coreutils)dirname invocation. Strip last file name component. 48* du: (coreutils)du invocation. Report on disk usage. 49* echo: (coreutils)echo invocation. Print a line of text. 50* env: (coreutils)env invocation. Modify the environment. 51* expand: (coreutils)expand invocation. Convert tabs to spaces. 52* expr: (coreutils)expr invocation. Evaluate expressions. 53* factor: (coreutils)factor invocation. Print prime factors 54* false: (coreutils)false invocation. Do nothing, unsuccessfully. 55* fmt: (coreutils)fmt invocation. Reformat paragraph text. 56* fold: (coreutils)fold invocation. Wrap long input lines. 57* groups: (coreutils)groups invocation. Print group names a user is in. 58* head: (coreutils)head invocation. Output the first part of files. 59* hostid: (coreutils)hostid invocation. Print numeric host identifier. 60* hostname: (coreutils)hostname invocation. Print or set system name. 61* id: (coreutils)id invocation. Print user identity. 62* install: (coreutils)install invocation. Copy files and set attributes. 63* join: (coreutils)join invocation. Join lines on a common field. 64* kill: (coreutils)kill invocation. Send a signal to processes. 65* link: (coreutils)link invocation. Make hard links between files. 66* ln: (coreutils)ln invocation. Make links between files. 67* logname: (coreutils)logname invocation. Print current login name. 68* ls: (coreutils)ls invocation. List directory contents. 69* md5sum: (coreutils)md5sum invocation. Print or check MD5 digests. 70* mkdir: (coreutils)mkdir invocation. Create directories. 71* mkfifo: (coreutils)mkfifo invocation. Create FIFOs (named pipes). 72* mknod: (coreutils)mknod invocation. Create special files. 73* mktemp: (coreutils)mktemp invocation. Create temporary files. 74* mv: (coreutils)mv invocation. Rename files. 75* nice: (coreutils)nice invocation. Modify niceness. 76* nl: (coreutils)nl invocation. Number lines and write files. 77* nohup: (coreutils)nohup invocation. Immunize to hangups. 78* nproc: (coreutils)nproc invocation. Print the number of processors. 79* numfmt: (coreutils)numfmt invocation. Reformat numbers. 80* od: (coreutils)od invocation. Dump files in octal, etc. 81* paste: (coreutils)paste invocation. Merge lines of files. 82* pathchk: (coreutils)pathchk invocation. Check file name portability. 83* pr: (coreutils)pr invocation. Paginate or columnate files. 84* printenv: (coreutils)printenv invocation. Print environment variables. 85* printf: (coreutils)printf invocation. Format and print data. 86* ptx: (coreutils)ptx invocation. Produce permuted indexes. 87* pwd: (coreutils)pwd invocation. Print working directory. 88* readlink: (coreutils)readlink invocation. Print referent of a symlink. 89* realpath: (coreutils)realpath invocation. Print resolved file names. 90* rm: (coreutils)rm invocation. Remove files. 91* rmdir: (coreutils)rmdir invocation. Remove empty directories. 92* runcon: (coreutils)runcon invocation. Run in specified SELinux CTX. 93* seq: (coreutils)seq invocation. Print numeric sequences 94* sha1sum: (coreutils)sha1sum invocation. Print or check SHA-1 digests. 95* sha2: (coreutils)sha2 utilities. Print or check SHA-2 digests. 96* shred: (coreutils)shred invocation. Remove files more securely. 97* shuf: (coreutils)shuf invocation. Shuffling text files. 98* sleep: (coreutils)sleep invocation. Delay for a specified time. 99* sort: (coreutils)sort invocation. Sort text files. 100* split: (coreutils)split invocation. Split into pieces. 101* stat: (coreutils)stat invocation. Report file(system) status. 102* stdbuf: (coreutils)stdbuf invocation. Modify stdio buffering. 103* stty: (coreutils)stty invocation. Print/change terminal settings. 104* sum: (coreutils)sum invocation. Print traditional checksum. 105* sync: (coreutils)sync invocation. Synchronize memory to disk. 106* tac: (coreutils)tac invocation. Reverse files. 107* tail: (coreutils)tail invocation. Output the last part of files. 108* tee: (coreutils)tee invocation. Redirect to multiple files. 109* test: (coreutils)test invocation. File/string tests. 110* timeout: (coreutils)timeout invocation. Run with time limit. 111* touch: (coreutils)touch invocation. Change file timestamps. 112* tr: (coreutils)tr invocation. Translate characters. 113* true: (coreutils)true invocation. Do nothing, successfully. 114* truncate: (coreutils)truncate invocation. Shrink/extend size of a file. 115* tsort: (coreutils)tsort invocation. Topological sort. 116* tty: (coreutils)tty invocation. Print terminal name. 117* uname: (coreutils)uname invocation. Print system information. 118* unexpand: (coreutils)unexpand invocation. Convert spaces to tabs. 119* uniq: (coreutils)uniq invocation. Uniquify files. 120* unlink: (coreutils)unlink invocation. Removal via unlink(2). 121* uptime: (coreutils)uptime invocation. Print uptime and load. 122* users: (coreutils)users invocation. Print current user names. 123* vdir: (coreutils)vdir invocation. List directories verbosely. 124* wc: (coreutils)wc invocation. Line, word, and byte counts. 125* who: (coreutils)who invocation. Print who is logged in. 126* whoami: (coreutils)whoami invocation. Print effective user ID. 127* yes: (coreutils)yes invocation. Print a string indefinitely. 128END-INFO-DIR-ENTRY 129 130 131File: coreutils.info, Node: Top, Next: Introduction, Up: (dir) 132 133GNU Coreutils 134************* 135 136This manual documents version 8.32 of the GNU core utilities, including 137the standard programs for text and file manipulation. 138 139 Copyright © 1994-2020 Free Software Foundation, Inc. 140 141 Permission is granted to copy, distribute and/or modify this 142 document under the terms of the GNU Free Documentation License, 143 Version 1.3 or any later version published by the Free Software 144 Foundation; with no Invariant Sections, with no Front-Cover Texts, 145 and with no Back-Cover Texts. A copy of the license is included in 146 the section entitled “GNU Free Documentation License”. 147 148* Menu: 149 150* Introduction:: Caveats, overview, and authors 151* Common options:: Common options 152* Output of entire files:: cat tac nl od base32 base64 basenc 153* Formatting file contents:: fmt pr fold 154* Output of parts of files:: head tail split csplit 155* Summarizing files:: wc sum cksum b2sum md5sum sha1sum sha2 156* Operating on sorted files:: sort shuf uniq comm ptx tsort 157* Operating on fields:: cut paste join 158* Operating on characters:: tr expand unexpand 159* Directory listing:: ls dir vdir dircolors 160* Basic operations:: cp dd install mv rm shred 161* Special file types:: mkdir rmdir unlink mkfifo mknod ln link readlink 162* Changing file attributes:: chgrp chmod chown touch 163* Disk usage:: df du stat sync truncate 164* Printing text:: echo printf yes 165* Conditions:: false true test expr 166* Redirection:: tee 167* File name manipulation:: dirname basename pathchk mktemp realpath 168* Working context:: pwd stty printenv tty 169* User information:: id logname whoami groups users who 170* System context:: date arch nproc uname hostname hostid uptime 171* SELinux context:: chcon runcon 172* Modified command invocation:: chroot env nice nohup stdbuf timeout 173* Process control:: kill 174* Delaying:: sleep 175* Numeric operations:: factor numfmt seq 176* File permissions:: Access modes 177* File timestamps:: File timestamp issues 178* Date input formats:: Specifying date strings 179* Version sort ordering:: Details on version-sort algorithm 180* Opening the software toolbox:: The software tools philosophy 181* GNU Free Documentation License:: Copying and sharing this manual 182* Concept index:: General index 183 184 — The Detailed Node Listing — 185 186Common Options 187 188* Exit status:: Indicating program success or failure 189* Backup options:: Backup options 190* Block size:: Block size 191* Floating point:: Floating point number representation 192* Signal specifications:: Specifying signals 193* Disambiguating names and IDs:: chgrp, chown, chroot, id: user and group syntax 194* Random sources:: Sources of random data 195* Target directory:: Target directory 196* Trailing slashes:: Trailing slashes 197* Traversing symlinks:: Traversing symlinks to directories 198* Treating / specially:: Treating / specially 199* Standards conformance:: Standards conformance 200* Multi-call invocation:: Multi-call program invocation 201 202Output of entire files 203 204* cat invocation:: Concatenate and write files 205* tac invocation:: Concatenate and write files in reverse 206* nl invocation:: Number lines and write files 207* od invocation:: Write files in octal or other formats 208* base32 invocation:: Transform data into printable data 209* base64 invocation:: Transform data into printable data 210* basenc invocation:: Transform data into printable data 211 212Formatting file contents 213 214* fmt invocation:: Reformat paragraph text 215* pr invocation:: Paginate or columnate files for printing 216* fold invocation:: Wrap input lines to fit in specified width 217 218Output of parts of files 219 220* head invocation:: Output the first part of files 221* tail invocation:: Output the last part of files 222* split invocation:: Split a file into fixed-size pieces 223* csplit invocation:: Split a file into context-determined pieces 224 225Summarizing files 226 227* wc invocation:: Print newline, word, and byte counts 228* sum invocation:: Print checksum and block counts 229* cksum invocation:: Print CRC checksum and byte counts 230* b2sum invocation:: Print or check BLAKE2 digests 231* md5sum invocation:: Print or check MD5 digests 232* sha1sum invocation:: Print or check SHA-1 digests 233* sha2 utilities:: Print or check SHA-2 digests 234 235Operating on sorted files 236 237* sort invocation:: Sort text files 238* shuf invocation:: Shuffle text files 239* uniq invocation:: Uniquify files 240* comm invocation:: Compare two sorted files line by line 241* ptx invocation:: Produce a permuted index of file contents 242* tsort invocation:: Topological sort 243 244‘ptx’: Produce permuted indexes 245 246* General options in ptx:: Options which affect general program behavior 247* Charset selection in ptx:: Underlying character set considerations 248* Input processing in ptx:: Input fields, contexts, and keyword selection 249* Output formatting in ptx:: Types of output format, and sizing the fields 250* Compatibility in ptx:: The GNU extensions to ‘ptx’ 251 252Operating on fields 253 254* cut invocation:: Print selected parts of lines 255* paste invocation:: Merge lines of files 256* join invocation:: Join lines on a common field 257 258Operating on characters 259 260* tr invocation:: Translate, squeeze, and/or delete characters 261* expand invocation:: Convert tabs to spaces 262* unexpand invocation:: Convert spaces to tabs 263 264‘tr’: Translate, squeeze, and/or delete characters 265 266* Character sets:: Specifying sets of characters 267* Translating:: Changing one set of characters to another 268* Squeezing and deleting:: Removing characters 269 270Directory listing 271 272* ls invocation:: List directory contents 273* dir invocation:: Briefly list directory contents 274* vdir invocation:: Verbosely list directory contents 275* dircolors invocation:: Color setup for ‘ls’ 276 277‘ls’: List directory contents 278 279* Which files are listed:: Which files are listed 280* What information is listed:: What information is listed 281* Sorting the output:: Sorting the output 282* General output formatting:: General output formatting 283* Formatting the file names:: Formatting the file names 284 285Basic operations 286 287* cp invocation:: Copy files and directories 288* dd invocation:: Convert and copy a file 289* install invocation:: Copy files and set attributes 290* mv invocation:: Move (rename) files 291* rm invocation:: Remove files or directories 292* shred invocation:: Remove files more securely 293 294Special file types 295 296* link invocation:: Make a hard link via the link syscall 297* ln invocation:: Make links between files 298* mkdir invocation:: Make directories 299* mkfifo invocation:: Make FIFOs (named pipes) 300* mknod invocation:: Make block or character special files 301* readlink invocation:: Print value of a symlink or canonical file name 302* rmdir invocation:: Remove empty directories 303* unlink invocation:: Remove files via unlink syscall 304 305Changing file attributes 306 307* chown invocation:: Change file owner and group 308* chgrp invocation:: Change group ownership 309* chmod invocation:: Change access permissions 310* touch invocation:: Change file timestamps 311 312Disk usage 313 314* df invocation:: Report file system disk space usage 315* du invocation:: Estimate file space usage 316* stat invocation:: Report file or file system status 317* sync invocation:: Synchronize cached writes to persistent storage 318* truncate invocation:: Shrink or extend the size of a file 319 320Printing text 321 322* echo invocation:: Print a line of text 323* printf invocation:: Format and print data 324* yes invocation:: Print a string until interrupted 325 326Conditions 327 328* false invocation:: Do nothing, unsuccessfully 329* true invocation:: Do nothing, successfully 330* test invocation:: Check file types and compare values 331* expr invocation:: Evaluate expressions 332 333‘test’: Check file types and compare values 334 335* File type tests:: File type tests 336* Access permission tests:: Access permission tests 337* File characteristic tests:: File characteristic tests 338* String tests:: String tests 339* Numeric tests:: Numeric tests 340 341‘expr’: Evaluate expression 342 343* String expressions:: + : match substr index length 344* Numeric expressions:: + - * / % 345* Relations for expr:: | & < <= = == != >= > 346* Examples of expr:: Examples of using ‘expr’ 347 348Redirection 349 350* tee invocation:: Redirect output to multiple files or processes 351 352File name manipulation 353 354* basename invocation:: Strip directory and suffix from a file name 355* dirname invocation:: Strip last file name component 356* pathchk invocation:: Check file name validity and portability 357* mktemp invocation:: Create temporary file or directory 358* realpath invocation:: Print resolved file names 359 360Working context 361 362* pwd invocation:: Print working directory 363* stty invocation:: Print or change terminal characteristics 364* printenv invocation:: Print all or some environment variables 365* tty invocation:: Print file name of terminal on standard input 366 367‘stty’: Print or change terminal characteristics 368 369* Control:: Control settings 370* Input:: Input settings 371* Output:: Output settings 372* Local:: Local settings 373* Combination:: Combination settings 374* Characters:: Special characters 375* Special:: Special settings 376 377User information 378 379* id invocation:: Print user identity 380* logname invocation:: Print current login name 381* whoami invocation:: Print effective user ID 382* groups invocation:: Print group names a user is in 383* users invocation:: Print login names of users currently logged in 384* who invocation:: Print who is currently logged in 385 386System context 387 388* arch invocation:: Print machine hardware name 389* date invocation:: Print or set system date and time 390* nproc invocation:: Print the number of processors 391* uname invocation:: Print system information 392* hostname invocation:: Print or set system name 393* hostid invocation:: Print numeric host identifier 394* uptime invocation:: Print system uptime and load 395 396‘date’: Print or set system date and time 397 398* Time conversion specifiers:: %[HIklMNpPrRsSTXzZ] 399* Date conversion specifiers:: %[aAbBcCdDeFgGhjmuUVwWxyY] 400* Literal conversion specifiers:: %[%nt] 401* Padding and other flags:: Pad with zeros, spaces, etc. 402* Setting the time:: Changing the system clock 403* Options for date:: Instead of the current time 404* Date input formats:: Specifying date strings 405* Examples of date:: Examples 406 407SELinux context 408 409* chcon invocation:: Change SELinux context of file 410* runcon invocation:: Run a command in specified SELinux context 411 412Modified command invocation 413 414* chroot invocation:: Run a command with a different root directory 415* env invocation:: Run a command in a modified environment 416* nice invocation:: Run a command with modified niceness 417* nohup invocation:: Run a command immune to hangups 418* stdbuf invocation:: Run a command with modified I/O buffering 419* timeout invocation:: Run a command with a time limit 420 421Process control 422 423* kill invocation:: Sending a signal to processes. 424 425Delaying 426 427* sleep invocation:: Delay for a specified time 428 429Numeric operations 430 431* factor invocation:: Print prime factors 432* numfmt invocation:: Reformat numbers 433* seq invocation:: Print numeric sequences 434 435 436File timestamps 437 438* File timestamps:: File timestamp issues 439 440File permissions 441 442* Mode Structure:: Structure of file mode bits 443* Symbolic Modes:: Mnemonic representation of file mode bits 444* Numeric Modes:: File mode bits as octal numbers 445* Directory Setuid and Setgid:: Set-user-ID and set-group-ID on directories 446 447Date input formats 448 449* General date syntax:: Common rules 450* Calendar date items:: 19 Dec 1994 451* Time of day items:: 9:20pm 452* Time zone items:: EST, PDT, UTC, ... 453* Combined date and time of day items:: 1972-09-24T20:02:00,000000-0500 454* Day of week items:: Monday and others 455* Relative items in date strings:: next tuesday, 2 years ago 456* Pure numbers in date strings:: 19931219, 1440 457* Seconds since the Epoch:: @1078100502 458* Specifying time zone rules:: TZ="America/New_York", TZ="UTC0" 459* Authors of parse_datetime:: Bellovin, Eggert, Salz, Berets, et al. 460 461Version sorting order 462 463* Version sort overview:: 464* Implementation Details:: 465* Differences from the official Debian Algorithm:: 466* Advanced Topics:: 467 468Opening the software toolbox 469 470* Toolbox introduction:: Toolbox introduction 471* I/O redirection:: I/O redirection 472* The who command:: The ‘who’ command 473* The cut command:: The ‘cut’ command 474* The sort command:: The ‘sort’ command 475* The uniq command:: The ‘uniq’ command 476* Putting the tools together:: Putting the tools together 477 478Copying This Manual 479 480* GNU Free Documentation License:: Copying and sharing this manual 481 482 483 484File: coreutils.info, Node: Introduction, Next: Common options, Prev: Top, Up: Top 485 4861 Introduction 487************** 488 489This manual is a work in progress: many sections make no attempt to 490explain basic concepts in a way suitable for novices. Thus, if you are 491interested, please get involved in improving this manual. The entire 492GNU community will benefit. 493 494 The GNU utilities documented here are mostly compatible with the 495POSIX standard. 496 497 Please report bugs to <bug-coreutils@gnu.org>. Include the version 498number, machine architecture, input files, and any other information 499needed to reproduce the bug: your input, what you expected, what you 500got, and why it is wrong. 501 502 If you have a problem with ‘sort’ or ‘date’, try using the ‘--debug’ 503option, as it can can often help find and fix problems without having to 504wait for an answer to a bug report. If the debug output does not 505suffice to fix the problem on your own, please compress and attach it to 506the rest of your bug report. 507 508 Although diffs are welcome, please include a description of the 509problem as well, since this is sometimes difficult to infer. *Note 510(gcc)Bugs::. 511 512 This manual was originally derived from the Unix man pages in the 513distributions, which were written by David MacKenzie and updated by Jim 514Meyering. What you are reading now is the authoritative documentation 515for these utilities; the man pages are no longer being maintained. The 516original ‘fmt’ man page was written by Ross Paterson. François Pinard 517did the initial conversion to Texinfo format. Karl Berry did the 518indexing, some reorganization, and editing of the results. Brian 519Youmans of the Free Software Foundation office staff combined the 520manuals for textutils, fileutils, and sh-utils to produce the present 521omnibus manual. Richard Stallman contributed his usual invaluable 522insights to the overall process. 523 524 525File: coreutils.info, Node: Common options, Next: Output of entire files, Prev: Introduction, Up: Top 526 5272 Common options 528**************** 529 530Certain options are available in all of these programs. Rather than 531writing identical descriptions for each of the programs, they are 532described here. (In fact, every GNU program accepts (or should accept) 533these options.) 534 535 Normally options and operands can appear in any order, and programs 536act as if all the options appear before any operands. For example, 537‘sort -r passwd -t :’ acts like ‘sort -r -t : passwd’, since ‘:’ is an 538option-argument of ‘-t’. However, if the ‘POSIXLY_CORRECT’ environment 539variable is set, options must appear before operands, unless otherwise 540specified for a particular command. 541 542 A few programs can usefully have trailing operands with leading ‘-’. 543With such a program, options must precede operands even if 544‘POSIXLY_CORRECT’ is not set, and this fact is noted in the program 545description. For example, the ‘env’ command’s options must appear 546before its operands, since in some cases the operands specify a command 547that itself contains options. 548 549 Most programs that accept long options recognize unambiguous 550abbreviations of those options. For example, ‘rmdir 551--ignore-fail-on-non-empty’ can be invoked as ‘rmdir --ignore-fail’ or 552even ‘rmdir --i’. Ambiguous options, such as ‘ls --h’, are identified 553as such. 554 555 Some of these programs recognize the ‘--help’ and ‘--version’ options 556only when one of them is the sole command line argument. For these 557programs, abbreviations of the long options are not always recognized. 558 559‘--help’ 560 Print a usage message listing all available options, then exit 561 successfully. 562 563‘--version’ 564 Print the version number, then exit successfully. 565 566‘--’ 567 Delimit the option list. Later arguments, if any, are treated as 568 operands even if they begin with ‘-’. For example, ‘sort -- -r’ 569 reads from the file named ‘-r’. 570 571 A single ‘-’ operand is not really an option, though it looks like 572one. It stands for a file operand, and some tools treat it as standard 573input, or as standard output if that is clear from the context. For 574example, ‘sort -’ reads from standard input, and is equivalent to plain 575‘sort’. Unless otherwise specified, a ‘-’ can appear as any operand 576that requires a file name. 577 578* Menu: 579 580* Exit status:: Indicating program success or failure. 581* Backup options:: -b -S, in some programs. 582* Block size:: BLOCK_SIZE and –block-size, in some programs. 583* Floating point:: Floating point number representation. 584* Signal specifications:: Specifying signals using the –signal option. 585* Disambiguating names and IDs:: chgrp, chown, chroot, id: user and group syntax 586* Random sources:: –random-source, in some programs. 587* Target directory:: Specifying a target directory, in some programs. 588* Trailing slashes:: –strip-trailing-slashes, in some programs. 589* Traversing symlinks:: -H, -L, or -P, in some programs. 590* Treating / specially:: –preserve-root and –no-preserve-root. 591* Special built-in utilities:: ‘break’, ‘:’, ... 592* Standards conformance:: Conformance to the POSIX standard. 593* Multi-call invocation:: Multi-call program invocation. 594 595 596File: coreutils.info, Node: Exit status, Next: Backup options, Up: Common options 597 5982.1 Exit status 599=============== 600 601Nearly every command invocation yields an integral “exit status” that 602can be used to change how other commands work. For the vast majority of 603commands, an exit status of zero indicates success. Failure is 604indicated by a nonzero value—typically ‘1’, though it may differ on 605unusual platforms as POSIX requires only that it be nonzero. 606 607 However, some of the programs documented here do produce other exit 608status values and a few associate different meanings with the values ‘0’ 609and ‘1’. Here are some of the exceptions: ‘chroot’, ‘env’, ‘expr’, 610‘nice’, ‘nohup’, ‘numfmt’, ‘printenv’, ‘sort’, ‘stdbuf’, ‘test’, 611‘timeout’, ‘tty’. 612 613 614File: coreutils.info, Node: Backup options, Next: Block size, Prev: Exit status, Up: Common options 615 6162.2 Backup options 617================== 618 619Some GNU programs (at least ‘cp’, ‘install’, ‘ln’, and ‘mv’) optionally 620make backups of files before writing new versions. These options 621control the details of these backups. The options are also briefly 622mentioned in the descriptions of the particular programs. 623 624‘-b’ 625‘--backup[=METHOD]’ 626 Make a backup of each file that would otherwise be overwritten or 627 removed. Without this option, the original versions are destroyed. 628 Use METHOD to determine the type of backups to make. When this 629 option is used but METHOD is not specified, then the value of the 630 ‘VERSION_CONTROL’ environment variable is used. And if 631 ‘VERSION_CONTROL’ is not set, the default backup type is 632 ‘existing’. 633 634 Note that the short form of this option, ‘-b’ does not accept any 635 argument. Using ‘-b’ is equivalent to using ‘--backup=existing’. 636 637 This option corresponds to the Emacs variable ‘version-control’; 638 the values for METHOD are the same as those used in Emacs. This 639 option also accepts more descriptive names. The valid METHODs are 640 (unique abbreviations are accepted): 641 642 ‘none’ 643 ‘off’ 644 Never make backups. 645 646 ‘numbered’ 647 ‘t’ 648 Always make numbered backups. 649 650 ‘existing’ 651 ‘nil’ 652 Make numbered backups of files that already have them, simple 653 backups of the others. 654 655 ‘simple’ 656 ‘never’ 657 Always make simple backups. Please note ‘never’ is not to be 658 confused with ‘none’. 659 660‘-S SUFFIX’ 661‘--suffix=SUFFIX’ 662 Append SUFFIX to each backup file made with ‘-b’. If this option 663 is not specified, the value of the ‘SIMPLE_BACKUP_SUFFIX’ 664 environment variable is used. And if ‘SIMPLE_BACKUP_SUFFIX’ is not 665 set, the default is ‘~’, just as in Emacs. 666 667 668File: coreutils.info, Node: Block size, Next: Floating point, Prev: Backup options, Up: Common options 669 6702.3 Block size 671============== 672 673Some GNU programs (at least ‘df’, ‘du’, and ‘ls’) display sizes in 674“blocks”. You can adjust the block size and method of display to make 675sizes easier to read. The block size used for display is independent of 676any file system block size. Fractional block counts are rounded up to 677the nearest integer. 678 679 The default block size is chosen by examining the following 680environment variables in turn; the first one that is set determines the 681block size. 682 683‘DF_BLOCK_SIZE’ 684 This specifies the default block size for the ‘df’ command. 685 Similarly, ‘DU_BLOCK_SIZE’ specifies the default for ‘du’ and 686 ‘LS_BLOCK_SIZE’ for ‘ls’. 687 688‘BLOCK_SIZE’ 689 This specifies the default block size for all three commands, if 690 the above command-specific environment variables are not set. 691 692‘BLOCKSIZE’ 693 This specifies the default block size for all values that are 694 normally printed as blocks, if neither ‘BLOCK_SIZE’ nor the above 695 command-specific environment variables are set. Unlike the other 696 environment variables, ‘BLOCKSIZE’ does not affect values that are 697 normally printed as byte counts, e.g., the file sizes contained in 698 ‘ls -l’ output. 699 700‘POSIXLY_CORRECT’ 701 If neither ‘COMMAND_BLOCK_SIZE’, nor ‘BLOCK_SIZE’, nor ‘BLOCKSIZE’ 702 is set, but this variable is set, the block size defaults to 512. 703 704 If none of the above environment variables are set, the block size 705currently defaults to 1024 bytes in most contexts, but this number may 706change in the future. For ‘ls’ file sizes, the block size defaults to 1 707byte. 708 709 A block size specification can be a positive integer specifying the 710number of bytes per block, or it can be ‘human-readable’ or ‘si’ to 711select a human-readable format. Integers may be followed by suffixes 712that are upward compatible with the SI prefixes 713(http://www.bipm.org/en/publications/si-brochure/chapter3.html) for 714decimal multiples and with the ISO/IEC 80000-13 (formerly IEC 60027-2) 715prefixes (https://physics.nist.gov/cuu/Units/binary.html) for binary 716multiples. 717 718 With human-readable formats, output sizes are followed by a size 719letter such as ‘M’ for megabytes. ‘BLOCK_SIZE=human-readable’ uses 720powers of 1024; ‘M’ stands for 1,048,576 bytes. ‘BLOCK_SIZE=si’ is 721similar, but uses powers of 1000 and appends ‘B’; ‘MB’ stands for 7221,000,000 bytes. 723 724 A block size specification preceded by ‘'’ causes output sizes to be 725displayed with thousands separators. The ‘LC_NUMERIC’ locale specifies 726the thousands separator and grouping. For example, in an American 727English locale, ‘--block-size="'1kB"’ would cause a size of 1234000 728bytes to be displayed as ‘1,234’. In the default C locale, there is no 729thousands separator so a leading ‘'’ has no effect. 730 731 An integer block size can be followed by a suffix to specify a 732multiple of that size. A bare size letter, or one followed by ‘iB’, 733specifies a multiple using powers of 1024. A size letter followed by 734‘B’ specifies powers of 1000 instead. For example, ‘1M’ and ‘1MiB’ are 735equivalent to ‘1048576’, whereas ‘1MB’ is equivalent to ‘1000000’. 736 737 A plain suffix without a preceding integer acts as if ‘1’ were 738prepended, except that it causes a size indication to be appended to the 739output. For example, ‘--block-size="kB"’ displays 3000 as ‘3kB’. 740 741 The following suffixes are defined. Large sizes like ‘1Y’ may be 742rejected by your computer due to limitations of its arithmetic. 743 744‘kB’ 745 kilobyte: 10^3 = 1000. 746‘k’ 747‘K’ 748‘KiB’ 749 kibibyte: 2^{10} = 1024. ‘K’ is special: the SI prefix is ‘k’ and 750 the ISO/IEC 80000-13 prefix is ‘Ki’, but tradition and POSIX use 751 ‘k’ to mean ‘KiB’. 752‘MB’ 753 megabyte: 10^6 = 1,000,000. 754‘M’ 755‘MiB’ 756 mebibyte: 2^{20} = 1,048,576. 757‘GB’ 758 gigabyte: 10^9 = 1,000,000,000. 759‘G’ 760‘GiB’ 761 gibibyte: 2^{30} = 1,073,741,824. 762‘TB’ 763 terabyte: 10^{12} = 1,000,000,000,000. 764‘T’ 765‘TiB’ 766 tebibyte: 2^{40} = 1,099,511,627,776. 767‘PB’ 768 petabyte: 10^{15} = 1,000,000,000,000,000. 769‘P’ 770‘PiB’ 771 pebibyte: 2^{50} = 1,125,899,906,842,624. 772‘EB’ 773 exabyte: 10^{18} = 1,000,000,000,000,000,000. 774‘E’ 775‘EiB’ 776 exbibyte: 2^{60} = 1,152,921,504,606,846,976. 777‘ZB’ 778 zettabyte: 10^{21} = 1,000,000,000,000,000,000,000 779‘Z’ 780‘ZiB’ 781 2^{70} = 1,180,591,620,717,411,303,424. 782‘YB’ 783 yottabyte: 10^{24} = 1,000,000,000,000,000,000,000,000. 784‘Y’ 785‘YiB’ 786 2^{80} = 1,208,925,819,614,629,174,706,176. 787 788 Block size defaults can be overridden by an explicit 789‘--block-size=SIZE’ option. The ‘-k’ option is equivalent to 790‘--block-size=1K’, which is the default unless the ‘POSIXLY_CORRECT’ 791environment variable is set. The ‘-h’ or ‘--human-readable’ option is 792equivalent to ‘--block-size=human-readable’. The ‘--si’ option is 793equivalent to ‘--block-size=si’. Note for ‘ls’ the ‘-k’ option does not 794control the display of the apparent file sizes, whereas the 795‘--block-size’ option does. 796 797 798File: coreutils.info, Node: Floating point, Next: Signal specifications, Prev: Block size, Up: Common options 799 8002.4 Floating point numbers 801========================== 802 803Commands that accept or produce floating point numbers employ the 804floating point representation of the underlying system, and suffer from 805rounding error, overflow, and similar floating-point issues. Almost all 806modern systems use IEEE-754 floating point, and it is typically portable 807to assume IEEE-754 behavior these days. IEEE-754 has positive and 808negative infinity, distinguishes positive from negative zero, and uses 809special values called NaNs to represent invalid computations such as 810dividing zero by itself. For more information, please see David 811Goldberg’s paper What Every Computer Scientist Should Know About 812Floating-Point Arithmetic 813(https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html). 814 815 Commands that accept floating point numbers as options, operands or 816input use the standard C functions ‘strtod’ and ‘strtold’ to convert 817from text to floating point numbers. These floating point numbers 818therefore can use scientific notation like ‘1.0e-34’ and ‘-10e100’. 819Commands that parse floating point also understand case-insensitive 820‘inf’, ‘infinity’, and ‘NaN’, although whether such values are useful 821depends on the command in question. Modern C implementations also 822accept hexadecimal floating point numbers such as ‘-0x.ep-3’, which 823stands for −14/16 times 2^-3, which equals −0.109375. *Note 824(libc)Parsing of Floats::. 825 826 Normally the ‘LC_NUMERIC’ locale determines the decimal-point 827character. However, some commands’ descriptions specify that they 828accept numbers in either the current or the C locale; for example, they 829treat ‘3.14’ like ‘3,14’ if the current locale uses comma as a decimal 830point. 831 832 833File: coreutils.info, Node: Signal specifications, Next: Disambiguating names and IDs, Prev: Floating point, Up: Common options 834 8352.5 Signal specifications 836========================= 837 838A SIGNAL may be a signal name like ‘HUP’, or a signal number like ‘1’, 839or an exit status of a process terminated by the signal. A signal name 840can be given in canonical form or prefixed by ‘SIG’. The case of the 841letters is ignored. The following signal names and numbers are 842supported on all POSIX compliant systems: 843 844‘HUP’ 845 1. Hangup. 846‘INT’ 847 2. Terminal interrupt. 848‘QUIT’ 849 3. Terminal quit. 850‘ABRT’ 851 6. Process abort. 852‘KILL’ 853 9. Kill (cannot be caught or ignored). 854‘ALRM’ 855 14. Alarm Clock. 856‘TERM’ 857 15. Termination. 858 859Other supported signal names have system-dependent corresponding 860numbers. All systems conforming to POSIX 1003.1-2001 also support the 861following signals: 862 863‘BUS’ 864 Access to an undefined portion of a memory object. 865‘CHLD’ 866 Child process terminated, stopped, or continued. 867‘CONT’ 868 Continue executing, if stopped. 869‘FPE’ 870 Erroneous arithmetic operation. 871‘ILL’ 872 Illegal Instruction. 873‘PIPE’ 874 Write on a pipe with no one to read it. 875‘SEGV’ 876 Invalid memory reference. 877‘STOP’ 878 Stop executing (cannot be caught or ignored). 879‘TSTP’ 880 Terminal stop. 881‘TTIN’ 882 Background process attempting read. 883‘TTOU’ 884 Background process attempting write. 885‘URG’ 886 High bandwidth data is available at a socket. 887‘USR1’ 888 User-defined signal 1. 889‘USR2’ 890 User-defined signal 2. 891 892POSIX 1003.1-2001 systems that support the XSI extension also support 893the following signals: 894 895‘POLL’ 896 Pollable event. 897‘PROF’ 898 Profiling timer expired. 899‘SYS’ 900 Bad system call. 901‘TRAP’ 902 Trace/breakpoint trap. 903‘VTALRM’ 904 Virtual timer expired. 905‘XCPU’ 906 CPU time limit exceeded. 907‘XFSZ’ 908 File size limit exceeded. 909 910POSIX 1003.1-2001 systems that support the XRT extension also support at 911least eight real-time signals called ‘RTMIN’, ‘RTMIN+1’, ..., ‘RTMAX-1’, 912‘RTMAX’. 913 914 915File: coreutils.info, Node: Disambiguating names and IDs, Next: Random sources, Prev: Signal specifications, Up: Common options 916 9172.6 chown, chgrp, chroot, id: Disambiguating user names and IDs 918=============================================================== 919 920Since the USER and GROUP arguments to these commands may be specified as 921names or numeric IDs, there is an apparent ambiguity. What if a user or 922group _name_ is a string of digits? (1) Should the command interpret it 923as a user name or as an ID? POSIX requires that these commands first 924attempt to resolve the specified string as a name, and only once that 925fails, then try to interpret it as an ID. This is troublesome when you 926want to specify a numeric ID, say 42, and it must work even in a 927pathological situation where ‘42’ is a user name that maps to some other 928user ID, say 1000. Simply invoking ‘chown 42 F’, will set ‘F’s owner ID 929to 1000—not what you intended. 930 931 GNU ‘chown’, ‘chgrp’, ‘chroot’, and ‘id’ provide a way to work around 932this, that at the same time may result in a significant performance 933improvement by eliminating a database look-up. Simply precede each 934numeric user ID and/or group ID with a ‘+’, in order to force its 935interpretation as an integer: 936 937 chown +42 F 938 chgrp +$numeric_group_id another-file 939 chown +0:+0 / 940 941 The name look-up process is skipped for each ‘+’-prefixed string, 942because a string containing ‘+’ is never a valid user or group name. 943This syntax is accepted on most common Unix systems, but not on Solaris 94410. 945 946 ---------- Footnotes ---------- 947 948 (1) Using a number as a user name is common in some environments. 949 950 951File: coreutils.info, Node: Random sources, Next: Target directory, Prev: Disambiguating names and IDs, Up: Common options 952 9532.7 Sources of random data 954========================== 955 956The ‘shuf’, ‘shred’, and ‘sort’ commands sometimes need random data to 957do their work. For example, ‘sort -R’ must choose a hash function at 958random, and it needs random data to make this selection. 959 960 By default these commands use an internal pseudo-random generator 961initialized by a small amount of entropy, but can be directed to use an 962external source with the ‘--random-source=FILE’ option. An error is 963reported if FILE does not contain enough bytes. 964 965 For example, the device file ‘/dev/urandom’ could be used as the 966source of random data. Typically, this device gathers environmental 967noise from device drivers and other sources into an entropy pool, and 968uses the pool to generate random bits. If the pool is short of data, 969the device reuses the internal pool to produce more bits, using a 970cryptographically secure pseudo-random number generator. But be aware 971that this device is not designed for bulk random data generation and is 972relatively slow. 973 974 ‘/dev/urandom’ suffices for most practical uses, but applications 975requiring high-value or long-term protection of private data may require 976an alternate data source like ‘/dev/random’ or ‘/dev/arandom’. The set 977of available sources depends on your operating system. 978 979 To reproduce the results of an earlier invocation of a command, you 980can save some random data into a file and then use that file as the 981random source in earlier and later invocations of the command. Rather 982than depending on a file, one can generate a reproducible arbitrary 983amount of pseudo-random data given a seed value, using for example: 984 985 get_seeded_random() 986 { 987 seed="$1" 988 openssl enc -aes-256-ctr -pass pass:"$seed" -nosalt \ 989 </dev/zero 2>/dev/null 990 } 991 992 shuf -i1-100 --random-source=<(get_seeded_random 42) 993 994 995File: coreutils.info, Node: Target directory, Next: Trailing slashes, Prev: Random sources, Up: Common options 996 9972.8 Target directory 998==================== 999 1000The ‘cp’, ‘install’, ‘ln’, and ‘mv’ commands normally treat the last 1001operand specially when it is a directory or a symbolic link to a 1002directory. For example, ‘cp source dest’ is equivalent to ‘cp source 1003dest/source’ if ‘dest’ is a directory. Sometimes this behavior is not 1004exactly what is wanted, so these commands support the following options 1005to allow more fine-grained control: 1006 1007‘-T’ 1008‘--no-target-directory’ 1009 Do not treat the last operand specially when it is a directory or a 1010 symbolic link to a directory. This can help avoid race conditions 1011 in programs that operate in a shared area. For example, when the 1012 command ‘mv /tmp/source /tmp/dest’ succeeds, there is no guarantee 1013 that ‘/tmp/source’ was renamed to ‘/tmp/dest’: it could have been 1014 renamed to ‘/tmp/dest/source’ instead, if some other process 1015 created ‘/tmp/dest’ as a directory. However, if ‘mv -T /tmp/source 1016 /tmp/dest’ succeeds, there is no question that ‘/tmp/source’ was 1017 renamed to ‘/tmp/dest’. 1018 1019 In the opposite situation, where you want the last operand to be 1020 treated as a directory and want a diagnostic otherwise, you can use 1021 the ‘--target-directory’ (‘-t’) option. 1022 1023‘-t DIRECTORY’ 1024‘--target-directory=DIRECTORY’ 1025 Use DIRECTORY as the directory component of each destination file 1026 name. 1027 1028 The interface for most programs is that after processing options 1029 and a finite (possibly zero) number of fixed-position arguments, 1030 the remaining argument list is either expected to be empty, or is a 1031 list of items (usually files) that will all be handled identically. 1032 The ‘xargs’ program is designed to work well with this convention. 1033 1034 The commands in the ‘mv’-family are unusual in that they take a 1035 variable number of arguments with a special case at the _end_ 1036 (namely, the target directory). This makes it nontrivial to 1037 perform some operations, e.g., “move all files from here to ../d/”, 1038 because ‘mv * ../d/’ might exhaust the argument space, and ‘ls | 1039 xargs ...’ doesn’t have a clean way to specify an extra final 1040 argument for each invocation of the subject command. (It can be 1041 done by going through a shell command, but that requires more human 1042 labor and brain power than it should.) 1043 1044 The ‘--target-directory’ (‘-t’) option allows the ‘cp’, ‘install’, 1045 ‘ln’, and ‘mv’ programs to be used conveniently with ‘xargs’. For 1046 example, you can move the files from the current directory to a 1047 sibling directory, ‘d’ like this: 1048 1049 ls | xargs mv -t ../d -- 1050 1051 However, this doesn’t move files whose names begin with ‘.’. If 1052 you use the GNU ‘find’ program, you can move those files too, with 1053 this command: 1054 1055 find . -mindepth 1 -maxdepth 1 \ 1056 | xargs mv -t ../d 1057 1058 But both of the above approaches fail if there are no files in the 1059 current directory, or if any file has a name containing a blank or 1060 some other special characters. The following example removes those 1061 limitations and requires both GNU ‘find’ and GNU ‘xargs’: 1062 1063 find . -mindepth 1 -maxdepth 1 -print0 \ 1064 | xargs --null --no-run-if-empty \ 1065 mv -t ../d 1066 1067The ‘--target-directory’ (‘-t’) and ‘--no-target-directory’ (‘-T’) 1068options cannot be combined. 1069 1070 1071File: coreutils.info, Node: Trailing slashes, Next: Traversing symlinks, Prev: Target directory, Up: Common options 1072 10732.9 Trailing slashes 1074==================== 1075 1076Some GNU programs (at least ‘cp’ and ‘mv’) allow you to remove any 1077trailing slashes from each SOURCE argument before operating on it. The 1078‘--strip-trailing-slashes’ option enables this behavior. 1079 1080 This is useful when a SOURCE argument may have a trailing slash and 1081specify a symbolic link to a directory. This scenario is in fact rather 1082common because some shells can automatically append a trailing slash 1083when performing file name completion on such symbolic links. Without 1084this option, ‘mv’, for example, (via the system’s rename function) must 1085interpret a trailing slash as a request to dereference the symbolic link 1086and so must rename the indirectly referenced _directory_ and not the 1087symbolic link. Although it may seem surprising that such behavior be 1088the default, it is required by POSIX and is consistent with other parts 1089of that standard. 1090 1091 1092File: coreutils.info, Node: Traversing symlinks, Next: Treating / specially, Prev: Trailing slashes, Up: Common options 1093 10942.10 Traversing symlinks 1095======================== 1096 1097The following options modify how ‘chown’ and ‘chgrp’ traverse a 1098hierarchy when the ‘--recursive’ (‘-R’) option is also specified. If 1099more than one of the following options is specified, only the final one 1100takes effect. These options specify whether processing a symbolic link 1101to a directory entails operating on just the symbolic link or on all 1102files in the hierarchy rooted at that directory. 1103 1104 These options are independent of ‘--dereference’ and 1105‘--no-dereference’ (‘-h’), which control whether to modify a symlink or 1106its referent. 1107 1108‘-H’ 1109 If ‘--recursive’ (‘-R’) is specified and a command line argument is 1110 a symbolic link to a directory, traverse it. 1111 1112‘-L’ 1113 In a recursive traversal, traverse every symbolic link to a 1114 directory that is encountered. 1115 1116‘-P’ 1117 Do not traverse any symbolic links. This is the default if none of 1118 ‘-H’, ‘-L’, or ‘-P’ is specified. 1119 1120 1121File: coreutils.info, Node: Treating / specially, Next: Special built-in utilities, Prev: Traversing symlinks, Up: Common options 1122 11232.11 Treating ‘/’ specially 1124=========================== 1125 1126Certain commands can operate destructively on entire hierarchies. For 1127example, if a user with appropriate privileges mistakenly runs ‘rm -rf / 1128tmp/junk’, that may remove all files on the entire system. Since there 1129are so few legitimate uses for such a command, GNU ‘rm’ normally 1130declines to operate on any directory that resolves to ‘/’. If you 1131really want to try to remove all the files on your system, you can use 1132the ‘--no-preserve-root’ option, but the default behavior, specified by 1133the ‘--preserve-root’ option, is safer for most purposes. 1134 1135 The commands ‘chgrp’, ‘chmod’ and ‘chown’ can also operate 1136destructively on entire hierarchies, so they too support these options. 1137Although, unlike ‘rm’, they don’t actually unlink files, these commands 1138are arguably more dangerous when operating recursively on ‘/’, since 1139they often work much more quickly, and hence damage more files before an 1140alert user can interrupt them. Tradition and POSIX require these 1141commands to operate recursively on ‘/’, so they default to 1142‘--no-preserve-root’, but using the ‘--preserve-root’ option makes them 1143safer for most purposes. For convenience you can specify 1144‘--preserve-root’ in an alias or in a shell function. 1145 1146 Note that the ‘--preserve-root’ option also ensures that ‘chgrp’ and 1147‘chown’ do not modify ‘/’ even when dereferencing a symlink pointing to 1148‘/’. 1149 1150 1151File: coreutils.info, Node: Special built-in utilities, Next: Standards conformance, Prev: Treating / specially, Up: Common options 1152 11532.12 Special built-in utilities 1154=============================== 1155 1156Some programs like ‘nice’ can invoke other programs; for example, the 1157command ‘nice cat file’ invokes the program ‘cat’ by executing the 1158command ‘cat file’. However, “special built-in utilities” like ‘exit’ 1159cannot be invoked this way. For example, the command ‘nice exit’ does 1160not have a well-defined behavior: it may generate an error message 1161instead of exiting. 1162 1163 Here is a list of the special built-in utilities that are 1164standardized by POSIX 1003.1-2004. 1165 1166 . : break continue eval exec exit export readonly return set shift 1167 times trap unset 1168 1169 For example, because ‘.’, ‘:’, and ‘exec’ are special, the commands 1170‘nice . foo.sh’, ‘nice :’, and ‘nice exec pwd’ do not work as you might 1171expect. 1172 1173 Many shells extend this list. For example, Bash has several extra 1174special built-in utilities like ‘history’, and ‘suspend’, and with Bash 1175the command ‘nice suspend’ generates an error message instead of 1176suspending. 1177 1178 1179File: coreutils.info, Node: Standards conformance, Next: Multi-call invocation, Prev: Special built-in utilities, Up: Common options 1180 11812.13 Standards conformance 1182========================== 1183 1184In a few cases, the GNU utilities’ default behavior is incompatible with 1185the POSIX standard. To suppress these incompatibilities, define the 1186‘POSIXLY_CORRECT’ environment variable. Unless you are checking for 1187POSIX conformance, you probably do not need to define ‘POSIXLY_CORRECT’. 1188 1189 Newer versions of POSIX are occasionally incompatible with older 1190versions. For example, older versions of POSIX required the command 1191‘sort +1’ to sort based on the second and succeeding fields in each 1192input line, but in POSIX 1003.1-2001 the same command is required to 1193sort the file named ‘+1’, and you must instead use the command ‘sort -k 11942’ to get the field-based sort. To complicate things further, POSIX 11951003.1-2008 allows an implementation to have either the old or the new 1196behavior. 1197 1198 The GNU utilities normally conform to the version of POSIX that is 1199standard for your system. To cause them to conform to a different 1200version of POSIX, define the ‘_POSIX2_VERSION’ environment variable to a 1201value of the form YYYYMM specifying the year and month the standard was 1202adopted. Three values are currently supported for ‘_POSIX2_VERSION’: 1203‘199209’ stands for POSIX 1003.2-1992, ‘200112’ stands for POSIX 12041003.1-2001, and ‘200809’ stands for POSIX 1003.1-2008. For example, if 1205you have a POSIX 1003.1-2001 system but are running software containing 1206traditional usage like ‘sort +1’ or ‘tail +10’, you can work around the 1207compatibility problems by setting ‘_POSIX2_VERSION=200809’ in your 1208environment. 1209 1210 1211File: coreutils.info, Node: Multi-call invocation, Prev: Standards conformance, Up: Common options 1212 12132.14 ‘coreutils’: Multi-call program 1214==================================== 1215 1216The ‘coreutils’ command invokes an individual utility, either implicitly 1217selected by the last component of the name used to invoke ‘coreutils’, 1218or explicitly with the ‘--coreutils-prog’ option. Synopsis: 1219 1220 coreutils --coreutils-prog=PROGRAM ... 1221 1222 The ‘coreutils’ command is not installed by default, so portable 1223scripts should not rely on its existence. 1224 1225 1226File: coreutils.info, Node: Output of entire files, Next: Formatting file contents, Prev: Common options, Up: Top 1227 12283 Output of entire files 1229************************ 1230 1231These commands read and write entire files, possibly transforming them 1232in some way. 1233 1234* Menu: 1235 1236* cat invocation:: Concatenate and write files. 1237* tac invocation:: Concatenate and write files in reverse. 1238* nl invocation:: Number lines and write files. 1239* od invocation:: Write files in octal or other formats. 1240* base32 invocation:: Transform data into printable data. 1241* base64 invocation:: Transform data into printable data. 1242* basenc invocation:: Transform data into printable data. 1243 1244 1245File: coreutils.info, Node: cat invocation, Next: tac invocation, Up: Output of entire files 1246 12473.1 ‘cat’: Concatenate and write files 1248====================================== 1249 1250‘cat’ copies each FILE (‘-’ means standard input), or standard input if 1251none are given, to standard output. Synopsis: 1252 1253 cat [OPTION] [FILE]... 1254 1255 The program accepts the following options. Also see *note Common 1256options::. 1257 1258‘-A’ 1259‘--show-all’ 1260 Equivalent to ‘-vET’. 1261 1262‘-b’ 1263‘--number-nonblank’ 1264 Number all nonempty output lines, starting with 1. 1265 1266‘-e’ 1267 Equivalent to ‘-vE’. 1268 1269‘-E’ 1270‘--show-ends’ 1271 Display a ‘$’ after the end of each line. 1272 1273‘-n’ 1274‘--number’ 1275 Number all output lines, starting with 1. This option is ignored 1276 if ‘-b’ is in effect. 1277 1278‘-s’ 1279‘--squeeze-blank’ 1280 Suppress repeated adjacent blank lines; output just one empty line 1281 instead of several. 1282 1283‘-t’ 1284 Equivalent to ‘-vT’. 1285 1286‘-T’ 1287‘--show-tabs’ 1288 Display TAB characters as ‘^I’. 1289 1290‘-u’ 1291 Ignored; for POSIX compatibility. 1292 1293‘-v’ 1294‘--show-nonprinting’ 1295 Display control characters except for LFD and TAB using ‘^’ 1296 notation and precede characters that have the high bit set with 1297 ‘M-’. 1298 1299 On systems like MS-DOS that distinguish between text and binary 1300files, ‘cat’ normally reads and writes in binary mode. However, ‘cat’ 1301reads in text mode if one of the options ‘-bensAE’ is used or if ‘cat’ 1302is reading from standard input and standard input is a terminal. 1303Similarly, ‘cat’ writes in text mode if one of the options ‘-bensAE’ is 1304used or if standard output is a terminal. 1305 1306 An exit status of zero indicates success, and a nonzero value 1307indicates failure. 1308 1309 Examples: 1310 1311 # Output f's contents, then standard input, then g's contents. 1312 cat f - g 1313 1314 # Copy standard input to standard output. 1315 cat 1316 1317 1318File: coreutils.info, Node: tac invocation, Next: nl invocation, Prev: cat invocation, Up: Output of entire files 1319 13203.2 ‘tac’: Concatenate and write files in reverse 1321================================================= 1322 1323‘tac’ copies each FILE (‘-’ means standard input), or standard input if 1324none are given, to standard output, reversing the records (lines by 1325default) in each separately. Synopsis: 1326 1327 tac [OPTION]... [FILE]... 1328 1329 “Records” are separated by instances of a string (newline by 1330default). By default, this separator string is attached to the end of 1331the record that it follows in the file. 1332 1333 The program accepts the following options. Also see *note Common 1334options::. 1335 1336‘-b’ 1337‘--before’ 1338 The separator is attached to the beginning of the record that it 1339 precedes in the file. 1340 1341‘-r’ 1342‘--regex’ 1343 Treat the separator string as a regular expression. 1344 1345‘-s SEPARATOR’ 1346‘--separator=SEPARATOR’ 1347 Use SEPARATOR as the record separator, instead of newline. Note an 1348 empty SEPARATOR is treated as a zero byte. I.e., input and output 1349 items are delimited with ASCII NUL. 1350 1351 On systems like MS-DOS that distinguish between text and binary 1352files, ‘tac’ reads and writes in binary mode. 1353 1354 An exit status of zero indicates success, and a nonzero value 1355indicates failure. 1356 1357 Example: 1358 1359 # Reverse a file character by character. 1360 tac -r -s 'x\|[^x]' 1361 1362 1363File: coreutils.info, Node: nl invocation, Next: od invocation, Prev: tac invocation, Up: Output of entire files 1364 13653.3 ‘nl’: Number lines and write files 1366====================================== 1367 1368‘nl’ writes each FILE (‘-’ means standard input), or standard input if 1369none are given, to standard output, with line numbers added to some or 1370all of the lines. Synopsis: 1371 1372 nl [OPTION]... [FILE]... 1373 1374 ‘nl’ decomposes its input into (logical) page sections; by default, 1375the line number is reset to 1 at each logical page section. ‘nl’ treats 1376all of the input files as a single document; it does not reset line 1377numbers or logical pages between files. 1378 1379 A logical page consists of three sections: header, body, and footer. 1380Any of the sections can be empty. Each can be numbered in a different 1381style from the others. 1382 1383 The beginnings of the sections of logical pages are indicated in the 1384input file by a line containing exactly one of these delimiter strings: 1385 1386‘\:\:\:’ 1387 start of header; 1388‘\:\:’ 1389 start of body; 1390‘\:’ 1391 start of footer. 1392 1393 The two characters from which these strings are made can be changed 1394from ‘\’ and ‘:’ via options (see below), but the pattern and length of 1395each string cannot be changed. 1396 1397 A section delimiter is replaced by an empty line on output. Any text 1398that comes before the first section delimiter string in the input file 1399is considered to be part of a body section, so ‘nl’ treats a file that 1400contains no section delimiters as a single body section. 1401 1402 The program accepts the following options. Also see *note Common 1403options::. 1404 1405‘-b STYLE’ 1406‘--body-numbering=STYLE’ 1407 Select the numbering style for lines in the body section of each 1408 logical page. When a line is not numbered, the current line number 1409 is not incremented, but the line number separator character is 1410 still prepended to the line. The styles are: 1411 1412 ‘a’ 1413 number all lines, 1414 ‘t’ 1415 number only nonempty lines (default for body), 1416 ‘n’ 1417 do not number lines (default for header and footer), 1418 ‘pBRE’ 1419 number only lines that contain a match for the basic regular 1420 expression BRE. *Note Regular Expressions: (grep)Regular 1421 Expressions. 1422 1423‘-d CD’ 1424‘--section-delimiter=CD’ 1425 Set the section delimiter characters to CD; default is ‘\:’. If 1426 only C is given, the second remains ‘:’. (Remember to protect ‘\’ 1427 or other metacharacters from shell expansion with quotes or extra 1428 backslashes.) 1429 1430‘-f STYLE’ 1431‘--footer-numbering=STYLE’ 1432 Analogous to ‘--body-numbering’. 1433 1434‘-h STYLE’ 1435‘--header-numbering=STYLE’ 1436 Analogous to ‘--body-numbering’. 1437 1438‘-i NUMBER’ 1439‘--line-increment=NUMBER’ 1440 Increment line numbers by NUMBER (default 1). 1441 1442‘-l NUMBER’ 1443‘--join-blank-lines=NUMBER’ 1444 Consider NUMBER (default 1) consecutive empty lines to be one 1445 logical line for numbering, and only number the last one. Where 1446 fewer than NUMBER consecutive empty lines occur, do not number 1447 them. An empty line is one that contains no characters, not even 1448 spaces or tabs. 1449 1450‘-n FORMAT’ 1451‘--number-format=FORMAT’ 1452 Select the line numbering format (default is ‘rn’): 1453 1454 ‘ln’ 1455 left justified, no leading zeros; 1456 ‘rn’ 1457 right justified, no leading zeros; 1458 ‘rz’ 1459 right justified, leading zeros. 1460 1461‘-p’ 1462‘--no-renumber’ 1463 Do not reset the line number at the start of a logical page. 1464 1465‘-s STRING’ 1466‘--number-separator=STRING’ 1467 Separate the line number from the text line in the output with 1468 STRING (default is the TAB character). 1469 1470‘-v NUMBER’ 1471‘--starting-line-number=NUMBER’ 1472 Set the initial line number on each logical page to NUMBER (default 1473 1). 1474 1475‘-w NUMBER’ 1476‘--number-width=NUMBER’ 1477 Use NUMBER characters for line numbers (default 6). 1478 1479 An exit status of zero indicates success, and a nonzero value 1480indicates failure. 1481 1482 1483File: coreutils.info, Node: od invocation, Next: base32 invocation, Prev: nl invocation, Up: Output of entire files 1484 14853.4 ‘od’: Write files in octal or other formats 1486=============================================== 1487 1488‘od’ writes an unambiguous representation of each FILE (‘-’ means 1489standard input), or standard input if none are given. Synopses: 1490 1491 od [OPTION]... [FILE]... 1492 od [-abcdfilosx]... [FILE] [[+]OFFSET[.][b]] 1493 od [OPTION]... --traditional [FILE] [[+]OFFSET[.][b] [[+]LABEL[.][b]]] 1494 1495 Each line of output consists of the offset in the input, followed by 1496groups of data from the file. By default, ‘od’ prints the offset in 1497octal, and each group of file data is a C ‘short int’’s worth of input 1498printed as a single octal number. 1499 1500 If OFFSET is given, it specifies how many input bytes to skip before 1501formatting and writing. By default, it is interpreted as an octal 1502number, but the optional trailing decimal point causes it to be 1503interpreted as decimal. If no decimal is specified and the offset 1504begins with ‘0x’ or ‘0X’ it is interpreted as a hexadecimal number. If 1505there is a trailing ‘b’, the number of bytes skipped will be OFFSET 1506multiplied by 512. 1507 1508 If a command is of both the first and second forms, the second form 1509is assumed if the last operand begins with ‘+’ or (if there are two 1510operands) a digit. For example, in ‘od foo 10’ and ‘od +10’ the ‘10’ is 1511an offset, whereas in ‘od 10’ the ‘10’ is a file name. 1512 1513 The program accepts the following options. Also see *note Common 1514options::. 1515 1516‘-A RADIX’ 1517‘--address-radix=RADIX’ 1518 Select the base in which file offsets are printed. RADIX can be 1519 one of the following: 1520 1521 ‘d’ 1522 decimal; 1523 ‘o’ 1524 octal; 1525 ‘x’ 1526 hexadecimal; 1527 ‘n’ 1528 none (do not print offsets). 1529 1530 The default is octal. 1531 1532‘--endian=ORDER’ 1533 Reorder input bytes, to handle inputs with differing byte orders, 1534 or to provide consistent output independent of the endian 1535 convention of the current system. Swapping is performed according 1536 to the specified ‘--type’ size and endian ORDER, which can be 1537 ‘little’ or ‘big’. 1538 1539‘-j BYTES’ 1540‘--skip-bytes=BYTES’ 1541 Skip BYTES input bytes before formatting and writing. If BYTES 1542 begins with ‘0x’ or ‘0X’, it is interpreted in hexadecimal; 1543 otherwise, if it begins with ‘0’, in octal; otherwise, in decimal. 1544 BYTES may be, or may be an integer optionally followed by, one of 1545 the following multiplicative suffixes: 1546 ‘b’ => 512 ("blocks") 1547 ‘KB’ => 1000 (KiloBytes) 1548 ‘K’ => 1024 (KibiBytes) 1549 ‘MB’ => 1000*1000 (MegaBytes) 1550 ‘M’ => 1024*1024 (MebiBytes) 1551 ‘GB’ => 1000*1000*1000 (GigaBytes) 1552 ‘G’ => 1024*1024*1024 (GibiBytes) 1553 and so on for ‘T’, ‘P’, ‘E’, ‘Z’, and ‘Y’. Binary prefixes can be 1554 used, too: ‘KiB’=‘K’, ‘MiB’=‘M’, and so on. 1555 1556‘-N BYTES’ 1557‘--read-bytes=BYTES’ 1558 Output at most BYTES bytes of the input. Prefixes and suffixes on 1559 ‘bytes’ are interpreted as for the ‘-j’ option. 1560 1561‘-S BYTES’ 1562‘--strings[=BYTES]’ 1563 Instead of the normal output, output only “string constants”: at 1564 least BYTES consecutive ASCII graphic characters, followed by a 1565 zero byte (ASCII NUL). Prefixes and suffixes on BYTES are 1566 interpreted as for the ‘-j’ option. 1567 1568 If BYTES is omitted with ‘--strings’, the default is 3. 1569 1570‘-t TYPE’ 1571‘--format=TYPE’ 1572 Select the format in which to output the file data. TYPE is a 1573 string of one or more of the below type indicator characters. If 1574 you include more than one type indicator character in a single TYPE 1575 string, or use this option more than once, ‘od’ writes one copy of 1576 each output line using each of the data types that you specified, 1577 in the order that you specified. 1578 1579 Adding a trailing “z” to any type specification appends a display 1580 of the single byte character representation of the printable 1581 characters to the output line generated by the type specification. 1582 1583 ‘a’ 1584 named character, ignoring high-order bit 1585 ‘c’ 1586 printable single byte character, C backslash escape or a 3 1587 digit octal sequence 1588 ‘d’ 1589 signed decimal 1590 ‘f’ 1591 floating point (*note Floating point::) 1592 ‘o’ 1593 octal 1594 ‘u’ 1595 unsigned decimal 1596 ‘x’ 1597 hexadecimal 1598 1599 The type ‘a’ outputs things like ‘sp’ for space, ‘nl’ for newline, 1600 and ‘nul’ for a zero byte. Only the least significant seven bits 1601 of each byte is used; the high-order bit is ignored. Type ‘c’ 1602 outputs ‘ ’, ‘\n’, and ‘\0’, respectively. 1603 1604 Except for types ‘a’ and ‘c’, you can specify the number of bytes 1605 to use in interpreting each number in the given data type by 1606 following the type indicator character with a decimal integer. 1607 Alternately, you can specify the size of one of the C compiler’s 1608 built-in data types by following the type indicator character with 1609 one of the following characters. For integers (‘d’, ‘o’, ‘u’, 1610 ‘x’): 1611 1612 ‘C’ 1613 char 1614 ‘S’ 1615 short 1616 ‘I’ 1617 int 1618 ‘L’ 1619 long 1620 1621 For floating point (‘f’): 1622 1623 F 1624 float 1625 D 1626 double 1627 L 1628 long double 1629 1630‘-v’ 1631‘--output-duplicates’ 1632 Output consecutive lines that are identical. By default, when two 1633 or more consecutive output lines would be identical, ‘od’ outputs 1634 only the first line, and puts just an asterisk on the following 1635 line to indicate the elision. 1636 1637‘-w[N]’ 1638‘--width[=N]’ 1639 Dump ‘n’ input bytes per output line. This must be a multiple of 1640 the least common multiple of the sizes associated with the 1641 specified output types. 1642 1643 If this option is not given at all, the default is 16. If N is 1644 omitted, the default is 32. 1645 1646 The next several options are shorthands for format specifications. 1647GNU ‘od’ accepts any combination of shorthands and format specification 1648options. These options accumulate. 1649 1650‘-a’ 1651 Output as named characters. Equivalent to ‘-t a’. 1652 1653‘-b’ 1654 Output as octal bytes. Equivalent to ‘-t o1’. 1655 1656‘-c’ 1657 Output as printable single byte characters, C backslash escapes or 1658 3 digit octal sequences. Equivalent to ‘-t c’. 1659 1660‘-d’ 1661 Output as unsigned decimal two-byte units. Equivalent to ‘-t u2’. 1662 1663‘-f’ 1664 Output as floats. Equivalent to ‘-t fF’. 1665 1666‘-i’ 1667 Output as decimal ints. Equivalent to ‘-t dI’. 1668 1669‘-l’ 1670 Output as decimal long ints. Equivalent to ‘-t dL’. 1671 1672‘-o’ 1673 Output as octal two-byte units. Equivalent to ‘-t o2’. 1674 1675‘-s’ 1676 Output as decimal two-byte units. Equivalent to ‘-t d2’. 1677 1678‘-x’ 1679 Output as hexadecimal two-byte units. Equivalent to ‘-t x2’. 1680 1681‘--traditional’ 1682 Recognize the non-option label argument that traditional ‘od’ 1683 accepted. The following syntax: 1684 1685 od --traditional [FILE] [[+]OFFSET[.][b] [[+]LABEL[.][b]]] 1686 1687 can be used to specify at most one file and optional arguments 1688 specifying an offset and a pseudo-start address, LABEL. The LABEL 1689 argument is interpreted just like OFFSET, but it specifies an 1690 initial pseudo-address. The pseudo-addresses are displayed in 1691 parentheses following any normal address. 1692 1693 An exit status of zero indicates success, and a nonzero value 1694indicates failure. 1695 1696 1697File: coreutils.info, Node: base32 invocation, Next: base64 invocation, Prev: od invocation, Up: Output of entire files 1698 16993.5 ‘base32’: Transform data into printable data 1700================================================ 1701 1702‘base32’ transforms data read from a file, or standard input, into (or 1703from) base32 encoded form. The base32 encoded form uses printable ASCII 1704characters to represent binary data. The usage and options of this 1705command are precisely the same as for ‘base64’. *Note base64 1706invocation::. 1707 1708 1709File: coreutils.info, Node: base64 invocation, Next: basenc invocation, Prev: base32 invocation, Up: Output of entire files 1710 17113.6 ‘base64’: Transform data into printable data 1712================================================ 1713 1714‘base64’ transforms data read from a file, or standard input, into (or 1715from) base64 encoded form. The base64 encoded form uses printable ASCII 1716characters to represent binary data. Synopses: 1717 1718 base64 [OPTION]... [FILE] 1719 base64 --decode [OPTION]... [FILE] 1720 1721 The base64 encoding expands data to roughly 133% of the original. 1722The base32 encoding expands data to roughly 160% of the original. The 1723format conforms to RFC 4648 (https://tools.ietf.org/search/rfc4648). 1724 1725 The program accepts the following options. Also see *note Common 1726options::. 1727 1728‘-w COLS’ 1729‘--wrap=COLS’ 1730 During encoding, wrap lines after COLS characters. This must be a 1731 positive number. 1732 1733 The default is to wrap after 76 characters. Use the value 0 to 1734 disable line wrapping altogether. 1735 1736‘-d’ 1737‘--decode’ 1738 Change the mode of operation, from the default of encoding data, to 1739 decoding data. Input is expected to be base64 encoded data, and 1740 the output will be the original data. 1741 1742‘-i’ 1743‘--ignore-garbage’ 1744 When decoding, newlines are always accepted. During decoding, 1745 ignore unrecognized bytes, to permit distorted data to be decoded. 1746 1747 An exit status of zero indicates success, and a nonzero value 1748indicates failure. 1749 1750 1751File: coreutils.info, Node: basenc invocation, Prev: base64 invocation, Up: Output of entire files 1752 17533.7 ‘basenc’: Transform data into printable data 1754================================================ 1755 1756‘basenc’ transforms data read from a file, or standard input, into (or 1757from) various common encoding forms. The encoded form uses printable 1758ASCII characters to represent binary data. 1759 1760 Synopses: 1761 1762 basenc ENCODING [OPTION]... [FILE] 1763 basenc ENCODING --decode [OPTION]... [FILE] 1764 1765 The ENCODING argument is required. If FILE is omitted, reads input 1766from stdin. The ‘-w/--wrap’,‘-i/--ignore-garbage’, ‘-d/--decode’ 1767options of this command are precisely the same as for ‘base64’. *Note 1768base64 invocation::. 1769 1770 Supported ENCODINGs are: 1771 1772‘--base64’ 1773 Encode into (or decode from with ‘-d/--decode’) base64 form. The 1774 format conforms to RFC 4648#4 1775 (https://tools.ietf.org/search/rfc4648#section-4). Equivalent to 1776 the ‘base64’ command. 1777 1778‘--base64url’ 1779 Encode into (or decode from with ‘-d/--decode’) file-and-url-safe 1780 base64 form (using ‘_’ and ‘-’ instead of ‘+’ and ‘/’). The format 1781 conforms to RFC 4648#5 1782 (https://tools.ietf.org/search/rfc4648#section-5). 1783 1784‘--base32’ 1785 Encode into (or decode from with ‘-d/--decode’) base32 form. The 1786 encoded data uses the ‘ABCDEFGHIJKLMNOPQRSTUVWXYZ234567=’ 1787 characters. The format conforms to RFC 4648#6 1788 (https://tools.ietf.org/search/rfc4648#section-6). Equivalent to 1789 the ‘base32’ command. 1790 1791‘--base32hex’ 1792 Encode into (or decode from with ‘-d/--decode’) Extended Hex 1793 Alphabet base32 form. The encoded data uses the 1794 ‘0123456789ABCDEFGHIJKLMNOPQRSTUV=’ characters. The format 1795 conforms to RFC 4648#7 1796 (https://tools.ietf.org/search/rfc4648#section-7). 1797 1798‘--base16’ 1799 Encode into (or decode from with ‘-d/--decode’) base16 1800 (hexadecimal) form. The encoded data uses the ‘0123456789ABCDEF’ 1801 characters. The format conforms to RFC 4648#8 1802 (https://tools.ietf.org/search/rfc4648#section-8). 1803 1804‘--base2lsbf’ 1805 Encode into (or decode from with ‘-d/--decode’) binary string form 1806 (‘0’ and ‘1’) with the _least_ significant bit of every byte first. 1807 1808‘--base2msbf’ 1809 Encode into (or decode from with ‘-d/--decode’) binary string form 1810 (‘0’ and ‘1’) with the _most_ significant bit of every byte first. 1811 1812‘--z85’ 1813 Encode into (or decode from with ‘-d/--decode’) Z85 form (a 1814 modified Ascii85 form). The encoded data uses the 1815 ‘0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTU VWXYZ.-:+=^!/*?&<>()[]{}@%$#’. 1816 characters. The format conforms to ZeroMQ spec:32/Z85 1817 (https://rfc.zeromq.org/spec:32/Z85/). 1818 1819 When encoding with ‘--z85’, input length must be a multiple of 4; 1820 when decoding with ‘--z85’, input length must be a multiple of 5. 1821 1822 Encoding/decoding examples: 1823 1824 $ printf '\376\117\202' | basenc --base64 1825 /k+C 1826 1827 $ printf '\376\117\202' | basenc --base64url 1828 _k-C 1829 1830 $ printf '\376\117\202' | basenc --base32 1831 7ZHYE=== 1832 1833 $ printf '\376\117\202' | basenc --base32hex 1834 VP7O4=== 1835 1836 $ printf '\376\117\202' | basenc --base16 1837 FE4F82 1838 1839 $ printf '\376\117\202' | basenc --base2lsbf 1840 011111111111001001000001 1841 1842 $ printf '\376\117\202' | basenc --base2msbf 1843 111111100100111110000010 1844 1845 $ printf '\376\117\202\000' | basenc --z85 1846 @.FaC 1847 1848 $ printf 01010100 | basenc --base2msbf --decode 1849 T 1850 1851 $ printf 01010100 | basenc --base2lsbf --decode 1852 * 1853 1854 1855File: coreutils.info, Node: Formatting file contents, Next: Output of parts of files, Prev: Output of entire files, Up: Top 1856 18574 Formatting file contents 1858************************** 1859 1860These commands reformat the contents of files. 1861 1862* Menu: 1863 1864* fmt invocation:: Reformat paragraph text. 1865* pr invocation:: Paginate or columnate files for printing. 1866* fold invocation:: Wrap input lines to fit in specified width. 1867 1868 1869File: coreutils.info, Node: fmt invocation, Next: pr invocation, Up: Formatting file contents 1870 18714.1 ‘fmt’: Reformat paragraph text 1872================================== 1873 1874‘fmt’ fills and joins lines to produce output lines of (at most) a given 1875number of characters (75 by default). Synopsis: 1876 1877 fmt [OPTION]... [FILE]... 1878 1879 ‘fmt’ reads from the specified FILE arguments (or standard input if 1880none are given), and writes to standard output. 1881 1882 By default, blank lines, spaces between words, and indentation are 1883preserved in the output; successive input lines with different 1884indentation are not joined; tabs are expanded on input and introduced on 1885output. 1886 1887 ‘fmt’ prefers breaking lines at the end of a sentence, and tries to 1888avoid line breaks after the first word of a sentence or before the last 1889word of a sentence. A “sentence break” is defined as either the end of 1890a paragraph or a word ending in any of ‘.?!’, followed by two spaces or 1891end of line, ignoring any intervening parentheses or quotes. Like TeX, 1892‘fmt’ reads entire “paragraphs” before choosing line breaks; the 1893algorithm is a variant of that given by Donald E. Knuth and Michael F. 1894Plass in “Breaking Paragraphs Into Lines”, ‘Software—Practice & 1895Experience’ 11, 11 (November 1981), 1119–1184. 1896 1897 The program accepts the following options. Also see *note Common 1898options::. 1899 1900‘-c’ 1901‘--crown-margin’ 1902 “Crown margin” mode: preserve the indentation of the first two 1903 lines within a paragraph, and align the left margin of each 1904 subsequent line with that of the second line. 1905 1906‘-t’ 1907‘--tagged-paragraph’ 1908 “Tagged paragraph” mode: like crown margin mode, except that if 1909 indentation of the first line of a paragraph is the same as the 1910 indentation of the second, the first line is treated as a one-line 1911 paragraph. 1912 1913‘-s’ 1914‘--split-only’ 1915 Split lines only. Do not join short lines to form longer ones. 1916 This prevents sample lines of code, and other such “formatted” text 1917 from being unduly combined. 1918 1919‘-u’ 1920‘--uniform-spacing’ 1921 Uniform spacing. Reduce spacing between words to one space, and 1922 spacing between sentences to two spaces. 1923 1924‘-WIDTH’ 1925‘-w WIDTH’ 1926‘--width=WIDTH’ 1927 Fill output lines up to WIDTH characters (default 75 or GOAL plus 1928 10, if GOAL is provided). 1929 1930‘-g GOAL’ 1931‘--goal=GOAL’ 1932 ‘fmt’ initially tries to make lines GOAL characters wide. By 1933 default, this is 7% shorter than WIDTH. 1934 1935‘-p PREFIX’ 1936‘--prefix=PREFIX’ 1937 Only lines beginning with PREFIX (possibly preceded by whitespace) 1938 are subject to formatting. The prefix and any preceding whitespace 1939 are stripped for the formatting and then re-attached to each 1940 formatted output line. One use is to format certain kinds of 1941 program comments, while leaving the code unchanged. 1942 1943 An exit status of zero indicates success, and a nonzero value 1944indicates failure. 1945 1946 1947File: coreutils.info, Node: pr invocation, Next: fold invocation, Prev: fmt invocation, Up: Formatting file contents 1948 19494.2 ‘pr’: Paginate or columnate files for printing 1950================================================== 1951 1952‘pr’ writes each FILE (‘-’ means standard input), or standard input if 1953none are given, to standard output, paginating and optionally outputting 1954in multicolumn format; optionally merges all FILEs, printing all in 1955parallel, one per column. Synopsis: 1956 1957 pr [OPTION]... [FILE]... 1958 1959 By default, a 5-line header is printed at each page: two blank lines; 1960a line with the date, the file name, and the page count; and two more 1961blank lines. A footer of five blank lines is also printed. The default 1962PAGE_LENGTH is 66 lines. The default number of text lines is therefore 196356. The text line of the header takes the form ‘DATE STRING PAGE’, with 1964spaces inserted around STRING so that the line takes up the full 1965PAGE_WIDTH. Here, DATE is the date (see the ‘-D’ or ‘--date-format’ 1966option for details), STRING is the centered header string, and PAGE 1967identifies the page number. The ‘LC_MESSAGES’ locale category affects 1968the spelling of PAGE; in the default C locale, it is ‘Page NUMBER’ where 1969NUMBER is the decimal page number. 1970 1971 Form feeds in the input cause page breaks in the output. Multiple 1972form feeds produce empty pages. 1973 1974 Columns are of equal width, separated by an optional string (default 1975is ‘space’). For multicolumn output, lines will always be truncated to 1976PAGE_WIDTH (default 72), unless you use the ‘-J’ option. For single 1977column output no line truncation occurs by default. Use ‘-W’ option to 1978truncate lines in that case. 1979 1980 The program accepts the following options. Also see *note Common 1981options::. 1982 1983‘+FIRST_PAGE[:LAST_PAGE]’ 1984‘--pages=FIRST_PAGE[:LAST_PAGE]’ 1985 Begin printing with page FIRST_PAGE and stop with LAST_PAGE. 1986 Missing ‘:LAST_PAGE’ implies end of file. While estimating the 1987 number of skipped pages each form feed in the input file results in 1988 a new page. Page counting with and without ‘+FIRST_PAGE’ is 1989 identical. By default, counting starts with the first page of 1990 input file (not first page printed). Line numbering may be altered 1991 by ‘-N’ option. 1992 1993‘-COLUMN’ 1994‘--columns=COLUMN’ 1995 With each single FILE, produce COLUMN columns of output (default is 1996 1) and print columns down, unless ‘-a’ is used. The column width 1997 is automatically decreased as COLUMN increases; unless you use the 1998 ‘-W/-w’ option to increase PAGE_WIDTH as well. This option might 1999 well cause some lines to be truncated. The number of lines in the 2000 columns on each page are balanced. The options ‘-e’ and ‘-i’ are 2001 on for multiple text-column output. Together with ‘-J’ option 2002 column alignment and line truncation is turned off. Lines of full 2003 length are joined in a free field format and ‘-S’ option may set 2004 field separators. ‘-COLUMN’ may not be used with ‘-m’ option. 2005 2006‘-a’ 2007‘--across’ 2008 With each single FILE, print columns across rather than down. The 2009 ‘-COLUMN’ option must be given with COLUMN greater than one. If a 2010 line is too long to fit in a column, it is truncated. 2011 2012‘-c’ 2013‘--show-control-chars’ 2014 Print control characters using hat notation (e.g., ‘^G’); print 2015 other nonprinting characters in octal backslash notation. By 2016 default, nonprinting characters are not changed. 2017 2018‘-d’ 2019‘--double-space’ 2020 Double space the output. 2021 2022‘-D FORMAT’ 2023‘--date-format=FORMAT’ 2024 Format header dates using FORMAT, using the same conventions as for 2025 the command ‘date +FORMAT’. *Note date invocation::. Except for 2026 directives, which start with ‘%’, characters in FORMAT are printed 2027 unchanged. You can use this option to specify an arbitrary string 2028 in place of the header date, e.g., ‘--date-format="Monday 2029 morning"’. 2030 2031 The default date format is ‘%Y-%m-%d %H:%M’ (for example, 2032 ‘2001-12-04 23:59’); but if the ‘POSIXLY_CORRECT’ environment 2033 variable is set and the ‘LC_TIME’ locale category specifies the 2034 POSIX locale, the default is ‘%b %e %H:%M %Y’ (for example, ‘Dec 4 2035 23:59 2001’. 2036 2037 Timestamps are listed according to the time zone rules specified by 2038 the ‘TZ’ environment variable, or by the system default rules if 2039 ‘TZ’ is not set. *Note Specifying the Time Zone with ‘TZ’: 2040 (libc)TZ Variable. 2041 2042‘-e[IN-TABCHAR[IN-TABWIDTH]]’ 2043‘--expand-tabs[=IN-TABCHAR[IN-TABWIDTH]]’ 2044 Expand TABs to spaces on input. Optional argument IN-TABCHAR is 2045 the input tab character (default is the TAB character). Second 2046 optional argument IN-TABWIDTH is the input tab character’s width 2047 (default is 8). 2048 2049‘-f’ 2050‘-F’ 2051‘--form-feed’ 2052 Use a form feed instead of newlines to separate output pages. This 2053 does not alter the default page length of 66 lines. 2054 2055‘-h HEADER’ 2056‘--header=HEADER’ 2057 Replace the file name in the header with the centered string 2058 HEADER. When using the shell, HEADER should be quoted and should 2059 be separated from ‘-h’ by a space. 2060 2061‘-i[OUT-TABCHAR[OUT-TABWIDTH]]’ 2062‘--output-tabs[=OUT-TABCHAR[OUT-TABWIDTH]]’ 2063 Replace spaces with TABs on output. Optional argument OUT-TABCHAR 2064 is the output tab character (default is the TAB character). Second 2065 optional argument OUT-TABWIDTH is the output tab character’s width 2066 (default is 8). 2067 2068‘-J’ 2069‘--join-lines’ 2070 Merge lines of full length. Used together with the column options 2071 ‘-COLUMN’, ‘-a -COLUMN’ or ‘-m’. Turns off ‘-W/-w’ line 2072 truncation; no column alignment used; may be used with 2073 ‘--sep-string[=STRING]’. ‘-J’ has been introduced (together with 2074 ‘-W’ and ‘--sep-string’) to disentangle the old (POSIX-compliant) 2075 options ‘-w’ and ‘-s’ along with the three column options. 2076 2077‘-l PAGE_LENGTH’ 2078‘--length=PAGE_LENGTH’ 2079 Set the page length to PAGE_LENGTH (default 66) lines, including 2080 the lines of the header [and the footer]. If PAGE_LENGTH is less 2081 than or equal to 10, the header and footer are omitted, as if the 2082 ‘-t’ option had been given. 2083 2084‘-m’ 2085‘--merge’ 2086 Merge and print all FILEs in parallel, one in each column. If a 2087 line is too long to fit in a column, it is truncated, unless the 2088 ‘-J’ option is used. ‘--sep-string[=STRING]’ may be used. Empty 2089 pages in some FILEs (form feeds set) produce empty columns, still 2090 marked by STRING. The result is a continuous line numbering and 2091 column marking throughout the whole merged file. Completely empty 2092 merged pages show no separators or line numbers. The default 2093 header becomes ‘DATE PAGE’ with spaces inserted in the middle; this 2094 may be used with the ‘-h’ or ‘--header’ option to fill up the 2095 middle blank part. 2096 2097‘-n[NUMBER-SEPARATOR[DIGITS]]’ 2098‘--number-lines[=NUMBER-SEPARATOR[DIGITS]]’ 2099 Provide DIGITS digit line numbering (default for DIGITS is 5). 2100 With multicolumn output the number occupies the first DIGITS column 2101 positions of each text column or only each line of ‘-m’ output. 2102 With single column output the number precedes each line just as 2103 ‘-m’ does. Default counting of the line numbers starts with the 2104 first line of the input file (not the first line printed, compare 2105 the ‘--page’ option and ‘-N’ option). Optional argument 2106 NUMBER-SEPARATOR is the character appended to the line number to 2107 separate it from the text followed. The default separator is the 2108 TAB character. In a strict sense a TAB is always printed with 2109 single column output only. The TAB width varies with the TAB 2110 position, e.g., with the left MARGIN specified by ‘-o’ option. 2111 With multicolumn output priority is given to ‘equal width of output 2112 columns’ (a POSIX specification). The TAB width is fixed to the 2113 value of the first column and does not change with different values 2114 of left MARGIN. That means a fixed number of spaces is always 2115 printed in the place of the NUMBER-SEPARATOR TAB. The tabification 2116 depends upon the output position. 2117 2118‘-N LINE_NUMBER’ 2119‘--first-line-number=LINE_NUMBER’ 2120 Start line counting with the number LINE_NUMBER at first line of 2121 first page printed (in most cases not the first line of the input 2122 file). 2123 2124‘-o MARGIN’ 2125‘--indent=MARGIN’ 2126 Indent each line with a margin MARGIN spaces wide (default is 2127 zero). The total page width is the size of the margin plus the 2128 PAGE_WIDTH set with the ‘-W/-w’ option. A limited overflow may 2129 occur with numbered single column output (compare ‘-n’ option). 2130 2131‘-r’ 2132‘--no-file-warnings’ 2133 Do not print a warning message when an argument FILE cannot be 2134 opened. (The exit status will still be nonzero, however.) 2135 2136‘-s[CHAR]’ 2137‘--separator[=CHAR]’ 2138 Separate columns by a single character CHAR. The default for CHAR 2139 is the TAB character without ‘-w’ and ‘no character’ with ‘-w’. 2140 Without ‘-s’ the default separator ‘space’ is set. ‘-s[char]’ 2141 turns off line truncation of all three column options 2142 (‘-COLUMN’|‘-a -COLUMN’|‘-m’) unless ‘-w’ is set. This is a 2143 POSIX-compliant formulation. 2144 2145‘-S[STRING]’ 2146‘--sep-string[=STRING]’ 2147 Use STRING to separate output columns. The ‘-S’ option doesn’t 2148 affect the ‘-W/-w’ option, unlike the ‘-s’ option which does. It 2149 does not affect line truncation or column alignment. Without ‘-S’, 2150 and with ‘-J’, ‘pr’ uses the default output separator, TAB. 2151 Without ‘-S’ or ‘-J’, ‘pr’ uses a ‘space’ (same as ‘-S" "’). If no 2152 ‘STRING’ argument is specified, ‘""’ is assumed. 2153 2154‘-t’ 2155‘--omit-header’ 2156 Do not print the usual header [and footer] on each page, and do not 2157 fill out the bottom of pages (with blank lines or a form feed). No 2158 page structure is produced, but form feeds set in the input files 2159 are retained. The predefined pagination is not changed. ‘-t’ or 2160 ‘-T’ may be useful together with other options; e.g.: ‘-t -e4’, 2161 expand TAB characters in the input file to 4 spaces but don’t make 2162 any other changes. Use of ‘-t’ overrides ‘-h’. 2163 2164‘-T’ 2165‘--omit-pagination’ 2166 Do not print header [and footer]. In addition eliminate all form 2167 feeds set in the input files. 2168 2169‘-v’ 2170‘--show-nonprinting’ 2171 Print nonprinting characters in octal backslash notation. 2172 2173‘-w PAGE_WIDTH’ 2174‘--width=PAGE_WIDTH’ 2175 Set page width to PAGE_WIDTH characters for multiple text-column 2176 output only (default for PAGE_WIDTH is 72). The specified 2177 PAGE_WIDTH is rounded down so that columns have equal width. 2178 ‘-s[CHAR]’ turns off the default page width and any line truncation 2179 and column alignment. Lines of full length are merged, regardless 2180 of the column options set. No PAGE_WIDTH setting is possible with 2181 single column output. A POSIX-compliant formulation. 2182 2183‘-W PAGE_WIDTH’ 2184‘--page_width=PAGE_WIDTH’ 2185 Set the page width to PAGE_WIDTH characters, honored with and 2186 without a column option. With a column option, the specified 2187 PAGE_WIDTH is rounded down so that columns have equal width. Text 2188 lines are truncated, unless ‘-J’ is used. Together with one of the 2189 three column options (‘-COLUMN’, ‘-a -COLUMN’ or ‘-m’) column 2190 alignment is always used. The separator options ‘-S’ or ‘-s’ don’t 2191 disable the ‘-W’ option. Default is 72 characters. Without ‘-W 2192 PAGE_WIDTH’ and without any of the column options NO line 2193 truncation is used (defined to keep downward compatibility and to 2194 meet most frequent tasks). That’s equivalent to ‘-W 72 -J’. The 2195 header line is never truncated. 2196 2197 An exit status of zero indicates success, and a nonzero value 2198indicates failure. 2199 2200 2201File: coreutils.info, Node: fold invocation, Prev: pr invocation, Up: Formatting file contents 2202 22034.3 ‘fold’: Wrap input lines to fit in specified width 2204====================================================== 2205 2206‘fold’ writes each FILE (‘-’ means standard input), or standard input if 2207none are given, to standard output, breaking long lines. Synopsis: 2208 2209 fold [OPTION]... [FILE]... 2210 2211 By default, ‘fold’ breaks lines wider than 80 columns. The output is 2212split into as many lines as necessary. 2213 2214 ‘fold’ counts screen columns by default; thus, a tab may count more 2215than one column, backspace decreases the column count, and carriage 2216return sets the column to zero. 2217 2218 The program accepts the following options. Also see *note Common 2219options::. 2220 2221‘-b’ 2222‘--bytes’ 2223 Count bytes rather than columns, so that tabs, backspaces, and 2224 carriage returns are each counted as taking up one column, just 2225 like other characters. 2226 2227‘-s’ 2228‘--spaces’ 2229 Break at word boundaries: the line is broken after the last blank 2230 before the maximum line length. If the line contains no such 2231 blanks, the line is broken at the maximum line length as usual. 2232 2233‘-w WIDTH’ 2234‘--width=WIDTH’ 2235 Use a maximum line length of WIDTH columns instead of 80. 2236 2237 For compatibility ‘fold’ supports an obsolete option syntax 2238 ‘-WIDTH’. New scripts should use ‘-w WIDTH’ instead. 2239 2240 An exit status of zero indicates success, and a nonzero value 2241indicates failure. 2242 2243 2244File: coreutils.info, Node: Output of parts of files, Next: Summarizing files, Prev: Formatting file contents, Up: Top 2245 22465 Output of parts of files 2247************************** 2248 2249These commands output pieces of the input. 2250 2251* Menu: 2252 2253* head invocation:: Output the first part of files. 2254* tail invocation:: Output the last part of files. 2255* split invocation:: Split a file into pieces. 2256* csplit invocation:: Split a file into context-determined pieces. 2257 2258 2259File: coreutils.info, Node: head invocation, Next: tail invocation, Up: Output of parts of files 2260 22615.1 ‘head’: Output the first part of files 2262========================================== 2263 2264‘head’ prints the first part (10 lines by default) of each FILE; it 2265reads from standard input if no files are given or when given a FILE of 2266‘-’. Synopsis: 2267 2268 head [OPTION]... [FILE]... 2269 2270 If more than one FILE is specified, ‘head’ prints a one-line header 2271consisting of: 2272 2273 ==> FILE NAME <== 2274 2275before the output for each FILE. 2276 2277 The program accepts the following options. Also see *note Common 2278options::. 2279 2280‘-c [-]NUM’ 2281‘--bytes=[-]NUM’ 2282 Print the first NUM bytes, instead of initial lines. However, if 2283 NUM is prefixed with a ‘-’, print all but the last NUM bytes of 2284 each file. NUM may be, or may be an integer optionally followed 2285 by, one of the following multiplicative suffixes: 2286 ‘b’ => 512 ("blocks") 2287 ‘KB’ => 1000 (KiloBytes) 2288 ‘K’ => 1024 (KibiBytes) 2289 ‘MB’ => 1000*1000 (MegaBytes) 2290 ‘M’ => 1024*1024 (MebiBytes) 2291 ‘GB’ => 1000*1000*1000 (GigaBytes) 2292 ‘G’ => 1024*1024*1024 (GibiBytes) 2293 and so on for ‘T’, ‘P’, ‘E’, ‘Z’, and ‘Y’. Binary prefixes can be 2294 used, too: ‘KiB’=‘K’, ‘MiB’=‘M’, and so on. 2295 2296‘-n [-]NUM’ 2297‘--lines=[-]NUM’ 2298 Output the first NUM lines. However, if NUM is prefixed with a 2299 ‘-’, print all but the last NUM lines of each file. Size 2300 multiplier suffixes are the same as with the ‘-c’ option. 2301 2302‘-q’ 2303‘--quiet’ 2304‘--silent’ 2305 Never print file name headers. 2306 2307‘-v’ 2308‘--verbose’ 2309 Always print file name headers. 2310 2311‘-z’ 2312‘--zero-terminated’ 2313 Delimit items with a zero byte rather than a newline (ASCII LF). 2314 I.e., treat input as items separated by ASCII NUL and terminate 2315 output items with ASCII NUL. This option can be useful in 2316 conjunction with ‘perl -0’ or ‘find -print0’ and ‘xargs -0’ which 2317 do the same in order to reliably handle arbitrary file names (even 2318 those containing blanks or other special characters). 2319 2320 For compatibility ‘head’ also supports an obsolete option syntax 2321‘-[NUM][bkm][cqv]’, which is recognized only if it is specified first. 2322NUM is a decimal number optionally followed by a size letter (‘b’, ‘k’, 2323‘m’) as in ‘-c’, or ‘l’ to mean count by lines, or other option letters 2324(‘cqv’). Scripts intended for standard hosts should use ‘-c NUM’ or ‘-n 2325NUM’ instead. If your script must also run on hosts that support only 2326the obsolete syntax, it is usually simpler to avoid ‘head’, e.g., by 2327using ‘sed 5q’ instead of ‘head -5’. 2328 2329 An exit status of zero indicates success, and a nonzero value 2330indicates failure. 2331 2332 2333File: coreutils.info, Node: tail invocation, Next: split invocation, Prev: head invocation, Up: Output of parts of files 2334 23355.2 ‘tail’: Output the last part of files 2336========================================= 2337 2338‘tail’ prints the last part (10 lines by default) of each FILE; it reads 2339from standard input if no files are given or when given a FILE of ‘-’. 2340Synopsis: 2341 2342 tail [OPTION]... [FILE]... 2343 2344 If more than one FILE is specified, ‘tail’ prints a one-line header 2345before the output for each FILE, consisting of: 2346 2347 ==> FILE NAME <== 2348 2349 For further processing of tail output, it can be useful to convert 2350the file headers to line prefixes, which can be done like: 2351 2352 tail ... | 2353 awk ' 2354 /^==> .* <==$/ {prefix=substr($0,5,length-8)":"; next} 2355 {print prefix$0} 2356 ' | ... 2357 2358 GNU ‘tail’ can output any amount of data (some other versions of 2359‘tail’ cannot). It also has no ‘-r’ option (print in reverse), since 2360reversing a file is really a different job from printing the end of a 2361file; BSD ‘tail’ (which is the one with ‘-r’) can only reverse files 2362that are at most as large as its buffer, which is typically 32 KiB. A 2363more reliable and versatile way to reverse files is the GNU ‘tac’ 2364command. 2365 2366 The program accepts the following options. Also see *note Common 2367options::. 2368 2369‘-c [+]NUM’ 2370‘--bytes=[+]NUM’ 2371 Output the last NUM bytes, instead of final lines. However, if NUM 2372 is prefixed with a ‘+’, start printing with byte NUM from the start 2373 of each file, instead of from the end. NUM may be, or may be an 2374 integer optionally followed by, one of the following multiplicative 2375 suffixes: 2376 ‘b’ => 512 ("blocks") 2377 ‘KB’ => 1000 (KiloBytes) 2378 ‘K’ => 1024 (KibiBytes) 2379 ‘MB’ => 1000*1000 (MegaBytes) 2380 ‘M’ => 1024*1024 (MebiBytes) 2381 ‘GB’ => 1000*1000*1000 (GigaBytes) 2382 ‘G’ => 1024*1024*1024 (GibiBytes) 2383 and so on for ‘T’, ‘P’, ‘E’, ‘Z’, and ‘Y’. Binary prefixes can be 2384 used, too: ‘KiB’=‘K’, ‘MiB’=‘M’, and so on. 2385 2386‘-f’ 2387‘--follow[=HOW]’ 2388 Loop forever trying to read more characters at the end of the file, 2389 presumably because the file is growing. If more than one file is 2390 given, ‘tail’ prints a header whenever it gets output from a 2391 different file, to indicate which file that output is from. 2392 2393 There are two ways to specify how you’d like to track files with 2394 this option, but that difference is noticeable only when a followed 2395 file is removed or renamed. If you’d like to continue to track the 2396 end of a growing file even after it has been unlinked, use 2397 ‘--follow=descriptor’. This is the default behavior, but it is not 2398 useful if you’re tracking a log file that may be rotated (removed 2399 or renamed, then reopened). In that case, use ‘--follow=name’ to 2400 track the named file, perhaps by reopening it periodically to see 2401 if it has been removed and recreated by some other program. Note 2402 that the inotify-based implementation handles this case without the 2403 need for any periodic reopening. 2404 2405 No matter which method you use, if the tracked file is determined 2406 to have shrunk, ‘tail’ prints a message saying the file has been 2407 truncated and resumes tracking from the start of the file, assuming 2408 it has been truncated to 0, which is the usual truncation operation 2409 for log files. 2410 2411 When a file is removed, ‘tail’’s behavior depends on whether it is 2412 following the name or the descriptor. When following by name, tail 2413 can detect that a file has been removed and gives a message to that 2414 effect, and if ‘--retry’ has been specified it will continue 2415 checking periodically to see if the file reappears. When following 2416 a descriptor, tail does not detect that the file has been unlinked 2417 or renamed and issues no message; even though the file may no 2418 longer be accessible via its original name, it may still be 2419 growing. 2420 2421 The option values ‘descriptor’ and ‘name’ may be specified only 2422 with the long form of the option, not with ‘-f’. 2423 2424 The ‘-f’ option is ignored if no FILE operand is specified and 2425 standard input is a FIFO or a pipe. Likewise, the ‘-f’ option has 2426 no effect for any operand specified as ‘-’, when standard input is 2427 a FIFO or a pipe. 2428 2429 With kernel inotify support, output is triggered by file changes 2430 and is generally very prompt. Otherwise, ‘tail’ sleeps for one 2431 second between checks— use ‘--sleep-interval=N’ to change that 2432 default—which can make the output appear slightly less responsive 2433 or bursty. When using tail without inotify support, you can make 2434 it more responsive by using a sub-second sleep interval, e.g., via 2435 an alias like this: 2436 2437 alias tail='tail -s.1' 2438 2439‘-F’ 2440 This option is the same as ‘--follow=name --retry’. That is, tail 2441 will attempt to reopen a file when it is removed. Should this 2442 fail, tail will keep trying until it becomes accessible again. 2443 2444‘--max-unchanged-stats=N’ 2445 When tailing a file by name, if there have been N (default n=5) 2446 consecutive iterations for which the file has not changed, then 2447 ‘open’/‘fstat’ the file to determine if that file name is still 2448 associated with the same device/inode-number pair as before. When 2449 following a log file that is rotated, this is approximately the 2450 number of seconds between when tail prints the last pre-rotation 2451 lines and when it prints the lines that have accumulated in the new 2452 log file. This option is meaningful only when polling (i.e., 2453 without inotify) and when following by name. 2454 2455‘-n [+]NUM’ 2456‘--lines=[+]’ 2457 Output the last NUM lines. However, if NUM is prefixed with a ‘+’, 2458 start printing with line NUM from the start of each file, instead 2459 of from the end. Size multiplier suffixes are the same as with the 2460 ‘-c’ option. 2461 2462‘--pid=PID’ 2463 When following by name or by descriptor, you may specify the 2464 process ID, PID, of the sole writer of all FILE arguments. Then, 2465 shortly after that process terminates, tail will also terminate. 2466 This will work properly only if the writer and the tailing process 2467 are running on the same machine. For example, to save the output 2468 of a build in a file and to watch the file grow, if you invoke 2469 ‘make’ and ‘tail’ like this then the tail process will stop when 2470 your build completes. Without this option, you would have had to 2471 kill the ‘tail -f’ process yourself. 2472 2473 $ make >& makerr & tail --pid=$! -f makerr 2474 2475 If you specify a PID that is not in use or that does not correspond 2476 to the process that is writing to the tailed files, then ‘tail’ may 2477 terminate long before any FILEs stop growing or it may not 2478 terminate until long after the real writer has terminated. Note 2479 that ‘--pid’ cannot be supported on some systems; ‘tail’ will print 2480 a warning if this is the case. 2481 2482‘-q’ 2483‘--quiet’ 2484‘--silent’ 2485 Never print file name headers. 2486 2487‘--retry’ 2488 Indefinitely try to open the specified file. This option is useful 2489 mainly when following (and otherwise issues a warning). 2490 2491 When following by file descriptor (i.e., with 2492 ‘--follow=descriptor’), this option only affects the initial open 2493 of the file, as after a successful open, ‘tail’ will start 2494 following the file descriptor. 2495 2496 When following by name (i.e., with ‘--follow=name’), ‘tail’ 2497 infinitely retries to re-open the given files until killed. 2498 2499 Without this option, when ‘tail’ encounters a file that doesn’t 2500 exist or is otherwise inaccessible, it reports that fact and never 2501 checks it again. 2502 2503‘-s NUMBER’ 2504‘--sleep-interval=NUMBER’ 2505 Change the number of seconds to wait between iterations (the 2506 default is 1.0). During one iteration, every specified file is 2507 checked to see if it has changed size. When ‘tail’ uses inotify, 2508 this polling-related option is usually ignored. However, if you 2509 also specify ‘--pid=P’, ‘tail’ checks whether process P is alive at 2510 least every NUMBER seconds. The NUMBER must be non-negative and 2511 can be a floating-point number in either the current or the C 2512 locale. *Note Floating point::. 2513 2514‘-v’ 2515‘--verbose’ 2516 Always print file name headers. 2517 2518‘-z’ 2519‘--zero-terminated’ 2520 Delimit items with a zero byte rather than a newline (ASCII LF). 2521 I.e., treat input as items separated by ASCII NUL and terminate 2522 output items with ASCII NUL. This option can be useful in 2523 conjunction with ‘perl -0’ or ‘find -print0’ and ‘xargs -0’ which 2524 do the same in order to reliably handle arbitrary file names (even 2525 those containing blanks or other special characters). 2526 2527 For compatibility ‘tail’ also supports an obsolete usage ‘tail 2528-[NUM][bcl][f] [FILE]’, which is recognized only if it does not conflict 2529with the usage described above. This obsolete form uses exactly one 2530option and at most one file. In the option, NUM is an optional decimal 2531number optionally followed by a size letter (‘b’, ‘c’, ‘l’) to mean 2532count by 512-byte blocks, bytes, or lines, optionally followed by ‘f’ 2533which has the same meaning as ‘-f’. 2534 2535 On systems not conforming to POSIX 1003.1-2001, the leading ‘-’ can 2536be replaced by ‘+’ in the traditional option syntax with the same 2537meaning as in counts, and on obsolete systems predating POSIX 25381003.1-2001 traditional usage overrides normal usage when the two 2539conflict. This behavior can be controlled with the ‘_POSIX2_VERSION’ 2540environment variable (*note Standards conformance::). 2541 2542 Scripts intended for use on standard hosts should avoid traditional 2543syntax and should use ‘-c NUM[b]’, ‘-n NUM’, and/or ‘-f’ instead. If 2544your script must also run on hosts that support only the traditional 2545syntax, you can often rewrite it to avoid problematic usages, e.g., by 2546using ‘sed -n '$p'’ rather than ‘tail -1’. If that’s not possible, the 2547script can use a test like ‘if tail -c +1 </dev/null >/dev/null 2>&1; 2548then ...’ to decide which syntax to use. 2549 2550 Even if your script assumes the standard behavior, you should still 2551beware usages whose behaviors differ depending on the POSIX version. 2552For example, avoid ‘tail - main.c’, since it might be interpreted as 2553either ‘tail main.c’ or as ‘tail -- - main.c’; avoid ‘tail -c 4’, since 2554it might mean either ‘tail -c4’ or ‘tail -c 10 4’; and avoid ‘tail +4’, 2555since it might mean either ‘tail ./+4’ or ‘tail -n +4’. 2556 2557 An exit status of zero indicates success, and a nonzero value 2558indicates failure. 2559 2560 2561File: coreutils.info, Node: split invocation, Next: csplit invocation, Prev: tail invocation, Up: Output of parts of files 2562 25635.3 ‘split’: Split a file into pieces. 2564====================================== 2565 2566‘split’ creates output files containing consecutive or interleaved 2567sections of INPUT (standard input if none is given or INPUT is ‘-’). 2568Synopsis: 2569 2570 split [OPTION] [INPUT [PREFIX]] 2571 2572 By default, ‘split’ puts 1000 lines of INPUT (or whatever is left 2573over for the last section), into each output file. 2574 2575 The output files’ names consist of PREFIX (‘x’ by default) followed 2576by a group of characters (‘aa’, ‘ab’, ... by default), such that 2577concatenating the output files in traditional sorted order by file name 2578produces the original input file (except ‘-nr/N’). By default split 2579will initially create files with two generated suffix characters, and 2580will increase this width by two when the next most significant position 2581reaches the last character. (‘yz’, ‘zaaa’, ‘zaab’, ...). In this way 2582an arbitrary number of output files are supported, which sort as 2583described above, even in the presence of an ‘--additional-suffix’ 2584option. If the ‘-a’ option is specified and the output file names are 2585exhausted, ‘split’ reports an error without deleting the output files 2586that it did create. 2587 2588 The program accepts the following options. Also see *note Common 2589options::. 2590 2591‘-l LINES’ 2592‘--lines=LINES’ 2593 Put LINES lines of INPUT into each output file. If ‘--separator’ 2594 is specified, then LINES determines the number of records. 2595 2596 For compatibility ‘split’ also supports an obsolete option syntax 2597 ‘-LINES’. New scripts should use ‘-l LINES’ instead. 2598 2599‘-b SIZE’ 2600‘--bytes=SIZE’ 2601 Put SIZE bytes of INPUT into each output file. SIZE may be, or may 2602 be an integer optionally followed by, one of the following 2603 multiplicative suffixes: 2604 ‘b’ => 512 ("blocks") 2605 ‘KB’ => 1000 (KiloBytes) 2606 ‘K’ => 1024 (KibiBytes) 2607 ‘MB’ => 1000*1000 (MegaBytes) 2608 ‘M’ => 1024*1024 (MebiBytes) 2609 ‘GB’ => 1000*1000*1000 (GigaBytes) 2610 ‘G’ => 1024*1024*1024 (GibiBytes) 2611 and so on for ‘T’, ‘P’, ‘E’, ‘Z’, and ‘Y’. Binary prefixes can be 2612 used, too: ‘KiB’=‘K’, ‘MiB’=‘M’, and so on. 2613 2614‘-C SIZE’ 2615‘--line-bytes=SIZE’ 2616 Put into each output file as many complete lines of INPUT as 2617 possible without exceeding SIZE bytes. Individual lines or records 2618 longer than SIZE bytes are broken into multiple files. SIZE has 2619 the same format as for the ‘--bytes’ option. If ‘--separator’ is 2620 specified, then LINES determines the number of records. 2621 2622‘--filter=COMMAND’ 2623 With this option, rather than simply writing to each output file, 2624 write through a pipe to the specified shell COMMAND for each output 2625 file. COMMAND should use the $FILE environment variable, which is 2626 set to a different output file name for each invocation of the 2627 command. For example, imagine that you have a 1TiB compressed file 2628 that, if uncompressed, would be too large to reside on disk, yet 2629 you must split it into individually-compressed pieces of a more 2630 manageable size. To do that, you might run this command: 2631 2632 xz -dc BIG.xz | split -b200G --filter='xz > $FILE.xz' - big- 2633 2634 Assuming a 10:1 compression ratio, that would create about fifty 2635 20GiB files with names ‘big-aa.xz’, ‘big-ab.xz’, ‘big-ac.xz’, etc. 2636 2637‘-n CHUNKS’ 2638‘--number=CHUNKS’ 2639 2640 Split INPUT to CHUNKS output files where CHUNKS may be: 2641 2642 N generate N files based on current size of INPUT 2643 K/N only output Kth of N to stdout 2644 l/N generate N files without splitting lines or records 2645 l/K/N likewise but only output Kth of N to stdout 2646 r/N like ‘l’ but use round robin distribution 2647 r/K/N likewise but only output Kth of N to stdout 2648 2649 Any excess bytes remaining after dividing the INPUT into N chunks, 2650 are assigned to the last chunk. Any excess bytes appearing after 2651 the initial calculation are discarded (except when using ‘r’ mode). 2652 2653 All N files are created even if there are fewer than N lines, or 2654 the INPUT is truncated. 2655 2656 For ‘l’ mode, chunks are approximately INPUT size / N. The INPUT 2657 is partitioned into N equal sized portions, with the last assigned 2658 any excess. If a line _starts_ within a partition it is written 2659 completely to the corresponding file. Since lines or records are 2660 not split even if they overlap a partition, the files written can 2661 be larger or smaller than the partition size, and even empty if a 2662 line/record is so long as to completely overlap the partition. 2663 2664 For ‘r’ mode, the size of INPUT is irrelevant, and so can be a pipe 2665 for example. 2666 2667‘-a LENGTH’ 2668‘--suffix-length=LENGTH’ 2669 Use suffixes of length LENGTH. If a LENGTH of 0 is specified, this 2670 is the same as if (any previous) ‘-a’ was not specified, and thus 2671 enables the default behavior, which starts the suffix length at 2, 2672 and unless ‘-n’ or ‘--numeric-suffixes=FROM’ is specified, will 2673 auto increase the length by 2 as required. 2674 2675‘-d’ 2676‘--numeric-suffixes[=FROM]’ 2677 Use digits in suffixes rather than lower-case letters. The 2678 numerical suffix counts from FROM if specified, 0 otherwise. 2679 2680 FROM is supported with the long form option, and is used to either 2681 set the initial suffix for a single run, or to set the suffix 2682 offset for independently split inputs, and consequently the auto 2683 suffix length expansion described above is disabled. Therefore you 2684 may also want to use option ‘-a’ to allow suffixes beyond ‘99’. 2685 Note if option ‘--number’ is specified and the number of files is 2686 less than FROM, a single run is assumed and the minimum suffix 2687 length required is automatically determined. 2688 2689‘-x’ 2690‘--hex-suffixes[=FROM]’ 2691 Like ‘--numeric-suffixes’, but use hexadecimal numbers (in lower 2692 case). 2693 2694‘--additional-suffix=SUFFIX’ 2695 Append an additional SUFFIX to output file names. SUFFIX must not 2696 contain slash. 2697 2698‘-e’ 2699‘--elide-empty-files’ 2700 Suppress the generation of zero-length output files. This can 2701 happen with the ‘--number’ option if a file is (truncated to be) 2702 shorter than the number requested, or if a line is so long as to 2703 completely span a chunk. The output file sequence numbers, always 2704 run consecutively even when this option is specified. 2705 2706‘-t SEPARATOR’ 2707‘--separator=SEPARATOR’ 2708 Use character SEPARATOR as the record separator instead of the 2709 default newline character (ASCII LF). To specify ASCII NUL as the 2710 separator, use the two-character string ‘\0’, e.g., ‘split -t 2711 '\0'’. 2712 2713‘-u’ 2714‘--unbuffered’ 2715 Immediately copy input to output in ‘--number r/...’ mode, which is 2716 a much slower mode of operation. 2717 2718‘--verbose’ 2719 Write a diagnostic just before each output file is opened. 2720 2721 An exit status of zero indicates success, and a nonzero value 2722indicates failure. 2723 2724 Here are a few examples to illustrate how the ‘--number’ (‘-n’) 2725option works: 2726 2727 Notice how, by default, one line may be split onto two or more: 2728 2729 $ seq -w 6 10 > k; split -n3 k; head xa? 2730 ==> xaa <== 2731 06 2732 07 2733 ==> xab <== 2734 2735 08 2736 0 2737 ==> xac <== 2738 9 2739 10 2740 2741 Use the "l/" modifier to suppress that: 2742 2743 $ seq -w 6 10 > k; split -nl/3 k; head xa? 2744 ==> xaa <== 2745 06 2746 07 2747 2748 ==> xab <== 2749 08 2750 09 2751 2752 ==> xac <== 2753 10 2754 2755 Use the "r/" modifier to distribute lines in a round-robin fashion: 2756 2757 $ seq -w 6 10 > k; split -nr/3 k; head xa? 2758 ==> xaa <== 2759 06 2760 09 2761 2762 ==> xab <== 2763 07 2764 10 2765 2766 ==> xac <== 2767 08 2768 2769 You can also extract just the Kth chunk. This extracts and prints 2770just the 7th "chunk" of 33: 2771 2772 $ seq 100 > k; split -nl/7/33 k 2773 20 2774 21 2775 22 2776 2777 2778File: coreutils.info, Node: csplit invocation, Prev: split invocation, Up: Output of parts of files 2779 27805.4 ‘csplit’: Split a file into context-determined pieces 2781========================================================= 2782 2783‘csplit’ creates zero or more output files containing sections of INPUT 2784(standard input if INPUT is ‘-’). Synopsis: 2785 2786 csplit [OPTION]... INPUT PATTERN... 2787 2788 The contents of the output files are determined by the PATTERN 2789arguments, as detailed below. An error occurs if a PATTERN argument 2790refers to a nonexistent line of the input file (e.g., if no remaining 2791line matches a given regular expression). After every PATTERN has been 2792matched, any remaining input is copied into one last output file. 2793 2794 By default, ‘csplit’ prints the number of bytes written to each 2795output file after it has been created. 2796 2797 The types of pattern arguments are: 2798 2799‘N’ 2800 Create an output file containing the input up to but not including 2801 line N (a positive integer). If followed by a repeat count, also 2802 create an output file containing the next N lines of the input file 2803 once for each repeat. 2804 2805‘/REGEXP/[OFFSET]’ 2806 Create an output file containing the current line up to (but not 2807 including) the next line of the input file that contains a match 2808 for REGEXP. The optional OFFSET is an integer. If it is given, 2809 the input up to (but not including) the matching line plus or minus 2810 OFFSET is put into the output file, and the line after that begins 2811 the next section of input. Note lines within a negative offset of 2812 a regexp pattern are not matched in subsequent regexp patterns. 2813 2814‘%REGEXP%[OFFSET]’ 2815 Like the previous type, except that it does not create an output 2816 file, so that section of the input file is effectively ignored. 2817 2818‘{REPEAT-COUNT}’ 2819 Repeat the previous pattern REPEAT-COUNT additional times. The 2820 REPEAT-COUNT can either be a positive integer or an asterisk, 2821 meaning repeat as many times as necessary until the input is 2822 exhausted. 2823 2824 The output files’ names consist of a prefix (‘xx’ by default) 2825followed by a suffix. By default, the suffix is an ascending sequence 2826of two-digit decimal numbers from ‘00’ to ‘99’. In any case, 2827concatenating the output files in sorted order by file name produces the 2828original input file, excluding portions skipped with a %REGEXP% pattern 2829or the ‘--suppress-matched’ option. 2830 2831 By default, if ‘csplit’ encounters an error or receives a hangup, 2832interrupt, quit, or terminate signal, it removes any output files that 2833it has created so far before it exits. 2834 2835 The program accepts the following options. Also see *note Common 2836options::. 2837 2838‘-f PREFIX’ 2839‘--prefix=PREFIX’ 2840 Use PREFIX as the output file name prefix. 2841 2842‘-b FORMAT’ 2843‘--suffix-format=FORMAT’ 2844 Use FORMAT as the output file name suffix. When this option is 2845 specified, the suffix string must include exactly one 2846 ‘printf(3)’-style conversion specification, possibly including 2847 format specification flags, a field width, a precision 2848 specifications, or all of these kinds of modifiers. The format 2849 letter must convert a binary unsigned integer argument to readable 2850 form. The format letters ‘d’ and ‘i’ are aliases for ‘u’, and the 2851 ‘u’, ‘o’, ‘x’, and ‘X’ conversions are allowed. The entire FORMAT 2852 is given (with the current output file number) to ‘sprintf(3)’ to 2853 form the file name suffixes for each of the individual output files 2854 in turn. If this option is used, the ‘--digits’ option is ignored. 2855 2856‘-n DIGITS’ 2857‘--digits=DIGITS’ 2858 Use output file names containing numbers that are DIGITS digits 2859 long instead of the default 2. 2860 2861‘-k’ 2862‘--keep-files’ 2863 Do not remove output files when errors are encountered. 2864 2865‘--suppress-matched’ 2866 Do not output lines matching the specified PATTERN. I.e., suppress 2867 the boundary line from the start of the second and subsequent 2868 splits. 2869 2870‘-z’ 2871‘--elide-empty-files’ 2872 Suppress the generation of zero-length output files. (In cases 2873 where the section delimiters of the input file are supposed to mark 2874 the first lines of each of the sections, the first output file will 2875 generally be a zero-length file unless you use this option.) The 2876 output file sequence numbers always run consecutively starting from 2877 0, even when this option is specified. 2878 2879‘-s’ 2880‘-q’ 2881‘--silent’ 2882‘--quiet’ 2883 Do not print counts of output file sizes. 2884 2885 An exit status of zero indicates success, and a nonzero value 2886indicates failure. 2887 2888 Here is an example of its usage. First, create an empty directory 2889for the exercise, and cd into it: 2890 2891 $ mkdir d && cd d 2892 2893 Now, split the sequence of 1..14 on lines that end with 0 or 5: 2894 2895 $ seq 14 | csplit - '/[05]$/' '{*}' 2896 8 2897 10 2898 15 2899 2900 Each number printed above is the size of an output file that csplit 2901has just created. List the names of those output files: 2902 2903 $ ls 2904 xx00 xx01 xx02 2905 2906 Use ‘head’ to show their contents: 2907 2908 $ head xx* 2909 ==> xx00 <== 2910 1 2911 2 2912 3 2913 4 2914 2915 ==> xx01 <== 2916 5 2917 6 2918 7 2919 8 2920 9 2921 2922 ==> xx02 <== 2923 10 2924 11 2925 12 2926 13 2927 14 2928 2929 Example of splitting input by empty lines: 2930 2931 $ csplit --suppress-matched INPUT.TXT '/^$/' '{*}' 2932 2933 2934File: coreutils.info, Node: Summarizing files, Next: Operating on sorted files, Prev: Output of parts of files, Up: Top 2935 29366 Summarizing files 2937******************* 2938 2939These commands generate just a few numbers representing entire contents 2940of files. 2941 2942* Menu: 2943 2944* wc invocation:: Print newline, word, and byte counts. 2945* sum invocation:: Print checksum and block counts. 2946* cksum invocation:: Print CRC checksum and byte counts. 2947* b2sum invocation:: Print or check BLAKE2 digests. 2948* md5sum invocation:: Print or check MD5 digests. 2949* sha1sum invocation:: Print or check SHA-1 digests. 2950* sha2 utilities:: Print or check SHA-2 digests. 2951 2952 2953File: coreutils.info, Node: wc invocation, Next: sum invocation, Up: Summarizing files 2954 29556.1 ‘wc’: Print newline, word, and byte counts 2956============================================== 2957 2958‘wc’ counts the number of bytes, characters, whitespace-separated words, 2959and newlines in each given FILE, or standard input if none are given or 2960for a FILE of ‘-’. Synopsis: 2961 2962 wc [OPTION]... [FILE]... 2963 2964 ‘wc’ prints one line of counts for each file, and if the file was 2965given as an argument, it prints the file name following the counts. If 2966more than one FILE is given, ‘wc’ prints a final line containing the 2967cumulative counts, with the file name ‘total’. The counts are printed 2968in this order: newlines, words, characters, bytes, maximum line length. 2969Each count is printed right-justified in a field with at least one space 2970between fields so that the numbers and file names normally line up 2971nicely in columns. The width of the count fields varies depending on 2972the inputs, so you should not depend on a particular field width. 2973However, as a GNU extension, if only one count is printed, it is 2974guaranteed to be printed without leading spaces. 2975 2976 By default, ‘wc’ prints three counts: the newline, words, and byte 2977counts. Options can specify that only certain counts be printed. 2978Options do not undo others previously given, so 2979 2980 wc --bytes --words 2981 2982prints both the byte counts and the word counts. 2983 2984 With the ‘--max-line-length’ option, ‘wc’ prints the length of the 2985longest line per file, and if there is more than one file it prints the 2986maximum (not the sum) of those lengths. The line lengths here are 2987measured in screen columns, according to the current locale and assuming 2988tab positions in every 8th column. 2989 2990 The program accepts the following options. Also see *note Common 2991options::. 2992 2993‘-c’ 2994‘--bytes’ 2995 Print only the byte counts. 2996 2997‘-m’ 2998‘--chars’ 2999 Print only the character counts. 3000 3001‘-w’ 3002‘--words’ 3003 Print only the word counts. 3004 3005‘-l’ 3006‘--lines’ 3007 Print only the newline counts. 3008 3009‘-L’ 3010‘--max-line-length’ 3011 Print only the maximum display widths. Tabs are set at every 8th 3012 column. Display widths of wide characters are considered. 3013 Non-printable characters are given 0 width. 3014 3015‘--files0-from=FILE’ 3016 Disallow processing files named on the command line, and instead 3017 process those named in file FILE; each name being terminated by a 3018 zero byte (ASCII NUL). This is useful when the list of file names 3019 is so long that it may exceed a command line length limitation. In 3020 such cases, running ‘wc’ via ‘xargs’ is undesirable because it 3021 splits the list into pieces and makes ‘wc’ print a total for each 3022 sublist rather than for the entire list. One way to produce a list 3023 of ASCII NUL terminated file names is with GNU ‘find’, using its 3024 ‘-print0’ predicate. If FILE is ‘-’ then the ASCII NUL terminated 3025 file names are read from standard input. 3026 3027 For example, to find the length of the longest line in any ‘.c’ or 3028 ‘.h’ file in the current hierarchy, do this: 3029 3030 find . -name '*.[ch]' -print0 | 3031 wc -L --files0-from=- | tail -n1 3032 3033 An exit status of zero indicates success, and a nonzero value 3034indicates failure. 3035 3036 3037File: coreutils.info, Node: sum invocation, Next: cksum invocation, Prev: wc invocation, Up: Summarizing files 3038 30396.2 ‘sum’: Print checksum and block counts 3040========================================== 3041 3042‘sum’ computes a 16-bit checksum for each given FILE, or standard input 3043if none are given or for a FILE of ‘-’. Synopsis: 3044 3045 sum [OPTION]... [FILE]... 3046 3047 ‘sum’ prints the checksum for each FILE followed by the number of 3048blocks in the file (rounded up). If more than one FILE is given, file 3049names are also printed (by default). (With the ‘--sysv’ option, 3050corresponding file names are printed when there is at least one file 3051argument.) 3052 3053 By default, GNU ‘sum’ computes checksums using an algorithm 3054compatible with BSD ‘sum’ and prints file sizes in units of 1024-byte 3055blocks. 3056 3057 The program accepts the following options. Also see *note Common 3058options::. 3059 3060‘-r’ 3061 Use the default (BSD compatible) algorithm. This option is 3062 included for compatibility with the System V ‘sum’. Unless ‘-s’ 3063 was also given, it has no effect. 3064 3065‘-s’ 3066‘--sysv’ 3067 Compute checksums using an algorithm compatible with System V 3068 ‘sum’’s default, and print file sizes in units of 512-byte blocks. 3069 3070 ‘sum’ is provided for compatibility; the ‘cksum’ program (see next 3071section) is preferable in new applications. 3072 3073 An exit status of zero indicates success, and a nonzero value 3074indicates failure. 3075 3076 3077File: coreutils.info, Node: cksum invocation, Next: b2sum invocation, Prev: sum invocation, Up: Summarizing files 3078 30796.3 ‘cksum’: Print CRC checksum and byte counts 3080=============================================== 3081 3082‘cksum’ computes a cyclic redundancy check (CRC) checksum for each given 3083FILE, or standard input if none are given or for a FILE of ‘-’. 3084Synopsis: 3085 3086 cksum [OPTION]... [FILE]... 3087 3088 ‘cksum’ prints the CRC checksum for each file along with the number 3089of bytes in the file, and the file name unless no arguments were given. 3090 3091 ‘cksum’ is typically used to ensure that files transferred by 3092unreliable means (e.g., netnews) have not been corrupted, by comparing 3093the ‘cksum’ output for the received files with the ‘cksum’ output for 3094the original files (typically given in the distribution). 3095 3096 The CRC algorithm is specified by the POSIX standard. It is not 3097compatible with the BSD or System V ‘sum’ algorithms (see the previous 3098section); it is more robust. 3099 3100 The only options are ‘--help’ and ‘--version’. *Note Common 3101options::. 3102 3103 An exit status of zero indicates success, and a nonzero value 3104indicates failure. 3105 3106 3107File: coreutils.info, Node: b2sum invocation, Next: md5sum invocation, Prev: cksum invocation, Up: Summarizing files 3108 31096.4 ‘b2sum’: Print or check BLAKE2 digests 3110========================================== 3111 3112‘b2sum’ computes a 512-bit checksum for each specified FILE. The same 3113usage and options as the ‘md5sum’ command are supported. *Note md5sum 3114invocation::. In addition ‘b2sum’ supports the following options. 3115 3116‘-l’ 3117‘--length’ 3118 Change (shorten) the default digest length. This is specified in 3119 bits and thus must be a multiple of 8. This option is ignored when 3120 ‘--check’ is specified, as the length is automatically determined 3121 when checking. 3122 3123 3124File: coreutils.info, Node: md5sum invocation, Next: sha1sum invocation, Prev: b2sum invocation, Up: Summarizing files 3125 31266.5 ‘md5sum’: Print or check MD5 digests 3127======================================== 3128 3129‘md5sum’ computes a 128-bit checksum (or “fingerprint” or 3130“message-digest”) for each specified FILE. 3131 3132 Note: The MD5 digest is more reliable than a simple CRC (provided by 3133the ‘cksum’ command) for detecting accidental file corruption, as the 3134chances of accidentally having two files with identical MD5 are 3135vanishingly small. However, it should not be considered secure against 3136malicious tampering: although finding a file with a given MD5 3137fingerprint is considered infeasible at the moment, it is known how to 3138modify certain files, including digital certificates, so that they 3139appear valid when signed with an MD5 digest. For more secure hashes, 3140consider using SHA-2, or the newer ‘b2sum’ command. *Note sha2 3141utilities::. *Note b2sum invocation::. 3142 3143 If a FILE is specified as ‘-’ or if no files are given ‘md5sum’ 3144computes the checksum for the standard input. ‘md5sum’ can also 3145determine whether a file and checksum are consistent. Synopsis: 3146 3147 md5sum [OPTION]... [FILE]... 3148 3149 For each FILE, ‘md5sum’ outputs by default, the MD5 checksum, a 3150space, a flag indicating binary or text input mode, and the file name. 3151Binary mode is indicated with ‘*’, text mode with ‘ ’ (space). Binary 3152mode is the default on systems where it’s significant, otherwise text 3153mode is the default. Without ‘--zero’, if FILE contains a backslash or 3154newline, the line is started with a backslash, and each problematic 3155character in the file name is escaped with a backslash, making the 3156output unambiguous even in the presence of arbitrary file names. If 3157FILE is omitted or specified as ‘-’, standard input is read. 3158 3159 The program accepts the following options. Also see *note Common 3160options::. 3161 3162‘-b’ 3163‘--binary’ 3164 Treat each input file as binary, by reading it in binary mode and 3165 outputting a ‘*’ flag. This is the inverse of ‘--text’. On 3166 systems like GNU that do not distinguish between binary and text 3167 files, this option merely flags each input mode as binary: the MD5 3168 checksum is unaffected. This option is the default on systems like 3169 MS-DOS that distinguish between binary and text files, except for 3170 reading standard input when standard input is a terminal. 3171 3172‘-c’ 3173‘--check’ 3174 Read file names and checksum information (not data) from each FILE 3175 (or from stdin if no FILE was specified) and report whether the 3176 checksums match the contents of the named files. The input to this 3177 mode of ‘md5sum’ is usually the output of a prior, 3178 checksum-generating run of ‘md5sum’. Three input formats are 3179 supported. Either the default output format described above, the 3180 ‘--tag’ output format, or the BSD reversed mode format which is 3181 similar to the default mode, but doesn’t use a character to 3182 distinguish binary and text modes. Output with ‘--zero’ enabled is 3183 not supported by ‘--check’. 3184 3185 For each such line, ‘md5sum’ reads the named file and computes its 3186 MD5 checksum. Then, if the computed message digest does not match 3187 the one on the line with the file name, the file is noted as having 3188 failed the test. Otherwise, the file passes the test. By default, 3189 for each valid line, one line is written to standard output 3190 indicating whether the named file passed the test. After all 3191 checks have been performed, if there were any failures, a warning 3192 is issued to standard error. Use the ‘--status’ option to inhibit 3193 that output. If any listed file cannot be opened or read, if any 3194 valid line has an MD5 checksum inconsistent with the associated 3195 file, or if no valid line is found, ‘md5sum’ exits with nonzero 3196 status. Otherwise, it exits successfully. 3197 3198‘--ignore-missing’ 3199 This option is useful only when verifying checksums. When 3200 verifying checksums, don’t fail or report any status for missing 3201 files. This is useful when verifying a subset of downloaded files 3202 given a larger list of checksums. 3203 3204‘--quiet’ 3205 This option is useful only when verifying checksums. When 3206 verifying checksums, don’t generate an ’OK’ message per 3207 successfully checked file. Files that fail the verification are 3208 reported in the default one-line-per-file format. If there is any 3209 checksum mismatch, print a warning summarizing the failures to 3210 standard error. 3211 3212‘--status’ 3213 This option is useful only when verifying checksums. When 3214 verifying checksums, don’t generate the default one-line-per-file 3215 diagnostic and don’t output the warning summarizing any failures. 3216 Failures to open or read a file still evoke individual diagnostics 3217 to standard error. If all listed files are readable and are 3218 consistent with the associated MD5 checksums, exit successfully. 3219 Otherwise exit with a status code indicating there was a failure. 3220 3221‘--tag’ 3222 Output BSD style checksums, which indicate the checksum algorithm 3223 used. As a GNU extension, if ‘--zero’ is not used, file names with 3224 problematic characters are escaped as described above, with the 3225 same escaping indicator of ‘\’ at the start of the line, being 3226 used. The ‘--tag’ option implies binary mode, and is disallowed 3227 with ‘--text’ mode as supporting that would unnecessarily 3228 complicate the output format, while providing little benefit. 3229 3230‘-t’ 3231‘--text’ 3232 Treat each input file as text, by reading it in text mode and 3233 outputting a ‘ ’ flag. This is the inverse of ‘--binary’. This 3234 option is the default on systems like GNU that do not distinguish 3235 between binary and text files. On other systems, it is the default 3236 for reading standard input when standard input is a terminal. This 3237 mode is never defaulted to if ‘--tag’ is used. 3238 3239‘-w’ 3240‘--warn’ 3241 When verifying checksums, warn about improperly formatted MD5 3242 checksum lines. This option is useful only if all but a few lines 3243 in the checked input are valid. 3244 3245‘--strict’ 3246 When verifying checksums, if one or more input line is invalid, 3247 exit nonzero after all warnings have been issued. 3248 3249‘-z’ 3250‘--zero’ 3251 Output a zero byte (ASCII NUL) at the end of each line, rather than 3252 a newline. This option enables other programs to parse the output 3253 even when that output would contain data with embedded newlines. 3254 Also file name escaping is not used. 3255 3256 An exit status of zero indicates success, and a nonzero value 3257indicates failure. 3258 3259 3260File: coreutils.info, Node: sha1sum invocation, Next: sha2 utilities, Prev: md5sum invocation, Up: Summarizing files 3261 32626.6 ‘sha1sum’: Print or check SHA-1 digests 3263=========================================== 3264 3265‘sha1sum’ computes a 160-bit checksum for each specified FILE. The 3266usage and options of this command are precisely the same as for 3267‘md5sum’. *Note md5sum invocation::. 3268 3269 Note: The SHA-1 digest is more reliable than a simple CRC (provided 3270by the ‘cksum’ command) for detecting accidental file corruption, as the 3271chances of accidentally having two files with identical SHA-1 are 3272vanishingly small. However, it should not be considered secure against 3273malicious tampering: although finding a file with a given SHA-1 3274fingerprint is considered infeasible at the moment, it is known how to 3275modify certain files, including digital certificates, so that they 3276appear valid when signed with an SHA-1 digest. For more secure hashes, 3277consider using SHA-2, or the newer ‘b2sum’ command. *Note sha2 3278utilities::. *Note b2sum invocation::. 3279 3280 3281File: coreutils.info, Node: sha2 utilities, Prev: sha1sum invocation, Up: Summarizing files 3282 32836.7 sha2 utilities: Print or check SHA-2 digests 3284================================================ 3285 3286The commands ‘sha224sum’, ‘sha256sum’, ‘sha384sum’ and ‘sha512sum’ 3287compute checksums of various lengths (respectively 224, 256, 384 and 512 3288bits), collectively known as the SHA-2 hashes. The usage and options of 3289these commands are precisely the same as for ‘md5sum’ and ‘sha1sum’. 3290*Note md5sum invocation::. 3291 3292 3293File: coreutils.info, Node: Operating on sorted files, Next: Operating on fields, Prev: Summarizing files, Up: Top 3294 32957 Operating on sorted files 3296*************************** 3297 3298These commands work with (or produce) sorted files. 3299 3300* Menu: 3301 3302* sort invocation:: Sort text files. 3303* shuf invocation:: Shuffle text files. 3304* uniq invocation:: Uniquify files. 3305* comm invocation:: Compare two sorted files line by line. 3306* ptx invocation:: Produce a permuted index of file contents. 3307* tsort invocation:: Topological sort. 3308 3309 3310File: coreutils.info, Node: sort invocation, Next: shuf invocation, Up: Operating on sorted files 3311 33127.1 ‘sort’: Sort text files 3313=========================== 3314 3315‘sort’ sorts, merges, or compares all the lines from the given files, or 3316standard input if none are given or for a FILE of ‘-’. By default, 3317‘sort’ writes the results to standard output. Synopsis: 3318 3319 sort [OPTION]... [FILE]... 3320 3321 Many options affect how ‘sort’ compares lines; if the results are 3322unexpected, try the ‘--debug’ option to see what happened. A pair of 3323lines is compared as follows: ‘sort’ compares each pair of fields (see 3324‘--key’), in the order specified on the command line, according to the 3325associated ordering options, until a difference is found or no fields 3326are left. If no key fields are specified, ‘sort’ uses a default key of 3327the entire line. Finally, as a last resort when all keys compare equal, 3328‘sort’ compares entire lines as if no ordering options other than 3329‘--reverse’ (‘-r’) were specified. The ‘--stable’ (‘-s’) option 3330disables this “last-resort comparison” so that lines in which all fields 3331compare equal are left in their original relative order. The ‘--unique’ 3332(‘-u’) option also disables the last-resort comparison. 3333 3334 Unless otherwise specified, all comparisons use the character 3335collating sequence specified by the ‘LC_COLLATE’ locale.(1) A line’s 3336trailing newline is not part of the line for comparison purposes. If 3337the final byte of an input file is not a newline, GNU ‘sort’ silently 3338supplies one. GNU ‘sort’ (as specified for all GNU utilities) has no 3339limit on input line length or restrictions on bytes allowed within 3340lines. 3341 3342 ‘sort’ has three modes of operation: sort (the default), merge, and 3343check for sortedness. The following options change the operation mode: 3344 3345‘-c’ 3346‘--check’ 3347‘--check=diagnose-first’ 3348 Check whether the given file is already sorted: if it is not all 3349 sorted, print a diagnostic containing the first out-of-order line 3350 and exit with a status of 1. Otherwise, exit successfully. At 3351 most one input file can be given. 3352 3353‘-C’ 3354‘--check=quiet’ 3355‘--check=silent’ 3356 Exit successfully if the given file is already sorted, and exit 3357 with status 1 otherwise. At most one input file can be given. 3358 This is like ‘-c’, except it does not print a diagnostic. 3359 3360‘-m’ 3361‘--merge’ 3362 Merge the given files by sorting them as a group. Each input file 3363 must always be individually sorted. It always works to sort 3364 instead of merge; merging is provided because it is faster, in the 3365 case where it works. 3366 3367 Exit status: 3368 3369 0 if no error occurred 3370 1 if invoked with ‘-c’ or ‘-C’ and the input is not sorted 3371 2 if an error occurred 3372 3373 If the environment variable ‘TMPDIR’ is set, ‘sort’ uses its value as 3374the directory for temporary files instead of ‘/tmp’. The 3375‘--temporary-directory’ (‘-T’) option in turn overrides the environment 3376variable. 3377 3378 The following options affect the ordering of output lines. They may 3379be specified globally or as part of a specific key field. If no key 3380fields are specified, global options apply to comparison of entire 3381lines; otherwise the global options are inherited by key fields that do 3382not specify any special options of their own. In pre-POSIX versions of 3383‘sort’, global options affect only later key fields, so portable shell 3384scripts should specify global options first. 3385 3386‘-b’ 3387‘--ignore-leading-blanks’ 3388 Ignore leading blanks when finding sort keys in each line. By 3389 default a blank is a space or a tab, but the ‘LC_CTYPE’ locale can 3390 change this. Note blanks may be ignored by your locale’s collating 3391 rules, but without this option they will be significant for 3392 character positions specified in keys with the ‘-k’ option. 3393 3394‘-d’ 3395‘--dictionary-order’ 3396 Sort in “phone directory” order: ignore all characters except 3397 letters, digits and blanks when sorting. By default letters and 3398 digits are those of ASCII and a blank is a space or a tab, but the 3399 ‘LC_CTYPE’ locale can change this. 3400 3401‘-f’ 3402‘--ignore-case’ 3403 Fold lowercase characters into the equivalent uppercase characters 3404 when comparing so that, for example, ‘b’ and ‘B’ sort as equal. 3405 The ‘LC_CTYPE’ locale determines character types. When used with 3406 ‘--unique’ those lower case equivalent lines are thrown away. 3407 (There is currently no way to throw away the upper case equivalent 3408 instead. (Any ‘--reverse’ given would only affect the final 3409 result, after the throwing away.)) 3410 3411‘-g’ 3412‘--general-numeric-sort’ 3413‘--sort=general-numeric’ 3414 Sort numerically, converting a prefix of each line to a long 3415 double-precision floating point number. *Note Floating point::. 3416 Do not report overflow, underflow, or conversion errors. Use the 3417 following collating sequence: 3418 3419 • Lines that do not start with numbers (all considered to be 3420 equal). 3421 • NaNs (“Not a Number” values, in IEEE floating point 3422 arithmetic) in a consistent but machine-dependent order. 3423 • Minus infinity. 3424 • Finite numbers in ascending numeric order (with -0 and +0 3425 equal). 3426 • Plus infinity. 3427 3428 Use this option only if there is no alternative; it is much slower 3429 than ‘--numeric-sort’ (‘-n’) and it can lose information when 3430 converting to floating point. 3431 3432‘-h’ 3433‘--human-numeric-sort’ 3434‘--sort=human-numeric’ 3435 Sort numerically, first by numeric sign (negative, zero, or 3436 positive); then by SI suffix (either empty, or ‘k’ or ‘K’, or one 3437 of ‘MGTPEZY’, in that order; *note Block size::); and finally by 3438 numeric value. For example, ‘1023M’ sorts before ‘1G’ because ‘M’ 3439 (mega) precedes ‘G’ (giga) as an SI suffix. This option sorts 3440 values that are consistently scaled to the nearest suffix, 3441 regardless of whether suffixes denote powers of 1000 or 1024, and 3442 it therefore sorts the output of any single invocation of the ‘df’, 3443 ‘du’, or ‘ls’ commands that are invoked with their 3444 ‘--human-readable’ or ‘--si’ options. The syntax for numbers is 3445 the same as for the ‘--numeric-sort’ option; the SI suffix must 3446 immediately follow the number. Note also the ‘numfmt’ command, 3447 which can be used to reformat numbers to human format _after_ the 3448 sort, thus often allowing sort to operate on more accurate numbers. 3449 3450‘-i’ 3451‘--ignore-nonprinting’ 3452 Ignore nonprinting characters. The ‘LC_CTYPE’ locale determines 3453 character types. This option has no effect if the stronger 3454 ‘--dictionary-order’ (‘-d’) option is also given. 3455 3456‘-M’ 3457‘--month-sort’ 3458‘--sort=month’ 3459 An initial string, consisting of any amount of blanks, followed by 3460 a month name abbreviation, is folded to UPPER case and compared in 3461 the order ‘JAN’ < ‘FEB’ < ... < ‘DEC’. Invalid names compare low 3462 to valid names. The ‘LC_TIME’ locale category determines the month 3463 spellings. By default a blank is a space or a tab, but the 3464 ‘LC_CTYPE’ locale can change this. 3465 3466‘-n’ 3467‘--numeric-sort’ 3468‘--sort=numeric’ 3469 Sort numerically. The number begins each line and consists of 3470 optional blanks, an optional ‘-’ sign, and zero or more digits 3471 possibly separated by thousands separators, optionally followed by 3472 a decimal-point character and zero or more digits. An empty number 3473 is treated as ‘0’. The ‘LC_NUMERIC’ locale specifies the 3474 decimal-point character and thousands separator. By default a 3475 blank is a space or a tab, but the ‘LC_CTYPE’ locale can change 3476 this. 3477 3478 Comparison is exact; there is no rounding error. 3479 3480 Neither a leading ‘+’ nor exponential notation is recognized. To 3481 compare such strings numerically, use the ‘--general-numeric-sort’ 3482 (‘-g’) option. 3483 3484‘-V’ 3485‘--version-sort’ 3486 Sort by version name and number. It behaves like a standard sort, 3487 except that each sequence of decimal digits is treated numerically 3488 as an index/version number. (*Note Version sort ordering::.) 3489 3490‘-r’ 3491‘--reverse’ 3492 Reverse the result of comparison, so that lines with greater key 3493 values appear earlier in the output instead of later. 3494 3495‘-R’ 3496‘--random-sort’ 3497‘--sort=random’ 3498 Sort by hashing the input keys and then sorting the hash values. 3499 Choose the hash function at random, ensuring that it is free of 3500 collisions so that differing keys have differing hash values. This 3501 is like a random permutation of the inputs (*note shuf 3502 invocation::), except that keys with the same value sort together. 3503 3504 If multiple random sort fields are specified, the same random hash 3505 function is used for all fields. To use different random hash 3506 functions for different fields, you can invoke ‘sort’ more than 3507 once. 3508 3509 The choice of hash function is affected by the ‘--random-source’ 3510 option. 3511 3512 Other options are: 3513 3514‘--compress-program=PROG’ 3515 Compress any temporary files with the program PROG. 3516 3517 With no arguments, PROG must compress standard input to standard 3518 output, and when given the ‘-d’ option it must decompress standard 3519 input to standard output. 3520 3521 Terminate with an error if PROG exits with nonzero status. 3522 3523 White space and the backslash character should not appear in PROG; 3524 they are reserved for future use. 3525 3526‘--files0-from=FILE’ 3527 Disallow processing files named on the command line, and instead 3528 process those named in file FILE; each name being terminated by a 3529 zero byte (ASCII NUL). This is useful when the list of file names 3530 is so long that it may exceed a command line length limitation. In 3531 such cases, running ‘sort’ via ‘xargs’ is undesirable because it 3532 splits the list into pieces and makes ‘sort’ print sorted output 3533 for each sublist rather than for the entire list. One way to 3534 produce a list of ASCII NUL terminated file names is with GNU 3535 ‘find’, using its ‘-print0’ predicate. If FILE is ‘-’ then the 3536 ASCII NUL terminated file names are read from standard input. 3537 3538‘-k POS1[,POS2]’ 3539‘--key=POS1[,POS2]’ 3540 Specify a sort field that consists of the part of the line between 3541 POS1 and POS2 (or the end of the line, if POS2 is omitted), 3542 _inclusive_. 3543 3544 In its simplest form POS specifies a field number (starting with 3545 1), with fields being separated by runs of blank characters, and by 3546 default those blanks being included in the comparison at the start 3547 of each field. To adjust the handling of blank characters see the 3548 ‘-b’ and ‘-t’ options. 3549 3550 More generally, each POS has the form ‘F[.C][OPTS]’, where F is the 3551 number of the field to use, and C is the number of the first 3552 character from the beginning of the field. Fields and character 3553 positions are numbered starting with 1; a character position of 3554 zero in POS2 indicates the field’s last character. If ‘.C’ is 3555 omitted from POS1, it defaults to 1 (the beginning of the field); 3556 if omitted from POS2, it defaults to 0 (the end of the field). 3557 OPTS are ordering options, allowing individual keys to be sorted 3558 according to different rules; see below for details. Keys can span 3559 multiple fields. 3560 3561 Example: To sort on the second field, use ‘--key=2,2’ (‘-k 2,2’). 3562 See below for more notes on keys and more examples. See also the 3563 ‘--debug’ option to help determine the part of the line being used 3564 in the sort. 3565 3566‘--debug’ 3567 Highlight the portion of each line used for sorting. Also issue 3568 warnings about questionable usage to stderr. 3569 3570‘--batch-size=NMERGE’ 3571 Merge at most NMERGE inputs at once. 3572 3573 When ‘sort’ has to merge more than NMERGE inputs, it merges them in 3574 groups of NMERGE, saving the result in a temporary file, which is 3575 then used as an input in a subsequent merge. 3576 3577 A large value of NMERGE may improve merge performance and decrease 3578 temporary storage utilization at the expense of increased memory 3579 usage and I/O. Conversely a small value of NMERGE may reduce 3580 memory requirements and I/O at the expense of temporary storage 3581 consumption and merge performance. 3582 3583 The value of NMERGE must be at least 2. The default value is 3584 currently 16, but this is implementation-dependent and may change 3585 in the future. 3586 3587 The value of NMERGE may be bounded by a resource limit for open 3588 file descriptors. The commands ‘ulimit -n’ or ‘getconf OPEN_MAX’ 3589 may display limits for your systems; these limits may be modified 3590 further if your program already has some files open, or if the 3591 operating system has other limits on the number of open files. If 3592 the value of NMERGE exceeds the resource limit, ‘sort’ silently 3593 uses a smaller value. 3594 3595‘-o OUTPUT-FILE’ 3596‘--output=OUTPUT-FILE’ 3597 Write output to OUTPUT-FILE instead of standard output. Normally, 3598 ‘sort’ reads all input before opening OUTPUT-FILE, so you can sort 3599 a file in place by using commands like ‘sort -o F F’ and ‘cat F | 3600 sort -o F’. However, it is often safer to output to an 3601 otherwise-unused file, as data may be lost if the system crashes or 3602 ‘sort’ encounters an I/O or other serious error while a file is 3603 being sorted in place. Also, ‘sort’ with ‘--merge’ (‘-m’) can open 3604 the output file before reading all input, so a command like ‘cat F 3605 | sort -m -o F - G’ is not safe as ‘sort’ might start writing ‘F’ 3606 before ‘cat’ is done reading it. 3607 3608 On newer systems, ‘-o’ cannot appear after an input file if 3609 ‘POSIXLY_CORRECT’ is set, e.g., ‘sort F -o F’. Portable scripts 3610 should specify ‘-o OUTPUT-FILE’ before any input files. 3611 3612‘--random-source=FILE’ 3613 Use FILE as a source of random data used to determine which random 3614 hash function to use with the ‘-R’ option. *Note Random sources::. 3615 3616‘-s’ 3617‘--stable’ 3618 3619 Make ‘sort’ stable by disabling its last-resort comparison. This 3620 option has no effect if no fields or global ordering options other 3621 than ‘--reverse’ (‘-r’) are specified. 3622 3623‘-S SIZE’ 3624‘--buffer-size=SIZE’ 3625 Use a main-memory sort buffer of the given SIZE. By default, SIZE 3626 is in units of 1024 bytes. Appending ‘%’ causes SIZE to be 3627 interpreted as a percentage of physical memory. Appending ‘K’ 3628 multiplies SIZE by 1024 (the default), ‘M’ by 1,048,576, ‘G’ by 3629 1,073,741,824, and so on for ‘T’, ‘P’, ‘E’, ‘Z’, and ‘Y’. 3630 Appending ‘b’ causes SIZE to be interpreted as a byte count, with 3631 no multiplication. 3632 3633 This option can improve the performance of ‘sort’ by causing it to 3634 start with a larger or smaller sort buffer than the default. 3635 However, this option affects only the initial buffer size. The 3636 buffer grows beyond SIZE if ‘sort’ encounters input lines larger 3637 than SIZE. 3638 3639‘-t SEPARATOR’ 3640‘--field-separator=SEPARATOR’ 3641 Use character SEPARATOR as the field separator when finding the 3642 sort keys in each line. By default, fields are separated by the 3643 empty string between a non-blank character and a blank character. 3644 By default a blank is a space or a tab, but the ‘LC_CTYPE’ locale 3645 can change this. 3646 3647 That is, given the input line ‘ foo bar’, ‘sort’ breaks it into 3648 fields ‘ foo’ and ‘ bar’. The field separator is not considered to 3649 be part of either the field preceding or the field following, so 3650 with ‘sort -t " "’ the same input line has three fields: an empty 3651 field, ‘foo’, and ‘bar’. However, fields that extend to the end of 3652 the line, as ‘-k 2’, or fields consisting of a range, as ‘-k 2,3’, 3653 retain the field separators present between the endpoints of the 3654 range. 3655 3656 To specify ASCII NUL as the field separator, use the two-character 3657 string ‘\0’, e.g., ‘sort -t '\0'’. 3658 3659‘-T TEMPDIR’ 3660‘--temporary-directory=TEMPDIR’ 3661 Use directory TEMPDIR to store temporary files, overriding the 3662 ‘TMPDIR’ environment variable. If this option is given more than 3663 once, temporary files are stored in all the directories given. If 3664 you have a large sort or merge that is I/O-bound, you can often 3665 improve performance by using this option to specify directories on 3666 different disks and controllers. 3667 3668‘--parallel=N’ 3669 Set the number of sorts run in parallel to N. By default, N is set 3670 to the number of available processors, but limited to 8, as there 3671 are diminishing performance gains after that. Note also that using 3672 N threads increases the memory usage by a factor of log N. Also 3673 see *note nproc invocation::. 3674 3675‘-u’ 3676‘--unique’ 3677 3678 Normally, output only the first of a sequence of lines that compare 3679 equal. For the ‘--check’ (‘-c’ or ‘-C’) option, check that no pair 3680 of consecutive lines compares equal. 3681 3682 This option also disables the default last-resort comparison. 3683 3684 The commands ‘sort -u’ and ‘sort | uniq’ are equivalent, but this 3685 equivalence does not extend to arbitrary ‘sort’ options. For 3686 example, ‘sort -n -u’ inspects only the value of the initial 3687 numeric string when checking for uniqueness, whereas ‘sort -n | 3688 uniq’ inspects the entire line. *Note uniq invocation::. 3689 3690‘-z’ 3691‘--zero-terminated’ 3692 Delimit items with a zero byte rather than a newline (ASCII LF). 3693 I.e., treat input as items separated by ASCII NUL and terminate 3694 output items with ASCII NUL. This option can be useful in 3695 conjunction with ‘perl -0’ or ‘find -print0’ and ‘xargs -0’ which 3696 do the same in order to reliably handle arbitrary file names (even 3697 those containing blanks or other special characters). 3698 3699 Historical (BSD and System V) implementations of ‘sort’ have differed 3700in their interpretation of some options, particularly ‘-b’, ‘-f’, and 3701‘-n’. GNU sort follows the POSIX behavior, which is usually (but not 3702always!) like the System V behavior. According to POSIX, ‘-n’ no 3703longer implies ‘-b’. For consistency, ‘-M’ has been changed in the same 3704way. This may affect the meaning of character positions in field 3705specifications in obscure cases. The only fix is to add an explicit 3706‘-b’. 3707 3708 A position in a sort field specified with ‘-k’ may have any of the 3709option letters ‘MbdfghinRrV’ appended to it, in which case no global 3710ordering options are inherited by that particular field. The ‘-b’ 3711option may be independently attached to either or both of the start and 3712end positions of a field specification, and if it is inherited from the 3713global options it will be attached to both. If input lines can contain 3714leading or adjacent blanks and ‘-t’ is not used, then ‘-k’ is typically 3715combined with ‘-b’ or an option that implicitly ignores leading blanks 3716(‘Mghn’) as otherwise the varying numbers of leading blanks in fields 3717can cause confusing results. 3718 3719 If the start position in a sort field specifier falls after the end 3720of the line or after the end field, the field is empty. If the ‘-b’ 3721option was specified, the ‘.C’ part of a field specification is counted 3722from the first nonblank character of the field. 3723 3724 On systems not conforming to POSIX 1003.1-2001, ‘sort’ supports a 3725traditional origin-zero syntax ‘+POS1 [-POS2]’ for specifying sort keys. 3726The traditional command ‘sort +A.X -B.Y’ is equivalent to ‘sort -k 3727A+1.X+1,B’ if Y is ‘0’ or absent, otherwise it is equivalent to ‘sort -k 3728A+1.X+1,B+1.Y’. 3729 3730 This traditional behavior can be controlled with the 3731‘_POSIX2_VERSION’ environment variable (*note Standards conformance::); 3732it can also be enabled when ‘POSIXLY_CORRECT’ is not set by using the 3733traditional syntax with ‘-POS2’ present. 3734 3735 Scripts intended for use on standard hosts should avoid traditional 3736syntax and should use ‘-k’ instead. For example, avoid ‘sort +2’, since 3737it might be interpreted as either ‘sort ./+2’ or ‘sort -k 3’. If your 3738script must also run on hosts that support only the traditional syntax, 3739it can use a test like ‘if sort -k 1 </dev/null >/dev/null 2>&1; then 3740...’ to decide which syntax to use. 3741 3742 Here are some examples to illustrate various combinations of options. 3743 3744 • Sort in descending (reverse) numeric order. 3745 3746 sort -n -r 3747 3748 • Run no more than 4 sorts concurrently, using a buffer size of 10M. 3749 3750 sort --parallel=4 -S 10M 3751 3752 • Sort alphabetically, omitting the first and second fields and the 3753 blanks at the start of the third field. This uses a single key 3754 composed of the characters beginning at the start of the first 3755 nonblank character in field three and extending to the end of each 3756 line. 3757 3758 sort -k 3b 3759 3760 • Sort numerically on the second field and resolve ties by sorting 3761 alphabetically on the third and fourth characters of field five. 3762 Use ‘:’ as the field delimiter. 3763 3764 sort -t : -k 2,2n -k 5.3,5.4 3765 3766 Note that if you had written ‘-k 2n’ instead of ‘-k 2,2n’ ‘sort’ 3767 would have used all characters beginning in the second field and 3768 extending to the end of the line as the primary _numeric_ key. For 3769 the large majority of applications, treating keys spanning more 3770 than one field as numeric will not do what you expect. 3771 3772 Also note that the ‘n’ modifier was applied to the field-end 3773 specifier for the first key. It would have been equivalent to 3774 specify ‘-k 2n,2’ or ‘-k 2n,2n’. All modifiers except ‘b’ apply to 3775 the associated _field_, regardless of whether the modifier 3776 character is attached to the field-start and/or the field-end part 3777 of the key specifier. 3778 3779 • Sort the password file on the fifth field and ignore any leading 3780 blanks. Sort lines with equal values in field five on the numeric 3781 user ID in field three. Fields are separated by ‘:’. 3782 3783 sort -t : -k 5b,5 -k 3,3n /etc/passwd 3784 sort -t : -n -k 5b,5 -k 3,3 /etc/passwd 3785 sort -t : -b -k 5,5 -k 3,3n /etc/passwd 3786 3787 These three commands have equivalent effect. The first specifies 3788 that the first key’s start position ignores leading blanks and the 3789 second key is sorted numerically. The other two commands rely on 3790 global options being inherited by sort keys that lack modifiers. 3791 The inheritance works in this case because ‘-k 5b,5b’ and ‘-k 5b,5’ 3792 are equivalent, as the location of a field-end lacking a ‘.C’ 3793 character position is not affected by whether initial blanks are 3794 skipped. 3795 3796 • Sort a set of log files, primarily by IPv4 address and secondarily 3797 by timestamp. If two lines’ primary and secondary keys are 3798 identical, output the lines in the same order that they were input. 3799 The log files contain lines that look like this: 3800 3801 4.150.156.3 - - [01/Apr/2004:06:31:51 +0000] message 1 3802 211.24.3.231 - - [24/Apr/2004:20:17:39 +0000] message 2 3803 3804 Fields are separated by exactly one space. Sort IPv4 addresses 3805 lexicographically, e.g., 212.61.52.2 sorts before 212.129.233.201 3806 because 61 is less than 129. 3807 3808 sort -s -t ' ' -k 4.9n -k 4.5M -k 4.2n -k 4.14,4.21 file*.log | 3809 sort -s -t '.' -k 1,1n -k 2,2n -k 3,3n -k 4,4n 3810 3811 This example cannot be done with a single ‘sort’ invocation, since 3812 IPv4 address components are separated by ‘.’ while dates come just 3813 after a space. So it is broken down into two invocations of 3814 ‘sort’: the first sorts by timestamp and the second by IPv4 3815 address. The timestamp is sorted by year, then month, then day, 3816 and finally by hour-minute-second field, using ‘-k’ to isolate each 3817 field. Except for hour-minute-second there’s no need to specify 3818 the end of each key field, since the ‘n’ and ‘M’ modifiers sort 3819 based on leading prefixes that cannot cross field boundaries. The 3820 IPv4 addresses are sorted lexicographically. The second sort uses 3821 ‘-s’ so that ties in the primary key are broken by the secondary 3822 key; the first sort uses ‘-s’ so that the combination of the two 3823 sorts is stable. 3824 3825 • Generate a tags file in case-insensitive sorted order. 3826 3827 find src -type f -print0 | sort -z -f | xargs -0 etags --append 3828 3829 The use of ‘-print0’, ‘-z’, and ‘-0’ in this case means that file 3830 names that contain blanks or other special characters are not 3831 broken up by the sort operation. 3832 3833 • Use the common DSU, Decorate Sort Undecorate idiom to sort lines 3834 according to their length. 3835 3836 awk '{print length, $0}' /etc/passwd | sort -n | cut -f2- -d' ' 3837 3838 In general this technique can be used to sort data that the ‘sort’ 3839 command does not support, or is inefficient at, sorting directly. 3840 3841 • Shuffle a list of directories, but preserve the order of files 3842 within each directory. For instance, one could use this to 3843 generate a music playlist in which albums are shuffled but the 3844 songs of each album are played in order. 3845 3846 ls */* | sort -t / -k 1,1R -k 2,2 3847 3848 ---------- Footnotes ---------- 3849 3850 (1) If you use a non-POSIX locale (e.g., by setting ‘LC_ALL’ to 3851‘en_US’), then ‘sort’ may produce output that is sorted differently than 3852you’re accustomed to. In that case, set the ‘LC_ALL’ environment 3853variable to ‘C’. Note that setting only ‘LC_COLLATE’ has two problems. 3854First, it is ineffective if ‘LC_ALL’ is also set. Second, it has 3855undefined behavior if ‘LC_CTYPE’ (or ‘LANG’, if ‘LC_CTYPE’ is unset) is 3856set to an incompatible value. For example, you get undefined behavior 3857if ‘LC_CTYPE’ is ‘ja_JP.PCK’ but ‘LC_COLLATE’ is ‘en_US.UTF-8’. 3858 3859 3860File: coreutils.info, Node: shuf invocation, Next: uniq invocation, Prev: sort invocation, Up: Operating on sorted files 3861 38627.2 ‘shuf’: Shuffling text 3863========================== 3864 3865‘shuf’ shuffles its input by outputting a random permutation of its 3866input lines. Each output permutation is equally likely. Synopses: 3867 3868 shuf [OPTION]... [FILE] 3869 shuf -e [OPTION]... [ARG]... 3870 shuf -i LO-HI [OPTION]... 3871 3872 ‘shuf’ has three modes of operation that affect where it obtains its 3873input lines. By default, it reads lines from standard input. The 3874following options change the operation mode: 3875 3876‘-e’ 3877‘--echo’ 3878 Treat each command-line operand as an input line. 3879 3880‘-i LO-HI’ 3881‘--input-range=LO-HI’ 3882 Act as if input came from a file containing the range of unsigned 3883 decimal integers LO...HI, one per line. 3884 3885 ‘shuf’’s other options can affect its behavior in all operation 3886modes: 3887 3888‘-n COUNT’ 3889‘--head-count=COUNT’ 3890 Output at most COUNT lines. By default, all input lines are 3891 output. 3892 3893‘-o OUTPUT-FILE’ 3894‘--output=OUTPUT-FILE’ 3895 Write output to OUTPUT-FILE instead of standard output. ‘shuf’ 3896 reads all input before opening OUTPUT-FILE, so you can safely 3897 shuffle a file in place by using commands like ‘shuf -o F <F’ and 3898 ‘cat F | shuf -o F’. 3899 3900‘--random-source=FILE’ 3901 Use FILE as a source of random data used to determine which 3902 permutation to generate. *Note Random sources::. 3903 3904‘-r’ 3905‘--repeat’ 3906 Repeat output values, that is, select with replacement. With this 3907 option the output is not a permutation of the input; instead, each 3908 output line is randomly chosen from all the inputs. This option is 3909 typically combined with ‘--head-count’; if ‘--head-count’ is not 3910 given, ‘shuf’ repeats indefinitely. 3911 3912‘-z’ 3913‘--zero-terminated’ 3914 Delimit items with a zero byte rather than a newline (ASCII LF). 3915 I.e., treat input as items separated by ASCII NUL and terminate 3916 output items with ASCII NUL. This option can be useful in 3917 conjunction with ‘perl -0’ or ‘find -print0’ and ‘xargs -0’ which 3918 do the same in order to reliably handle arbitrary file names (even 3919 those containing blanks or other special characters). 3920 3921 For example: 3922 3923 shuf <<EOF 3924 A man, 3925 a plan, 3926 a canal: 3927 Panama! 3928 EOF 3929 3930might produce the output 3931 3932 Panama! 3933 A man, 3934 a canal: 3935 a plan, 3936 3937Similarly, the command: 3938 3939 shuf -e clubs hearts diamonds spades 3940 3941might output: 3942 3943 clubs 3944 diamonds 3945 spades 3946 hearts 3947 3948and the command ‘shuf -i 1-4’ might output: 3949 3950 4 3951 2 3952 1 3953 3 3954 3955The above examples all have four input lines, so ‘shuf’ might produce 3956any of the twenty-four possible permutations of the input. In general, 3957if there are N input lines, there are N! (i.e., N factorial, or N * (N 3958- 1) * ... * 1) possible output permutations. 3959 3960To output 50 random numbers each in the range 0 through 9, use: 3961 3962 shuf -r -n 50 -i 0-9 3963 3964To simulate 100 coin flips, use: 3965 3966 shuf -r -n 100 -e Head Tail 3967 3968 An exit status of zero indicates success, and a nonzero value 3969indicates failure. 3970 3971 3972File: coreutils.info, Node: uniq invocation, Next: comm invocation, Prev: shuf invocation, Up: Operating on sorted files 3973 39747.3 ‘uniq’: Uniquify files 3975========================== 3976 3977‘uniq’ writes the unique lines in the given ‘input’, or standard input 3978if nothing is given or for an INPUT name of ‘-’. Synopsis: 3979 3980 uniq [OPTION]... [INPUT [OUTPUT]] 3981 3982 By default, ‘uniq’ prints its input lines, except that it discards 3983all but the first of adjacent repeated lines, so that no output lines 3984are repeated. Optionally, it can instead discard lines that are not 3985repeated, or all repeated lines. 3986 3987 The input need not be sorted, but repeated input lines are detected 3988only if they are adjacent. If you want to discard non-adjacent 3989duplicate lines, perhaps you want to use ‘sort -u’. *Note sort 3990invocation::. 3991 3992 Comparisons honor the rules specified by the ‘LC_COLLATE’ locale 3993category. 3994 3995 If no OUTPUT file is specified, ‘uniq’ writes to standard output. 3996 3997 The program accepts the following options. Also see *note Common 3998options::. 3999 4000‘-f N’ 4001‘--skip-fields=N’ 4002 Skip N fields on each line before checking for uniqueness. Use a 4003 null string for comparison if a line has fewer than N fields. 4004 Fields are sequences of non-space non-tab characters that are 4005 separated from each other by at least one space or tab. 4006 4007 For compatibility ‘uniq’ supports a traditional option syntax ‘-N’. 4008 New scripts should use ‘-f N’ instead. 4009 4010‘-s N’ 4011‘--skip-chars=N’ 4012 Skip N characters before checking for uniqueness. Use a null 4013 string for comparison if a line has fewer than N characters. If 4014 you use both the field and character skipping options, fields are 4015 skipped over first. 4016 4017 On systems not conforming to POSIX 1003.1-2001, ‘uniq’ supports a 4018 traditional option syntax ‘+N’. Although this traditional behavior 4019 can be controlled with the ‘_POSIX2_VERSION’ environment variable 4020 (*note Standards conformance::), portable scripts should avoid 4021 commands whose behavior depends on this variable. For example, use 4022 ‘uniq ./+10’ or ‘uniq -s 10’ rather than the ambiguous ‘uniq +10’. 4023 4024‘-c’ 4025‘--count’ 4026 Print the number of times each line occurred along with the line. 4027 4028‘-i’ 4029‘--ignore-case’ 4030 Ignore differences in case when comparing lines. 4031 4032‘-d’ 4033‘--repeated’ 4034 Discard lines that are not repeated. When used by itself, this 4035 option causes ‘uniq’ to print the first copy of each repeated line, 4036 and nothing else. 4037 4038‘-D’ 4039‘--all-repeated[=DELIMIT-METHOD]’ 4040 Do not discard the second and subsequent repeated input lines, but 4041 discard lines that are not repeated. This option is useful mainly 4042 in conjunction with other options e.g., to ignore case or to 4043 compare only selected fields. The optional DELIMIT-METHOD, 4044 supported with the long form option, specifies how to delimit 4045 groups of repeated lines, and must be one of the following: 4046 4047 ‘none’ 4048 Do not delimit groups of repeated lines. This is equivalent 4049 to ‘--all-repeated’ (‘-D’). 4050 4051 ‘prepend’ 4052 Output a newline before each group of repeated lines. With 4053 ‘--zero-terminated’ (‘-z’), use a zero byte (ASCII NUL) 4054 instead of a newline as the delimiter. 4055 4056 ‘separate’ 4057 Separate groups of repeated lines with a single newline. This 4058 is the same as using ‘prepend’, except that no delimiter is 4059 inserted before the first group, and hence may be better 4060 suited for output direct to users. With ‘--zero-terminated’ 4061 (‘-z’), use a zero byte (ASCII NUL) instead of a newline as 4062 the delimiter. 4063 4064 Note that when groups are delimited and the input stream contains 4065 blank lines, then the output is ambiguous. To avoid that, filter 4066 the input through ‘tr -s '\n'’ to remove blank lines. 4067 4068 This is a GNU extension. 4069 4070‘--group[=DELIMIT-METHOD]’ 4071 Output all lines, and delimit each unique group. With 4072 ‘--zero-terminated’ (‘-z’), use a zero byte (ASCII NUL) instead of 4073 a newline as the delimiter. The optional DELIMIT-METHOD specifies 4074 how to delimit groups, and must be one of the following: 4075 4076 ‘separate’ 4077 Separate unique groups with a single delimiter. This is the 4078 default delimiting method if none is specified, and better 4079 suited for output direct to users. 4080 4081 ‘prepend’ 4082 Output a delimiter before each group of unique items. 4083 4084 ‘append’ 4085 Output a delimiter after each group of unique items. 4086 4087 ‘both’ 4088 Output a delimiter around each group of unique items. 4089 4090 Note that when groups are delimited and the input stream contains 4091 blank lines, then the output is ambiguous. To avoid that, filter 4092 the input through ‘tr -s '\n'’ to remove blank lines. 4093 4094 This is a GNU extension. 4095 4096‘-u’ 4097‘--unique’ 4098 Discard the last line that would be output for a repeated input 4099 group. When used by itself, this option causes ‘uniq’ to print 4100 unique lines, and nothing else. 4101 4102‘-w N’ 4103‘--check-chars=N’ 4104 Compare at most N characters on each line (after skipping any 4105 specified fields and characters). By default the entire rest of 4106 the lines are compared. 4107 4108‘-z’ 4109‘--zero-terminated’ 4110 Delimit items with a zero byte rather than a newline (ASCII LF). 4111 I.e., treat input as items separated by ASCII NUL and terminate 4112 output items with ASCII NUL. This option can be useful in 4113 conjunction with ‘perl -0’ or ‘find -print0’ and ‘xargs -0’ which 4114 do the same in order to reliably handle arbitrary file names (even 4115 those containing blanks or other special characters). Note with 4116 ‘-z’ the newline character is treated as a field separator. 4117 4118 An exit status of zero indicates success, and a nonzero value 4119indicates failure. 4120 4121 4122File: coreutils.info, Node: comm invocation, Next: ptx invocation, Prev: uniq invocation, Up: Operating on sorted files 4123 41247.4 ‘comm’: Compare two sorted files line by line 4125================================================= 4126 4127‘comm’ writes to standard output lines that are common, and lines that 4128are unique, to two input files; a file name of ‘-’ means standard input. 4129Synopsis: 4130 4131 comm [OPTION]... FILE1 FILE2 4132 4133 Before ‘comm’ can be used, the input files must be sorted using the 4134collating sequence specified by the ‘LC_COLLATE’ locale. If an input 4135file ends in a non-newline character, a newline is silently appended. 4136The ‘sort’ command with no options always outputs a file that is 4137suitable input to ‘comm’. 4138 4139 With no options, ‘comm’ produces three-column output. Column one 4140contains lines unique to FILE1, column two contains lines unique to 4141FILE2, and column three contains lines common to both files. Columns 4142are separated by a single TAB character. 4143 4144 The options ‘-1’, ‘-2’, and ‘-3’ suppress printing of the 4145corresponding columns (and separators). Also see *note Common 4146options::. 4147 4148 Unlike some other comparison utilities, ‘comm’ has an exit status 4149that does not depend on the result of the comparison. Upon normal 4150completion ‘comm’ produces an exit code of zero. If there is an error 4151it exits with nonzero status. 4152 4153 If the ‘--check-order’ option is given, unsorted inputs will cause a 4154fatal error message. If the option ‘--nocheck-order’ is given, unsorted 4155inputs will never cause an error message. If neither of these options 4156is given, wrongly sorted inputs are diagnosed only if an input file is 4157found to contain unpairable lines. If an input file is diagnosed as 4158being unsorted, the ‘comm’ command will exit with a nonzero status (and 4159the output should not be used). 4160 4161 Forcing ‘comm’ to process wrongly sorted input files containing 4162unpairable lines by specifying ‘--nocheck-order’ is not guaranteed to 4163produce any particular output. The output will probably not correspond 4164with whatever you hoped it would be. 4165 4166‘--check-order’ 4167 Fail with an error message if either input file is wrongly ordered. 4168 4169‘--nocheck-order’ 4170 Do not check that both input files are in sorted order. 4171 4172 Other options are: 4173 4174‘--output-delimiter=STR’ 4175 Print STR between adjacent output columns, rather than the default 4176 of a single TAB character. 4177 4178 The delimiter STR may not be empty. 4179 4180‘--total’ 4181 Output a summary at the end. 4182 4183 Similar to the regular output, column one contains the total number 4184 of lines unique to FILE1, column two contains the total number of 4185 lines unique to FILE2, and column three contains the total number 4186 of lines common to both files, followed by the word ‘total’ in the 4187 additional column four. 4188 4189 In the following example, ‘comm’ omits the regular output (‘-123’), 4190 thus just printing the summary: 4191 4192 $ printf '%s\n' a b c d e > file1 4193 $ printf '%s\n' b c d e f g > file2 4194 $ comm --total -123 file1 file2 4195 1 2 4 total 4196 4197 This option is a GNU extension. Portable scripts should use ‘wc’ 4198 to get the totals, e.g. for the above example files: 4199 4200 $ comm -23 file1 file2 | wc -l # number of lines only in file1 4201 1 4202 $ comm -13 file1 file2 | wc -l # number of lines only in file2 4203 2 4204 $ comm -12 file1 file2 | wc -l # number of lines common to both files 4205 4 4206 4207‘-z’ 4208‘--zero-terminated’ 4209 Delimit items with a zero byte rather than a newline (ASCII LF). 4210 I.e., treat input as items separated by ASCII NUL and terminate 4211 output items with ASCII NUL. This option can be useful in 4212 conjunction with ‘perl -0’ or ‘find -print0’ and ‘xargs -0’ which 4213 do the same in order to reliably handle arbitrary file names (even 4214 those containing blanks or other special characters). 4215 4216 4217File: coreutils.info, Node: ptx invocation, Next: tsort invocation, Prev: comm invocation, Up: Operating on sorted files 4218 42197.5 ‘ptx’: Produce permuted indexes 4220=================================== 4221 4222‘ptx’ reads a text file and essentially produces a permuted index, with 4223each keyword in its context. The calling sketch is either one of: 4224 4225 ptx [OPTION ...] [FILE ...] 4226 ptx -G [OPTION ...] [INPUT [OUTPUT]] 4227 4228 The ‘-G’ (or its equivalent: ‘--traditional’) option disables all GNU 4229extensions and reverts to traditional mode, thus introducing some 4230limitations and changing several of the program’s default option values. 4231When ‘-G’ is not specified, GNU extensions are always enabled. GNU 4232extensions to ‘ptx’ are documented wherever appropriate in this 4233document. *Note Compatibility in ptx::, for the full list. 4234 4235 Individual options are explained in the following sections. 4236 4237 When GNU extensions are enabled, there may be zero, one or several 4238FILEs after the options. If there is no FILE, the program reads the 4239standard input. If there is one or several FILEs, they give the name of 4240input files which are all read in turn, as if all the input files were 4241concatenated. However, there is a full contextual break between each 4242file and, when automatic referencing is requested, file names and line 4243numbers refer to individual text input files. In all cases, the program 4244outputs the permuted index to the standard output. 4245 4246 When GNU extensions are _not_ enabled, that is, when the program 4247operates in traditional mode, there may be zero, one or two parameters 4248besides the options. If there are no parameters, the program reads the 4249standard input and outputs the permuted index to the standard output. 4250If there is only one parameter, it names the text INPUT to be read 4251instead of the standard input. If two parameters are given, they give 4252respectively the name of the INPUT file to read and the name of the 4253OUTPUT file to produce. _Be very careful_ to note that, in this case, 4254the contents of file given by the second parameter is destroyed. This 4255behavior is dictated by System V ‘ptx’ compatibility; GNU Standards 4256normally discourage output parameters not introduced by an option. 4257 4258 Note that for _any_ file named as the value of an option or as an 4259input text file, a single dash ‘-’ may be used, in which case standard 4260input is assumed. However, it would not make sense to use this 4261convention more than once per program invocation. 4262 4263* Menu: 4264 4265* General options in ptx:: Options which affect general program behavior. 4266* Charset selection in ptx:: Underlying character set considerations. 4267* Input processing in ptx:: Input fields, contexts, and keyword selection. 4268* Output formatting in ptx:: Types of output format, and sizing the fields. 4269* Compatibility in ptx:: 4270 4271 4272File: coreutils.info, Node: General options in ptx, Next: Charset selection in ptx, Up: ptx invocation 4273 42747.5.1 General options 4275--------------------- 4276 4277‘-G’ 4278‘--traditional’ 4279 As already explained, this option disables all GNU extensions to 4280 ‘ptx’ and switches to traditional mode. 4281 4282‘--help’ 4283 Print a short help on standard output, then exit without further 4284 processing. 4285 4286‘--version’ 4287 Print the program version on standard output, then exit without 4288 further processing. 4289 4290 An exit status of zero indicates success, and a nonzero value 4291indicates failure. 4292 4293 4294File: coreutils.info, Node: Charset selection in ptx, Next: Input processing in ptx, Prev: General options in ptx, Up: ptx invocation 4295 42967.5.2 Charset selection 4297----------------------- 4298 4299As it is set up now, the program assumes that the input file is coded 4300using 8-bit ISO 8859-1 code, also known as Latin-1 character set, 4301_unless_ it is compiled for MS-DOS, in which case it uses the character 4302set of the IBM-PC. (GNU ‘ptx’ is not known to work on smaller MS-DOS 4303machines anymore.) Compared to 7-bit ASCII, the set of characters which 4304are letters is different; this alters the behavior of regular expression 4305matching. Thus, the default regular expression for a keyword allows 4306foreign or diacriticized letters. Keyword sorting, however, is still 4307crude; it obeys the underlying character set ordering quite blindly. 4308 4309‘-f’ 4310‘--ignore-case’ 4311 Fold lower case letters to upper case for sorting. 4312 4313 4314File: coreutils.info, Node: Input processing in ptx, Next: Output formatting in ptx, Prev: Charset selection in ptx, Up: ptx invocation 4315 43167.5.3 Word selection and input processing 4317----------------------------------------- 4318 4319‘-b FILE’ 4320‘--break-file=FILE’ 4321 4322 This option provides an alternative (to ‘-W’) method of describing 4323 which characters make up words. It introduces the name of a file 4324 which contains a list of characters which can_not_ be part of one 4325 word; this file is called the “Break file”. Any character which is 4326 not part of the Break file is a word constituent. If both options 4327 ‘-b’ and ‘-W’ are specified, then ‘-W’ has precedence and ‘-b’ is 4328 ignored. 4329 4330 When GNU extensions are enabled, the only way to avoid newline as a 4331 break character is to write all the break characters in the file 4332 with no newline at all, not even at the end of the file. When GNU 4333 extensions are disabled, spaces, tabs and newlines are always 4334 considered as break characters even if not included in the Break 4335 file. 4336 4337‘-i FILE’ 4338‘--ignore-file=FILE’ 4339 4340 The file associated with this option contains a list of words which 4341 will never be taken as keywords in concordance output. It is 4342 called the “Ignore file”. The file contains exactly one word in 4343 each line; the end of line separation of words is not subject to 4344 the value of the ‘-S’ option. 4345 4346‘-o FILE’ 4347‘--only-file=FILE’ 4348 4349 The file associated with this option contains a list of words which 4350 will be retained in concordance output; any word not mentioned in 4351 this file is ignored. The file is called the “Only file”. The 4352 file contains exactly one word in each line; the end of line 4353 separation of words is not subject to the value of the ‘-S’ option. 4354 4355 There is no default for the Only file. When both an Only file and 4356 an Ignore file are specified, a word is considered a keyword only 4357 if it is listed in the Only file and not in the Ignore file. 4358 4359‘-r’ 4360‘--references’ 4361 4362 On each input line, the leading sequence of non-white space 4363 characters will be taken to be a reference that has the purpose of 4364 identifying this input line in the resulting permuted index. *Note 4365 Output formatting in ptx::, for more information about reference 4366 production. Using this option changes the default value for option 4367 ‘-S’. 4368 4369 Using this option, the program does not try very hard to remove 4370 references from contexts in output, but it succeeds in doing so 4371 _when_ the context ends exactly at the newline. If option ‘-r’ is 4372 used with ‘-S’ default value, or when GNU extensions are disabled, 4373 this condition is always met and references are completely excluded 4374 from the output contexts. 4375 4376‘-S REGEXP’ 4377‘--sentence-regexp=REGEXP’ 4378 4379 This option selects which regular expression will describe the end 4380 of a line or the end of a sentence. In fact, this regular 4381 expression is not the only distinction between end of lines or end 4382 of sentences, and input line boundaries have no special 4383 significance outside this option. By default, when GNU extensions 4384 are enabled and if ‘-r’ option is not used, end of sentences are 4385 used. In this case, this REGEX is imported from GNU Emacs: 4386 4387 [.?!][]\"')}]*\\($\\|\t\\| \\)[ \t\n]* 4388 4389 Whenever GNU extensions are disabled or if ‘-r’ option is used, end 4390 of lines are used; in this case, the default REGEXP is just: 4391 4392 \n 4393 4394 Using an empty REGEXP is equivalent to completely disabling end of 4395 line or end of sentence recognition. In this case, the whole file 4396 is considered to be a single big line or sentence. The user might 4397 want to disallow all truncation flag generation as well, through 4398 option ‘-F ""’. *Note Syntax of Regular Expressions: 4399 (emacs)Regexps. 4400 4401 When the keywords happen to be near the beginning of the input line 4402 or sentence, this often creates an unused area at the beginning of 4403 the output context line; when the keywords happen to be near the 4404 end of the input line or sentence, this often creates an unused 4405 area at the end of the output context line. The program tries to 4406 fill those unused areas by wrapping around context in them; the 4407 tail of the input line or sentence is used to fill the unused area 4408 on the left of the output line; the head of the input line or 4409 sentence is used to fill the unused area on the right of the output 4410 line. 4411 4412 As a matter of convenience to the user, many usual backslashed 4413 escape sequences from the C language are recognized and converted 4414 to the corresponding characters by ‘ptx’ itself. 4415 4416‘-W REGEXP’ 4417‘--word-regexp=REGEXP’ 4418 4419 This option selects which regular expression will describe each 4420 keyword. By default, if GNU extensions are enabled, a word is a 4421 sequence of letters; the REGEXP used is ‘\w+’. When GNU extensions 4422 are disabled, a word is by default anything which ends with a 4423 space, a tab or a newline; the REGEXP used is ‘[^ \t\n]+’. 4424 4425 An empty REGEXP is equivalent to not using this option. *Note 4426 Syntax of Regular Expressions: (emacs)Regexps. 4427 4428 As a matter of convenience to the user, many usual backslashed 4429 escape sequences, as found in the C language, are recognized and 4430 converted to the corresponding characters by ‘ptx’ itself. 4431 4432 4433File: coreutils.info, Node: Output formatting in ptx, Next: Compatibility in ptx, Prev: Input processing in ptx, Up: ptx invocation 4434 44357.5.4 Output formatting 4436----------------------- 4437 4438Output format is mainly controlled by the ‘-O’ and ‘-T’ options 4439described in the table below. When neither ‘-O’ nor ‘-T’ are selected, 4440and if GNU extensions are enabled, the program chooses an output format 4441suitable for a dumb terminal. Each keyword occurrence is output to the 4442center of one line, surrounded by its left and right contexts. Each 4443field is properly justified, so the concordance output can be readily 4444observed. As a special feature, if automatic references are selected by 4445option ‘-A’ and are output before the left context, that is, if option 4446‘-R’ is _not_ selected, then a colon is added after the reference; this 4447nicely interfaces with GNU Emacs ‘next-error’ processing. In this 4448default output format, each white space character, like newline and tab, 4449is merely changed to exactly one space, with no special attempt to 4450compress consecutive spaces. This might change in the future. Except 4451for those white space characters, every other character of the 4452underlying set of 256 characters is transmitted verbatim. 4453 4454 Output format is further controlled by the following options. 4455 4456‘-g NUMBER’ 4457‘--gap-size=NUMBER’ 4458 4459 Select the size of the minimum white space gap between the fields 4460 on the output line. 4461 4462‘-w NUMBER’ 4463‘--width=NUMBER’ 4464 4465 Select the maximum output width of each final line. If references 4466 are used, they are included or excluded from the maximum output 4467 width depending on the value of option ‘-R’. If this option is not 4468 selected, that is, when references are output before the left 4469 context, the maximum output width takes into account the maximum 4470 length of all references. If this option is selected, that is, 4471 when references are output after the right context, the maximum 4472 output width does not take into account the space taken by 4473 references, nor the gap that precedes them. 4474 4475‘-A’ 4476‘--auto-reference’ 4477 4478 Select automatic references. Each input line will have an 4479 automatic reference made up of the file name and the line ordinal, 4480 with a single colon between them. However, the file name will be 4481 empty when standard input is being read. If both ‘-A’ and ‘-r’ are 4482 selected, then the input reference is still read and skipped, but 4483 the automatic reference is used at output time, overriding the 4484 input reference. 4485 4486‘-R’ 4487‘--right-side-refs’ 4488 4489 In the default output format, when option ‘-R’ is not used, any 4490 references produced by the effect of options ‘-r’ or ‘-A’ are 4491 placed to the far right of output lines, after the right context. 4492 With default output format, when the ‘-R’ option is specified, 4493 references are rather placed at the beginning of each output line, 4494 before the left context. For any other output format, option ‘-R’ 4495 is ignored, with one exception: with ‘-R’ the width of references 4496 is _not_ taken into account in total output width given by ‘-w’. 4497 4498 This option is automatically selected whenever GNU extensions are 4499 disabled. 4500 4501‘-F STRING’ 4502‘--flag-truncation=STRING’ 4503 4504 This option will request that any truncation in the output be 4505 reported using the string STRING. Most output fields theoretically 4506 extend towards the beginning or the end of the current line, or 4507 current sentence, as selected with option ‘-S’. But there is a 4508 maximum allowed output line width, changeable through option ‘-w’, 4509 which is further divided into space for various output fields. 4510 When a field has to be truncated because it cannot extend beyond 4511 the beginning or the end of the current line to fit in, then a 4512 truncation occurs. By default, the string used is a single slash, 4513 as in ‘-F /’. 4514 4515 STRING may have more than one character, as in ‘-F ...’. Also, in 4516 the particular case when STRING is empty (‘-F ""’), truncation 4517 flagging is disabled, and no truncation marks are appended in this 4518 case. 4519 4520 As a matter of convenience to the user, many usual backslashed 4521 escape sequences, as found in the C language, are recognized and 4522 converted to the corresponding characters by ‘ptx’ itself. 4523 4524‘-M STRING’ 4525‘--macro-name=STRING’ 4526 4527 Select another STRING to be used instead of ‘xx’, while generating 4528 output suitable for ‘nroff’, ‘troff’ or TeX. 4529 4530‘-O’ 4531‘--format=roff’ 4532 4533 Choose an output format suitable for ‘nroff’ or ‘troff’ processing. 4534 Each output line will look like: 4535 4536 .xx "TAIL" "BEFORE" "KEYWORD_AND_AFTER" "HEAD" "REF" 4537 4538 so it will be possible to write a ‘.xx’ roff macro to take care of 4539 the output typesetting. This is the default output format when GNU 4540 extensions are disabled. Option ‘-M’ can be used to change ‘xx’ to 4541 another macro name. 4542 4543 In this output format, each non-graphical character, like newline 4544 and tab, is merely changed to exactly one space, with no special 4545 attempt to compress consecutive spaces. Each quote character ‘"’ 4546 is doubled so it will be correctly processed by ‘nroff’ or ‘troff’. 4547 4548‘-T’ 4549‘--format=tex’ 4550 4551 Choose an output format suitable for TeX processing. Each output 4552 line will look like: 4553 4554 \xx {TAIL}{BEFORE}{KEYWORD}{AFTER}{HEAD}{REF} 4555 4556 so it will be possible to write a ‘\xx’ definition to take care of 4557 the output typesetting. Note that when references are not being 4558 produced, that is, neither option ‘-A’ nor option ‘-r’ is selected, 4559 the last parameter of each ‘\xx’ call is inhibited. Option ‘-M’ 4560 can be used to change ‘xx’ to another macro name. 4561 4562 In this output format, some special characters, like ‘$’, ‘%’, ‘&’, 4563 ‘#’ and ‘_’ are automatically protected with a backslash. Curly 4564 brackets ‘{’, ‘}’ are protected with a backslash and a pair of 4565 dollar signs (to force mathematical mode). The backslash itself 4566 produces the sequence ‘\backslash{}’. Circumflex and tilde 4567 diacritical marks produce the sequence ‘^\{ }’ and ‘~\{ }’ 4568 respectively. Other diacriticized characters of the underlying 4569 character set produce an appropriate TeX sequence as far as 4570 possible. The other non-graphical characters, like newline and 4571 tab, and all other characters which are not part of ASCII, are 4572 merely changed to exactly one space, with no special attempt to 4573 compress consecutive spaces. Let me know how to improve this 4574 special character processing for TeX. 4575 4576 4577File: coreutils.info, Node: Compatibility in ptx, Prev: Output formatting in ptx, Up: ptx invocation 4578 45797.5.5 The GNU extensions to ‘ptx’ 4580--------------------------------- 4581 4582This version of ‘ptx’ contains a few features which do not exist in 4583System V ‘ptx’. These extra features are suppressed by using the ‘-G’ 4584command line option, unless overridden by other command line options. 4585Some GNU extensions cannot be recovered by overriding, so the simple 4586rule is to avoid ‘-G’ if you care about GNU extensions. Here are the 4587differences between this program and System V ‘ptx’. 4588 4589 • This program can read many input files at once, it always writes 4590 the resulting concordance on standard output. On the other hand, 4591 System V ‘ptx’ reads only one file and sends the result to standard 4592 output or, if a second FILE parameter is given on the command, to 4593 that FILE. 4594 4595 Having output parameters not introduced by options is a dangerous 4596 practice which GNU avoids as far as possible. So, for using ‘ptx’ 4597 portably between GNU and System V, you should always use it with a 4598 single input file, and always expect the result on standard output. 4599 You might also want to automatically configure in a ‘-G’ option to 4600 ‘ptx’ calls in products using ‘ptx’, if the configurator finds that 4601 the installed ‘ptx’ accepts ‘-G’. 4602 4603 • The only options available in System V ‘ptx’ are options ‘-b’, 4604 ‘-f’, ‘-g’, ‘-i’, ‘-o’, ‘-r’, ‘-t’ and ‘-w’. All other options are 4605 GNU extensions and are not repeated in this enumeration. Moreover, 4606 some options have a slightly different meaning when GNU extensions 4607 are enabled, as explained below. 4608 4609 • By default, concordance output is not formatted for ‘troff’ or 4610 ‘nroff’. It is rather formatted for a dumb terminal. ‘troff’ or 4611 ‘nroff’ output may still be selected through option ‘-O’. 4612 4613 • Unless ‘-R’ option is used, the maximum reference width is 4614 subtracted from the total output line width. With GNU extensions 4615 disabled, width of references is not taken into account in the 4616 output line width computations. 4617 4618 • All 256 bytes, even ASCII NUL bytes, are always read and processed 4619 from input file with no adverse effect, even if GNU extensions are 4620 disabled. However, System V ‘ptx’ does not accept 8-bit 4621 characters, a few control characters are rejected, and the tilde 4622 ‘~’ is also rejected. 4623 4624 • Input line length is only limited by available memory, even if GNU 4625 extensions are disabled. However, System V ‘ptx’ processes only 4626 the first 200 characters in each line. 4627 4628 • The break (non-word) characters default to be every character 4629 except all letters of the underlying character set, diacriticized 4630 or not. When GNU extensions are disabled, the break characters 4631 default to space, tab and newline only. 4632 4633 • The program makes better use of output line width. If GNU 4634 extensions are disabled, the program rather tries to imitate System 4635 V ‘ptx’, but still, there are some slight disposition glitches this 4636 program does not completely reproduce. 4637 4638 • The user can specify both an Ignore file and an Only file. This is 4639 not allowed with System V ‘ptx’. 4640 4641 4642File: coreutils.info, Node: tsort invocation, Prev: ptx invocation, Up: Operating on sorted files 4643 46447.6 ‘tsort’: Topological sort 4645============================= 4646 4647‘tsort’ performs a topological sort on the given FILE, or standard input 4648if no input file is given or for a FILE of ‘-’. For more details and 4649some history, see *note tsort background::. Synopsis: 4650 4651 tsort [OPTION] [FILE] 4652 4653 ‘tsort’ reads its input as pairs of strings, separated by blanks, 4654indicating a partial ordering. The output is a total ordering that 4655corresponds to the given partial ordering. 4656 4657 For example 4658 4659 tsort <<EOF 4660 a b c 4661 d 4662 e f 4663 b c d e 4664 EOF 4665 4666will produce the output 4667 4668 a 4669 b 4670 c 4671 d 4672 e 4673 f 4674 4675 Consider a more realistic example. You have a large set of functions 4676all in one file, and they may all be declared static except one. 4677Currently that one (say ‘main’) is the first function defined in the 4678file, and the ones it calls directly follow it, followed by those they 4679call, etc. Let’s say that you are determined to take advantage of 4680prototypes, so you have to choose between declaring all of those 4681functions (which means duplicating a lot of information from the 4682definitions) and rearranging the functions so that as many as possible 4683are defined before they are used. One way to automate the latter 4684process is to get a list for each function of the functions it calls 4685directly. Many programs can generate such lists. They describe a call 4686graph. Consider the following list, in which a given line indicates 4687that the function on the left calls the one on the right directly. 4688 4689 main parse_options 4690 main tail_file 4691 main tail_forever 4692 tail_file pretty_name 4693 tail_file write_header 4694 tail_file tail 4695 tail_forever recheck 4696 tail_forever pretty_name 4697 tail_forever write_header 4698 tail_forever dump_remainder 4699 tail tail_lines 4700 tail tail_bytes 4701 tail_lines start_lines 4702 tail_lines dump_remainder 4703 tail_lines file_lines 4704 tail_lines pipe_lines 4705 tail_bytes xlseek 4706 tail_bytes start_bytes 4707 tail_bytes dump_remainder 4708 tail_bytes pipe_bytes 4709 file_lines dump_remainder 4710 recheck pretty_name 4711 4712 then you can use ‘tsort’ to produce an ordering of those functions 4713that satisfies your requirement. 4714 4715 example$ tsort call-graph | tac 4716 dump_remainder 4717 start_lines 4718 file_lines 4719 pipe_lines 4720 xlseek 4721 start_bytes 4722 pipe_bytes 4723 tail_lines 4724 tail_bytes 4725 pretty_name 4726 write_header 4727 tail 4728 recheck 4729 parse_options 4730 tail_file 4731 tail_forever 4732 main 4733 4734 ‘tsort’ detects any cycles in the input and writes the first cycle 4735encountered to standard error. 4736 4737 Note that for a given partial ordering, generally there is no unique 4738total ordering. In the context of the call graph above, the function 4739‘parse_options’ may be placed anywhere in the list as long as it 4740precedes ‘main’. 4741 4742 The only options are ‘--help’ and ‘--version’. *Note Common 4743options::. 4744 4745 An exit status of zero indicates success, and a nonzero value 4746indicates failure. 4747 4748* Menu: 4749 4750* tsort background:: Where tsort came from. 4751 4752 4753File: coreutils.info, Node: tsort background, Up: tsort invocation 4754 47557.6.1 ‘tsort’: Background 4756------------------------- 4757 4758‘tsort’ exists because very early versions of the Unix linker processed 4759an archive file exactly once, and in order. As ‘ld’ read each object in 4760the archive, it decided whether it was needed in the program based on 4761whether it defined any symbols which were undefined at that point in the 4762link. 4763 4764 This meant that dependencies within the archive had to be handled 4765specially. For example, ‘scanf’ probably calls ‘read’. That means that 4766in a single pass through an archive, it was important for ‘scanf.o’ to 4767appear before read.o, because otherwise a program which calls ‘scanf’ 4768but not ‘read’ might end up with an unexpected unresolved reference to 4769‘read’. 4770 4771 The way to address this problem was to first generate a set of 4772dependencies of one object file on another. This was done by a shell 4773script called ‘lorder’. The GNU tools don’t provide a version of 4774lorder, as far as I know, but you can still find it in BSD 4775distributions. 4776 4777 Then you ran ‘tsort’ over the ‘lorder’ output, and you used the 4778resulting sort to define the order in which you added objects to the 4779archive. 4780 4781 This whole procedure has been obsolete since about 1980, because Unix 4782archives now contain a symbol table (traditionally built by ‘ranlib’, 4783now generally built by ‘ar’ itself), and the Unix linker uses the symbol 4784table to effectively make multiple passes over an archive file. 4785 4786 Anyhow, that’s where tsort came from. To solve an old problem with 4787the way the linker handled archive files, which has since been solved in 4788different ways. 4789 4790 4791File: coreutils.info, Node: Operating on fields, Next: Operating on characters, Prev: Operating on sorted files, Up: Top 4792 47938 Operating on fields 4794********************* 4795 4796* Menu: 4797 4798* cut invocation:: Print selected parts of lines. 4799* paste invocation:: Merge lines of files. 4800* join invocation:: Join lines on a common field. 4801 4802 4803File: coreutils.info, Node: cut invocation, Next: paste invocation, Up: Operating on fields 4804 48058.1 ‘cut’: Print selected parts of lines 4806======================================== 4807 4808‘cut’ writes to standard output selected parts of each line of each 4809input file, or standard input if no files are given or for a file name 4810of ‘-’. Synopsis: 4811 4812 cut OPTION... [FILE]... 4813 4814 In the table which follows, the BYTE-LIST, CHARACTER-LIST, and 4815FIELD-LIST are one or more numbers or ranges (two numbers separated by a 4816dash) separated by commas. Bytes, characters, and fields are numbered 4817starting at 1. Incomplete ranges may be given: ‘-M’ means ‘1-M’; ‘N-’ 4818means ‘N’ through end of line or last field. The list elements can be 4819repeated, can overlap, and can be specified in any order; but the 4820selected input is written in the same order that it is read, and is 4821written exactly once. 4822 4823 The program accepts the following options. Also see *note Common 4824options::. 4825 4826‘-b BYTE-LIST’ 4827‘--bytes=BYTE-LIST’ 4828 Select for printing only the bytes in positions listed in 4829 BYTE-LIST. Tabs and backspaces are treated like any other 4830 character; they take up 1 byte. If an output delimiter is 4831 specified, (see the description of ‘--output-delimiter’), then 4832 output that string between ranges of selected bytes. 4833 4834‘-c CHARACTER-LIST’ 4835‘--characters=CHARACTER-LIST’ 4836 Select for printing only the characters in positions listed in 4837 CHARACTER-LIST. The same as ‘-b’ for now, but internationalization 4838 will change that. Tabs and backspaces are treated like any other 4839 character; they take up 1 character. If an output delimiter is 4840 specified, (see the description of ‘--output-delimiter’), then 4841 output that string between ranges of selected bytes. 4842 4843‘-f FIELD-LIST’ 4844‘--fields=FIELD-LIST’ 4845 Select for printing only the fields listed in FIELD-LIST. Fields 4846 are separated by a TAB character by default. Also print any line 4847 that contains no delimiter character, unless the ‘--only-delimited’ 4848 (‘-s’) option is specified. 4849 4850 Note ‘awk’ supports more sophisticated field processing, like 4851 reordering fields, and handling fields aligned with blank 4852 characters. By default ‘awk’ uses (and discards) runs of blank 4853 characters to separate fields, and ignores leading and trailing 4854 blanks. 4855 awk '{print $2}' # print the second field 4856 awk '{print $(NF-1)}' # print the penultimate field 4857 awk '{print $2,$1}' # reorder the first two fields 4858 Note while ‘cut’ accepts field specifications in arbitrary order, 4859 output is always in the order encountered in the file. 4860 4861 In the unlikely event that ‘awk’ is unavailable, one can use the 4862 ‘join’ command, to process blank characters as ‘awk’ does above. 4863 join -a1 -o 1.2 - /dev/null # print the second field 4864 join -a1 -o 1.2,1.1 - /dev/null # reorder the first two fields 4865 4866‘-d INPUT_DELIM_BYTE’ 4867‘--delimiter=INPUT_DELIM_BYTE’ 4868 With ‘-f’, use the first byte of INPUT_DELIM_BYTE as the input 4869 fields separator (default is TAB). 4870 4871‘-n’ 4872 Do not split multi-byte characters (no-op for now). 4873 4874‘-s’ 4875‘--only-delimited’ 4876 For ‘-f’, do not print lines that do not contain the field 4877 separator character. Normally, any line without a field separator 4878 is printed verbatim. 4879 4880‘--output-delimiter=OUTPUT_DELIM_STRING’ 4881 With ‘-f’, output fields are separated by OUTPUT_DELIM_STRING. The 4882 default with ‘-f’ is to use the input delimiter. When using ‘-b’ 4883 or ‘-c’ to select ranges of byte or character offsets (as opposed 4884 to ranges of fields), output OUTPUT_DELIM_STRING between 4885 non-overlapping ranges of selected bytes. 4886 4887‘--complement’ 4888 This option is a GNU extension. Select for printing the complement 4889 of the bytes, characters or fields selected with the ‘-b’, ‘-c’ or 4890 ‘-f’ options. In other words, do _not_ print the bytes, characters 4891 or fields specified via those options. This option is useful when 4892 you have many fields and want to print all but a few of them. 4893 4894‘-z’ 4895‘--zero-terminated’ 4896 Delimit items with a zero byte rather than a newline (ASCII LF). 4897 I.e., treat input as items separated by ASCII NUL and terminate 4898 output items with ASCII NUL. This option can be useful in 4899 conjunction with ‘perl -0’ or ‘find -print0’ and ‘xargs -0’ which 4900 do the same in order to reliably handle arbitrary file names (even 4901 those containing blanks or other special characters). 4902 4903 An exit status of zero indicates success, and a nonzero value 4904indicates failure. 4905 4906 4907File: coreutils.info, Node: paste invocation, Next: join invocation, Prev: cut invocation, Up: Operating on fields 4908 49098.2 ‘paste’: Merge lines of files 4910================================= 4911 4912‘paste’ writes to standard output lines consisting of sequentially 4913corresponding lines of each given file, separated by a TAB character. 4914Standard input is used for a file name of ‘-’ or if no input files are 4915given. 4916 4917 Synopsis: 4918 4919 paste [OPTION]... [FILE]... 4920 4921 For example, with: 4922 $ cat num2 4923 1 4924 2 4925 $ cat let3 4926 a 4927 b 4928 c 4929 4930 Take lines sequentially from each file: 4931 $ paste num2 let3 4932 1 a 4933 2 b 4934 c 4935 4936 Duplicate lines from a file: 4937 $ paste num2 let3 num2 4938 1 a 1 4939 2 b 2 4940 c 4941 4942 Intermix lines from stdin: 4943 $ paste - let3 - < num2 4944 1 a 2 4945 b 4946 c 4947 4948 Join consecutive lines with a space: 4949 $ seq 4 | paste -d ' ' - - 4950 1 2 4951 3 4 4952 4953 The program accepts the following options. Also see *note Common 4954options::. 4955 4956‘-s’ 4957‘--serial’ 4958 Paste the lines of one file at a time rather than one line from 4959 each file. Using the above example data: 4960 4961 $ paste -s num2 let3 4962 1 2 4963 a b c 4964 4965‘-d DELIM-LIST’ 4966‘--delimiters=DELIM-LIST’ 4967 Consecutively use the characters in DELIM-LIST instead of TAB to 4968 separate merged lines. When DELIM-LIST is exhausted, start again 4969 at its beginning. Using the above example data: 4970 4971 $ paste -d '%_' num2 let3 num2 4972 1%a_1 4973 2%b_2 4974 %c_ 4975 4976‘-z’ 4977‘--zero-terminated’ 4978 Delimit items with a zero byte rather than a newline (ASCII LF). 4979 I.e., treat input as items separated by ASCII NUL and terminate 4980 output items with ASCII NUL. This option can be useful in 4981 conjunction with ‘perl -0’ or ‘find -print0’ and ‘xargs -0’ which 4982 do the same in order to reliably handle arbitrary file names (even 4983 those containing blanks or other special characters). 4984 4985 An exit status of zero indicates success, and a nonzero value 4986indicates failure. 4987 4988 4989File: coreutils.info, Node: join invocation, Prev: paste invocation, Up: Operating on fields 4990 49918.3 ‘join’: Join lines on a common field 4992======================================== 4993 4994‘join’ writes to standard output a line for each pair of input lines 4995that have identical join fields. Synopsis: 4996 4997 join [OPTION]... FILE1 FILE2 4998 4999 Either FILE1 or FILE2 (but not both) can be ‘-’, meaning standard 5000input. FILE1 and FILE2 should be sorted on the join fields. 5001 5002 $ cat file1 5003 a 1 5004 b 2 5005 e 5 5006 5007 $ cat file2 5008 a X 5009 e Y 5010 f Z 5011 5012 $ join file1 file2 5013 a 1 X 5014 e 5 Y 5015 5016‘join’’s default behavior (when no options are given): 5017 • the join field is the first field in each line; 5018 • fields in the input are separated by one or more blanks, with 5019 leading blanks on the line ignored; 5020 • fields in the output are separated by a space; 5021 • each output line consists of the join field, the remaining fields 5022 from FILE1, then the remaining fields from FILE2. 5023 5024* Menu: 5025 5026* General options in join:: Options which affect general program behavior. 5027* Sorting files for join:: Using ‘sort’ before ‘join’. 5028* Working with fields:: Joining on different fields. 5029* Paired and unpaired lines:: Controlling ‘join’’s field matching. 5030* Header lines:: Working with header lines in files. 5031* Set operations:: Union, Intersection and Difference of files. 5032 5033 5034File: coreutils.info, Node: General options in join, Next: Sorting files for join, Up: join invocation 5035 50368.3.1 General options 5037--------------------- 5038 5039The program accepts the following options. Also see *note Common 5040options::. 5041 5042‘-a FILE-NUMBER’ 5043 Print a line for each unpairable line in file FILE-NUMBER (either 5044 ‘1’ or ‘2’), in addition to the normal output. 5045 5046‘--check-order’ 5047 Fail with an error message if either input file is wrongly ordered. 5048 5049‘--nocheck-order’ 5050 Do not check that both input files are in sorted order. This is 5051 the default. 5052 5053‘-e STRING’ 5054 Replace those output fields that are missing in the input with 5055 STRING. I.e., missing fields specified with the ‘-12jo’ options. 5056 5057‘--header’ 5058 Treat the first line of each input file as a header line. The 5059 header lines will be joined and printed as the first output line. 5060 If ‘-o’ is used to specify output format, the header line will be 5061 printed according to the specified format. The header lines will 5062 not be checked for ordering even if ‘--check-order’ is specified. 5063 Also if the header lines from each file do not match, the heading 5064 fields from the first file will be used. 5065 5066‘-i’ 5067‘--ignore-case’ 5068 Ignore differences in case when comparing keys. With this option, 5069 the lines of the input files must be ordered in the same way. Use 5070 ‘sort -f’ to produce this ordering. 5071 5072‘-1 FIELD’ 5073 Join on field FIELD (a positive integer) of file 1. 5074 5075‘-2 FIELD’ 5076 Join on field FIELD (a positive integer) of file 2. 5077 5078‘-j FIELD’ 5079 Equivalent to ‘-1 FIELD -2 FIELD’. 5080 5081‘-o FIELD-LIST’ 5082‘-o auto’ 5083 If the keyword ‘auto’ is specified, infer the output format from 5084 the first line in each file. This is the same as the default 5085 output format but also ensures the same number of fields are output 5086 for each line. Missing fields are replaced with the ‘-e’ option 5087 and extra fields are discarded. 5088 5089 Otherwise, construct each output line according to the format in 5090 FIELD-LIST. Each element in FIELD-LIST is either the single 5091 character ‘0’ or has the form M.N where the file number, M, is ‘1’ 5092 or ‘2’ and N is a positive field number. 5093 5094 A field specification of ‘0’ denotes the join field. In most 5095 cases, the functionality of the ‘0’ field spec may be reproduced 5096 using the explicit M.N that corresponds to the join field. 5097 However, when printing unpairable lines (using either of the ‘-a’ 5098 or ‘-v’ options), there is no way to specify the join field using 5099 M.N in FIELD-LIST if there are unpairable lines in both files. To 5100 give ‘join’ that functionality, POSIX invented the ‘0’ field 5101 specification notation. 5102 5103 The elements in FIELD-LIST are separated by commas or blanks. 5104 Blank separators typically need to be quoted for the shell. For 5105 example, the commands ‘join -o 1.2,2.2’ and ‘join -o '1.2 2.2'’ are 5106 equivalent. 5107 5108 All output lines—including those printed because of any -a or -v 5109 option—are subject to the specified FIELD-LIST. 5110 5111‘-t CHAR’ 5112 Use character CHAR as the input and output field separator. Treat 5113 as significant each occurrence of CHAR in the input file. Use 5114 ‘sort -t CHAR’, without the ‘-b’ option of ‘sort’, to produce this 5115 ordering. If ‘join -t ''’ is specified, the whole line is 5116 considered, matching the default operation of sort. If ‘-t '\0'’ 5117 is specified then the ASCII NUL character is used to delimit the 5118 fields. 5119 5120‘-v FILE-NUMBER’ 5121 Print a line for each unpairable line in file FILE-NUMBER (either 5122 ‘1’ or ‘2’), instead of the normal output. 5123 5124‘-z’ 5125‘--zero-terminated’ 5126 Delimit items with a zero byte rather than a newline (ASCII LF). 5127 I.e., treat input as items separated by ASCII NUL and terminate 5128 output items with ASCII NUL. This option can be useful in 5129 conjunction with ‘perl -0’ or ‘find -print0’ and ‘xargs -0’ which 5130 do the same in order to reliably handle arbitrary file names (even 5131 those containing blanks or other special characters). Note with 5132 ‘-z’ the newline character is treated as a field separator. 5133 5134 An exit status of zero indicates success, and a nonzero value 5135indicates failure. 5136 5137 If the ‘--check-order’ option is given, unsorted inputs will cause a 5138fatal error message. If the option ‘--nocheck-order’ is given, unsorted 5139inputs will never cause an error message. If neither of these options 5140is given, wrongly sorted inputs are diagnosed only if an input file is 5141found to contain unpairable lines, and when both input files are non 5142empty. If an input file is diagnosed as being unsorted, the ‘join’ 5143command will exit with a nonzero status (and the output should not be 5144used). 5145 5146 Forcing ‘join’ to process wrongly sorted input files containing 5147unpairable lines by specifying ‘--nocheck-order’ is not guaranteed to 5148produce any particular output. The output will probably not correspond 5149with whatever you hoped it would be. 5150 5151 5152File: coreutils.info, Node: Sorting files for join, Next: Working with fields, Prev: General options in join, Up: join invocation 5153 51548.3.2 Pre-sorting 5155----------------- 5156 5157‘join’ requires sorted input files. Each input file should be sorted 5158according to the key (=field/column number) used in ‘join’. The 5159recommended sorting option is ‘sort -k 1b,1’ (assuming the desired key 5160is in the first column). 5161 5162Typical usage: 5163 $ sort -k 1b,1 file1 > file1.sorted 5164 $ sort -k 1b,1 file2 > file2.sorted 5165 $ join file1.sorted file2.sorted > file3 5166 5167 Normally, the sort order is that of the collating sequence specified 5168by the ‘LC_COLLATE’ locale. Unless the ‘-t’ option is given, the sort 5169comparison ignores blanks at the start of the join field, as in ‘sort 5170-b’. If the ‘--ignore-case’ option is given, the sort comparison 5171ignores the case of characters in the join field, as in ‘sort -f’: 5172 5173 $ sort -k 1bf,1 file1 > file1.sorted 5174 $ sort -k 1bf,1 file2 > file2.sorted 5175 $ join --ignore-case file1.sorted file2.sorted > file3 5176 5177 The ‘sort’ and ‘join’ commands should use consistent locales and 5178options if the output of ‘sort’ is fed to ‘join’. You can use a command 5179like ‘sort -k 1b,1’ to sort a file on its default join field, but if you 5180select a non-default locale, join field, separator, or comparison 5181options, then you should do so consistently between ‘join’ and ‘sort’. 5182 5183To avoid any locale-related issues, it is recommended to use the ‘C’ 5184locale for both commands: 5185 5186 $ LC_ALL=C sort -k 1b,1 file1 > file1.sorted 5187 $ LC_ALL=C sort -k 1b,1 file2 > file2.sorted 5188 $ LC_ALL=C join file1.sorted file2.sorted > file3 5189 5190 5191File: coreutils.info, Node: Working with fields, Next: Paired and unpaired lines, Prev: Sorting files for join, Up: join invocation 5192 51938.3.3 Working with fields 5194------------------------- 5195 5196Use ‘-1’,‘-2’ to set the key fields for each of the input files. Ensure 5197the preceding ‘sort’ commands operated on the same fields. 5198 5199The following example joins two files, using the values from seventh 5200field of the first file and the third field of the second file: 5201 5202 $ sort -k 7b,7 file1 > file1.sorted 5203 $ sort -k 3b,3 file2 > file2.sorted 5204 $ join -1 7 -2 3 file1.sorted file2.sorted > file3 5205 5206If the field number is the same for both files, use ‘-j’: 5207 5208 $ sort -k4b,4 file1 > file1.sorted 5209 $ sort -k4b,4 file2 > file2.sorted 5210 $ join -j4 file1.sorted file2.sorted > file3 5211 5212Both ‘sort’ and ‘join’ operate of whitespace-delimited fields. To 5213specify a different delimiter, use ‘-t’ in _both_: 5214 5215 $ sort -t, -k3b,3 file1 > file1.sorted 5216 $ sort -t, -k3b,3 file2 > file2.sorted 5217 $ join -t, -j3 file1.sorted file2.sorted > file3 5218 5219To specify a tab (ASCII 0x09) character instead of whitespace, use (1): 5220 5221 $ sort -t$'\t' -k3b,3 file1 > file1.sorted 5222 $ sort -t$'\t' -k3b,3 file2 > file2.sorted 5223 $ join -t$'\t' -j3 file1.sorted file2.sorted > file3 5224 5225If ‘join -t ''’ is specified then the whole line is considered which 5226matches the default operation of sort: 5227 5228 $ sort file1 > file1.sorted 5229 $ sort file2 > file2.sorted 5230 $ join -t '' file1.sorted file2.sorted > file3 5231 5232 ---------- Footnotes ---------- 5233 5234 (1) the ‘$'\t'’ is supported in most modern shells. For older 5235shells, use a literal tab 5236 5237 5238File: coreutils.info, Node: Paired and unpaired lines, Next: Header lines, Prev: Working with fields, Up: join invocation 5239 52408.3.4 Controlling ‘join’’s field matching 5241----------------------------------------- 5242 5243In this section the ‘sort’ commands are omitted for brevity. Sorting 5244the files before joining is still required. 5245 5246 ‘join’’s default behavior is to print only lines common to both input 5247files. Use ‘-a’ and ‘-v’ to print unpairable lines from one or both 5248files. 5249 5250All examples below use the following two (pre-sorted) input files: 5251 5252 $ cat file1 $ cat file2 5253 a 1 a A 5254 b 2 c C 5255 5256Command Outcome 5257 5258-------------------------------------------------------------------------- 5259 $ join file1 file2 common lines (_intersection_) 5260 a 1 A 5261 $ join -a 1 file1 file2 common lines _and_ unpaired lines 5262 a 1 A from the first file 5263 b 2 5264 $ join -a 2 file1 file2 common lines _and_ unpaired lines 5265 a 1 A from the second file 5266 c C 5267 $ join -a 1 -a 2 file1 file2 all lines (paired and unpaired) 5268 a 1 A from both files (_union_). 5269 b 2 see note below regarding ‘-o 5270 c C auto’. 5271 5272 $ join -v 1 file1 file2 unpaired lines from the first file 5273 b 2 (_difference_) 5274 5275 $ join -v 2 file1 file2 unpaired lines from the second 5276 c C file (_difference_) 5277 5278 $ join -v 1 -v 2 file1 file2 unpaired lines from both files, 5279 b 2 omitting common lines (_symmetric 5280 c C difference_). 5281 5282 5283The ‘-o auto -e X’ options are useful when dealing with unpaired lines. 5284The following example prints all lines (common and unpaired) from both 5285files. Without ‘-o auto’ it is not easy to discern which fields 5286originate from which file: 5287 5288 $ join -a 1 -a 2 file1 file2 5289 a 1 A 5290 b 2 5291 c C 5292 5293 $ join -o auto -e X -a 1 -a 2 file1 file2 5294 a 1 A 5295 b 2 X 5296 c X C 5297 5298 If the input has no unpairable lines, a GNU extension is available; 5299the sort order can be any order that considers two fields to be equal if 5300and only if the sort comparison described above considers them to be 5301equal. For example: 5302 5303 $ cat file1 5304 a a1 5305 c c1 5306 b b1 5307 5308 $ cat file2 5309 a a2 5310 c c2 5311 b b2 5312 5313 $ join file1 file2 5314 a a1 a2 5315 c c1 c2 5316 b b1 b2 5317 5318 5319File: coreutils.info, Node: Header lines, Next: Set operations, Prev: Paired and unpaired lines, Up: join invocation 5320 53218.3.5 Header lines 5322------------------ 5323 5324The ‘--header’ option can be used when the files to join have a header 5325line which is not sorted: 5326 5327 $ cat file1 5328 Name Age 5329 Alice 25 5330 Charlie 34 5331 5332 $ cat file2 5333 Name Country 5334 Alice France 5335 Bob Spain 5336 5337 $ join --header -o auto -e NA -a1 -a2 file1 file2 5338 Name Age Country 5339 Alice 25 France 5340 Bob NA Spain 5341 Charlie 34 NA 5342 5343 To sort a file with a header line, use GNU ‘sed -u’. The following 5344example sort the files but keeps the first line of each file in place: 5345 5346 $ ( sed -u 1q ; sort -k2b,2 ) < file1 > file1.sorted 5347 $ ( sed -u 1q ; sort -k2b,2 ) < file2 > file2.sorted 5348 $ join --header -o auto -e NA -a1 -a2 file1.sorted file2.sorted > file3 5349 5350 5351File: coreutils.info, Node: Set operations, Prev: Header lines, Up: join invocation 5352 53538.3.6 Union, Intersection and Difference of files 5354------------------------------------------------- 5355 5356Combine ‘sort’, ‘uniq’ and ‘join’ to perform the equivalent of set 5357operations on files: 5358 5359Command outcome 5360-------------------------------------------------------------------------- 5361‘sort -u file1 file2’ Union of unsorted files 5362 5363‘sort file1 file2 | uniq -d’ Intersection of unsorted files 5364 5365‘sort file1 file1 file2 | uniq -u’ Difference of unsorted files 5366 5367‘sort file1 file2 | uniq -u’ Symmetric Difference of unsorted 5368 files 5369 5370‘join -t '' -a1 -a2 file1 file2’ Union of sorted files 5371 5372‘join -t '' file1 file2’ Intersection of sorted files 5373 5374‘join -t '' -v2 file1 file2’ Difference of sorted files 5375 5376‘join -t '' -v1 -v2 file1 file2’ Symmetric Difference of sorted 5377 files 5378 5379 5380 All examples above operate on entire lines and not on specific 5381fields: ‘sort’ without ‘-k’ and ‘join -t ''’ both consider entire lines 5382as the key. 5383 5384 5385File: coreutils.info, Node: Operating on characters, Next: Directory listing, Prev: Operating on fields, Up: Top 5386 53879 Operating on characters 5388************************* 5389 5390These commands operate on individual characters. 5391 5392* Menu: 5393 5394* tr invocation:: Translate, squeeze, and/or delete characters. 5395* expand invocation:: Convert tabs to spaces. 5396* unexpand invocation:: Convert spaces to tabs. 5397 5398 5399File: coreutils.info, Node: tr invocation, Next: expand invocation, Up: Operating on characters 5400 54019.1 ‘tr’: Translate, squeeze, and/or delete characters 5402====================================================== 5403 5404Synopsis: 5405 5406 tr [OPTION]... SET1 [SET2] 5407 5408 ‘tr’ copies standard input to standard output, performing one of the 5409following operations: 5410 5411 • translate, and optionally squeeze repeated characters in the 5412 result, 5413 • squeeze repeated characters, 5414 • delete characters, 5415 • delete characters, then squeeze repeated characters from the 5416 result. 5417 5418 The SET1 and (if given) SET2 arguments define ordered sets of 5419characters, referred to below as SET1 and SET2. These sets are the 5420characters of the input that ‘tr’ operates on. The ‘--complement’ 5421(‘-c’, ‘-C’) option replaces SET1 with its complement (all of the 5422characters that are not in SET1). 5423 5424 Currently ‘tr’ fully supports only single-byte characters. 5425Eventually it will support multibyte characters; when it does, the ‘-C’ 5426option will cause it to complement the set of characters, whereas ‘-c’ 5427will cause it to complement the set of values. This distinction will 5428matter only when some values are not characters, and this is possible 5429only in locales using multibyte encodings when the input contains 5430encoding errors. 5431 5432 The program accepts the ‘--help’ and ‘--version’ options. *Note 5433Common options::. Options must precede operands. 5434 5435 An exit status of zero indicates success, and a nonzero value 5436indicates failure. 5437 5438* Menu: 5439 5440* Character sets:: Specifying sets of characters. 5441* Translating:: Changing one set of characters to another. 5442* Squeezing and deleting:: Removing characters. 5443 5444 5445File: coreutils.info, Node: Character sets, Next: Translating, Up: tr invocation 5446 54479.1.1 Specifying sets of characters 5448----------------------------------- 5449 5450The format of the SET1 and SET2 arguments resembles the format of 5451regular expressions; however, they are not regular expressions, only 5452lists of characters. Most characters simply represent themselves in 5453these strings, but the strings can contain the shorthands listed below, 5454for convenience. Some of them can be used only in SET1 or SET2, as 5455noted below. 5456 5457Backslash escapes 5458 5459 The following backslash escape sequences are recognized: 5460 5461 ‘\a’ 5462 Control-G. 5463 ‘\b’ 5464 Control-H. 5465 ‘\f’ 5466 Control-L. 5467 ‘\n’ 5468 Control-J. 5469 ‘\r’ 5470 Control-M. 5471 ‘\t’ 5472 Control-I. 5473 ‘\v’ 5474 Control-K. 5475 ‘\OOO’ 5476 The 8-bit character with the value given by OOO, which is 1 to 5477 3 octal digits. Note that ‘\400’ is interpreted as the 5478 two-byte sequence, ‘\040’ ‘0’. 5479 ‘\\’ 5480 A backslash. 5481 5482 While a backslash followed by a character not listed above is 5483 interpreted as that character, the backslash also effectively 5484 removes any special significance, so it is useful to escape ‘[’, 5485 ‘]’, ‘*’, and ‘-’. 5486 5487Ranges 5488 5489 The notation ‘M-N’ expands to all of the characters from M through 5490 N, in ascending order. M should collate before N; if it doesn’t, 5491 an error results. As an example, ‘0-9’ is the same as 5492 ‘0123456789’. 5493 5494 GNU ‘tr’ does not support the System V syntax that uses square 5495 brackets to enclose ranges. Translations specified in that format 5496 sometimes work as expected, since the brackets are often 5497 transliterated to themselves. However, they should be avoided 5498 because they sometimes behave unexpectedly. For example, ‘tr -d 5499 '[0-9]'’ deletes brackets as well as digits. 5500 5501 Many historically common and even accepted uses of ranges are not 5502 portable. For example, on EBCDIC hosts using the ‘A-Z’ range will 5503 not do what most would expect because ‘A’ through ‘Z’ are not 5504 contiguous as they are in ASCII. If you can rely on a POSIX 5505 compliant version of ‘tr’, then the best way to work around this is 5506 to use character classes (see below). Otherwise, it is most 5507 portable (and most ugly) to enumerate the members of the ranges. 5508 5509Repeated characters 5510 5511 The notation ‘[C*N]’ in SET2 expands to N copies of character C. 5512 Thus, ‘[y*6]’ is the same as ‘yyyyyy’. The notation ‘[C*]’ in 5513 STRING2 expands to as many copies of C as are needed to make SET2 5514 as long as SET1. If N begins with ‘0’, it is interpreted in octal, 5515 otherwise in decimal. 5516 5517Character classes 5518 5519 The notation ‘[:CLASS:]’ expands to all of the characters in the 5520 (predefined) class CLASS. The characters expand in no particular 5521 order, except for the ‘upper’ and ‘lower’ classes, which expand in 5522 ascending order. When the ‘--delete’ (‘-d’) and 5523 ‘--squeeze-repeats’ (‘-s’) options are both given, any character 5524 class can be used in SET2. Otherwise, only the character classes 5525 ‘lower’ and ‘upper’ are accepted in SET2, and then only if the 5526 corresponding character class (‘upper’ and ‘lower’, respectively) 5527 is specified in the same relative position in SET1. Doing this 5528 specifies case conversion. The class names are given below; an 5529 error results when an invalid class name is given. 5530 5531 ‘alnum’ 5532 Letters and digits. 5533 ‘alpha’ 5534 Letters. 5535 ‘blank’ 5536 Horizontal whitespace. 5537 ‘cntrl’ 5538 Control characters. 5539 ‘digit’ 5540 Digits. 5541 ‘graph’ 5542 Printable characters, not including space. 5543 ‘lower’ 5544 Lowercase letters. 5545 ‘print’ 5546 Printable characters, including space. 5547 ‘punct’ 5548 Punctuation characters. 5549 ‘space’ 5550 Horizontal or vertical whitespace. 5551 ‘upper’ 5552 Uppercase letters. 5553 ‘xdigit’ 5554 Hexadecimal digits. 5555 5556Equivalence classes 5557 5558 The syntax ‘[=C=]’ expands to all of the characters that are 5559 equivalent to C, in no particular order. Equivalence classes are a 5560 relatively recent invention intended to support non-English 5561 alphabets. But there seems to be no standard way to define them or 5562 determine their contents. Therefore, they are not fully 5563 implemented in GNU ‘tr’; each character’s equivalence class 5564 consists only of that character, which is of no particular use. 5565 5566 5567File: coreutils.info, Node: Translating, Next: Squeezing and deleting, Prev: Character sets, Up: tr invocation 5568 55699.1.2 Translating 5570----------------- 5571 5572‘tr’ performs translation when SET1 and SET2 are both given and the 5573‘--delete’ (‘-d’) option is not given. ‘tr’ translates each character 5574of its input that is in SET1 to the corresponding character in SET2. 5575Characters not in SET1 are passed through unchanged. When a character 5576appears more than once in SET1 and the corresponding characters in SET2 5577are not all the same, only the final one is used. For example, these 5578two commands are equivalent: 5579 5580 tr aaa xyz 5581 tr a z 5582 5583 A common use of ‘tr’ is to convert lowercase characters to uppercase. 5584This can be done in many ways. Here are three of them: 5585 5586 tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ 5587 tr a-z A-Z 5588 tr '[:lower:]' '[:upper:]' 5589 5590But note that using ranges like ‘a-z’ above is not portable. 5591 5592 When ‘tr’ is performing translation, SET1 and SET2 typically have the 5593same length. If SET1 is shorter than SET2, the extra characters at the 5594end of SET2 are ignored. 5595 5596 On the other hand, making SET1 longer than SET2 is not portable; 5597POSIX says that the result is undefined. In this situation, BSD ‘tr’ 5598pads SET2 to the length of SET1 by repeating the last character of SET2 5599as many times as necessary. System V ‘tr’ truncates SET1 to the length 5600of SET2. 5601 5602 By default, GNU ‘tr’ handles this case like BSD ‘tr’. When the 5603‘--truncate-set1’ (‘-t’) option is given, GNU ‘tr’ handles this case 5604like the System V ‘tr’ instead. This option is ignored for operations 5605other than translation. 5606 5607 Acting like System V ‘tr’ in this case breaks the relatively common 5608BSD idiom: 5609 5610 tr -cs A-Za-z0-9 '\012' 5611 5612because it converts only zero bytes (the first element in the complement 5613of SET1), rather than all non-alphanumerics, to newlines. 5614 5615By the way, the above idiom is not portable because it uses ranges, and 5616it assumes that the octal code for newline is 012. Assuming a POSIX 5617compliant ‘tr’, here is a better way to write it: 5618 5619 tr -cs '[:alnum:]' '[\n*]' 5620 5621 5622File: coreutils.info, Node: Squeezing and deleting, Prev: Translating, Up: tr invocation 5623 56249.1.3 Squeezing repeats and deleting 5625------------------------------------ 5626 5627When given just the ‘--delete’ (‘-d’) option, ‘tr’ removes any input 5628characters that are in SET1. 5629 5630 When given just the ‘--squeeze-repeats’ (‘-s’) option and not 5631translating, ‘tr’ replaces each input sequence of a repeated character 5632that is in SET1 with a single occurrence of that character. 5633 5634 When given both ‘--delete’ and ‘--squeeze-repeats’, ‘tr’ first 5635performs any deletions using SET1, then squeezes repeats from any 5636remaining characters using SET2. 5637 5638 The ‘--squeeze-repeats’ option may also be used when translating, in 5639which case ‘tr’ first performs translation, then squeezes repeats from 5640any remaining characters using SET2. 5641 5642 Here are some examples to illustrate various combinations of options: 5643 5644 • Remove all zero bytes: 5645 5646 tr -d '\0' 5647 5648 • Put all words on lines by themselves. This converts all 5649 non-alphanumeric characters to newlines, then squeezes each string 5650 of repeated newlines into a single newline: 5651 5652 tr -cs '[:alnum:]' '[\n*]' 5653 5654 • Convert each sequence of repeated newlines to a single newline. 5655 I.e., delete blank lines: 5656 5657 tr -s '\n' 5658 5659 • Find doubled occurrences of words in a document. For example, 5660 people often write “the the” with the repeated words separated by a 5661 newline. The Bourne shell script below works first by converting 5662 each sequence of punctuation and blank characters to a single 5663 newline. That puts each “word” on a line by itself. Next it maps 5664 all uppercase characters to lower case, and finally it runs ‘uniq’ 5665 with the ‘-d’ option to print out only the words that were 5666 repeated. 5667 5668 #!/bin/sh 5669 cat -- "$@" \ 5670 | tr -s '[:punct:][:blank:]' '[\n*]' \ 5671 | tr '[:upper:]' '[:lower:]' \ 5672 | uniq -d 5673 5674 • Deleting a small set of characters is usually straightforward. For 5675 example, to remove all ‘a’s, ‘x’s, and ‘M’s you would do this: 5676 5677 tr -d axM 5678 5679 However, when ‘-’ is one of those characters, it can be tricky 5680 because ‘-’ has special meanings. Performing the same task as 5681 above but also removing all ‘-’ characters, we might try ‘tr -d 5682 -axM’, but that would fail because ‘tr’ would try to interpret ‘-a’ 5683 as a command-line option. Alternatively, we could try putting the 5684 hyphen inside the string, ‘tr -d a-xM’, but that wouldn’t work 5685 either because it would make ‘tr’ interpret ‘a-x’ as the range of 5686 characters ‘a’...‘x’ rather than the three. One way to solve the 5687 problem is to put the hyphen at the end of the list of characters: 5688 5689 tr -d axM- 5690 5691 Or you can use ‘--’ to terminate option processing: 5692 5693 tr -d -- -axM 5694 5695 More generally, use the character class notation ‘[=c=]’ with ‘-’ 5696 (or any other character) in place of the ‘c’: 5697 5698 tr -d '[=-=]axM' 5699 5700 Note how single quotes are used in the above example to protect the 5701 square brackets from interpretation by a shell. 5702 5703 5704File: coreutils.info, Node: expand invocation, Next: unexpand invocation, Prev: tr invocation, Up: Operating on characters 5705 57069.2 ‘expand’: Convert tabs to spaces 5707==================================== 5708 5709‘expand’ writes the contents of each given FILE, or standard input if 5710none are given or for a FILE of ‘-’, to standard output, with tab 5711characters converted to the appropriate number of spaces. Synopsis: 5712 5713 expand [OPTION]... [FILE]... 5714 5715 By default, ‘expand’ converts all tabs to spaces. It preserves 5716backspace characters in the output; they decrement the column count for 5717tab calculations. The default action is equivalent to ‘-t 8’ (set tabs 5718every 8 columns). 5719 5720 The program accepts the following options. Also see *note Common 5721options::. 5722 5723‘-t TAB1[,TAB2]...’ 5724‘--tabs=TAB1[,TAB2]...’ 5725 If only one tab stop is given, set the tabs TAB1 spaces apart 5726 (default is 8). Otherwise, set the tabs at columns TAB1, TAB2, ... 5727 (numbered from 0), and replace any tabs beyond the last tab stop 5728 given with single spaces. Tab stops can be separated by blanks as 5729 well as by commas. 5730 5731 As a GNU extension the last TAB specified can be prefixed with a 5732 ‘/’ to indicate a tab size to use for remaining positions. For 5733 example, ‘--tabs=2,4,/8’ will set tab stops at position 2 and 4, 5734 and every multiple of 8 after that. 5735 5736 Also the last TAB specified can be prefixed with a ‘+’ to indicate 5737 a tab size to use for remaining positions, offset from the final 5738 explicitly specified tab stop. For example, to ignore the 1 5739 character gutter present in diff output, one can specify a 1 5740 character offset using ‘--tabs=1,+8’, which will set tab stops at 5741 positions 1,9,17,... 5742 5743 For compatibility, GNU ‘expand’ also accepts the obsolete option 5744 syntax, ‘-T1[,T2]...’. New scripts should use ‘-t T1[,T2]...’ 5745 instead. 5746 5747‘-i’ 5748‘--initial’ 5749 Only convert initial tabs (those that precede all non-space or 5750 non-tab characters) on each line to spaces. 5751 5752 An exit status of zero indicates success, and a nonzero value 5753indicates failure. 5754 5755 5756File: coreutils.info, Node: unexpand invocation, Prev: expand invocation, Up: Operating on characters 5757 57589.3 ‘unexpand’: Convert spaces to tabs 5759====================================== 5760 5761‘unexpand’ writes the contents of each given FILE, or standard input if 5762none are given or for a FILE of ‘-’, to standard output, converting 5763blanks at the beginning of each line into as many tab characters as 5764needed. In the default POSIX locale, a “blank” is a space or a tab; 5765other locales may specify additional blank characters. Synopsis: 5766 5767 unexpand [OPTION]... [FILE]... 5768 5769 By default, ‘unexpand’ converts only initial blanks (those that 5770precede all non-blank characters) on each line. It preserves backspace 5771characters in the output; they decrement the column count for tab 5772calculations. By default, tabs are set at every 8th column. 5773 5774 The program accepts the following options. Also see *note Common 5775options::. 5776 5777‘-t TAB1[,TAB2]...’ 5778‘--tabs=TAB1[,TAB2]...’ 5779 If only one tab stop is given, set the tabs TAB1 columns apart 5780 instead of the default 8. Otherwise, set the tabs at columns TAB1, 5781 TAB2, ... (numbered from 0), and leave blanks beyond the tab stops 5782 given unchanged. Tab stops can be separated by blanks as well as 5783 by commas. 5784 5785 As a GNU extension the last TAB specified can be prefixed with a 5786 ‘/’ to indicate a tab size to use for remaining positions. For 5787 example, ‘--tabs=2,4,/8’ will set tab stops at position 2 and 4, 5788 and every multiple of 8 after that. 5789 5790 Also the last TAB specified can be prefixed with a ‘+’ to indicate 5791 a tab size to use for remaining positions, offset from the final 5792 explicitly specified tab stop. For example, to ignore the 1 5793 character gutter present in diff output, one can specify a 1 5794 character offset using ‘--tabs=1,+8’, which will set tab stops at 5795 positions 1,9,17,... 5796 5797 This option implies the ‘-a’ option. 5798 5799 For compatibility, GNU ‘unexpand’ supports the obsolete option 5800 syntax, ‘-TAB1[,TAB2]...’, where tab stops must be separated by 5801 commas. (Unlike ‘-t’, this obsolete option does not imply ‘-a’.) 5802 New scripts should use ‘--first-only -t TAB1[,TAB2]...’ instead. 5803 5804‘-a’ 5805‘--all’ 5806 Also convert all sequences of two or more blanks just before a tab 5807 stop, even if they occur after non-blank characters in a line. 5808 5809 An exit status of zero indicates success, and a nonzero value 5810indicates failure. 5811 5812 5813File: coreutils.info, Node: Directory listing, Next: Basic operations, Prev: Operating on characters, Up: Top 5814 581510 Directory listing 5816******************** 5817 5818This chapter describes the ‘ls’ command and its variants ‘dir’ and 5819‘vdir’, which list information about files. 5820 5821* Menu: 5822 5823* ls invocation:: List directory contents. 5824* dir invocation:: Briefly ls. 5825* vdir invocation:: Verbosely ls. 5826* dircolors invocation:: Color setup for ls, etc. 5827 5828 5829File: coreutils.info, Node: ls invocation, Next: dir invocation, Up: Directory listing 5830 583110.1 ‘ls’: List directory contents 5832================================== 5833 5834The ‘ls’ program lists information about files (of any type, including 5835directories). Options and file arguments can be intermixed arbitrarily, 5836as usual. 5837 5838 For non-option command-line arguments that are directories, by 5839default ‘ls’ lists the contents of directories, not recursively, and 5840omitting files with names beginning with ‘.’. For other non-option 5841arguments, by default ‘ls’ lists just the file name. If no non-option 5842argument is specified, ‘ls’ operates on the current directory, acting as 5843if it had been invoked with a single argument of ‘.’. 5844 5845 By default, the output is sorted alphabetically, according to the 5846locale settings in effect.(1) If standard output is a terminal, the 5847output is in columns (sorted vertically) and control characters are 5848output as question marks; otherwise, the output is listed one per line 5849and control characters are output as-is. 5850 5851 Because ‘ls’ is such a fundamental program, it has accumulated many 5852options over the years. They are described in the subsections below; 5853within each section, options are listed alphabetically (ignoring case). 5854The division of options into the subsections is not absolute, since some 5855options affect more than one aspect of ‘ls’’s operation. 5856 5857 Exit status: 5858 5859 0 success 5860 1 minor problems (e.g., failure to access a file or directory not 5861 specified as a command line argument. This happens when listing a 5862 directory in which entries are actively being removed or renamed.) 5863 2 serious trouble (e.g., memory exhausted, invalid option, failure 5864 to access a file or directory specified as a command line argument 5865 or a directory loop) 5866 5867 Also see *note Common options::. 5868 5869* Menu: 5870 5871* Which files are listed:: 5872* What information is listed:: 5873* Sorting the output:: 5874* General output formatting:: 5875* Formatting file timestamps:: 5876* Formatting the file names:: 5877 5878 ---------- Footnotes ---------- 5879 5880 (1) If you use a non-POSIX locale (e.g., by setting ‘LC_ALL’ to 5881‘en_US’), then ‘ls’ may produce output that is sorted differently than 5882you’re accustomed to. In that case, set the ‘LC_ALL’ environment 5883variable to ‘C’. 5884 5885 5886File: coreutils.info, Node: Which files are listed, Next: What information is listed, Up: ls invocation 5887 588810.1.1 Which files are listed 5889----------------------------- 5890 5891These options determine which files ‘ls’ lists information for. By 5892default, ‘ls’ lists files and the contents of any directories on the 5893command line, except that in directories it ignores files whose names 5894start with ‘.’. 5895 5896‘-a’ 5897‘--all’ 5898 In directories, do not ignore file names that start with ‘.’. 5899 5900‘-A’ 5901‘--almost-all’ 5902 In directories, do not ignore all file names that start with ‘.’; 5903 ignore only ‘.’ and ‘..’. The ‘--all’ (‘-a’) option overrides this 5904 option. 5905 5906‘-B’ 5907‘--ignore-backups’ 5908 In directories, ignore files that end with ‘~’. This option is 5909 equivalent to ‘--ignore='*~' --ignore='.*~'’. 5910 5911‘-d’ 5912‘--directory’ 5913 List just the names of directories, as with other types of files, 5914 rather than listing their contents. Do not follow symbolic links 5915 listed on the command line unless the ‘--dereference-command-line’ 5916 (‘-H’), ‘--dereference’ (‘-L’), or 5917 ‘--dereference-command-line-symlink-to-dir’ options are specified. 5918 5919‘-H’ 5920‘--dereference-command-line’ 5921 If a command line argument specifies a symbolic link, show 5922 information for the file the link references rather than for the 5923 link itself. 5924 5925‘--dereference-command-line-symlink-to-dir’ 5926 Do not dereference symbolic links, with one exception: if a command 5927 line argument specifies a symbolic link that refers to a directory, 5928 show information for that directory rather than for the link 5929 itself. This is the default behavior when no other 5930 dereferencing-related option has been specified (‘--classify’ 5931 (‘-F’), ‘--directory’ (‘-d’), (‘-l’), ‘--dereference’ (‘-L’), or 5932 ‘--dereference-command-line’ (‘-H’)). 5933 5934‘--group-directories-first’ 5935 Group all the directories before the files and then sort the 5936 directories and the files separately using the selected sort key 5937 (see –sort option). That is, this option specifies a primary sort 5938 key, and the –sort option specifies a secondary key. However, any 5939 use of ‘--sort=none’ (‘-U’) disables this option altogether. 5940 5941‘--hide=PATTERN’ 5942 In directories, ignore files whose names match the shell pattern 5943 PATTERN, unless the ‘--all’ (‘-a’) or ‘--almost-all’ (‘-A’) is also 5944 given. This option acts like ‘--ignore=PATTERN’ except that it has 5945 no effect if ‘--all’ (‘-a’) or ‘--almost-all’ (‘-A’) is also given. 5946 5947 This option can be useful in shell aliases. For example, if ‘lx’ 5948 is an alias for ‘ls --hide='*~'’ and ‘ly’ is an alias for ‘ls 5949 --ignore='*~'’, then the command ‘lx -A’ lists the file ‘README~’ 5950 even though ‘ly -A’ would not. 5951 5952‘-I PATTERN’ 5953‘--ignore=PATTERN’ 5954 In directories, ignore files whose names match the shell pattern 5955 (not regular expression) PATTERN. As in the shell, an initial ‘.’ 5956 in a file name does not match a wildcard at the start of PATTERN. 5957 Sometimes it is useful to give this option several times. For 5958 example, 5959 5960 $ ls --ignore='.??*' --ignore='.[^.]' --ignore='#*' 5961 5962 The first option ignores names of length 3 or more that start with 5963 ‘.’, the second ignores all two-character names that start with ‘.’ 5964 except ‘..’, and the third ignores names that start with ‘#’. 5965 5966‘-L’ 5967‘--dereference’ 5968 When showing file information for a symbolic link, show information 5969 for the file the link references rather than the link itself. 5970 However, even with this option, ‘ls’ still prints the name of the 5971 link itself, not the name of the file that the link points to. 5972 5973‘-R’ 5974‘--recursive’ 5975 List the contents of all directories recursively. 5976 5977 5978File: coreutils.info, Node: What information is listed, Next: Sorting the output, Prev: Which files are listed, Up: ls invocation 5979 598010.1.2 What information is listed 5981--------------------------------- 5982 5983These options affect the information that ‘ls’ displays. By default, 5984only file names are shown. 5985 5986‘--author’ 5987 List each file’s author when producing long format directory 5988 listings. In GNU/Hurd, file authors can differ from their owners, 5989 but in other operating systems the two are the same. 5990 5991‘-D’ 5992‘--dired’ 5993 With the long listing (‘-l’) format, print an additional line after 5994 the main output: 5995 5996 //DIRED// BEG1 END1 BEG2 END2 ... 5997 5998 The BEGN and ENDN are unsigned integers that record the byte 5999 position of the beginning and end of each file name in the output. 6000 This makes it easy for Emacs to find the names, even when they 6001 contain unusual characters such as space or newline, without fancy 6002 searching. 6003 6004 If directories are being listed recursively (‘-R’), output a 6005 similar line with offsets for each subdirectory name: 6006 6007 //SUBDIRED// BEG1 END1 ... 6008 6009 Finally, output a line of the form: 6010 6011 //DIRED-OPTIONS// --quoting-style=WORD 6012 6013 where WORD is the quoting style (*note Formatting the file 6014 names::). 6015 6016 Here is an actual example: 6017 6018 $ mkdir -p a/sub/deeper a/sub2 6019 $ touch a/f1 a/f2 6020 $ touch a/sub/deeper/file 6021 $ ls -gloRF --dired a 6022 a: 6023 total 8 6024 -rw-r--r-- 1 0 Jun 10 12:27 f1 6025 -rw-r--r-- 1 0 Jun 10 12:27 f2 6026 drwxr-xr-x 3 4096 Jun 10 12:27 sub/ 6027 drwxr-xr-x 2 4096 Jun 10 12:27 sub2/ 6028 6029 a/sub: 6030 total 4 6031 drwxr-xr-x 2 4096 Jun 10 12:27 deeper/ 6032 6033 a/sub/deeper: 6034 total 0 6035 -rw-r--r-- 1 0 Jun 10 12:27 file 6036 6037 a/sub2: 6038 total 0 6039 //DIRED// 48 50 84 86 120 123 158 162 217 223 282 286 6040 //SUBDIRED// 2 3 167 172 228 240 290 296 6041 //DIRED-OPTIONS// --quoting-style=literal 6042 6043 Note that the pairs of offsets on the ‘//DIRED//’ line above 6044 delimit these names: ‘f1’, ‘f2’, ‘sub’, ‘sub2’, ‘deeper’, ‘file’. 6045 The offsets on the ‘//SUBDIRED//’ line delimit the following 6046 directory names: ‘a’, ‘a/sub’, ‘a/sub/deeper’, ‘a/sub2’. 6047 6048 Here is an example of how to extract the fifth entry name, 6049 ‘deeper’, corresponding to the pair of offsets, 222 and 228: 6050 6051 $ ls -gloRF --dired a > out 6052 $ dd bs=1 skip=222 count=6 < out 2>/dev/null; echo 6053 deeper 6054 6055 Note that although the listing above includes a trailing slash for 6056 the ‘deeper’ entry, the offsets select the name without the 6057 trailing slash. However, if you invoke ‘ls’ with ‘--dired’ along 6058 with an option like ‘--escape’ (aka ‘-b’) and operate on a file 6059 whose name contains special characters, notice that the backslash 6060 _is_ included: 6061 6062 $ touch 'a b' 6063 $ ls -blog --dired 'a b' 6064 -rw-r--r-- 1 0 Jun 10 12:28 a\ b 6065 //DIRED// 30 34 6066 //DIRED-OPTIONS// --quoting-style=escape 6067 6068 If you use a quoting style that adds quote marks (e.g., 6069 ‘--quoting-style=c’), then the offsets include the quote marks. So 6070 beware that the user may select the quoting style via the 6071 environment variable ‘QUOTING_STYLE’. Hence, applications using 6072 ‘--dired’ should either specify an explicit 6073 ‘--quoting-style=literal’ option (aka ‘-N’ or ‘--literal’) on the 6074 command line, or else be prepared to parse the escaped names. 6075 6076‘--full-time’ 6077 Produce long format directory listings, and list times in full. It 6078 is equivalent to using ‘--format=long’ with ‘--time-style=full-iso’ 6079 (*note Formatting file timestamps::). 6080 6081‘-g’ 6082 Produce long format directory listings, but don’t display owner 6083 information. 6084 6085‘-G’ 6086‘--no-group’ 6087 Inhibit display of group information in a long format directory 6088 listing. (This is the default in some non-GNU versions of ‘ls’, so 6089 we provide this option for compatibility.) 6090 6091‘-h’ 6092‘--human-readable’ 6093 Append a size letter to each size, such as ‘M’ for mebibytes. 6094 Powers of 1024 are used, not 1000; ‘M’ stands for 1,048,576 bytes. 6095 This option is equivalent to ‘--block-size=human-readable’. Use 6096 the ‘--si’ option if you prefer powers of 1000. 6097 6098‘-i’ 6099‘--inode’ 6100 Print the inode number (also called the file serial number and 6101 index number) of each file to the left of the file name. (This 6102 number uniquely identifies each file within a particular file 6103 system.) 6104 6105‘-l’ 6106‘--format=long’ 6107‘--format=verbose’ 6108 In addition to the name of each file, print the file type, file 6109 mode bits, number of hard links, owner name, group name, size, and 6110 timestamp (*note Formatting file timestamps::), normally the 6111 modification timestamp (the mtime, *note File timestamps::). If 6112 the owner or group name cannot be determined, print the owner or 6113 group ID instead, right-justified as a cue that it is a number 6114 rather than a textual name. Print question marks for other 6115 information that cannot be determined. 6116 6117 Normally the size is printed as a byte count without punctuation, 6118 but this can be overridden (*note Block size::). For example, ‘-h’ 6119 prints an abbreviated, human-readable count, and 6120 ‘--block-size="'1"’ prints a byte count with the thousands 6121 separator of the current locale. 6122 6123 For each directory that is listed, preface the files with a line 6124 ‘total BLOCKS’, where BLOCKS is the total disk allocation for all 6125 files in that directory. The block size currently defaults to 1024 6126 bytes, but this can be overridden (*note Block size::). The BLOCKS 6127 computed counts each hard link separately; this is arguably a 6128 deficiency. 6129 6130 The file type is one of the following characters: 6131 6132 ‘-’ 6133 regular file 6134 ‘b’ 6135 block special file 6136 ‘c’ 6137 character special file 6138 ‘C’ 6139 high performance (“contiguous data”) file 6140 ‘d’ 6141 directory 6142 ‘D’ 6143 door (Solaris 2.5 and up) 6144 ‘l’ 6145 symbolic link 6146 ‘M’ 6147 off-line (“migrated”) file (Cray DMF) 6148 ‘n’ 6149 network special file (HP-UX) 6150 ‘p’ 6151 FIFO (named pipe) 6152 ‘P’ 6153 port (Solaris 10 and up) 6154 ‘s’ 6155 socket 6156 ‘?’ 6157 some other file type 6158 6159 The file mode bits listed are similar to symbolic mode 6160 specifications (*note Symbolic Modes::). But ‘ls’ combines 6161 multiple bits into the third character of each set of permissions 6162 as follows: 6163 6164 ‘s’ 6165 If the set-user-ID or set-group-ID bit and the corresponding 6166 executable bit are both set. 6167 6168 ‘S’ 6169 If the set-user-ID or set-group-ID bit is set but the 6170 corresponding executable bit is not set. 6171 6172 ‘t’ 6173 If the restricted deletion flag or sticky bit, and the 6174 other-executable bit, are both set. The restricted deletion 6175 flag is another name for the sticky bit. *Note Mode 6176 Structure::. 6177 6178 ‘T’ 6179 If the restricted deletion flag or sticky bit is set but the 6180 other-executable bit is not set. 6181 6182 ‘x’ 6183 If the executable bit is set and none of the above apply. 6184 6185 ‘-’ 6186 Otherwise. 6187 6188 Following the file mode bits is a single character that specifies 6189 whether an alternate access method such as an access control list 6190 applies to the file. When the character following the file mode 6191 bits is a space, there is no alternate access method. When it is a 6192 printing character, then there is such a method. 6193 6194 GNU ‘ls’ uses a ‘.’ character to indicate a file with a security 6195 context, but no other alternate access method. 6196 6197 A file with any other combination of alternate access methods is 6198 marked with a ‘+’ character. 6199 6200‘-n’ 6201‘--numeric-uid-gid’ 6202 Produce long format directory listings, but display right-justified 6203 numeric user and group IDs instead of left-justified owner and 6204 group names. 6205 6206‘-o’ 6207 Produce long format directory listings, but don’t display group 6208 information. It is equivalent to using ‘--format=long’ with 6209 ‘--no-group’ . 6210 6211‘-s’ 6212‘--size’ 6213 Print the disk allocation of each file to the left of the file 6214 name. This is the amount of disk space used by the file, which is 6215 usually a bit more than the file’s size, but it can be less if the 6216 file has holes. 6217 6218 Normally the disk allocation is printed in units of 1024 bytes, but 6219 this can be overridden (*note Block size::). 6220 6221 For files that are NFS-mounted from an HP-UX system to a BSD 6222 system, this option reports sizes that are half the correct values. 6223 On HP-UX systems, it reports sizes that are twice the correct 6224 values for files that are NFS-mounted from BSD systems. This is 6225 due to a flaw in HP-UX; it also affects the HP-UX ‘ls’ program. 6226 6227‘--si’ 6228 Append an SI-style abbreviation to each size, such as ‘M’ for 6229 megabytes. Powers of 1000 are used, not 1024; ‘M’ stands for 6230 1,000,000 bytes. This option is equivalent to ‘--block-size=si’. 6231 Use the ‘-h’ or ‘--human-readable’ option if you prefer powers of 6232 1024. 6233 6234‘-Z’ 6235‘--context’ 6236 Display the SELinux security context or ‘?’ if none is found. When 6237 used with the ‘-l’ option, print the security context to the left 6238 of the size column. 6239 6240 6241File: coreutils.info, Node: Sorting the output, Next: General output formatting, Prev: What information is listed, Up: ls invocation 6242 624310.1.3 Sorting the output 6244------------------------- 6245 6246These options change the order in which ‘ls’ sorts the information it 6247outputs. By default, sorting is done by character code (e.g., ASCII 6248order). 6249 6250‘-c’ 6251‘--time=ctime’ 6252‘--time=status’ 6253 If the long listing format (e.g., ‘-l’, ‘-o’) is being used, print 6254 the status change timestamp (the ctime) instead of the mtime. When 6255 explicitly sorting by time (‘--sort=time’ or ‘-t’) or when not 6256 using a long listing format, sort according to the ctime. *Note 6257 File timestamps::. 6258 6259‘-f’ 6260 Primarily, like ‘-U’—do not sort; list the files in whatever order 6261 they are stored in the directory. But also enable ‘-a’ (list all 6262 files) and disable ‘-l’, ‘--color’, and ‘-s’ (if they were 6263 specified before the ‘-f’). 6264 6265‘-r’ 6266‘--reverse’ 6267 Reverse whatever the sorting method is—e.g., list files in reverse 6268 alphabetical order, youngest first, smallest first, or whatever. 6269 6270‘-S’ 6271‘--sort=size’ 6272 Sort by file size, largest first. 6273 6274‘-t’ 6275‘--sort=time’ 6276 Sort by modification timestamp (mtime) by default, newest first. 6277 The timestamp to order by can be changed with the ‘--time’ option. 6278 *Note File timestamps::. 6279 6280‘-u’ 6281‘--time=atime’ 6282‘--time=access’ 6283‘--time=use’ 6284 If the long listing format (e.g., ‘--format=long’) is being used, 6285 print the last access timestamp (the atime). When explicitly 6286 sorting by time (‘--sort=time’ or ‘-t’) or when not using a long 6287 listing format, sort according to the atime. *Note File 6288 timestamps::. 6289 6290‘--time=birth’ 6291‘--time=creation’ 6292 If the long listing format (e.g., ‘--format=long’) is being used, 6293 print the file creation timestamp if available. When explicitly 6294 sorting by time (‘--sort=time’ or ‘-t’) or when not using a long 6295 listing format, sort according to the birth time. *Note File 6296 timestamps::. 6297 6298‘-U’ 6299‘--sort=none’ 6300 Do not sort; list the files in whatever order they are stored in 6301 the directory. (Do not do any of the other unrelated things that 6302 ‘-f’ does.) This is especially useful when listing very large 6303 directories, since not doing any sorting can be noticeably faster. 6304 6305‘-v’ 6306‘--sort=version’ 6307 Sort by version name and number, lowest first. It behaves like a 6308 default sort, except that each sequence of decimal digits is 6309 treated numerically as an index/version number. (*Note Version 6310 sort ordering::.) 6311 6312‘-X’ 6313‘--sort=extension’ 6314 Sort directory contents alphabetically by file extension 6315 (characters after the last ‘.’); files with no extension are sorted 6316 first. 6317 6318 6319File: coreutils.info, Node: General output formatting, Next: Formatting file timestamps, Prev: Sorting the output, Up: ls invocation 6320 632110.1.4 General output formatting 6322-------------------------------- 6323 6324These options affect the appearance of the overall output. 6325 6326‘-1’ 6327‘--format=single-column’ 6328 List one file per line. This is the default for ‘ls’ when standard 6329 output is not a terminal. See also the ‘-b’ and ‘-q’ options to 6330 suppress direct output of newline characters within a file name. 6331 6332‘-C’ 6333‘--format=vertical’ 6334 List files in columns, sorted vertically. This is the default for 6335 ‘ls’ if standard output is a terminal. It is always the default 6336 for the ‘dir’ program. GNU ‘ls’ uses variable width columns to 6337 display as many files as possible in the fewest lines. 6338 6339‘--color [=WHEN]’ 6340 Specify whether to use color for distinguishing file types. WHEN 6341 may be omitted, or one of: 6342 • none - Do not use color at all. This is the default. 6343 • auto - Only use color if standard output is a terminal. 6344 • always - Always use color. 6345 Specifying ‘--color’ and no WHEN is equivalent to ‘--color=always’. 6346 If piping a colorized listing through a pager like ‘less’, use the 6347 ‘-R’ option to pass the color codes to the terminal. 6348 6349 Note that using the ‘--color’ option may incur a noticeable 6350 performance penalty when run in a directory with very many entries, 6351 because the default settings require that ‘ls’ ‘stat’ every single 6352 file it lists. However, if you would like most of the file-type 6353 coloring but can live without the other coloring options (e.g., 6354 executable, orphan, sticky, other-writable, capability), use 6355 ‘dircolors’ to set the ‘LS_COLORS’ environment variable like this, 6356 eval $(dircolors -p | perl -pe \ 6357 's/^((CAP|S[ET]|O[TR]|M|E)\w+).*/$1 00/' | dircolors -) 6358 and on a ‘dirent.d_type’-capable file system, ‘ls’ will perform 6359 only one ‘stat’ call per command line argument. 6360 6361‘-F’ 6362‘--classify’ 6363‘--indicator-style=classify’ 6364 Append a character to each file name indicating the file type. 6365 Also, for regular files that are executable, append ‘*’. The file 6366 type indicators are ‘/’ for directories, ‘@’ for symbolic links, 6367 ‘|’ for FIFOs, ‘=’ for sockets, ‘>’ for doors, and nothing for 6368 regular files. Do not follow symbolic links listed on the command 6369 line unless the ‘--dereference-command-line’ (‘-H’), 6370 ‘--dereference’ (‘-L’), or 6371 ‘--dereference-command-line-symlink-to-dir’ options are specified. 6372 6373‘--file-type’ 6374‘--indicator-style=file-type’ 6375 Append a character to each file name indicating the file type. 6376 This is like ‘-F’, except that executables are not marked. 6377 6378‘--hyperlink [=WHEN]’ 6379 Output codes recognized by some terminals to link to files using 6380 the ‘file://’ URI format. WHEN may be omitted, or one of: 6381 • none - Do not use hyperlinks at all. This is the default. 6382 • auto - Only use hyperlinks if standard output is a terminal. 6383 • always - Always use hyperlinks. 6384 Specifying ‘--hyperlink’ and no WHEN is equivalent to 6385 ‘--hyperlink=always’. 6386 6387‘--indicator-style=WORD’ 6388 Append a character indicator with style WORD to entry names, as 6389 follows: 6390 6391 ‘none’ 6392 Do not append any character indicator; this is the default. 6393 ‘slash’ 6394 Append ‘/’ for directories. This is the same as the ‘-p’ 6395 option. 6396 ‘file-type’ 6397 Append ‘/’ for directories, ‘@’ for symbolic links, ‘|’ for 6398 FIFOs, ‘=’ for sockets, and nothing for regular files. This 6399 is the same as the ‘--file-type’ option. 6400 ‘classify’ 6401 Append ‘*’ for executable regular files, otherwise behave as 6402 for ‘file-type’. This is the same as the ‘-F’ or ‘--classify’ 6403 option. 6404 6405‘-k’ 6406‘--kibibytes’ 6407 Set the default block size to its normal value of 1024 bytes, 6408 overriding any contrary specification in environment variables 6409 (*note Block size::). If ‘--block-size’, ‘-h’, ‘--human-readable’, 6410 or ‘--si’ options are used, they take precedence over ‘-k’ or 6411 ‘--kibibytes’ even if ‘-k’ or ‘--kibibytes’ is placed after the 6412 other options. 6413 6414 The ‘-k’ or ‘--kibibytes’ option affects the per-directory block 6415 count written by the ‘-l’ and similar options, and the size written 6416 by the ‘-s’ or ‘--size’ option. It does not affect the file size 6417 written by ‘-l’. 6418 6419‘-m’ 6420‘--format=commas’ 6421 List files horizontally, with as many as will fit on each line, 6422 separated by ‘, ’ (a comma and a space). 6423 6424‘-p’ 6425‘--indicator-style=slash’ 6426 Append a ‘/’ to directory names. 6427 6428‘-x’ 6429‘--format=across’ 6430‘--format=horizontal’ 6431 List the files in columns, sorted horizontally. 6432 6433‘-T COLS’ 6434‘--tabsize=COLS’ 6435 Assume that each tab stop is COLS columns wide. The default is 8. 6436 ‘ls’ uses tabs where possible in the output, for efficiency. If 6437 COLS is zero, do not use tabs at all. 6438 6439 Some terminal emulators might not properly align columns to the 6440 right of a TAB following a non-ASCII byte. You can avoid that 6441 issue by using the ‘-T0’ option or put ‘TABSIZE=0’ in your 6442 environment, to tell ‘ls’ to align using spaces, not tabs. 6443 6444‘-w COLS’ 6445‘--width=COLS’ 6446 Assume the screen is COLS columns wide. The default is taken from 6447 the terminal settings if possible; otherwise the environment 6448 variable ‘COLUMNS’ is used if it is set; otherwise the default is 6449 80. With a COLS value of ‘0’, there is no limit on the length of 6450 the output line, and that single output line will be delimited with 6451 spaces, not tabs. 6452 6453 6454File: coreutils.info, Node: Formatting file timestamps, Next: Formatting the file names, Prev: General output formatting, Up: ls invocation 6455 645610.1.5 Formatting file timestamps 6457--------------------------------- 6458 6459By default, file timestamps are listed in abbreviated form, using a date 6460like ‘Mar 30 2002’ for non-recent timestamps, and a date-without-year 6461and time like ‘Mar 30 23:45’ for recent timestamps. This format can 6462change depending on the current locale as detailed below. 6463 6464 A timestamp is considered to be “recent” if it is less than six 6465months old, and is not dated in the future. If a timestamp dated today 6466is not listed in recent form, the timestamp is in the future, which 6467means you probably have clock skew problems which may break programs 6468like ‘make’ that rely on file timestamps. *Note File timestamps::. 6469 6470 Timestamps are listed according to the time zone rules specified by 6471the ‘TZ’ environment variable, or by the system default rules if ‘TZ’ is 6472not set. *Note Specifying the Time Zone with ‘TZ’: (libc)TZ Variable. 6473 6474 The following option changes how file timestamps are printed. 6475 6476‘--time-style=STYLE’ 6477 List timestamps in style STYLE. The STYLE should be one of the 6478 following: 6479 6480 ‘+FORMAT’ 6481 List timestamps using FORMAT, where FORMAT is interpreted like 6482 the format argument of ‘date’ (*note date invocation::). For 6483 example, ‘--time-style="+%Y-%m-%d %H:%M:%S"’ causes ‘ls’ to 6484 list timestamps like ‘2002-03-30 23:45:56’. As with ‘date’, 6485 FORMAT’s interpretation is affected by the ‘LC_TIME’ locale 6486 category. 6487 6488 If FORMAT contains two format strings separated by a newline, 6489 the former is used for non-recent files and the latter for 6490 recent files; if you want output columns to line up, you may 6491 need to insert spaces in one of the two formats. 6492 6493 ‘full-iso’ 6494 List timestamps in full using ISO 8601-like date, time, and 6495 time zone components with nanosecond precision, e.g., 6496 ‘2002-03-30 23:45:56.477817180 -0700’. This style is 6497 equivalent to ‘+%Y-%m-%d %H:%M:%S.%N %z’. 6498 6499 This is useful because the time output includes all the 6500 information that is available from the operating system. For 6501 example, this can help explain ‘make’’s behavior, since GNU 6502 ‘make’ uses the full timestamp to determine whether a file is 6503 out of date. 6504 6505 ‘long-iso’ 6506 List ISO 8601 date and time components with minute precision, 6507 e.g., ‘2002-03-30 23:45’. These timestamps are shorter than 6508 ‘full-iso’ timestamps, and are usually good enough for 6509 everyday work. This style is equivalent to ‘+%Y-%m-%d %H:%M’. 6510 6511 ‘iso’ 6512 List ISO 8601 dates for non-recent timestamps (e.g., 6513 ‘2002-03-30 ’), and ISO 8601-like month, day, hour, and minute 6514 for recent timestamps (e.g., ‘03-30 23:45’). These timestamps 6515 are uglier than ‘long-iso’ timestamps, but they carry nearly 6516 the same information in a smaller space and their brevity 6517 helps ‘ls’ output fit within traditional 80-column output 6518 lines. The following two ‘ls’ invocations are equivalent: 6519 6520 newline=' 6521 ' 6522 ls -l --time-style="+%Y-%m-%d $newline%m-%d %H:%M" 6523 ls -l --time-style="iso" 6524 6525 ‘locale’ 6526 List timestamps in a locale-dependent form. For example, a 6527 Finnish locale might list non-recent timestamps like ‘maalis 6528 30 2002’ and recent timestamps like ‘maalis 30 23:45’. 6529 Locale-dependent timestamps typically consume more space than 6530 ‘iso’ timestamps and are harder for programs to parse because 6531 locale conventions vary so widely, but they are easier for 6532 many people to read. 6533 6534 The ‘LC_TIME’ locale category specifies the timestamp format. 6535 The default POSIX locale uses timestamps like ‘Mar 30 2002’ 6536 and ‘Mar 30 23:45’; in this locale, the following two ‘ls’ 6537 invocations are equivalent: 6538 6539 newline=' 6540 ' 6541 ls -l --time-style="+%b %e %Y$newline%b %e %H:%M" 6542 ls -l --time-style="locale" 6543 6544 Other locales behave differently. For example, in a German 6545 locale, ‘--time-style="locale"’ might be equivalent to 6546 ‘--time-style="+%e. %b %Y $newline%e. %b %H:%M"’ and might 6547 generate timestamps like ‘30. Mär 2002 ’ and ‘30. Mär 23:45’. 6548 6549 ‘posix-STYLE’ 6550 List POSIX-locale timestamps if the ‘LC_TIME’ locale category 6551 is POSIX, STYLE timestamps otherwise. For example, the 6552 ‘posix-long-iso’ style lists timestamps like ‘Mar 30 2002’ 6553 and ‘Mar 30 23:45’ when in the POSIX locale, and like 6554 ‘2002-03-30 23:45’ otherwise. 6555 6556 You can specify the default value of the ‘--time-style’ option with 6557the environment variable ‘TIME_STYLE’; if ‘TIME_STYLE’ is not set the 6558default style is ‘locale’. GNU Emacs 21.3 and later use the ‘--dired’ 6559option and therefore can parse any date format, but if you are using 6560Emacs 21.1 or 21.2 and specify a non-POSIX locale you may need to set 6561‘TIME_STYLE="posix-long-iso"’. 6562 6563 To avoid certain denial-of-service attacks, timestamps that would be 6564longer than 1000 bytes may be treated as errors. 6565 6566 6567File: coreutils.info, Node: Formatting the file names, Prev: Formatting file timestamps, Up: ls invocation 6568 656910.1.6 Formatting the file names 6570-------------------------------- 6571 6572These options change how file names themselves are printed. 6573 6574‘-b’ 6575‘--escape’ 6576‘--quoting-style=escape’ 6577 Quote nongraphic characters in file names using alphabetic and 6578 octal backslash sequences like those used in C. 6579 6580‘-N’ 6581‘--literal’ 6582‘--quoting-style=literal’ 6583 Do not quote file names. However, with ‘ls’ nongraphic characters 6584 are still printed as question marks if the output is a terminal and 6585 you do not specify the ‘--show-control-chars’ option. 6586 6587‘-q’ 6588‘--hide-control-chars’ 6589 Print question marks instead of nongraphic characters in file 6590 names. This is the default if the output is a terminal and the 6591 program is ‘ls’. 6592 6593‘-Q’ 6594‘--quote-name’ 6595‘--quoting-style=c’ 6596 Enclose file names in double quotes and quote nongraphic characters 6597 as in C. 6598 6599‘--quoting-style=WORD’ 6600 Use style WORD to quote file names and other strings that may 6601 contain arbitrary characters. The WORD should be one of the 6602 following: 6603 6604 ‘literal’ 6605 Output strings as-is; this is the same as the ‘-N’ or 6606 ‘--literal’ option. 6607 ‘shell’ 6608 Quote strings for the shell if they contain shell 6609 metacharacters or would cause ambiguous output. The quoting 6610 is suitable for POSIX-compatible shells like ‘bash’, but it 6611 does not always work for incompatible shells like ‘csh’. 6612 ‘shell-always’ 6613 Quote strings for the shell, even if they would normally not 6614 require quoting. 6615 ‘shell-escape’ 6616 Like ‘shell’, but also quoting non-printable characters using 6617 the POSIX proposed ‘$''’ syntax suitable for most shells. 6618 ‘shell-escape-always’ 6619 Like ‘shell-escape’, but quote strings even if they would 6620 normally not require quoting. 6621 ‘c’ 6622 Quote strings as for C character string literals, including 6623 the surrounding double-quote characters; this is the same as 6624 the ‘-Q’ or ‘--quote-name’ option. 6625 ‘escape’ 6626 Quote strings as for C character string literals, except omit 6627 the surrounding double-quote characters; this is the same as 6628 the ‘-b’ or ‘--escape’ option. 6629 ‘clocale’ 6630 Quote strings as for C character string literals, except use 6631 surrounding quotation marks appropriate for the locale. 6632 ‘locale’ 6633 Quote strings as for C character string literals, except use 6634 surrounding quotation marks appropriate for the locale, and 6635 quote 'like this' instead of "like this" in the default C 6636 locale. This looks nicer on many displays. 6637 6638 You can specify the default value of the ‘--quoting-style’ option 6639 with the environment variable ‘QUOTING_STYLE’. If that environment 6640 variable is not set, the default value is ‘shell-escape’ when the 6641 output is a terminal, and ‘literal’ otherwise. 6642 6643‘--show-control-chars’ 6644 Print nongraphic characters as-is in file names. This is the 6645 default unless the output is a terminal and the program is ‘ls’. 6646 6647 6648File: coreutils.info, Node: dir invocation, Next: vdir invocation, Prev: ls invocation, Up: Directory listing 6649 665010.2 ‘dir’: Briefly list directory contents 6651=========================================== 6652 6653‘dir’ is equivalent to ‘ls -C -b’; that is, by default files are listed 6654in columns, sorted vertically, and special characters are represented by 6655backslash escape sequences. 6656 6657 *Note ‘ls’: ls invocation. 6658 6659 6660File: coreutils.info, Node: vdir invocation, Next: dircolors invocation, Prev: dir invocation, Up: Directory listing 6661 666210.3 ‘vdir’: Verbosely list directory contents 6663============================================== 6664 6665‘vdir’ is equivalent to ‘ls -l -b’; that is, by default files are listed 6666in long format and special characters are represented by backslash 6667escape sequences. 6668 6669 *Note ‘ls’: ls invocation. 6670 6671 6672File: coreutils.info, Node: dircolors invocation, Prev: vdir invocation, Up: Directory listing 6673 667410.4 ‘dircolors’: Color setup for ‘ls’ 6675====================================== 6676 6677‘dircolors’ outputs a sequence of shell commands to set up the terminal 6678for color output from ‘ls’ (and ‘dir’, etc.). Typical usage: 6679 6680 eval "$(dircolors [OPTION]... [FILE])" 6681 6682 If FILE is specified, ‘dircolors’ reads it to determine which colors 6683to use for which file types and extensions. Otherwise, a precompiled 6684database is used. For details on the format of these files, run 6685‘dircolors --print-database’. 6686 6687 To make ‘dircolors’ read a ‘~/.dircolors’ file if it exists, you can 6688put the following lines in your ‘~/.bashrc’ (or adapt them to your 6689favorite shell): 6690 6691 d=.dircolors 6692 test -r $d && eval "$(dircolors $d)" 6693 6694 The output is a shell command to set the ‘LS_COLORS’ environment 6695variable. You can specify the shell syntax to use on the command line, 6696or ‘dircolors’ will guess it from the value of the ‘SHELL’ environment 6697variable. 6698 6699 The program accepts the following options. Also see *note Common 6700options::. 6701 6702‘-b’ 6703‘--sh’ 6704‘--bourne-shell’ 6705 Output Bourne shell commands. This is the default if the ‘SHELL’ 6706 environment variable is set and does not end with ‘csh’ or ‘tcsh’. 6707 6708‘-c’ 6709‘--csh’ 6710‘--c-shell’ 6711 Output C shell commands. This is the default if ‘SHELL’ ends with 6712 ‘csh’ or ‘tcsh’. 6713 6714‘-p’ 6715‘--print-database’ 6716 Print the (compiled-in) default color configuration database. This 6717 output is itself a valid configuration file, and is fairly 6718 descriptive of the possibilities. 6719 6720 An exit status of zero indicates success, and a nonzero value 6721indicates failure. 6722 6723 6724File: coreutils.info, Node: Basic operations, Next: Special file types, Prev: Directory listing, Up: Top 6725 672611 Basic operations 6727******************* 6728 6729This chapter describes the commands for basic file manipulation: 6730copying, moving (renaming), and deleting (removing). 6731 6732* Menu: 6733 6734* cp invocation:: Copy files. 6735* dd invocation:: Convert and copy a file. 6736* install invocation:: Copy files and set attributes. 6737* mv invocation:: Move (rename) files. 6738* rm invocation:: Remove files or directories. 6739* shred invocation:: Remove files more securely. 6740 6741 6742File: coreutils.info, Node: cp invocation, Next: dd invocation, Up: Basic operations 6743 674411.1 ‘cp’: Copy files and directories 6745===================================== 6746 6747‘cp’ copies files (or, optionally, directories). The copy is completely 6748independent of the original. You can either copy one file to another, 6749or copy arbitrarily many files to a destination directory. Synopses: 6750 6751 cp [OPTION]... [-T] SOURCE DEST 6752 cp [OPTION]... SOURCE... DIRECTORY 6753 cp [OPTION]... -t DIRECTORY SOURCE... 6754 6755 • If two file names are given, ‘cp’ copies the first file to the 6756 second. 6757 6758 • If the ‘--target-directory’ (‘-t’) option is given, or failing that 6759 if the last file is a directory and the ‘--no-target-directory’ 6760 (‘-T’) option is not given, ‘cp’ copies each SOURCE file to the 6761 specified directory, using the SOURCEs’ names. 6762 6763 Generally, files are written just as they are read. For exceptions, 6764see the ‘--sparse’ option below. 6765 6766 By default, ‘cp’ does not copy directories. However, the ‘-R’, ‘-a’, 6767and ‘-r’ options cause ‘cp’ to copy recursively by descending into 6768source directories and copying files to corresponding destination 6769directories. 6770 6771 When copying from a symbolic link, ‘cp’ normally follows the link 6772only when not copying recursively or when ‘--link’ (‘-l’) is used. This 6773default can be overridden with the ‘--archive’ (‘-a’), ‘-d’, 6774‘--dereference’ (‘-L’), ‘--no-dereference’ (‘-P’), and ‘-H’ options. If 6775more than one of these options is specified, the last one silently 6776overrides the others. 6777 6778 When copying to a symbolic link, ‘cp’ follows the link only when it 6779refers to an existing regular file. However, when copying to a dangling 6780symbolic link, ‘cp’ refuses by default, and fails with a diagnostic, 6781since the operation is inherently dangerous. This behavior is contrary 6782to historical practice and to POSIX. Set ‘POSIXLY_CORRECT’ to make ‘cp’ 6783attempt to create the target of a dangling destination symlink, in spite 6784of the possible risk. Also, when an option like ‘--backup’ or ‘--link’ 6785acts to rename or remove the destination before copying, ‘cp’ renames or 6786removes the symbolic link rather than the file it points to. 6787 6788 By default, ‘cp’ copies the contents of special files only when not 6789copying recursively. This default can be overridden with the 6790‘--copy-contents’ option. 6791 6792 ‘cp’ generally refuses to copy a file onto itself, with the following 6793exception: if ‘--force --backup’ is specified with SOURCE and DEST 6794identical, and referring to a regular file, ‘cp’ will make a backup 6795file, either regular or numbered, as specified in the usual ways (*note 6796Backup options::). This is useful when you simply want to make a backup 6797of an existing file before changing it. 6798 6799 The program accepts the following options. Also see *note Common 6800options::. 6801 6802‘-a’ 6803‘--archive’ 6804 Preserve as much as possible of the structure and attributes of the 6805 original files in the copy (but do not attempt to preserve internal 6806 directory structure; i.e., ‘ls -U’ may list the entries in a copied 6807 directory in a different order). Try to preserve SELinux security 6808 context and extended attributes (xattr), but ignore any failure to 6809 do that and print no corresponding diagnostic. Equivalent to ‘-dR 6810 --preserve=all’ with the reduced diagnostics. 6811 6812‘--attributes-only’ 6813 Copy only the specified attributes of the source file to the 6814 destination. If the destination already exists, do not alter its 6815 contents. See the ‘--preserve’ option for controlling which 6816 attributes to copy. 6817 6818‘-b’ 6819‘--backup[=METHOD]’ 6820 *Note Backup options::. Make a backup of each file that would 6821 otherwise be overwritten or removed. As a special case, ‘cp’ makes 6822 a backup of SOURCE when the force and backup options are given and 6823 SOURCE and DEST are the same name for an existing, regular file. 6824 One useful application of this combination of options is this tiny 6825 Bourne shell script: 6826 6827 #!/bin/sh 6828 # Usage: backup FILE... 6829 # Create a GNU-style backup of each listed FILE. 6830 fail=0 6831 for i; do 6832 cp --backup --force --preserve=all -- "$i" "$i" || fail=1 6833 done 6834 exit $fail 6835 6836‘--copy-contents’ 6837 If copying recursively, copy the contents of any special files 6838 (e.g., FIFOs and device files) as if they were regular files. This 6839 means trying to read the data in each source file and writing it to 6840 the destination. It is usually a mistake to use this option, as it 6841 normally has undesirable effects on special files like FIFOs and 6842 the ones typically found in the ‘/dev’ directory. In most cases, 6843 ‘cp -R --copy-contents’ will hang indefinitely trying to read from 6844 FIFOs and special files like ‘/dev/console’, and it will fill up 6845 your destination disk if you use it to copy ‘/dev/zero’. This 6846 option has no effect unless copying recursively, and it does not 6847 affect the copying of symbolic links. 6848 6849‘-d’ 6850 Copy symbolic links as symbolic links rather than copying the files 6851 that they point to, and preserve hard links between source files in 6852 the copies. Equivalent to ‘--no-dereference --preserve=links’. 6853 6854‘-f’ 6855‘--force’ 6856 When copying without this option and an existing destination file 6857 cannot be opened for writing, the copy fails. However, with 6858 ‘--force’, when a destination file cannot be opened, ‘cp’ then 6859 tries to recreate the file by first removing it. Note ‘--force’ 6860 alone will not remove dangling symlinks. When this option is 6861 combined with ‘--link’ (‘-l’) or ‘--symbolic-link’ (‘-s’), the 6862 destination link is replaced, and unless ‘--backup’ (‘-b’) is also 6863 given there is no brief moment when the destination does not exist. 6864 Also see the description of ‘--remove-destination’. 6865 6866 This option is independent of the ‘--interactive’ or ‘-i’ option: 6867 neither cancels the effect of the other. 6868 6869 This option is ignored when the ‘--no-clobber’ or ‘-n’ option is 6870 also used. 6871 6872‘-H’ 6873 If a command line argument specifies a symbolic link, then copy the 6874 file it points to rather than the symbolic link itself. However, 6875 copy (preserving its nature) any symbolic link that is encountered 6876 via recursive traversal. 6877 6878‘-i’ 6879‘--interactive’ 6880 When copying a file other than a directory, prompt whether to 6881 overwrite an existing destination file. The ‘-i’ option overrides 6882 a previous ‘-n’ option. 6883 6884‘-l’ 6885‘--link’ 6886 Make hard links instead of copies of non-directories. 6887 6888‘-L’ 6889‘--dereference’ 6890 Follow symbolic links when copying from them. With this option, 6891 ‘cp’ cannot create a symbolic link. For example, a symlink (to 6892 regular file) in the source tree will be copied to a regular file 6893 in the destination tree. 6894 6895‘-n’ 6896‘--no-clobber’ 6897 Do not overwrite an existing file; silently do nothing instead. 6898 This option overrides a previous ‘-i’ option. This option is 6899 mutually exclusive with ‘-b’ or ‘--backup’ option. 6900 6901‘-P’ 6902‘--no-dereference’ 6903 Copy symbolic links as symbolic links rather than copying the files 6904 that they point to. This option affects only symbolic links in the 6905 source; symbolic links in the destination are always followed if 6906 possible. 6907 6908‘-p’ 6909‘--preserve[=ATTRIBUTE_LIST]’ 6910 Preserve the specified attributes of the original files. If 6911 specified, the ATTRIBUTE_LIST must be a comma-separated list of one 6912 or more of the following strings: 6913 6914 ‘mode’ 6915 Preserve the file mode bits and access control lists. 6916 ‘ownership’ 6917 Preserve the owner and group. On most modern systems, only 6918 users with appropriate privileges may change the owner of a 6919 file, and ordinary users may preserve the group ownership of a 6920 file only if they happen to be a member of the desired group. 6921 ‘timestamps’ 6922 Preserve the times of last access and last modification, when 6923 possible. On older systems, it is not possible to preserve 6924 these attributes when the affected file is a symbolic link. 6925 However, many systems now provide the ‘utimensat’ function, 6926 which makes it possible even for symbolic links. 6927 ‘links’ 6928 Preserve in the destination files any links between 6929 corresponding source files. Note that with ‘-L’ or ‘-H’, this 6930 option can convert symbolic links to hard links. For example, 6931 $ mkdir c; : > a; ln -s a b; cp -aH a b c; ls -i1 c 6932 74161745 a 6933 74161745 b 6934 Note the inputs: ‘b’ is a symlink to regular file ‘a’, yet the 6935 files in destination directory, ‘c/’, are hard-linked. Since 6936 ‘-a’ implies ‘--no-dereference’ it would copy the symlink, but 6937 the later ‘-H’ tells ‘cp’ to dereference the command line 6938 arguments where it then sees two files with the same inode 6939 number. Then the ‘--preserve=links’ option also implied by 6940 ‘-a’ will preserve the perceived hard link. 6941 6942 Here is a similar example that exercises ‘cp’’s ‘-L’ option: 6943 $ mkdir b c; (cd b; : > a; ln -s a b); cp -aL b c; ls -i1 c/b 6944 74163295 a 6945 74163295 b 6946 6947 ‘context’ 6948 Preserve SELinux security context of the file, or fail with 6949 full diagnostics. 6950 ‘xattr’ 6951 Preserve extended attributes of the file, or fail with full 6952 diagnostics. If ‘cp’ is built without xattr support, ignore 6953 this option. If SELinux context, ACLs or Capabilities are 6954 implemented using xattrs, they are preserved implicitly by 6955 this option as well, i.e., even without specifying 6956 ‘--preserve=mode’ or ‘--preserve=context’. 6957 ‘all’ 6958 Preserve all file attributes. Equivalent to specifying all of 6959 the above, but with the difference that failure to preserve 6960 SELinux security context or extended attributes does not 6961 change ‘cp’’s exit status. In contrast to ‘-a’, all but 6962 ‘Operation not supported’ warnings are output. 6963 6964 Using ‘--preserve’ with no ATTRIBUTE_LIST is equivalent to 6965 ‘--preserve=mode,ownership,timestamps’. 6966 6967 In the absence of this option, the permissions of existing 6968 destination files are unchanged. Each new file is created with the 6969 mode of the corresponding source file minus the set-user-ID, 6970 set-group-ID, and sticky bits as the create mode; the operating 6971 system then applies either the umask or a default ACL, possibly 6972 resulting in a more restrictive file mode. *Note File 6973 permissions::. 6974 6975‘--no-preserve=ATTRIBUTE_LIST’ 6976 Do not preserve the specified attributes. The ATTRIBUTE_LIST has 6977 the same form as for ‘--preserve’. 6978 6979‘--parents’ 6980 Form the name of each destination file by appending to the target 6981 directory a slash and the specified name of the source file. The 6982 last argument given to ‘cp’ must be the name of an existing 6983 directory. For example, the command: 6984 6985 cp --parents a/b/c existing_dir 6986 6987 copies the file ‘a/b/c’ to ‘existing_dir/a/b/c’, creating any 6988 missing intermediate directories. 6989 6990‘-R’ 6991‘-r’ 6992‘--recursive’ 6993 Copy directories recursively. By default, do not follow symbolic 6994 links in the source unless used together with the ‘--link’ (‘-l’) 6995 option; see the ‘--archive’ (‘-a’), ‘-d’, ‘--dereference’ (‘-L’), 6996 ‘--no-dereference’ (‘-P’), and ‘-H’ options. Special files are 6997 copied by creating a destination file of the same type as the 6998 source; see the ‘--copy-contents’ option. It is not portable to 6999 use ‘-r’ to copy symbolic links or special files. On some non-GNU 7000 systems, ‘-r’ implies the equivalent of ‘-L’ and ‘--copy-contents’ 7001 for historical reasons. Also, it is not portable to use ‘-R’ to 7002 copy symbolic links unless you also specify ‘-P’, as POSIX allows 7003 implementations that dereference symbolic links by default. 7004 7005‘--reflink[=WHEN]’ 7006 Perform a lightweight, copy-on-write (COW) copy, if supported by 7007 the file system. Once it has succeeded, beware that the source and 7008 destination files share the same disk data blocks as long as they 7009 remain unmodified. Thus, if a disk I/O error affects data blocks 7010 of one of the files, the other suffers the same fate. 7011 7012 The WHEN value can be one of the following: 7013 7014 ‘always’ 7015 The default behavior: if the copy-on-write operation is not 7016 supported then report the failure for each file and exit with 7017 a failure status. 7018 7019 ‘auto’ 7020 If the copy-on-write operation is not supported then fall back 7021 to the standard copy behavior. 7022 7023 ‘never’ 7024 Disable copy-on-write operation and use the standard copy 7025 behavior. 7026 7027 This option is overridden by the ‘--link’, ‘--symbolic-link’ and 7028 ‘--attributes-only’ options, thus allowing it to be used to 7029 configure the default data copying behavior for ‘cp’. For example, 7030 with the following alias, ‘cp’ will use the minimum amount of space 7031 supported by the file system. 7032 7033 alias cp='cp --reflink=auto --sparse=always' 7034 7035‘--remove-destination’ 7036 Remove each existing destination file before attempting to open it 7037 (contrast with ‘-f’ above). 7038 7039‘--sparse=WHEN’ 7040 A “sparse file” contains “holes”—a sequence of zero bytes that does 7041 not occupy any physical disk blocks; the ‘read’ system call reads 7042 these as zeros. This can both save considerable disk space and 7043 increase speed, since many binary files contain lots of consecutive 7044 zero bytes. By default, ‘cp’ detects holes in input source files 7045 via a crude heuristic and makes the corresponding output file 7046 sparse as well. Only regular files may be sparse. 7047 7048 The WHEN value can be one of the following: 7049 7050 ‘auto’ 7051 The default behavior: if the input file is sparse, attempt to 7052 make the output file sparse, too. However, if an output file 7053 exists but refers to a non-regular file, then do not attempt 7054 to make it sparse. 7055 7056 ‘always’ 7057 For each sufficiently long sequence of zero bytes in the input 7058 file, attempt to create a corresponding hole in the output 7059 file, even if the input file does not appear to be sparse. 7060 This is useful when the input file resides on a file system 7061 that does not support sparse files (for example, ‘efs’ file 7062 systems in SGI IRIX 5.3 and earlier), but the output file is 7063 on a type of file system that does support them. Holes may be 7064 created only in regular files, so if the destination file is 7065 of some other type, ‘cp’ does not even try to make it sparse. 7066 7067 ‘never’ 7068 Never make the output file sparse. This is useful in creating 7069 a file for use with the ‘mkswap’ command, since such a file 7070 must not have any holes. 7071 7072‘--strip-trailing-slashes’ 7073 Remove any trailing slashes from each SOURCE argument. *Note 7074 Trailing slashes::. 7075 7076‘-s’ 7077‘--symbolic-link’ 7078 Make symbolic links instead of copies of non-directories. All 7079 source file names must be absolute (starting with ‘/’) unless the 7080 destination files are in the current directory. This option merely 7081 results in an error message on systems that do not support symbolic 7082 links. 7083 7084‘-S SUFFIX’ 7085‘--suffix=SUFFIX’ 7086 Append SUFFIX to each backup file made with ‘-b’. *Note Backup 7087 options::. 7088 7089‘-t DIRECTORY’ 7090‘--target-directory=DIRECTORY’ 7091 Specify the destination DIRECTORY. *Note Target directory::. 7092 7093‘-T’ 7094‘--no-target-directory’ 7095 Do not treat the last operand specially when it is a directory or a 7096 symbolic link to a directory. *Note Target directory::. 7097 7098‘-u’ 7099‘--update’ 7100 Do not copy a non-directory that has an existing destination with 7101 the same or newer modification timestamp. If timestamps are being 7102 preserved, the comparison is to the source timestamp truncated to 7103 the resolutions of the destination file system and of the system 7104 calls used to update timestamps; this avoids duplicate work if 7105 several ‘cp -pu’ commands are executed with the same source and 7106 destination. This option is ignored if the ‘-n’ or ‘--no-clobber’ 7107 option is also specified. Also, if ‘--preserve=links’ is also 7108 specified (like with ‘cp -au’ for example), that will take 7109 precedence; consequently, depending on the order that files are 7110 processed from the source, newer files in the destination may be 7111 replaced, to mirror hard links in the source. 7112 7113‘-v’ 7114‘--verbose’ 7115 Print the name of each file before copying it. 7116 7117‘-x’ 7118‘--one-file-system’ 7119 Skip subdirectories that are on different file systems from the one 7120 that the copy started on. However, mount point directories _are_ 7121 copied. 7122 7123‘-Z’ 7124‘--context[=CONTEXT]’ 7125 Without a specified CONTEXT, adjust the SELinux security context 7126 according to the system default type for destination files, 7127 similarly to the ‘restorecon’ command. The long form of this 7128 option with a specific context specified, will set the context for 7129 newly created files only. With a specified context, if both 7130 SELinux and SMACK are disabled, a warning is issued. This option 7131 is mutually exclusive with the ‘--preserve=context’ option, and 7132 overrides the ‘--preserve=all’ and ‘-a’ options. 7133 7134 An exit status of zero indicates success, and a nonzero value 7135indicates failure. 7136 7137 7138File: coreutils.info, Node: dd invocation, Next: install invocation, Prev: cp invocation, Up: Basic operations 7139 714011.2 ‘dd’: Convert and copy a file 7141================================== 7142 7143‘dd’ copies a file (from standard input to standard output, by default) 7144with a changeable I/O block size, while optionally performing 7145conversions on it. Synopses: 7146 7147 dd [OPERAND]... 7148 dd OPTION 7149 7150 The only options are ‘--help’ and ‘--version’. *Note Common 7151options::. ‘dd’ accepts the following operands, whose syntax was 7152inspired by the DD (data definition) statement of OS/360 JCL. 7153 7154‘if=FILE’ 7155 Read from FILE instead of standard input. 7156 7157‘of=FILE’ 7158 Write to FILE instead of standard output. Unless ‘conv=notrunc’ is 7159 given, ‘dd’ truncates FILE to zero bytes (or the size specified 7160 with ‘seek=’). 7161 7162‘ibs=BYTES’ 7163 Set the input block size to BYTES. This makes ‘dd’ read BYTES per 7164 block. The default is 512 bytes. 7165 7166‘obs=BYTES’ 7167 Set the output block size to BYTES. This makes ‘dd’ write BYTES 7168 per block. The default is 512 bytes. 7169 7170‘bs=BYTES’ 7171 Set both input and output block sizes to BYTES. This makes ‘dd’ 7172 read and write BYTES per block, overriding any ‘ibs’ and ‘obs’ 7173 settings. In addition, if no data-transforming ‘conv’ operand is 7174 specified, input is copied to the output as soon as it’s read, even 7175 if it is smaller than the block size. 7176 7177‘cbs=BYTES’ 7178 Set the conversion block size to BYTES. When converting 7179 variable-length records to fixed-length ones (‘conv=block’) or the 7180 reverse (‘conv=unblock’), use BYTES as the fixed record length. 7181 7182‘skip=N’ 7183 Skip N ‘ibs’-byte blocks in the input file before copying. If 7184 ‘iflag=skip_bytes’ is specified, N is interpreted as a byte count 7185 rather than a block count. 7186 7187‘seek=N’ 7188 Skip N ‘obs’-byte blocks in the output file before copying. if 7189 ‘oflag=seek_bytes’ is specified, N is interpreted as a byte count 7190 rather than a block count. 7191 7192‘count=N’ 7193 Copy N ‘ibs’-byte blocks from the input file, instead of everything 7194 until the end of the file. if ‘iflag=count_bytes’ is specified, N 7195 is interpreted as a byte count rather than a block count. Note if 7196 the input may return short reads as could be the case when reading 7197 from a pipe for example, ‘iflag=fullblock’ will ensure that 7198 ‘count=’ corresponds to complete input blocks rather than the 7199 traditional POSIX specified behavior of counting input read 7200 operations. 7201 7202‘status=LEVEL’ 7203 Specify the amount of information printed. If this operand is 7204 given multiple times, the last one takes precedence. The LEVEL 7205 value can be one of the following: 7206 7207 ‘none’ 7208 Do not print any informational or warning messages to stderr. 7209 Error messages are output as normal. 7210 7211 ‘noxfer’ 7212 Do not print the final transfer rate and volume statistics 7213 that normally make up the last status line. 7214 7215 ‘progress’ 7216 Print the transfer rate and volume statistics on stderr, when 7217 processing each input block. Statistics are output on a 7218 single line at most once every second, but updates can be 7219 delayed when waiting on I/O. 7220 7221 Transfer information is normally output to stderr upon receipt of 7222 the ‘INFO’ signal or when ‘dd’ exits, and defaults to the following 7223 form in the C locale: 7224 7225 7287+1 records in 7226 116608+0 records out 7227 59703296 bytes (60 MB, 57 MiB) copied, 0.0427974 s, 1.4 GB/s 7228 7229 The notation ‘W+P’ stands for W whole blocks and P partial blocks. 7230 A partial block occurs when a read or write operation succeeds but 7231 transfers less data than the block size. An additional line like 7232 ‘1 truncated record’ or ‘10 truncated records’ is output after the 7233 ‘records out’ line if ‘conv=block’ processing truncated one or more 7234 input records. 7235 7236‘conv=CONVERSION[,CONVERSION]...’ 7237 Convert the file as specified by the CONVERSION argument(s). (No 7238 spaces around any comma(s).) 7239 7240 Conversions: 7241 7242 ‘ascii’ 7243 Convert EBCDIC to ASCII, using the conversion table specified 7244 by POSIX. This provides a 1:1 translation for all 256 bytes. 7245 This implies ‘conv=unblock’; input is converted to ASCII 7246 before trailing spaces are deleted. 7247 7248 ‘ebcdic’ 7249 Convert ASCII to EBCDIC. This is the inverse of the ‘ascii’ 7250 conversion. This implies ‘conv=block’; trailing spaces are 7251 added before being converted to EBCDIC. 7252 7253 ‘ibm’ 7254 This acts like ‘conv=ebcdic’, except it uses the alternate 7255 conversion table specified by POSIX. This is not a 1:1 7256 translation, but reflects common historical practice for ‘~’, 7257 ‘[’, and ‘]’. 7258 7259 The ‘ascii’, ‘ebcdic’, and ‘ibm’ conversions are mutually 7260 exclusive. If you use any of these conversions, you should 7261 also use the ‘cbs=’ operand. 7262 7263 ‘block’ 7264 For each line in the input, output ‘cbs’ bytes, replacing the 7265 input newline with a space and truncating or padding input 7266 lines with spaces as necessary. 7267 7268 ‘unblock’ 7269 Remove any trailing spaces in each ‘cbs’-sized input block, 7270 and append a newline. 7271 7272 The ‘block’ and ‘unblock’ conversions are mutually exclusive. 7273 7274 ‘lcase’ 7275 Change uppercase letters to lowercase. 7276 7277 ‘ucase’ 7278 Change lowercase letters to uppercase. 7279 7280 The ‘lcase’ and ‘ucase’ conversions are mutually exclusive. 7281 7282 ‘sparse’ 7283 Try to seek rather than write NUL output blocks. On a file 7284 system that supports sparse files, this will create sparse 7285 output when extending the output file. Be careful when using 7286 this conversion in conjunction with ‘conv=notrunc’ or 7287 ‘oflag=append’. With ‘conv=notrunc’, existing data in the 7288 output file corresponding to NUL blocks from the input, will 7289 be untouched. With ‘oflag=append’ the seeks performed will be 7290 ineffective. Similarly, when the output is a device rather 7291 than a file, NUL input blocks are not copied, and therefore 7292 this conversion is most useful with virtual or pre zeroed 7293 devices. 7294 7295 ‘swab’ 7296 Swap every pair of input bytes. GNU ‘dd’, unlike others, 7297 works when an odd number of bytes are read—the last byte is 7298 simply copied (since there is nothing to swap it with). 7299 7300 ‘sync’ 7301 Pad every input block to size of ‘ibs’ with trailing zero 7302 bytes. When used with ‘block’ or ‘unblock’, pad with spaces 7303 instead of zero bytes. 7304 7305 The following “conversions” are really file flags and don’t affect 7306 internal processing: 7307 7308 ‘excl’ 7309 Fail if the output file already exists; ‘dd’ must create the 7310 output file itself. 7311 7312 ‘nocreat’ 7313 Do not create the output file; the output file must already 7314 exist. 7315 7316 The ‘excl’ and ‘nocreat’ conversions are mutually exclusive. 7317 7318 ‘notrunc’ 7319 Do not truncate the output file. 7320 7321 ‘noerror’ 7322 Continue after read errors. 7323 7324 ‘fdatasync’ 7325 Synchronize output data just before finishing. This forces a 7326 physical write of output data. 7327 7328 ‘fsync’ 7329 Synchronize output data and metadata just before finishing. 7330 This forces a physical write of output data and metadata. 7331 7332‘iflag=FLAG[,FLAG]...’ 7333 Access the input file using the flags specified by the FLAG 7334 argument(s). (No spaces around any comma(s).) 7335 7336‘oflag=FLAG[,FLAG]...’ 7337 Access the output file using the flags specified by the FLAG 7338 argument(s). (No spaces around any comma(s).) 7339 7340 Here are the flags. Not every flag is supported on every operating 7341 system. 7342 7343 ‘append’ 7344 Write in append mode, so that even if some other process is 7345 writing to this file, every ‘dd’ write will append to the 7346 current contents of the file. This flag makes sense only for 7347 output. If you combine this flag with the ‘of=FILE’ operand, 7348 you should also specify ‘conv=notrunc’ unless you want the 7349 output file to be truncated before being appended to. 7350 7351 ‘cio’ 7352 Use concurrent I/O mode for data. This mode performs direct 7353 I/O and drops the POSIX requirement to serialize all I/O to 7354 the same file. A file cannot be opened in CIO mode and with a 7355 standard open at the same time. 7356 7357 ‘direct’ 7358 Use direct I/O for data, avoiding the buffer cache. Note that 7359 the kernel may impose restrictions on read or write buffer 7360 sizes. For example, with an ext4 destination file system and 7361 a Linux-based kernel, using ‘oflag=direct’ will cause writes 7362 to fail with ‘EINVAL’ if the output buffer size is not a 7363 multiple of 512. 7364 7365 ‘directory’ 7366 7367 Fail unless the file is a directory. Most operating systems 7368 do not allow I/O to a directory, so this flag has limited 7369 utility. 7370 7371 ‘dsync’ 7372 Use synchronized I/O for data. For the output file, this 7373 forces a physical write of output data on each write. For the 7374 input file, this flag can matter when reading from a remote 7375 file that has been written to synchronously by some other 7376 process. Metadata (e.g., last-access and last-modified time) 7377 is not necessarily synchronized. 7378 7379 ‘sync’ 7380 Use synchronized I/O for both data and metadata. 7381 7382 ‘nocache’ 7383 Request to discard the system data cache for a file. When 7384 count=0 all cached data for the file is specified, otherwise 7385 the cache is dropped for the processed portion of the file. 7386 Also when count=0, failure to discard the cache is diagnosed 7387 and reflected in the exit status. 7388 7389 Note data that is not already persisted to storage will not be 7390 discarded from cache, so note the use of the ‘sync’ 7391 conversions in the examples below, which are used to maximize 7392 the effectiveness of the ‘nocache’ flag. 7393 7394 Here are some usage examples: 7395 7396 # Advise to drop cache for whole file 7397 dd if=ifile iflag=nocache count=0 7398 7399 # Ensure drop cache for the whole file 7400 dd of=ofile oflag=nocache conv=notrunc,fdatasync count=0 7401 7402 # Advise to drop cache for part of file 7403 # Note the kernel will only consider complete and 7404 # already persisted pages. 7405 dd if=ifile iflag=nocache skip=10 count=10 of=/dev/null 7406 7407 # Stream data using just the read-ahead cache. 7408 # See also the ‘direct’ flag. 7409 dd if=ifile of=ofile iflag=nocache oflag=nocache,sync 7410 7411 ‘nonblock’ 7412 Use non-blocking I/O. 7413 7414 ‘noatime’ 7415 Do not update the file’s access timestamp. *Note File 7416 timestamps::. Some older file systems silently ignore this 7417 flag, so it is a good idea to test it on your files before 7418 relying on it. 7419 7420 ‘noctty’ 7421 Do not assign the file to be a controlling terminal for ‘dd’. 7422 This has no effect when the file is not a terminal. On many 7423 hosts (e.g., GNU/Linux hosts), this flag has no effect at all. 7424 7425 ‘nofollow’ 7426 Do not follow symbolic links. 7427 7428 ‘nolinks’ 7429 Fail if the file has multiple hard links. 7430 7431 ‘binary’ 7432 Use binary I/O. This flag has an effect only on nonstandard 7433 platforms that distinguish binary from text I/O. 7434 7435 ‘text’ 7436 Use text I/O. Like ‘binary’, this flag has no effect on 7437 standard platforms. 7438 7439 ‘fullblock’ 7440 Accumulate full blocks from input. The ‘read’ system call may 7441 return early if a full block is not available. When that 7442 happens, continue calling ‘read’ to fill the remainder of the 7443 block. This flag can be used only with ‘iflag’. This flag is 7444 useful with pipes for example as they may return short reads. 7445 In that case, this flag is needed to ensure that a ‘count=’ 7446 argument is interpreted as a block count rather than a count 7447 of read operations. 7448 7449 ‘count_bytes’ 7450 Interpret the ‘count=’ operand as a byte count, rather than a 7451 block count, which allows specifying a length that is not a 7452 multiple of the I/O block size. This flag can be used only 7453 with ‘iflag’. 7454 7455 ‘skip_bytes’ 7456 Interpret the ‘skip=’ operand as a byte count, rather than a 7457 block count, which allows specifying an offset that is not a 7458 multiple of the I/O block size. This flag can be used only 7459 with ‘iflag’. 7460 7461 ‘seek_bytes’ 7462 Interpret the ‘seek=’ operand as a byte count, rather than a 7463 block count, which allows specifying an offset that is not a 7464 multiple of the I/O block size. This flag can be used only 7465 with ‘oflag’. 7466 7467 These flags are not supported on all systems, and ‘dd’ rejects 7468 attempts to use them when they are not supported. When reading 7469 from standard input or writing to standard output, the ‘nofollow’ 7470 and ‘noctty’ flags should not be specified, and the other flags 7471 (e.g., ‘nonblock’) can affect how other processes behave with the 7472 affected file descriptors, even after ‘dd’ exits. 7473 7474 The numeric-valued strings above (N and BYTES) can be followed by a 7475multiplier: ‘b’=512, ‘c’=1, ‘w’=2, ‘xM’=M, or any of the standard block 7476size suffixes like ‘k’=1024 (*note Block size::). 7477 7478 Any block size you specify via ‘bs=’, ‘ibs=’, ‘obs=’, ‘cbs=’ should 7479not be too large—values larger than a few megabytes are generally 7480wasteful or (as in the gigabyte..exabyte case) downright 7481counterproductive or error-inducing. 7482 7483 To process data that is at an offset or size that is not a multiple 7484of the I/O block size, you can use the ‘skip_bytes’, ‘seek_bytes’ and 7485‘count_bytes’ flags. Alternatively the traditional method of separate 7486‘dd’ invocations can be used. For example, the following shell commands 7487copy data in 512 KiB blocks between a disk and a tape, but do not save 7488or restore a 4 KiB label at the start of the disk: 7489 7490 disk=/dev/rdsk/c0t1d0s2 7491 tape=/dev/rmt/0 7492 7493 # Copy all but the label from disk to tape. 7494 (dd bs=4k skip=1 count=0 && dd bs=512k) <$disk >$tape 7495 7496 # Copy from tape back to disk, but leave the disk label alone. 7497 (dd bs=4k seek=1 count=0 && dd bs=512k) <$tape >$disk 7498 7499 For failing disks, other tools come with a great variety of extra 7500functionality to ease the saving of as much data as possible before the 7501disk finally dies, e.g. GNU ‘ddrescue’ 7502(https://www.gnu.org/software/ddrescue/). However, in some cases such a 7503tool is not available or the administrator feels more comfortable with 7504the handling of ‘dd’. As a simple rescue method, call ‘dd’ as shown in 7505the following example: the operand ‘conv=noerror,sync’ is used to 7506continue after read errors and to pad out bad reads with NULs, while 7507‘iflag=fullblock’ caters for short reads (which traditionally never 7508occur on disk based devices): 7509 7510 # Rescue data from an (unmounted!) partition of a failing disk. 7511 dd conv=noerror,sync iflag=fullblock </dev/sda1 > /mnt/rescue.img 7512 7513 Sending an ‘INFO’ signal (or ‘USR1’ signal where that is unavailable) 7514to a running ‘dd’ process makes it print I/O statistics to standard 7515error and then resume copying. In the example below, ‘dd’ is run in the 7516background to copy 5GB of data. The ‘kill’ command makes it output 7517intermediate I/O statistics, and when ‘dd’ completes normally or is 7518killed by the ‘SIGINT’ signal, it outputs the final statistics. 7519 7520 # Ignore the signal so we never inadvertently terminate the dd child. 7521 # Note this is not needed when SIGINFO is available. 7522 trap '' USR1 7523 7524 # Run dd with the fullblock iflag to avoid short reads 7525 # which can be triggered by reception of signals. 7526 dd iflag=fullblock if=/dev/zero of=/dev/null count=5000000 bs=1000 & pid=$! 7527 7528 # Output stats every second. 7529 while kill -s USR1 $pid 2>/dev/null; do sleep 1; done 7530 7531 The above script will output in the following format: 7532 7533 3441325+0 records in 7534 3441325+0 records out 7535 3441325000 bytes (3.4 GB, 3.2 GiB) copied, 1.00036 s, 3.4 GB/s 7536 5000000+0 records in 7537 5000000+0 records out 7538 5000000000 bytes (5.0 GB, 4.7 GiB) copied, 1.44433 s, 3.5 GB/s 7539 7540 The ‘status=progress’ operand periodically updates the last line of 7541the transfer statistics above. 7542 7543 On systems lacking the ‘INFO’ signal ‘dd’ responds to the ‘USR1’ 7544signal instead, unless the ‘POSIXLY_CORRECT’ environment variable is 7545set. 7546 7547 An exit status of zero indicates success, and a nonzero value 7548indicates failure. 7549 7550 7551File: coreutils.info, Node: install invocation, Next: mv invocation, Prev: dd invocation, Up: Basic operations 7552 755311.3 ‘install’: Copy files and set attributes 7554============================================= 7555 7556‘install’ copies files while setting their file mode bits and, if 7557possible, their owner and group. Synopses: 7558 7559 install [OPTION]... [-T] SOURCE DEST 7560 install [OPTION]... SOURCE... DIRECTORY 7561 install [OPTION]... -t DIRECTORY SOURCE... 7562 install [OPTION]... -d DIRECTORY... 7563 7564 • If two file names are given, ‘install’ copies the first file to the 7565 second. 7566 7567 • If the ‘--target-directory’ (‘-t’) option is given, or failing that 7568 if the last file is a directory and the ‘--no-target-directory’ 7569 (‘-T’) option is not given, ‘install’ copies each SOURCE file to 7570 the specified directory, using the SOURCEs’ names. 7571 7572 • If the ‘--directory’ (‘-d’) option is given, ‘install’ creates each 7573 DIRECTORY and any missing parent directories. Parent directories 7574 are created with mode ‘u=rwx,go=rx’ (755), regardless of the ‘-m’ 7575 option or the current umask. *Note Directory Setuid and Setgid::, 7576 for how the set-user-ID and set-group-ID bits of parent directories 7577 are inherited. 7578 7579 ‘install’ is similar to ‘cp’, but allows you to control the 7580attributes of destination files. It is typically used in Makefiles to 7581copy programs into their destination directories. It refuses to copy 7582files onto themselves. 7583 7584 ‘install’ never preserves extended attributes (xattr). 7585 7586 The program accepts the following options. Also see *note Common 7587options::. 7588 7589‘-b’ 7590‘--backup[=METHOD]’ 7591 *Note Backup options::. Make a backup of each file that would 7592 otherwise be overwritten or removed. 7593 7594‘-C’ 7595‘--compare’ 7596 Compare each pair of source and destination files, and if the 7597 destination has identical content and any specified owner, group, 7598 permissions, and possibly SELinux context, then do not modify the 7599 destination at all. Note this option is best used in conjunction 7600 with ‘--user’, ‘--group’ and ‘--mode’ options, lest ‘install’ 7601 incorrectly determines the default attributes that installed files 7602 would have (as it doesn’t consider setgid directories and POSIX 7603 default ACLs for example). This could result in redundant copies 7604 or attributes that are not reset to the correct defaults. 7605 7606‘-c’ 7607 Ignored; for compatibility with old Unix versions of ‘install’. 7608 7609‘-D’ 7610 Create any missing parent directories of DEST, then copy SOURCE to 7611 DEST. Explicitly specifying the ‘--target-directory=DIR’ will 7612 similarly ensure the presence of that hierarchy before copying 7613 SOURCE arguments. 7614 7615‘-d’ 7616‘--directory’ 7617 Create any missing parent directories, giving them the default 7618 attributes. Then create each given directory, setting their owner, 7619 group and mode as given on the command line or to the defaults. 7620 7621‘-g GROUP’ 7622‘--group=GROUP’ 7623 Set the group ownership of installed files or directories to GROUP. 7624 The default is the process’s current group. GROUP may be either a 7625 group name or a numeric group ID. 7626 7627‘-m MODE’ 7628‘--mode=MODE’ 7629 Set the file mode bits for the installed file or directory to MODE, 7630 which can be either an octal number, or a symbolic mode as in 7631 ‘chmod’, with ‘a=’ (no access allowed to anyone) as the point of 7632 departure (*note File permissions::). The default mode is 7633 ‘u=rwx,go=rx,a-s’—read, write, and execute for the owner, read and 7634 execute for group and other, and with set-user-ID and set-group-ID 7635 disabled. This default is not quite the same as ‘755’, since it 7636 disables instead of preserving set-user-ID and set-group-ID on 7637 directories. *Note Directory Setuid and Setgid::. 7638 7639‘-o OWNER’ 7640‘--owner=OWNER’ 7641 If ‘install’ has appropriate privileges (is run as root), set the 7642 ownership of installed files or directories to OWNER. The default 7643 is ‘root’. OWNER may be either a user name or a numeric user ID. 7644 7645‘--preserve-context’ 7646 Preserve the SELinux security context of files and directories. 7647 Failure to preserve the context in all of the files or directories 7648 will result in an exit status of 1. If SELinux is disabled then 7649 print a warning and ignore the option. 7650 7651‘-p’ 7652‘--preserve-timestamps’ 7653 Set the time of last access and the time of last modification of 7654 each installed file to match those of each corresponding original 7655 file. When a file is installed without this option, its last 7656 access and last modification timestamps are both set to the time of 7657 installation. This option is useful if you want to use the last 7658 modification timestamps of installed files to keep track of when 7659 they were last built as opposed to when they were last installed. 7660 7661‘-s’ 7662‘--strip’ 7663 Strip the symbol tables from installed binary executables. 7664 7665‘--strip-program=PROGRAM’ 7666 Program used to strip binaries. 7667 7668‘-S SUFFIX’ 7669‘--suffix=SUFFIX’ 7670 Append SUFFIX to each backup file made with ‘-b’. *Note Backup 7671 options::. 7672 7673‘-t DIRECTORY’ 7674‘--target-directory=DIRECTORY’ 7675 Specify the destination DIRECTORY. *Note Target directory::. Also 7676 specifying the ‘-D’ option will ensure the directory is present. 7677 7678‘-T’ 7679‘--no-target-directory’ 7680 Do not treat the last operand specially when it is a directory or a 7681 symbolic link to a directory. *Note Target directory::. 7682 7683‘-v’ 7684‘--verbose’ 7685 Print the name of each file before copying it. 7686 7687‘-Z’ 7688‘--context[=CONTEXT]’ 7689 Without a specified CONTEXT, adjust the SELinux security context 7690 according to the system default type for destination files, 7691 similarly to the ‘restorecon’ command. The long form of this 7692 option with a specific context specified, will set the context for 7693 newly created files only. With a specified context, if both 7694 SELinux and SMACK are disabled, a warning is issued. This option 7695 is mutually exclusive with the ‘--preserve-context’ option. 7696 7697 An exit status of zero indicates success, and a nonzero value 7698indicates failure. 7699 7700 7701File: coreutils.info, Node: mv invocation, Next: rm invocation, Prev: install invocation, Up: Basic operations 7702 770311.4 ‘mv’: Move (rename) files 7704============================== 7705 7706‘mv’ moves or renames files (or directories). Synopses: 7707 7708 mv [OPTION]... [-T] SOURCE DEST 7709 mv [OPTION]... SOURCE... DIRECTORY 7710 mv [OPTION]... -t DIRECTORY SOURCE... 7711 7712 • If two file names are given, ‘mv’ moves the first file to the 7713 second. 7714 7715 • If the ‘--target-directory’ (‘-t’) option is given, or failing that 7716 if the last file is a directory and the ‘--no-target-directory’ 7717 (‘-T’) option is not given, ‘mv’ moves each SOURCE file to the 7718 specified directory, using the SOURCEs’ names. 7719 7720 ‘mv’ can move any type of file from one file system to another. 7721Prior to version ‘4.0’ of the fileutils, ‘mv’ could move only regular 7722files between file systems. For example, now ‘mv’ can move an entire 7723directory hierarchy including special device files from one partition to 7724another. It first uses some of the same code that’s used by ‘cp -a’ to 7725copy the requested directories and files, then (assuming the copy 7726succeeded) it removes the originals. If the copy fails, then the part 7727that was copied to the destination partition is removed. If you were to 7728copy three directories from one partition to another and the copy of the 7729first directory succeeded, but the second didn’t, the first would be 7730left on the destination partition and the second and third would be left 7731on the original partition. 7732 7733 ‘mv’ always tries to copy extended attributes (xattr), which may 7734include SELinux context, ACLs or Capabilities. Upon failure all but 7735‘Operation not supported’ warnings are output. 7736 7737 If a destination file exists but is normally unwritable, standard 7738input is a terminal, and the ‘-f’ or ‘--force’ option is not given, ‘mv’ 7739prompts the user for whether to replace the file. (You might own the 7740file, or have write permission on its directory.) If the response is 7741not affirmative, the file is skipped. 7742 7743 _Warning_: Avoid specifying a source name with a trailing slash, when 7744it might be a symlink to a directory. Otherwise, ‘mv’ may do something 7745very surprising, since its behavior depends on the underlying rename 7746system call. On a system with a modern Linux-based kernel, it fails 7747with ‘errno=ENOTDIR’. However, on other systems (at least FreeBSD 6.1 7748and Solaris 10) it silently renames not the symlink but rather the 7749directory referenced by the symlink. *Note Trailing slashes::. 7750 7751 _Note_: ‘mv’ will only replace empty directories in the destination. 7752Conflicting populated directories are skipped with a diagnostic. 7753 7754 The program accepts the following options. Also see *note Common 7755options::. 7756 7757‘-b’ 7758‘--backup[=METHOD]’ 7759 *Note Backup options::. Make a backup of each file that would 7760 otherwise be overwritten or removed. 7761 7762‘-f’ 7763‘--force’ 7764 Do not prompt the user before removing a destination file. If you 7765 specify more than one of the ‘-i’, ‘-f’, ‘-n’ options, only the 7766 final one takes effect. 7767 7768‘-i’ 7769‘--interactive’ 7770 Prompt whether to overwrite each existing destination file, 7771 regardless of its permissions. If the response is not affirmative, 7772 the file is skipped. If you specify more than one of the ‘-i’, 7773 ‘-f’, ‘-n’ options, only the final one takes effect. 7774 7775‘-n’ 7776‘--no-clobber’ 7777 Do not overwrite an existing file; silently do nothing instead. If 7778 you specify more than one of the ‘-i’, ‘-f’, ‘-n’ options, only the 7779 final one takes effect. This option is mutually exclusive with 7780 ‘-b’ or ‘--backup’ option. 7781 7782‘-u’ 7783‘--update’ 7784 Do not move a non-directory that has an existing destination with 7785 the same or newer modification timestamp. If the move is across 7786 file system boundaries, the comparison is to the source timestamp 7787 truncated to the resolutions of the destination file system and of 7788 the system calls used to update timestamps; this avoids duplicate 7789 work if several ‘mv -u’ commands are executed with the same source 7790 and destination. This option is ignored if the ‘-n’ or 7791 ‘--no-clobber’ option is also specified. 7792 7793‘-v’ 7794‘--verbose’ 7795 Print the name of each file before moving it. 7796 7797‘--strip-trailing-slashes’ 7798 Remove any trailing slashes from each SOURCE argument. *Note 7799 Trailing slashes::. 7800 7801‘-S SUFFIX’ 7802‘--suffix=SUFFIX’ 7803 Append SUFFIX to each backup file made with ‘-b’. *Note Backup 7804 options::. 7805 7806‘-t DIRECTORY’ 7807‘--target-directory=DIRECTORY’ 7808 Specify the destination DIRECTORY. *Note Target directory::. 7809 7810‘-T’ 7811‘--no-target-directory’ 7812 Do not treat the last operand specially when it is a directory or a 7813 symbolic link to a directory. *Note Target directory::. 7814 7815‘-Z’ 7816‘--context’ 7817 This option functions similarly to the ‘restorecon’ command, by 7818 adjusting the SELinux security context according to the system 7819 default type for destination files and each created directory. 7820 7821 An exit status of zero indicates success, and a nonzero value 7822indicates failure. 7823 7824 7825File: coreutils.info, Node: rm invocation, Next: shred invocation, Prev: mv invocation, Up: Basic operations 7826 782711.5 ‘rm’: Remove files or directories 7828====================================== 7829 7830‘rm’ removes each given FILE. By default, it does not remove 7831directories. Synopsis: 7832 7833 rm [OPTION]... [FILE]... 7834 7835 If the ‘-I’ or ‘--interactive=once’ option is given, and there are 7836more than three files or the ‘-r’, ‘-R’, or ‘--recursive’ are given, 7837then ‘rm’ prompts the user for whether to proceed with the entire 7838operation. If the response is not affirmative, the entire command is 7839aborted. 7840 7841 Otherwise, if a file is unwritable, standard input is a terminal, and 7842the ‘-f’ or ‘--force’ option is not given, or the ‘-i’ or 7843‘--interactive=always’ option _is_ given, ‘rm’ prompts the user for 7844whether to remove the file. If the response is not affirmative, the 7845file is skipped. 7846 7847 Any attempt to remove a file whose last file name component is ‘.’ or 7848‘..’ is rejected without any prompting, as mandated by POSIX. 7849 7850 _Warning_: If you use ‘rm’ to remove a file, it is usually possible 7851to recover the contents of that file. If you want more assurance that 7852the contents are unrecoverable, consider using ‘shred’. 7853 7854 The program accepts the following options. Also see *note Common 7855options::. 7856 7857‘-d’ 7858‘--dir’ 7859 Remove the listed directories if they are empty. 7860 7861‘-f’ 7862‘--force’ 7863 Ignore nonexistent files and missing operands, and never prompt the 7864 user. Ignore any previous ‘--interactive’ (‘-i’) option. 7865 7866‘-i’ 7867 Prompt whether to remove each file. If the response is not 7868 affirmative, the file is skipped. Ignore any previous ‘--force’ 7869 (‘-f’) option. Equivalent to ‘--interactive=always’. 7870 7871‘-I’ 7872 Prompt once whether to proceed with the command, if more than three 7873 files are named or if a recursive removal is requested. Ignore any 7874 previous ‘--force’ (‘-f’) option. Equivalent to 7875 ‘--interactive=once’. 7876 7877‘--interactive [=WHEN]’ 7878 Specify when to issue an interactive prompt. WHEN may be omitted, 7879 or one of: 7880 • never - Do not prompt at all. 7881 • once - Prompt once if more than three files are named or if a 7882 recursive removal is requested. Equivalent to ‘-I’. 7883 • always - Prompt for every file being removed. Equivalent to 7884 ‘-i’. 7885 ‘--interactive’ with no WHEN is equivalent to 7886 ‘--interactive=always’. 7887 7888‘--one-file-system’ 7889 When removing a hierarchy recursively, skip any directory that is 7890 on a file system different from that of the corresponding command 7891 line argument. This option is useful when removing a build 7892 “chroot” hierarchy, which normally contains no valuable data. 7893 However, it is not uncommon to bind-mount ‘/home’ into such a 7894 hierarchy, to make it easier to use one’s start-up file. The catch 7895 is that it’s easy to forget to unmount ‘/home’. Then, when you use 7896 ‘rm -rf’ to remove your normally throw-away chroot, that command 7897 will remove everything under ‘/home’, too. Use the 7898 ‘--one-file-system’ option, and it will warn about and skip 7899 directories on other file systems. Of course, this will not save 7900 your ‘/home’ if it and your chroot happen to be on the same file 7901 system. See also ‘--preserve-root=all’ to protect command line 7902 arguments themselves. 7903 7904‘--preserve-root [=all]’ 7905 Fail upon any attempt to remove the root directory, ‘/’, when used 7906 with the ‘--recursive’ option. This is the default behavior. 7907 *Note Treating / specially::. When ‘all’ is specified, reject any 7908 command line argument that is not on the same file system as its 7909 parent. 7910 7911‘--no-preserve-root’ 7912 Do not treat ‘/’ specially when removing recursively. This option 7913 is not recommended unless you really want to remove all the files 7914 on your computer. *Note Treating / specially::. 7915 7916‘-r’ 7917‘-R’ 7918‘--recursive’ 7919 Remove the listed directories and their contents recursively. 7920 7921‘-v’ 7922‘--verbose’ 7923 Print the name of each file before removing it. 7924 7925 One common question is how to remove files whose names begin with a 7926‘-’. GNU ‘rm’, like every program that uses the ‘getopt’ function to 7927parse its arguments, lets you use the ‘--’ option to indicate that all 7928following arguments are non-options. To remove a file called ‘-f’ in 7929the current directory, you could type either: 7930 7931 rm -- -f 7932 7933or: 7934 7935 rm ./-f 7936 7937 The Unix ‘rm’ program’s use of a single ‘-’ for this purpose predates 7938the development of the ‘getopt’ standard syntax. 7939 7940 An exit status of zero indicates success, and a nonzero value 7941indicates failure. 7942 7943 7944File: coreutils.info, Node: shred invocation, Prev: rm invocation, Up: Basic operations 7945 794611.6 ‘shred’: Remove files more securely 7947======================================== 7948 7949‘shred’ overwrites devices or files, to help prevent even extensive 7950forensics from recovering the data. 7951 7952 Ordinarily when you remove a file (*note rm invocation::), its data 7953and metadata are not actually destroyed. Only the file’s directory 7954entry is removed, and the file’s storage is reclaimed only when no 7955process has the file open and no other directory entry links to the 7956file. And even if file’s data and metadata’s storage space is freed for 7957further reuse, there are undelete utilities that will attempt to 7958reconstruct the file from the data in freed storage, and that can bring 7959the file back if the storage was not rewritten. 7960 7961 On a busy system with a nearly-full device, space can get reused in a 7962few seconds. But there is no way to know for sure. And although the 7963undelete utilities and already-existing processes require insider or 7964superuser access, you may be wary of the superuser, of processes running 7965on your behalf, or of attackers that can physically access the storage 7966device. So if you have sensitive data, you may want to be sure that 7967recovery is not possible by plausible attacks like these. 7968 7969 The best way to remove something irretrievably is to destroy the 7970media it’s on with acid, melt it down, or the like. For cheap removable 7971media this is often the preferred method. However, some storage devices 7972are expensive or are harder to destroy, so the ‘shred’ utility tries to 7973achieve a similar effect non-destructively, by overwriting the file with 7974non-sensitive data. 7975 7976 *Please note* that ‘shred’ relies on a crucial assumption: that the 7977file system and hardware overwrite data in place. Although this is 7978common and is the traditional way to do things, but many modern file 7979system designs do not satisfy this assumption. Exceptions include: 7980 7981 • Log-structured or journaled file systems, such as ext3/ext4 (in 7982 ‘data=journal’ mode), Btrfs, NTFS, ReiserFS, XFS, ZFS, file systems 7983 supplied with AIX and Solaris, etc., when they are configured to 7984 journal data. 7985 7986 • File systems that write redundant data and carry on even if some 7987 writes fail, such as RAID-based file systems. 7988 7989 • File systems that make snapshots, such as Network Appliance’s NFS 7990 server. 7991 7992 • File systems that cache in temporary locations, such as NFS version 7993 3 clients. 7994 7995 • Compressed file systems. 7996 7997 For ext3 and ext4 file systems, ‘shred’ is less effective when the 7998file system is in ‘data=journal’ mode, which journals file data in 7999addition to just metadata. In both the ‘data=ordered’ (default) and 8000‘data=writeback’ modes, ‘shred’ works as usual. The ext3/ext4 8001journaling modes can be changed by adding the ‘data=something’ option to 8002the mount options for a particular file system in the ‘/etc/fstab’ file, 8003as documented in the ‘mount’ man page (‘man mount’). Alternatively, if 8004you know how large the journal is, you can shred the journal by 8005shredding enough file data so that the journal cycles around and fills 8006up with shredded data. 8007 8008 If you are not sure how your file system operates, then you should 8009assume that it does not overwrite data in place, which means ‘shred’ 8010cannot reliably operate on regular files in your file system. 8011 8012 Generally speaking, it is more reliable to shred a device than a 8013file, since this bypasses file system design issues mentioned above. 8014However, devices are also problematic for shredding, for reasons such as 8015the following: 8016 8017 • Solid-state storage devices (SSDs) typically do wear leveling to 8018 prolong service life, and this means writes are distributed to 8019 other blocks by the hardware, so “overwritten” data blocks are 8020 still present in the underlying device. 8021 8022 • Most storage devices map out bad blocks invisibly to the 8023 application; if the bad blocks contain sensitive data, ‘shred’ 8024 won’t be able to destroy it. 8025 8026 • With some obsolete storage technologies, it may be possible to take 8027 (say) a floppy disk back to a laboratory and use a lot of sensitive 8028 (and expensive) equipment to look for the faint “echoes” of the 8029 original data underneath the overwritten data. With these older 8030 technologies, if the file has been overwritten only once, it’s 8031 reputedly not even that hard. Luckily, this kind of data recovery 8032 has become difficult, and there is no public evidence that today’s 8033 higher-density storage devices can be analyzed in this way. 8034 8035 The ‘shred’ command can use many overwrite passes, with data 8036 patterns chosen to maximize the damage they do to the old data. By 8037 default the patterns are designed for best effect on hard drives 8038 using now-obsolete technology; for newer devices, a single pass 8039 should suffice. For more details, see the source code and Peter 8040 Gutmann’s paper ‘Secure Deletion of Data from Magnetic and 8041 Solid-State Memory’ 8042 (https://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html), from 8043 the proceedings of the Sixth USENIX Security Symposium (San Jose, 8044 California, July 22–25, 1996). 8045 8046 ‘shred’ makes no attempt to detect or report these problems, just as 8047it makes no attempt to do anything about backups. However, since it is 8048more reliable to shred devices than files, ‘shred’ by default does not 8049deallocate or remove the output file. This default is more suitable for 8050devices, which typically cannot be deallocated and should not be 8051removed. 8052 8053 Finally, consider the risk of backups and mirrors. File system 8054backups and remote mirrors may contain copies of the file that cannot be 8055removed, and that will allow a shredded file to be recovered later. So 8056if you keep any data you may later want to destroy using ‘shred’, be 8057sure that it is not backed up or mirrored. 8058 8059 shred [OPTION]... FILE[...] 8060 8061 The program accepts the following options. Also see *note Common 8062options::. 8063 8064‘-f’ 8065‘--force’ 8066 Override file permissions if necessary to allow overwriting. 8067 8068‘-n NUMBER’ 8069‘--iterations=NUMBER’ 8070 By default, ‘shred’ uses 3 passes of overwrite. You can reduce 8071 this to save time, or increase it if you think it’s appropriate. 8072 After 25 passes all of the internal overwrite patterns will have 8073 been used at least once. 8074 8075‘--random-source=FILE’ 8076 Use FILE as a source of random data used to overwrite and to choose 8077 pass ordering. *Note Random sources::. 8078 8079‘-s BYTES’ 8080‘--size=BYTES’ 8081 Shred the first BYTES bytes of the file. The default is to shred 8082 the whole file. BYTES can be followed by a size specification like 8083 ‘K’, ‘M’, or ‘G’ to specify a multiple. *Note Block size::. 8084 8085‘-u’ 8086‘--remove[=HOW]’ 8087 After shredding a file, deallocate it (if possible) and then remove 8088 it. If a file has multiple links, only the named links will be 8089 removed. Often the file name is less sensitive than the file data, 8090 in which case the optional HOW parameter, supported with the long 8091 form option, gives control of how to more efficiently remove each 8092 directory entry. The ‘unlink’ parameter will just use a standard 8093 unlink call, ‘wipe’ will also first obfuscate bytes in the name, 8094 and ‘wipesync’ will also sync each obfuscated byte in the name to 8095 disk. Note ‘wipesync’ is the default method, but can be expensive, 8096 requiring a sync for every character in every file. This can 8097 become significant with many files, or is redundant if your file 8098 system provides synchronous metadata updates. 8099 8100‘-v’ 8101‘--verbose’ 8102 Display to standard error all status updates as sterilization 8103 proceeds. 8104 8105‘-x’ 8106‘--exact’ 8107 By default, ‘shred’ rounds the size of a regular file up to the 8108 next multiple of the file system block size to fully erase the 8109 slack space in the last block of the file. This space may contain 8110 portions of the current system memory on some systems for example. 8111 Use ‘--exact’ to suppress that behavior. Thus, by default if you 8112 shred a 10-byte regular file on a system with 512-byte blocks, the 8113 resulting file will be 512 bytes long. With this option, shred 8114 does not increase the apparent size of the file. 8115 8116‘-z’ 8117‘--zero’ 8118 Normally, the last pass that ‘shred’ writes is made up of random 8119 data. If this would be conspicuous on your storage device (for 8120 example, because it looks like encrypted data), or you just think 8121 it’s tidier, the ‘--zero’ option adds an additional overwrite pass 8122 with all zero bits. This is in addition to the number of passes 8123 specified by the ‘--iterations’ option. 8124 8125 You might use the following command to erase the file system you 8126created on a USB flash drive. This command typically takes several 8127minutes, depending on the drive’s size and write speed. On modern 8128storage devices a single pass should be adequate, and will take one 8129third the time of the default three-pass approach. 8130 8131 shred -v -n 1 /dev/sdd1 8132 8133 Similarly, to erase all data on a selected partition of your hard 8134disk, you could give a command like the following. 8135 8136 # 1 pass, write pseudo-random data; 3x faster than the default 8137 shred -v -n1 /dev/sda5 8138 8139 To be on the safe side, use at least one pass that overwrites using 8140pseudo-random data. I.e., don’t be tempted to use ‘-n0 --zero’, in case 8141some disk controller optimizes the process of writing blocks of all 8142zeros, and thereby does not clear all bytes in a block. Some SSDs may 8143do just that. 8144 8145 A FILE of ‘-’ denotes standard output. The intended use of this is 8146to shred a removed temporary file. For example: 8147 8148 i=$(mktemp) 8149 exec 3<>"$i" 8150 rm -- "$i" 8151 echo "Hello, world" >&3 8152 shred - >&3 8153 exec 3>- 8154 8155 However, the command ‘shred - >file’ does not shred the contents of 8156FILE, since the shell truncates FILE before invoking ‘shred’. Use the 8157command ‘shred file’ or (if using a Bourne-compatible shell) the command 8158‘shred - 1<>file’ instead. 8159 8160 An exit status of zero indicates success, and a nonzero value 8161indicates failure. 8162 8163 8164File: coreutils.info, Node: Special file types, Next: Changing file attributes, Prev: Basic operations, Up: Top 8165 816612 Special file types 8167********************* 8168 8169This chapter describes commands which create special types of files (and 8170‘rmdir’, which removes directories, one special file type). 8171 8172 Although Unix-like operating systems have markedly fewer special file 8173types than others, not _everything_ can be treated only as the 8174undifferentiated byte stream of “normal files”. For example, when a 8175file is created or removed, the system must record this information, 8176which it does in a “directory”—a special type of file. Although you can 8177read directories as normal files, if you’re curious, in order for the 8178system to do its job it must impose a structure, a certain order, on the 8179bytes of the file. Thus it is a “special” type of file. 8180 8181 Besides directories, other special file types include named pipes 8182(FIFOs), symbolic links, sockets, and so-called “special files”. 8183 8184* Menu: 8185 8186* link invocation:: Make a hard link via the link syscall 8187* ln invocation:: Make links between files. 8188* mkdir invocation:: Make directories. 8189* mkfifo invocation:: Make FIFOs (named pipes). 8190* mknod invocation:: Make block or character special files. 8191* readlink invocation:: Print value of a symlink or canonical file name. 8192* rmdir invocation:: Remove empty directories. 8193* unlink invocation:: Remove files via the unlink syscall 8194 8195 8196File: coreutils.info, Node: link invocation, Next: ln invocation, Up: Special file types 8197 819812.1 ‘link’: Make a hard link via the link syscall 8199================================================== 8200 8201‘link’ creates a single hard link at a time. It is a minimalist 8202interface to the system-provided ‘link’ function. *Note (libc)Hard 8203Links::. It avoids the bells and whistles of the more commonly-used 8204‘ln’ command (*note ln invocation::). Synopsis: 8205 8206 link FILENAME LINKNAME 8207 8208 FILENAME must specify an existing file, and LINKNAME must specify a 8209nonexistent entry in an existing directory. ‘link’ simply calls ‘link 8210(FILENAME, LINKNAME)’ to create the link. 8211 8212 On a GNU system, this command acts like ‘ln --directory 8213--no-target-directory FILENAME LINKNAME’. However, the ‘--directory’ 8214and ‘--no-target-directory’ options are not specified by POSIX, and the 8215‘link’ command is more portable in practice. 8216 8217 If FILENAME is a symbolic link, it is unspecified whether LINKNAME 8218will be a hard link to the symbolic link or to the target of the 8219symbolic link. Use ‘ln -P’ or ‘ln -L’ to specify which behavior is 8220desired. 8221 8222 An exit status of zero indicates success, and a nonzero value 8223indicates failure. 8224 8225 8226File: coreutils.info, Node: ln invocation, Next: mkdir invocation, Prev: link invocation, Up: Special file types 8227 822812.2 ‘ln’: Make links between files 8229=================================== 8230 8231‘ln’ makes links between files. By default, it makes hard links; with 8232the ‘-s’ option, it makes symbolic (or “soft”) links. Synopses: 8233 8234 ln [OPTION]... [-T] TARGET LINKNAME 8235 ln [OPTION]... TARGET 8236 ln [OPTION]... TARGET... DIRECTORY 8237 ln [OPTION]... -t DIRECTORY TARGET... 8238 8239 • If two file names are given, ‘ln’ creates a link to the first file 8240 from the second. 8241 8242 • If one TARGET is given, ‘ln’ creates a link to that file in the 8243 current directory. 8244 8245 • If the ‘--target-directory’ (‘-t’) option is given, or failing that 8246 if the last file is a directory and the ‘--no-target-directory’ 8247 (‘-T’) option is not given, ‘ln’ creates a link to each TARGET file 8248 in the specified directory, using the TARGETs’ names. 8249 8250 Normally ‘ln’ does not replace existing files. Use the ‘--force’ 8251(‘-f’) option to replace them unconditionally, the ‘--interactive’ 8252(‘-i’) option to replace them conditionally, and the ‘--backup’ (‘-b’) 8253option to rename them. Unless the ‘--backup’ (‘-b’) option is used 8254there is no brief moment when the destination does not exist; this is an 8255extension to POSIX. 8256 8257 A “hard link” is another name for an existing file; the link and the 8258original are indistinguishable. Technically speaking, they share the 8259same inode, and the inode contains all the information about a 8260file—indeed, it is not incorrect to say that the inode _is_ the file. 8261Most systems prohibit making a hard link to a directory; on those where 8262it is allowed, only the super-user can do so (and with caution, since 8263creating a cycle will cause problems to many other utilities). Hard 8264links cannot cross file system boundaries. (These restrictions are not 8265mandated by POSIX, however.) 8266 8267 “Symbolic links” (“symlinks” for short), on the other hand, are a 8268special file type (which not all kernels support: System V release 3 8269(and older) systems lack symlinks) in which the link file actually 8270refers to a different file, by name. When most operations (opening, 8271reading, writing, and so on) are passed the symbolic link file, the 8272kernel automatically “dereferences” the link and operates on the target 8273of the link. But some operations (e.g., removing) work on the link file 8274itself, rather than on its target. The owner and group of a symlink are 8275not significant to file access performed through the link, but do have 8276implications on deleting a symbolic link from a directory with the 8277restricted deletion bit set. On the GNU system, the mode of a symlink 8278has no significance and cannot be changed, but on some BSD systems, the 8279mode can be changed and will affect whether the symlink will be 8280traversed in file name resolution. *Note (libc)Symbolic Links::. 8281 8282 Symbolic links can contain arbitrary strings; a “dangling symlink” 8283occurs when the string in the symlink does not resolve to a file. There 8284are no restrictions against creating dangling symbolic links. There are 8285trade-offs to using absolute or relative symlinks. An absolute symlink 8286always points to the same file, even if the directory containing the 8287link is moved. However, if the symlink is visible from more than one 8288machine (such as on a networked file system), the file pointed to might 8289not always be the same. A relative symbolic link is resolved in 8290relation to the directory that contains the link, and is often useful in 8291referring to files on the same device without regards to what name that 8292device is mounted on when accessed via networked machines. 8293 8294 When creating a relative symlink in a different location than the 8295current directory, the resolution of the symlink will be different than 8296the resolution of the same string from the current directory. 8297Therefore, many users prefer to first change directories to the location 8298where the relative symlink will be created, so that tab-completion or 8299other file resolution will find the same target as what will be placed 8300in the symlink. 8301 8302 The program accepts the following options. Also see *note Common 8303options::. 8304 8305‘-b’ 8306‘--backup[=METHOD]’ 8307 *Note Backup options::. Make a backup of each file that would 8308 otherwise be overwritten or removed. 8309 8310‘-d’ 8311‘-F’ 8312‘--directory’ 8313 Allow users with appropriate privileges to attempt to make hard 8314 links to directories. However, note that this will probably fail 8315 due to system restrictions, even for the super-user. 8316 8317‘-f’ 8318‘--force’ 8319 Remove existing destination files. 8320 8321‘-i’ 8322‘--interactive’ 8323 Prompt whether to remove existing destination files. 8324 8325‘-L’ 8326‘--logical’ 8327 If ‘-s’ is not in effect, and the source file is a symbolic link, 8328 create the hard link to the file referred to by the symbolic link, 8329 rather than the symbolic link itself. 8330 8331‘-n’ 8332‘--no-dereference’ 8333 Do not treat the last operand specially when it is a symbolic link 8334 to a directory. Instead, treat it as if it were a normal file. 8335 8336 When the destination is an actual directory (not a symlink to one), 8337 there is no ambiguity. The link is created in that directory. But 8338 when the specified destination is a symlink to a directory, there 8339 are two ways to treat the user’s request. ‘ln’ can treat the 8340 destination just as it would a normal directory and create the link 8341 in it. On the other hand, the destination can be viewed as a 8342 non-directory—as the symlink itself. In that case, ‘ln’ must 8343 delete or backup that symlink before creating the new link. The 8344 default is to treat a destination that is a symlink to a directory 8345 just like a directory. 8346 8347 This option is weaker than the ‘--no-target-directory’ (‘-T’) 8348 option, so it has no effect if both options are given. 8349 8350‘-P’ 8351‘--physical’ 8352 If ‘-s’ is not in effect, and the source file is a symbolic link, 8353 create the hard link to the symbolic link itself. On platforms 8354 where this is not supported by the kernel, this option creates a 8355 symbolic link with identical contents; since symbolic link contents 8356 cannot be edited, any file name resolution performed through either 8357 link will be the same as if a hard link had been created. 8358 8359‘-r’ 8360‘--relative’ 8361 Make symbolic links relative to the link location. 8362 8363 Example: 8364 8365 ln -srv /a/file /tmp 8366 '/tmp/file' -> '../a/file' 8367 8368 Relative symbolic links are generated based on their canonicalized 8369 containing directory, and canonicalized targets. I.e., all 8370 symbolic links in these file names will be resolved. *Note 8371 realpath invocation::, which gives greater control over relative 8372 file name generation, as demonstrated in the following example: 8373 8374 ln--relative() { 8375 test "$1" = --no-symlinks && { nosym=$1; shift; } 8376 target="$1"; 8377 test -d "$2" && link="$2/." || link="$2" 8378 rtarget="$(realpath $nosym -m "$target" \ 8379 --relative-to "$(dirname "$link")")" 8380 ln -s -v "$rtarget" "$link" 8381 } 8382 8383‘-s’ 8384‘--symbolic’ 8385 Make symbolic links instead of hard links. This option merely 8386 produces an error message on systems that do not support symbolic 8387 links. 8388 8389‘-S SUFFIX’ 8390‘--suffix=SUFFIX’ 8391 Append SUFFIX to each backup file made with ‘-b’. *Note Backup 8392 options::. 8393 8394‘-t DIRECTORY’ 8395‘--target-directory=DIRECTORY’ 8396 Specify the destination DIRECTORY. *Note Target directory::. 8397 8398‘-T’ 8399‘--no-target-directory’ 8400 Do not treat the last operand specially when it is a directory or a 8401 symbolic link to a directory. *Note Target directory::. 8402 8403‘-v’ 8404‘--verbose’ 8405 Print the name of each file after linking it successfully. 8406 8407 If ‘-L’ and ‘-P’ are both given, the last one takes precedence. If 8408‘-s’ is also given, ‘-L’ and ‘-P’ are silently ignored. If neither 8409option is given, then this implementation defaults to ‘-P’ if the system 8410‘link’ supports hard links to symbolic links (such as the GNU system), 8411and ‘-L’ if ‘link’ follows symbolic links (such as on BSD). 8412 8413 An exit status of zero indicates success, and a nonzero value 8414indicates failure. 8415 8416 Examples: 8417 8418 Bad Example: 8419 8420 # Create link ../a pointing to a in that directory. 8421 # Not really useful because it points to itself. 8422 ln -s a .. 8423 8424 Better Example: 8425 8426 # Change to the target before creating symlinks to avoid being confused. 8427 cd .. 8428 ln -s adir/a . 8429 8430 Bad Example: 8431 8432 # Hard coded file names don't move well. 8433 ln -s $(pwd)/a /some/dir/ 8434 8435 Better Example: 8436 8437 # Relative file names survive directory moves and also 8438 # work across networked file systems. 8439 ln -s afile anotherfile 8440 ln -s ../adir/afile yetanotherfile 8441 8442 8443File: coreutils.info, Node: mkdir invocation, Next: mkfifo invocation, Prev: ln invocation, Up: Special file types 8444 844512.3 ‘mkdir’: Make directories 8446============================== 8447 8448‘mkdir’ creates directories with the specified names. Synopsis: 8449 8450 mkdir [OPTION]... NAME... 8451 8452 ‘mkdir’ creates each directory NAME in the order given. It reports 8453an error if NAME already exists, unless the ‘-p’ option is given and 8454NAME is a directory. 8455 8456 The program accepts the following options. Also see *note Common 8457options::. 8458 8459‘-m MODE’ 8460‘--mode=MODE’ 8461 Set the file permission bits of created directories to MODE, which 8462 uses the same syntax as in ‘chmod’ and uses ‘a=rwx’ (read, write 8463 and execute allowed for everyone) for the point of the departure. 8464 *Note File permissions::. 8465 8466 Normally the directory has the desired file mode bits at the moment 8467 it is created. As a GNU extension, MODE may also mention special 8468 mode bits, but in this case there may be a temporary window during 8469 which the directory exists but its special mode bits are incorrect. 8470 *Note Directory Setuid and Setgid::, for how the set-user-ID and 8471 set-group-ID bits of directories are inherited unless overridden in 8472 this way. 8473 8474‘-p’ 8475‘--parents’ 8476 Make any missing parent directories for each argument, setting 8477 their file permission bits to the umask modified by ‘u+wx’. Ignore 8478 existing parent directories, and do not change their file 8479 permission bits. 8480 8481 To set the file permission bits of any newly-created parent 8482 directories to a value that includes ‘u+wx’, you can set the umask 8483 before invoking ‘mkdir’. For example, if the shell command ‘(umask 8484 u=rwx,go=rx; mkdir -p P/Q)’ creates the parent ‘P’ it sets the 8485 parent’s permission bits to ‘u=rwx,go=rx’. To set a parent’s 8486 special mode bits as well, you can invoke ‘chmod’ after ‘mkdir’. 8487 *Note Directory Setuid and Setgid::, for how the set-user-ID and 8488 set-group-ID bits of newly-created parent directories are 8489 inherited. 8490 8491‘-v’ 8492‘--verbose’ 8493 Print a message for each created directory. This is most useful 8494 with ‘--parents’. 8495 8496‘-Z’ 8497‘--context[=CONTEXT]’ 8498 Without a specified CONTEXT, adjust the SELinux security context 8499 according to the system default type for destination files, 8500 similarly to the ‘restorecon’ command. The long form of this 8501 option with a specific context specified, will set the context for 8502 newly created files only. With a specified context, if both 8503 SELinux and SMACK are disabled, a warning is issued. 8504 8505 An exit status of zero indicates success, and a nonzero value 8506indicates failure. 8507 8508 8509File: coreutils.info, Node: mkfifo invocation, Next: mknod invocation, Prev: mkdir invocation, Up: Special file types 8510 851112.4 ‘mkfifo’: Make FIFOs (named pipes) 8512======================================= 8513 8514‘mkfifo’ creates FIFOs (also called “named pipes”) with the specified 8515names. Synopsis: 8516 8517 mkfifo [OPTION] NAME... 8518 8519 A “FIFO” is a special file type that permits independent processes to 8520communicate. One process opens the FIFO file for writing, and another 8521for reading, after which data can flow as with the usual anonymous pipe 8522in shells or elsewhere. 8523 8524 The program accepts the following options. Also see *note Common 8525options::. 8526 8527‘-m MODE’ 8528‘--mode=MODE’ 8529 Set the mode of created FIFOs to MODE, which is symbolic as in 8530 ‘chmod’ and uses ‘a=rw’ (read and write allowed for everyone) for 8531 the point of departure. MODE should specify only file permission 8532 bits. *Note File permissions::. 8533 8534‘-Z’ 8535‘--context[=CONTEXT]’ 8536 Without a specified CONTEXT, adjust the SELinux security context 8537 according to the system default type for destination files, 8538 similarly to the ‘restorecon’ command. The long form of this 8539 option with a specific context specified, will set the context for 8540 newly created files only. With a specified context, if both 8541 SELinux and SMACK are disabled, a warning is issued. 8542 8543 An exit status of zero indicates success, and a nonzero value 8544indicates failure. 8545 8546 8547File: coreutils.info, Node: mknod invocation, Next: readlink invocation, Prev: mkfifo invocation, Up: Special file types 8548 854912.5 ‘mknod’: Make block or character special files 8550=================================================== 8551 8552‘mknod’ creates a FIFO, character special file, or block special file 8553with the specified name. Synopsis: 8554 8555 mknod [OPTION]... NAME TYPE [MAJOR MINOR] 8556 8557 Unlike the phrase “special file type” above, the term “special file” 8558has a technical meaning on Unix: something that can generate or receive 8559data. Usually this corresponds to a physical piece of hardware, e.g., a 8560printer or a disk. (These files are typically created at 8561system-configuration time.) The ‘mknod’ command is what creates files 8562of this type. Such devices can be read either a character at a time or 8563a “block” (many characters) at a time, hence we say there are “block 8564special” files and “character special” files. 8565 8566 Due to shell aliases and built-in ‘mknod’ functions, using an 8567unadorned ‘mknod’ interactively or in a script may get you different 8568functionality than that described here. Invoke it via ‘env’ (i.e., ‘env 8569mknod ...’) to avoid interference from the shell. 8570 8571 The arguments after NAME specify the type of file to make: 8572 8573‘p’ 8574 for a FIFO 8575 8576‘b’ 8577 for a block special file 8578 8579‘c’ 8580 for a character special file 8581 8582 When making a block or character special file, the major and minor 8583device numbers must be given after the file type. If a major or minor 8584device number begins with ‘0x’ or ‘0X’, it is interpreted as 8585hexadecimal; otherwise, if it begins with ‘0’, as octal; otherwise, as 8586decimal. 8587 8588 The program accepts the following options. Also see *note Common 8589options::. 8590 8591‘-m MODE’ 8592‘--mode=MODE’ 8593 Set the mode of created files to MODE, which is symbolic as in 8594 ‘chmod’ and uses ‘a=rw’ as the point of departure. MODE should 8595 specify only file permission bits. *Note File permissions::. 8596 8597‘-Z’ 8598‘--context[=CONTEXT]’ 8599 Without a specified CONTEXT, adjust the SELinux security context 8600 according to the system default type for destination files, 8601 similarly to the ‘restorecon’ command. The long form of this 8602 option with a specific context specified, will set the context for 8603 newly created files only. With a specified context, if both 8604 SELinux and SMACK are disabled, a warning is issued. 8605 8606 An exit status of zero indicates success, and a nonzero value 8607indicates failure. 8608 8609 8610File: coreutils.info, Node: readlink invocation, Next: rmdir invocation, Prev: mknod invocation, Up: Special file types 8611 861212.6 ‘readlink’: Print value of a symlink or canonical file name 8613================================================================ 8614 8615‘readlink’ may work in one of two supported modes: 8616 8617‘Readlink mode’ 8618 8619 ‘readlink’ outputs the value of the given symbolic links. If 8620 ‘readlink’ is invoked with an argument other than the name of a 8621 symbolic link, it produces no output and exits with a nonzero exit 8622 code. 8623 8624‘Canonicalize mode’ 8625 8626 ‘readlink’ outputs the absolute name of the given files which 8627 contain no ‘.’, ‘..’ components nor any repeated separators (‘/’) 8628 or symbolic links. Note the ‘realpath’ command is the preferred 8629 command to use for canonicalization. *Note realpath invocation::. 8630 8631 readlink [OPTION]... FILE... 8632 8633 By default, ‘readlink’ operates in readlink mode. 8634 8635 The program accepts the following options. Also see *note Common 8636options::. 8637 8638‘-f’ 8639‘--canonicalize’ 8640 Activate canonicalize mode. If any component of the file name 8641 except the last one is missing or unavailable, ‘readlink’ produces 8642 no output and exits with a nonzero exit code. A trailing slash is 8643 ignored. 8644 8645‘-e’ 8646‘--canonicalize-existing’ 8647 Activate canonicalize mode. If any component is missing or 8648 unavailable, ‘readlink’ produces no output and exits with a nonzero 8649 exit code. A trailing slash requires that the name resolve to a 8650 directory. 8651 8652‘-m’ 8653‘--canonicalize-missing’ 8654 Activate canonicalize mode. If any component is missing or 8655 unavailable, ‘readlink’ treats it as a directory. 8656 8657‘-n’ 8658‘--no-newline’ 8659 Do not print the output delimiter, when a single FILE is specified. 8660 Print a warning if specified along with multiple FILEs. 8661 8662‘-s’ 8663‘-q’ 8664‘--silent’ 8665‘--quiet’ 8666 Suppress most error messages. On by default. 8667 8668‘-v’ 8669‘--verbose’ 8670 Report error messages. 8671 8672‘-z’ 8673‘--zero’ 8674 Output a zero byte (ASCII NUL) at the end of each line, rather than 8675 a newline. This option enables other programs to parse the output 8676 even when that output would contain data with embedded newlines. 8677 8678 The ‘readlink’ utility first appeared in OpenBSD 2.1. 8679 8680 The ‘realpath’ command without options, operates like ‘readlink’ in 8681canonicalize mode. 8682 8683 An exit status of zero indicates success, and a nonzero value 8684indicates failure. 8685 8686 8687File: coreutils.info, Node: rmdir invocation, Next: unlink invocation, Prev: readlink invocation, Up: Special file types 8688 868912.7 ‘rmdir’: Remove empty directories 8690====================================== 8691 8692‘rmdir’ removes empty directories. Synopsis: 8693 8694 rmdir [OPTION]... DIRECTORY... 8695 8696 If any DIRECTORY argument does not refer to an existing empty 8697directory, it is an error. 8698 8699 The program accepts the following options. Also see *note Common 8700options::. 8701 8702‘--ignore-fail-on-non-empty’ 8703 Ignore each failure to remove a directory that is solely because 8704 the directory is non-empty. 8705 8706‘-p’ 8707‘--parents’ 8708 Remove DIRECTORY, then try to remove each component of DIRECTORY. 8709 So, for example, ‘rmdir -p a/b/c’ is similar to ‘rmdir a/b/c a/b 8710 a’. As such, it fails if any of those directories turns out not to 8711 be empty. Use the ‘--ignore-fail-on-non-empty’ option to make it 8712 so such a failure does not evoke a diagnostic and does not cause 8713 ‘rmdir’ to exit unsuccessfully. 8714 8715‘-v’ 8716‘--verbose’ 8717 Give a diagnostic for each successful removal. DIRECTORY is 8718 removed. 8719 8720 *Note rm invocation::, for how to remove non-empty directories 8721(recursively). 8722 8723 An exit status of zero indicates success, and a nonzero value 8724indicates failure. 8725 8726 8727File: coreutils.info, Node: unlink invocation, Prev: rmdir invocation, Up: Special file types 8728 872912.8 ‘unlink’: Remove files via the unlink syscall 8730================================================== 8731 8732‘unlink’ deletes a single specified file name. It is a minimalist 8733interface to the system-provided ‘unlink’ function. *Note 8734(libc)Deleting Files::. Synopsis: It avoids the bells and whistles of 8735the more commonly-used ‘rm’ command (*note rm invocation::). 8736 8737 unlink FILENAME 8738 8739 On some systems ‘unlink’ can be used to delete the name of a 8740directory. On others, it can be used that way only by a privileged 8741user. In the GNU system ‘unlink’ can never delete the name of a 8742directory. 8743 8744 The ‘unlink’ command honors the ‘--help’ and ‘--version’ options. To 8745remove a file whose name begins with ‘-’, prefix the name with ‘./’, 8746e.g., ‘unlink ./--help’. 8747 8748 An exit status of zero indicates success, and a nonzero value 8749indicates failure. 8750 8751 8752File: coreutils.info, Node: Changing file attributes, Next: Disk usage, Prev: Special file types, Up: Top 8753 875413 Changing file attributes 8755*************************** 8756 8757A file is not merely its contents, a name, and a file type (*note 8758Special file types::). A file also has an owner (a user ID), a group (a 8759group ID), permissions (what the owner can do with the file, what people 8760in the group can do, and what everyone else can do), various timestamps, 8761and other information. Collectively, we call these a file’s 8762“attributes”. 8763 8764 These commands change file attributes. 8765 8766* Menu: 8767 8768* chown invocation:: Change file owners and groups. 8769* chgrp invocation:: Change file groups. 8770* chmod invocation:: Change access permissions. 8771* touch invocation:: Change file timestamps. 8772 8773 8774File: coreutils.info, Node: chown invocation, Next: chgrp invocation, Up: Changing file attributes 8775 877613.1 ‘chown’: Change file owner and group 8777========================================= 8778 8779‘chown’ changes the user and/or group ownership of each given FILE to 8780NEW-OWNER or to the user and group of an existing reference file. 8781Synopsis: 8782 8783 chown [OPTION]... {NEW-OWNER | --reference=REF_FILE} FILE... 8784 8785 If used, NEW-OWNER specifies the new owner and/or group as follows 8786(with no embedded white space): 8787 8788 [OWNER] [ : [GROUP] ] 8789 8790 Specifically: 8791 8792OWNER 8793 If only an OWNER (a user name or numeric user ID) is given, that 8794 user is made the owner of each given file, and the files’ group is 8795 not changed. 8796 8797OWNER‘:’GROUP 8798 If the OWNER is followed by a colon and a GROUP (a group name or 8799 numeric group ID), with no spaces between them, the group ownership 8800 of the files is changed as well (to GROUP). 8801 8802OWNER‘:’ 8803 If a colon but no group name follows OWNER, that user is made the 8804 owner of the files and the group of the files is changed to OWNER’s 8805 login group. 8806 8807‘:’GROUP 8808 If the colon and following GROUP are given, but the owner is 8809 omitted, only the group of the files is changed; in this case, 8810 ‘chown’ performs the same function as ‘chgrp’. 8811 8812‘:’ 8813 If only a colon is given, or if NEW-OWNER is empty, neither the 8814 owner nor the group is changed. 8815 8816 If OWNER or GROUP is intended to represent a numeric user or group 8817ID, then you may specify it with a leading ‘+’. *Note Disambiguating 8818names and IDs::. 8819 8820 Some older scripts may still use ‘.’ in place of the ‘:’ separator. 8821POSIX 1003.1-2001 (*note Standards conformance::) does not require 8822support for that, but for backward compatibility GNU ‘chown’ supports 8823‘.’ so long as no ambiguity results. New scripts should avoid the use 8824of ‘.’ because it is not portable, and because it has undesirable 8825results if the entire OWNER‘.’GROUP happens to identify a user whose 8826name contains ‘.’. 8827 8828 It is system dependent whether a user can change the group to an 8829arbitrary one, or the more portable behavior of being restricted to 8830setting a group of which the user is a member. 8831 8832 The ‘chown’ command sometimes clears the set-user-ID or set-group-ID 8833permission bits. This behavior depends on the policy and functionality 8834of the underlying ‘chown’ system call, which may make system-dependent 8835file mode modifications outside the control of the ‘chown’ command. For 8836example, the ‘chown’ command might not affect those bits when invoked by 8837a user with appropriate privileges, or when the bits signify some 8838function other than executable permission (e.g., mandatory locking). 8839When in doubt, check the underlying system behavior. 8840 8841 The program accepts the following options. Also see *note Common 8842options::. 8843 8844‘-c’ 8845‘--changes’ 8846 Verbosely describe the action for each FILE whose ownership 8847 actually changes. 8848 8849‘-f’ 8850‘--silent’ 8851‘--quiet’ 8852 Do not print error messages about files whose ownership cannot be 8853 changed. 8854 8855‘--from=OLD-OWNER’ 8856 Change a FILE’s ownership only if it has current attributes 8857 specified by OLD-OWNER. OLD-OWNER has the same form as NEW-OWNER 8858 described above. This option is useful primarily from a security 8859 standpoint in that it narrows considerably the window of potential 8860 abuse. For example, to reflect a user ID numbering change for one 8861 user’s files without an option like this, ‘root’ might run 8862 8863 find / -owner OLDUSER -print0 | xargs -0 chown -h NEWUSER 8864 8865 But that is dangerous because the interval between when the ‘find’ 8866 tests the existing file’s owner and when the ‘chown’ is actually 8867 run may be quite large. One way to narrow the gap would be to 8868 invoke chown for each file as it is found: 8869 8870 find / -owner OLDUSER -exec chown -h NEWUSER {} \; 8871 8872 But that is very slow if there are many affected files. With this 8873 option, it is safer (the gap is narrower still) though still not 8874 perfect: 8875 8876 chown -h -R --from=OLDUSER NEWUSER / 8877 8878‘--dereference’ 8879 Do not act on symbolic links themselves but rather on what they 8880 point to. This is the default when not operating recursively. 8881 8882 Combining this dereferencing option with the ‘--recursive’ option 8883 may create a security risk: During the traversal of the directory 8884 tree, an attacker may be able to introduce a symlink to an 8885 arbitrary target; when the tool reaches that, the operation will be 8886 performed on the target of that symlink, possibly allowing the 8887 attacker to escalate privileges. 8888 8889‘-h’ 8890‘--no-dereference’ 8891 Act on symbolic links themselves instead of what they point to. 8892 This mode relies on the ‘lchown’ system call. On systems that do 8893 not provide the ‘lchown’ system call, ‘chown’ fails when a file 8894 specified on the command line is a symbolic link. By default, no 8895 diagnostic is issued for symbolic links encountered during a 8896 recursive traversal, but see ‘--verbose’. 8897 8898‘--preserve-root’ 8899 Fail upon any attempt to recursively change the root directory, 8900 ‘/’. Without ‘--recursive’, this option has no effect. *Note 8901 Treating / specially::. 8902 8903‘--no-preserve-root’ 8904 Cancel the effect of any preceding ‘--preserve-root’ option. *Note 8905 Treating / specially::. 8906 8907‘--reference=REF_FILE’ 8908 Change the user and group of each FILE to be the same as those of 8909 REF_FILE. If REF_FILE is a symbolic link, do not use the user and 8910 group of the symbolic link, but rather those of the file it refers 8911 to. 8912 8913‘-v’ 8914‘--verbose’ 8915 Output a diagnostic for every file processed. If a symbolic link 8916 is encountered during a recursive traversal on a system without the 8917 ‘lchown’ system call, and ‘--no-dereference’ is in effect, then 8918 issue a diagnostic saying neither the symbolic link nor its 8919 referent is being changed. 8920 8921‘-R’ 8922‘--recursive’ 8923 Recursively change ownership of directories and their contents. 8924 8925‘-H’ 8926 If ‘--recursive’ (‘-R’) is specified and a command line argument is 8927 a symbolic link to a directory, traverse it. *Note Traversing 8928 symlinks::. 8929 8930‘-L’ 8931 In a recursive traversal, traverse every symbolic link to a 8932 directory that is encountered. 8933 8934 Combining this dereferencing option with the ‘--recursive’ option 8935 may create a security risk: During the traversal of the directory 8936 tree, an attacker may be able to introduce a symlink to an 8937 arbitrary target; when the tool reaches that, the operation will be 8938 performed on the target of that symlink, possibly allowing the 8939 attacker to escalate privileges. 8940 8941 *Note Traversing symlinks::. 8942 8943‘-P’ 8944 Do not traverse any symbolic links. This is the default if none of 8945 ‘-H’, ‘-L’, or ‘-P’ is specified. *Note Traversing symlinks::. 8946 8947 An exit status of zero indicates success, and a nonzero value 8948indicates failure. 8949 8950 Examples: 8951 8952 # Change the owner of /u to "root". 8953 chown root /u 8954 8955 # Likewise, but also change its group to "staff". 8956 chown root:staff /u 8957 8958 # Change the owner of /u and subfiles to "root". 8959 chown -hR root /u 8960 8961 8962File: coreutils.info, Node: chgrp invocation, Next: chmod invocation, Prev: chown invocation, Up: Changing file attributes 8963 896413.2 ‘chgrp’: Change group ownership 8965==================================== 8966 8967‘chgrp’ changes the group ownership of each given FILE to GROUP (which 8968can be either a group name or a numeric group ID) or to the group of an 8969existing reference file. *Note chown invocation::. Synopsis: 8970 8971 chgrp [OPTION]... {GROUP | --reference=REF_FILE} FILE... 8972 8973 If GROUP is intended to represent a numeric group ID, then you may 8974specify it with a leading ‘+’. *Note Disambiguating names and IDs::. 8975 8976 It is system dependent whether a user can change the group to an 8977arbitrary one, or the more portable behavior of being restricted to 8978setting a group of which the user is a member. 8979 8980 The program accepts the following options. Also see *note Common 8981options::. 8982 8983‘-c’ 8984‘--changes’ 8985 Verbosely describe the action for each FILE whose group actually 8986 changes. 8987 8988‘-f’ 8989‘--silent’ 8990‘--quiet’ 8991 Do not print error messages about files whose group cannot be 8992 changed. 8993 8994‘--dereference’ 8995 Do not act on symbolic links themselves but rather on what they 8996 point to. This is the default when not operating recursively. 8997 8998 Combining this dereferencing option with the ‘--recursive’ option 8999 may create a security risk: During the traversal of the directory 9000 tree, an attacker may be able to introduce a symlink to an 9001 arbitrary target; when the tool reaches that, the operation will be 9002 performed on the target of that symlink, possibly allowing the 9003 attacker to escalate privileges. 9004 9005‘-h’ 9006‘--no-dereference’ 9007 Act on symbolic links themselves instead of what they point to. 9008 This mode relies on the ‘lchown’ system call. On systems that do 9009 not provide the ‘lchown’ system call, ‘chgrp’ fails when a file 9010 specified on the command line is a symbolic link. By default, no 9011 diagnostic is issued for symbolic links encountered during a 9012 recursive traversal, but see ‘--verbose’. 9013 9014‘--preserve-root’ 9015 Fail upon any attempt to recursively change the root directory, 9016 ‘/’. Without ‘--recursive’, this option has no effect. *Note 9017 Treating / specially::. 9018 9019‘--no-preserve-root’ 9020 Cancel the effect of any preceding ‘--preserve-root’ option. *Note 9021 Treating / specially::. 9022 9023‘--reference=REF_FILE’ 9024 Change the group of each FILE to be the same as that of REF_FILE. 9025 If REF_FILE is a symbolic link, do not use the group of the 9026 symbolic link, but rather that of the file it refers to. 9027 9028‘-v’ 9029‘--verbose’ 9030 Output a diagnostic for every file processed. If a symbolic link 9031 is encountered during a recursive traversal on a system without the 9032 ‘lchown’ system call, and ‘--no-dereference’ is in effect, then 9033 issue a diagnostic saying neither the symbolic link nor its 9034 referent is being changed. 9035 9036‘-R’ 9037‘--recursive’ 9038 Recursively change the group ownership of directories and their 9039 contents. 9040 9041‘-H’ 9042 If ‘--recursive’ (‘-R’) is specified and a command line argument is 9043 a symbolic link to a directory, traverse it. *Note Traversing 9044 symlinks::. 9045 9046‘-L’ 9047 In a recursive traversal, traverse every symbolic link to a 9048 directory that is encountered. 9049 9050 Combining this dereferencing option with the ‘--recursive’ option 9051 may create a security risk: During the traversal of the directory 9052 tree, an attacker may be able to introduce a symlink to an 9053 arbitrary target; when the tool reaches that, the operation will be 9054 performed on the target of that symlink, possibly allowing the 9055 attacker to escalate privileges. 9056 9057 *Note Traversing symlinks::. 9058 9059‘-P’ 9060 Do not traverse any symbolic links. This is the default if none of 9061 ‘-H’, ‘-L’, or ‘-P’ is specified. *Note Traversing symlinks::. 9062 9063 An exit status of zero indicates success, and a nonzero value 9064indicates failure. 9065 9066 Examples: 9067 9068 # Change the group of /u to "staff". 9069 chgrp staff /u 9070 9071 # Change the group of /u and subfiles to "staff". 9072 chgrp -hR staff /u 9073 9074 9075File: coreutils.info, Node: chmod invocation, Next: touch invocation, Prev: chgrp invocation, Up: Changing file attributes 9076 907713.3 ‘chmod’: Change access permissions 9078======================================= 9079 9080‘chmod’ changes the access permissions of the named files. Synopsis: 9081 9082 chmod [OPTION]... {MODE | --reference=REF_FILE} FILE... 9083 9084 ‘chmod’ never changes the permissions of symbolic links, since the 9085‘chmod’ system call cannot change their permissions. This is not a 9086problem since the permissions of symbolic links are never used. 9087However, for each symbolic link listed on the command line, ‘chmod’ 9088changes the permissions of the pointed-to file. In contrast, ‘chmod’ 9089ignores symbolic links encountered during recursive directory 9090traversals. 9091 9092 Only a process whose effective user ID matches the user ID of the 9093file, or a process with appropriate privileges, is permitted to change 9094the file mode bits of a file. 9095 9096 A successful use of ‘chmod’ clears the set-group-ID bit of a regular 9097file if the file’s group ID does not match the user’s effective group ID 9098or one of the user’s supplementary group IDs, unless the user has 9099appropriate privileges. Additional restrictions may cause the 9100set-user-ID and set-group-ID bits of MODE or REF_FILE to be ignored. 9101This behavior depends on the policy and functionality of the underlying 9102‘chmod’ system call. When in doubt, check the underlying system 9103behavior. 9104 9105 If used, MODE specifies the new file mode bits. For details, see the 9106section on *note File permissions::. If you really want MODE to have a 9107leading ‘-’, you should use ‘--’ first, e.g., ‘chmod -- -w file’. 9108Typically, though, ‘chmod a-w file’ is preferable, and ‘chmod -w file’ 9109(without the ‘--’) complains if it behaves differently from what ‘chmod 9110a-w file’ would do. 9111 9112 The program accepts the following options. Also see *note Common 9113options::. 9114 9115‘-c’ 9116‘--changes’ 9117 Verbosely describe the action for each FILE whose permissions 9118 actually changes. 9119 9120‘-f’ 9121‘--silent’ 9122‘--quiet’ 9123 Do not print error messages about files whose permissions cannot be 9124 changed. 9125 9126‘--preserve-root’ 9127 Fail upon any attempt to recursively change the root directory, 9128 ‘/’. Without ‘--recursive’, this option has no effect. *Note 9129 Treating / specially::. 9130 9131‘--no-preserve-root’ 9132 Cancel the effect of any preceding ‘--preserve-root’ option. *Note 9133 Treating / specially::. 9134 9135‘-v’ 9136‘--verbose’ 9137 Verbosely describe the action or non-action taken for every FILE. 9138 9139‘--reference=REF_FILE’ 9140 Change the mode of each FILE to be the same as that of REF_FILE. 9141 *Note File permissions::. If REF_FILE is a symbolic link, do not 9142 use the mode of the symbolic link, but rather that of the file it 9143 refers to. 9144 9145‘-R’ 9146‘--recursive’ 9147 Recursively change permissions of directories and their contents. 9148 9149 An exit status of zero indicates success, and a nonzero value 9150indicates failure. 9151 9152 Examples: 9153 9154 # Change file permissions of FOO to be world readable 9155 # and user writable, with no other permissions. 9156 chmod 644 foo 9157 chmod a=r,u+w foo 9158 9159 # Add user and group execute permissions to FOO. 9160 chmod +110 file 9161 chmod ug+x file 9162 9163 # Set file permissions of DIR and subsidiary files to 9164 # be the umask default, assuming execute permissions for 9165 # directories and for files already executable. 9166 chmod -R a=,+rwX dir 9167 9168 9169File: coreutils.info, Node: touch invocation, Prev: chmod invocation, Up: Changing file attributes 9170 917113.4 ‘touch’: Change file timestamps 9172==================================== 9173 9174‘touch’ changes the access and/or modification timestamps of the 9175specified files. Synopsis: 9176 9177 touch [OPTION]... FILE... 9178 9179 Any FILE argument that does not exist is created empty, unless option 9180‘--no-create’ (‘-c’) or ‘--no-dereference’ (‘-h’) was in effect. 9181 9182 A FILE argument string of ‘-’ is handled specially and causes ‘touch’ 9183to change the times of the file associated with standard output. 9184 9185 By default, ‘touch’ sets file timestamps to the current time. 9186Because ‘touch’ acts on its operands left to right, the resulting 9187timestamps of earlier and later operands may disagree. 9188 9189 When setting file timestamps to the current time, ‘touch’ can change 9190the timestamps for files that the user does not own but has write 9191permission for. Otherwise, the user must own the files. Some older 9192systems have a further restriction: the user must own the files unless 9193both the access and modification timestamps are being set to the current 9194time. 9195 9196 The ‘touch’ command cannot set a file’s status change timestamp to a 9197user-specified value, and cannot change the file’s birth time (if 9198supported) at all. Also, ‘touch’ has issues similar to those affecting 9199all programs that update file timestamps. For example, ‘touch’ may set 9200a file’s timestamp to a value that differs slightly from the requested 9201time. *Note File timestamps::. 9202 9203 Timestamps assume the time zone rules specified by the ‘TZ’ 9204environment variable, or by the system default rules if ‘TZ’ is not set. 9205*Note Specifying the Time Zone with ‘TZ’: (libc)TZ Variable. You can 9206avoid ambiguities during daylight saving transitions by using UTC 9207timestamps. 9208 9209 The program accepts the following options. Also see *note Common 9210options::. 9211 9212‘-a’ 9213‘--time=atime’ 9214‘--time=access’ 9215‘--time=use’ 9216 Change the access timestamp only. *Note File timestamps::. 9217 9218‘-c’ 9219‘--no-create’ 9220 Do not warn about or create files that do not exist. 9221 9222‘-d TIME’ 9223‘--date=TIME’ 9224 Use TIME instead of the current time. It can contain month names, 9225 time zones, ‘am’ and ‘pm’, ‘yesterday’, etc. For example, 9226 ‘--date="2004-02-27 14:19:13.489392193 +0530"’ specifies the 9227 instant of time that is 489,392,193 nanoseconds after February 27, 9228 2004 at 2:19:13 PM in a time zone that is 5 hours and 30 minutes 9229 east of UTC. *Note Date input formats::. File systems that do not 9230 support high-resolution timestamps silently ignore any excess 9231 precision here. 9232 9233‘-f’ 9234 Ignored; for compatibility with BSD versions of ‘touch’. 9235 9236‘-h’ 9237‘--no-dereference’ 9238 Attempt to change the timestamps of a symbolic link, rather than 9239 what the link refers to. When using this option, empty files are 9240 not created, but option ‘-c’ must also be used to avoid warning 9241 about files that do not exist. Not all systems support changing 9242 the timestamps of symlinks, since underlying system support for 9243 this action was not required until POSIX 2008. Also, on some 9244 systems, the mere act of examining a symbolic link changes the 9245 access timestamp, such that only changes to the modification 9246 timestamp will persist long enough to be observable. When coupled 9247 with option ‘-r’, a reference timestamp is taken from a symbolic 9248 link rather than the file it refers to. 9249 9250‘-m’ 9251‘--time=mtime’ 9252‘--time=modify’ 9253 Change the modification timestamp only. 9254 9255‘-r FILE’ 9256‘--reference=FILE’ 9257 Use the times of the reference FILE instead of the current time. 9258 If this option is combined with the ‘--date=TIME’ (‘-d TIME’) 9259 option, the reference FILE’s time is the origin for any relative 9260 TIMEs given, but is otherwise ignored. For example, ‘-r foo -d '-5 9261 seconds'’ specifies a timestamp equal to five seconds before the 9262 corresponding timestamp for ‘foo’. If FILE is a symbolic link, the 9263 reference timestamp is taken from the target of the symlink, unless 9264 ‘-h’ was also in effect. 9265 9266‘-t [[CC]YY]MMDDHHMM[.SS]’ 9267 Use the argument (optional four-digit or two-digit years, months, 9268 days, hours, minutes, optional seconds) instead of the current 9269 time. If the year is specified with only two digits, then CC is 20 9270 for years in the range 0 ... 68, and 19 for years in 69 ... 99. If 9271 no digits of the year are specified, the argument is interpreted as 9272 a date in the current year. On the atypical systems that support 9273 leap seconds, SS may be ‘60’. 9274 9275 On systems predating POSIX 1003.1-2001, ‘touch’ supports an obsolete 9276syntax, as follows. If no timestamp is given with any of the ‘-d’, 9277‘-r’, or ‘-t’ options, and if there are two or more FILEs and the first 9278FILE is of the form ‘MMDDHHMM[YY]’ and this would be a valid argument to 9279the ‘-t’ option (if the YY, if any, were moved to the front), and if the 9280represented year is in the range 1969–1999, that argument is interpreted 9281as the time for the other files instead of as a file name. Although 9282this obsolete behavior can be controlled with the ‘_POSIX2_VERSION’ 9283environment variable (*note Standards conformance::), portable scripts 9284should avoid commands whose behavior depends on this variable. For 9285example, use ‘touch ./12312359 main.c’ or ‘touch -t 12312359 main.c’ 9286rather than the ambiguous ‘touch 12312359 main.c’. 9287 9288 An exit status of zero indicates success, and a nonzero value 9289indicates failure. 9290 9291 9292File: coreutils.info, Node: Disk usage, Next: Printing text, Prev: Changing file attributes, Up: Top 9293 929414 Disk usage 9295************* 9296 9297No disk can hold an infinite amount of data. These commands report how 9298much disk storage is in use or available, report other file and file 9299status information, and write buffers to disk. 9300 9301* Menu: 9302 9303* df invocation:: Report file system disk space usage. 9304* du invocation:: Estimate file space usage. 9305* stat invocation:: Report file or file system status. 9306* sync invocation:: Synchronize cached writes to persistent storage. 9307* truncate invocation:: Shrink or extend the size of a file. 9308 9309 9310File: coreutils.info, Node: df invocation, Next: du invocation, Up: Disk usage 9311 931214.1 ‘df’: Report file system disk space usage 9313============================================== 9314 9315‘df’ reports the amount of disk space used and available on file 9316systems. Synopsis: 9317 9318 df [OPTION]... [FILE]... 9319 9320 With no arguments, ‘df’ reports the space used and available on all 9321currently mounted file systems (of all types). Otherwise, ‘df’ reports 9322on the file system containing each argument FILE. 9323 9324 Normally the disk space is printed in units of 1024 bytes, but this 9325can be overridden (*note Block size::). Non-integer quantities are 9326rounded up to the next higher unit. 9327 9328 For bind mounts and without arguments, ‘df’ only outputs the 9329statistics for that device with the shortest mount point name in the 9330list of file systems (MTAB), i.e., it hides duplicate entries, unless 9331the ‘-a’ option is specified. 9332 9333 With the same logic, ‘df’ elides a mount entry of a dummy pseudo 9334device if there is another mount entry of a real block device for that 9335mount point with the same device number, e.g. the early-boot pseudo 9336file system ‘rootfs’ is not shown per default when already the real root 9337device has been mounted. 9338 9339 If an argument FILE resolves to a special file containing a mounted 9340file system, ‘df’ shows the space available on that file system rather 9341than on the file system containing the device node. GNU ‘df’ does not 9342attempt to determine the disk usage on unmounted file systems, because 9343on most kinds of systems doing so requires extremely nonportable 9344intimate knowledge of file system structures. 9345 9346 The program accepts the following options. Also see *note Common 9347options::. 9348 9349‘-a’ 9350‘--all’ 9351 Include in the listing dummy, duplicate, or inaccessible file 9352 systems, which are omitted by default. Dummy file systems are 9353 typically special purpose pseudo file systems such as ‘/proc’, with 9354 no associated storage. Duplicate file systems are local or remote 9355 file systems that are mounted at separate locations in the local 9356 file hierarchy, or bind mounted locations. Inaccessible file 9357 systems are those which are mounted but subsequently over-mounted 9358 by another file system at that point, or otherwise inaccessible due 9359 to permissions of the mount point etc. 9360 9361‘-B SIZE’ 9362‘--block-size=SIZE’ 9363 Scale sizes by SIZE before printing them (*note Block size::). For 9364 example, ‘-BG’ prints sizes in units of 1,073,741,824 bytes. 9365 9366‘-h’ 9367‘--human-readable’ 9368 Append a size letter to each size, such as ‘M’ for mebibytes. 9369 Powers of 1024 are used, not 1000; ‘M’ stands for 1,048,576 bytes. 9370 This option is equivalent to ‘--block-size=human-readable’. Use 9371 the ‘--si’ option if you prefer powers of 1000. 9372 9373‘-H’ 9374 Equivalent to ‘--si’. 9375 9376‘-i’ 9377‘--inodes’ 9378 List inode usage information instead of block usage. An inode 9379 (short for index node) contains information about a file such as 9380 its owner, permissions, timestamps, and location on the disk. 9381 9382‘-k’ 9383 Print sizes in 1024-byte blocks, overriding the default block size 9384 (*note Block size::). This option is equivalent to 9385 ‘--block-size=1K’. 9386 9387‘-l’ 9388‘--local’ 9389 Limit the listing to local file systems. By default, remote file 9390 systems are also listed. 9391 9392‘--no-sync’ 9393 Do not invoke the ‘sync’ system call before getting any usage data. 9394 This may make ‘df’ run significantly faster on systems with many 9395 disks, but on some systems (notably SunOS) the results may be 9396 slightly out of date. This is the default. 9397 9398‘--output’ 9399‘--output[=FIELD_LIST]’ 9400 Use the output format defined by FIELD_LIST, or print all fields if 9401 FIELD_LIST is omitted. In the latter case, the order of the 9402 columns conforms to the order of the field descriptions below. 9403 9404 The use of the ‘--output’ together with each of the options ‘-i’, 9405 ‘-P’, and ‘-T’ is mutually exclusive. 9406 9407 FIELD_LIST is a comma-separated list of columns to be included in 9408 ‘df’’s output and therefore effectively controls the order of 9409 output columns. Each field can thus be used at the place of 9410 choice, but yet must only be used once. 9411 9412 Valid field names in the FIELD_LIST are: 9413 ‘source’ 9414 The source of the mount point, usually a device. 9415 ‘fstype’ 9416 File system type. 9417 9418 ‘itotal’ 9419 Total number of inodes. 9420 ‘iused’ 9421 Number of used inodes. 9422 ‘iavail’ 9423 Number of available inodes. 9424 ‘ipcent’ 9425 Percentage of IUSED divided by ITOTAL. 9426 9427 ‘size’ 9428 Total number of blocks. 9429 ‘used’ 9430 Number of used blocks. 9431 ‘avail’ 9432 Number of available blocks. 9433 ‘pcent’ 9434 Percentage of USED divided by SIZE. 9435 9436 ‘file’ 9437 The file name if specified on the command line. 9438 ‘target’ 9439 The mount point. 9440 9441 The fields for block and inodes statistics are affected by the 9442 scaling options like ‘-h’ as usual. 9443 9444 The definition of the FIELD_LIST can even be split among several 9445 ‘--output’ uses. 9446 9447 #!/bin/sh 9448 # Print the TARGET (i.e., the mount point) along with their percentage 9449 # statistic regarding the blocks and the inodes. 9450 df --out=target --output=pcent,ipcent 9451 9452 # Print all available fields. 9453 df --o 9454 9455‘-P’ 9456‘--portability’ 9457 Use the POSIX output format. This is like the default format 9458 except for the following: 9459 9460 1. The information about each file system is always printed on 9461 exactly one line; a mount device is never put on a line by 9462 itself. This means that if the mount device name is more than 9463 20 characters long (e.g., for some network mounts), the 9464 columns are misaligned. 9465 9466 2. The labels in the header output line are changed to conform to 9467 POSIX. 9468 9469 3. The default block size and output format are unaffected by the 9470 ‘DF_BLOCK_SIZE’, ‘BLOCK_SIZE’ and ‘BLOCKSIZE’ environment 9471 variables. However, the default block size is still affected 9472 by ‘POSIXLY_CORRECT’: it is 512 if ‘POSIXLY_CORRECT’ is set, 9473 1024 otherwise. *Note Block size::. 9474 9475‘--si’ 9476 Append an SI-style abbreviation to each size, such as ‘M’ for 9477 megabytes. Powers of 1000 are used, not 1024; ‘M’ stands for 9478 1,000,000 bytes. This option is equivalent to ‘--block-size=si’. 9479 Use the ‘-h’ or ‘--human-readable’ option if you prefer powers of 9480 1024. 9481 9482‘--sync’ 9483 Invoke the ‘sync’ system call before getting any usage data. On 9484 some systems (notably SunOS), doing this yields more up to date 9485 results, but in general this option makes ‘df’ much slower, 9486 especially when there are many or very busy file systems. 9487 9488‘--total’ 9489 Print a grand total of all arguments after all arguments have been 9490 processed. This can be used to find out the total disk size, usage 9491 and available space of all listed devices. If no arguments are 9492 specified df will try harder to elide file systems insignificant to 9493 the total available space, by suppressing duplicate remote file 9494 systems. 9495 9496 For the grand total line, ‘df’ prints ‘"total"’ into the SOURCE 9497 column, and ‘"-"’ into the TARGET column. If there is no SOURCE 9498 column (see ‘--output’), then ‘df’ prints ‘"total"’ into the TARGET 9499 column, if present. 9500 9501‘-t FSTYPE’ 9502‘--type=FSTYPE’ 9503 Limit the listing to file systems of type FSTYPE. Multiple file 9504 system types can be specified by giving multiple ‘-t’ options. By 9505 default, nothing is omitted. 9506 9507‘-T’ 9508‘--print-type’ 9509 Print each file system’s type. The types printed here are the same 9510 ones you can include or exclude with ‘-t’ and ‘-x’. The particular 9511 types printed are whatever is supported by the system. Here are 9512 some of the common names (this list is certainly not exhaustive): 9513 9514 ‘nfs’ 9515 An NFS file system, i.e., one mounted over a network from 9516 another machine. This is the one type name which seems to be 9517 used uniformly by all systems. 9518 9519 ‘ext2, ext3, ext4, xfs, btrfs...’ 9520 A file system on a locally-mounted hard disk. (The system 9521 might even support more than one type here; Linux does.) 9522 9523 ‘iso9660, cdfs’ 9524 A file system on a CD or DVD drive. HP-UX uses ‘cdfs’, most 9525 other systems use ‘iso9660’. 9526 9527 ‘ntfs,fat’ 9528 File systems used by MS-Windows / MS-DOS. 9529 9530‘-x FSTYPE’ 9531‘--exclude-type=FSTYPE’ 9532 Limit the listing to file systems not of type FSTYPE. Multiple 9533 file system types can be eliminated by giving multiple ‘-x’ 9534 options. By default, no file system types are omitted. 9535 9536‘-v’ 9537 Ignored; for compatibility with System V versions of ‘df’. 9538 9539 ‘df’ is installed only on systems that have usable mount tables, so 9540portable scripts should not rely on its existence. 9541 9542 An exit status of zero indicates success, and a nonzero value 9543indicates failure. Failure includes the case where no output is 9544generated, so you can inspect the exit status of a command like ‘df -t 9545ext3 -t reiserfs DIR’ to test whether DIR is on a file system of type 9546‘ext3’ or ‘reiserfs’. 9547 9548 Since the list of file systems (MTAB) is needed to determine the file 9549system type, failure includes the cases when that list cannot be read 9550and one or more of the options ‘-a’, ‘-l’, ‘-t’ or ‘-x’ is used together 9551with a file name argument. 9552 9553 9554File: coreutils.info, Node: du invocation, Next: stat invocation, Prev: df invocation, Up: Disk usage 9555 955614.2 ‘du’: Estimate file space usage 9557==================================== 9558 9559‘du’ reports the amount of disk space used by the set of specified files 9560and for each subdirectory (of directory arguments). Synopsis: 9561 9562 du [OPTION]... [FILE]... 9563 9564 With no arguments, ‘du’ reports the disk space for the current 9565directory. Normally the disk space is printed in units of 1024 bytes, 9566but this can be overridden (*note Block size::). Non-integer quantities 9567are rounded up to the next higher unit. 9568 9569 If two or more hard links point to the same file, only one of the 9570hard links is counted. The FILE argument order affects which links are 9571counted, and changing the argument order may change the numbers and 9572entries that ‘du’ outputs. 9573 9574 The program accepts the following options. Also see *note Common 9575options::. 9576 9577‘-0’ 9578‘--null’ 9579 Output a zero byte (ASCII NUL) at the end of each line, rather than 9580 a newline. This option enables other programs to parse the output 9581 even when that output would contain data with embedded newlines. 9582 9583‘-a’ 9584‘--all’ 9585 Show counts for all files, not just directories. 9586 9587‘--apparent-size’ 9588 Print apparent sizes, rather than disk usage. The apparent size of 9589 a file is the number of bytes reported by ‘wc -c’ on regular files, 9590 or more generally, ‘ls -l --block-size=1’ or ‘stat --format=%s’. 9591 For example, a file containing the word ‘zoo’ with no newline 9592 would, of course, have an apparent size of 3. Such a small file 9593 may require anywhere from 0 to 16 KiB or more of disk space, 9594 depending on the type and configuration of the file system on which 9595 the file resides. However, a sparse file created with this 9596 command: 9597 9598 dd bs=1 seek=2GiB if=/dev/null of=big 9599 9600 has an apparent size of 2 GiB, yet on most modern systems, it 9601 actually uses almost no disk space. 9602 9603‘-B SIZE’ 9604‘--block-size=SIZE’ 9605 Scale sizes by SIZE before printing them (*note Block size::). For 9606 example, ‘-BG’ prints sizes in units of 1,073,741,824 bytes. 9607 9608‘-b’ 9609‘--bytes’ 9610 Equivalent to ‘--apparent-size --block-size=1’. 9611 9612‘-c’ 9613‘--total’ 9614 Print a grand total of all arguments after all arguments have been 9615 processed. This can be used to find out the total disk usage of a 9616 given set of files or directories. 9617 9618‘-D’ 9619‘--dereference-args’ 9620 Dereference symbolic links that are command line arguments. Does 9621 not affect other symbolic links. This is helpful for finding out 9622 the disk usage of directories, such as ‘/usr/tmp’, which are often 9623 symbolic links. 9624 9625‘-d DEPTH’ 9626‘--max-depth=DEPTH’ 9627 Show the total for each directory (and file if –all) that is at 9628 most MAX_DEPTH levels down from the root of the hierarchy. The 9629 root is at level 0, so ‘du --max-depth=0’ is equivalent to ‘du -s’. 9630 9631‘--files0-from=FILE’ 9632 Disallow processing files named on the command line, and instead 9633 process those named in file FILE; each name being terminated by a 9634 zero byte (ASCII NUL). This is useful when the list of file names 9635 is so long that it may exceed a command line length limitation. In 9636 such cases, running ‘du’ via ‘xargs’ is undesirable because it 9637 splits the list into pieces and makes ‘du’ print with the ‘--total’ 9638 (‘-c’) option for each sublist rather than for the entire list. 9639 One way to produce a list of ASCII NUL terminated file names is 9640 with GNU ‘find’, using its ‘-print0’ predicate. If FILE is ‘-’ 9641 then the ASCII NUL terminated file names are read from standard 9642 input. 9643 9644‘-H’ 9645 Equivalent to ‘--dereference-args’ (‘-D’). 9646 9647‘-h’ 9648‘--human-readable’ 9649 Append a size letter to each size, such as ‘M’ for mebibytes. 9650 Powers of 1024 are used, not 1000; ‘M’ stands for 1,048,576 bytes. 9651 This option is equivalent to ‘--block-size=human-readable’. Use 9652 the ‘--si’ option if you prefer powers of 1000. 9653 9654‘--inodes’ 9655 List inode usage information instead of block usage. This option 9656 is useful for finding directories which contain many files, and 9657 therefore eat up most of the inodes space of a file system (see 9658 ‘df’, option ‘--inodes’). It can well be combined with the options 9659 ‘-a’, ‘-c’, ‘-h’, ‘-l’, ‘-s’, ‘-S’, ‘-t’ and ‘-x’; however, passing 9660 other options regarding the block size, for example ‘-b’, ‘-m’ and 9661 ‘--apparent-size’, is ignored. 9662 9663‘-k’ 9664 Print sizes in 1024-byte blocks, overriding the default block size 9665 (*note Block size::). This option is equivalent to 9666 ‘--block-size=1K’. 9667 9668‘-L’ 9669‘--dereference’ 9670 Dereference symbolic links (show the disk space used by the file or 9671 directory that the link points to instead of the space used by the 9672 link). 9673 9674‘-l’ 9675‘--count-links’ 9676 Count the size of all files, even if they have appeared already (as 9677 a hard link). 9678 9679‘-m’ 9680 Print sizes in 1,048,576-byte blocks, overriding the default block 9681 size (*note Block size::). This option is equivalent to 9682 ‘--block-size=1M’. 9683 9684‘-P’ 9685‘--no-dereference’ 9686 For each symbolic links encountered by ‘du’, consider the disk 9687 space used by the symbolic link. 9688 9689‘-S’ 9690‘--separate-dirs’ 9691 Normally, in the output of ‘du’ (when not using ‘--summarize’), the 9692 size listed next to a directory name, D, represents the sum of 9693 sizes of all entries beneath D as well as the size of D itself. 9694 With ‘--separate-dirs’, the size reported for a directory name, D, 9695 will exclude the size of any subdirectories. 9696 9697‘--si’ 9698 Append an SI-style abbreviation to each size, such as ‘M’ for 9699 megabytes. Powers of 1000 are used, not 1024; ‘M’ stands for 9700 1,000,000 bytes. This option is equivalent to ‘--block-size=si’. 9701 Use the ‘-h’ or ‘--human-readable’ option if you prefer powers of 9702 1024. 9703 9704‘-s’ 9705‘--summarize’ 9706 Display only a total for each argument. 9707 9708‘-t SIZE’ 9709‘--threshold=SIZE’ 9710 Exclude entries based on a given SIZE. The SIZE refers to used 9711 blocks in normal mode (*note Block size::), or inodes count in 9712 conjunction with the ‘--inodes’ option. 9713 9714 If SIZE is positive, then ‘du’ will only print entries with a size 9715 greater than or equal to that. 9716 9717 If SIZE is negative, then ‘du’ will only print entries with a size 9718 smaller than or equal to that. 9719 9720 Although GNU ‘find’ can be used to find files of a certain size, 9721 ‘du’’s ‘--threshold’ option can be used to also filter directories 9722 based on a given size. 9723 9724 Please note that the ‘--threshold’ option can be combined with the 9725 ‘--apparent-size’ option, and in this case would elide entries 9726 based on its apparent size. 9727 9728 Please note that the ‘--threshold’ option can be combined with the 9729 ‘--inodes’ option, and in this case would elide entries based on 9730 its inodes count. 9731 9732 Here’s how you would use ‘--threshold’ to find directories with a 9733 size greater than or equal to 200 megabytes: 9734 9735 du --threshold=200MB 9736 9737 Here’s how you would use ‘--threshold’ to find directories and 9738 files - note the ‘-a’ - with an apparent size smaller than or equal 9739 to 500 bytes: 9740 9741 du -a -t -500 --apparent-size 9742 9743 Here’s how you would use ‘--threshold’ to find directories on the 9744 root file system with more than 20000 inodes used in the directory 9745 tree below: 9746 9747 du --inodes -x --threshold=20000 / 9748 9749‘--time’ 9750 Show the most recent modification timestamp (mtime) of any file in 9751 the directory, or any of its subdirectories. *Note File 9752 timestamps::. 9753 9754‘--time=ctime’ 9755‘--time=status’ 9756‘--time=use’ 9757 Show the most recent status change timestamp (ctime) of any file in 9758 the directory, or any of its subdirectories. *Note File 9759 timestamps::. 9760 9761‘--time=atime’ 9762‘--time=access’ 9763 Show the most recent access timestamp (atime) of any file in the 9764 directory, or any of its subdirectories. *Note File timestamps::. 9765 9766‘--time-style=STYLE’ 9767 List timestamps in style STYLE. This option has an effect only if 9768 the ‘--time’ option is also specified. The STYLE should be one of 9769 the following: 9770 9771 ‘+FORMAT’ 9772 List timestamps using FORMAT, where FORMAT is interpreted like 9773 the format argument of ‘date’ (*note date invocation::). For 9774 example, ‘--time-style="+%Y-%m-%d %H:%M:%S"’ causes ‘du’ to 9775 list timestamps like ‘2002-03-30 23:45:56’. As with ‘date’, 9776 FORMAT’s interpretation is affected by the ‘LC_TIME’ locale 9777 category. 9778 9779 ‘full-iso’ 9780 List timestamps in full using ISO 8601-like date, time, and 9781 time zone components with nanosecond precision, e.g., 9782 ‘2002-03-30 23:45:56.477817180 -0700’. This style is 9783 equivalent to ‘+%Y-%m-%d %H:%M:%S.%N %z’. 9784 9785 ‘long-iso’ 9786 List ISO 8601 date and time components with minute precision, 9787 e.g., ‘2002-03-30 23:45’. These timestamps are shorter than 9788 ‘full-iso’ timestamps, and are usually good enough for 9789 everyday work. This style is equivalent to ‘+%Y-%m-%d %H:%M’. 9790 9791 ‘iso’ 9792 List ISO 8601 dates for timestamps, e.g., ‘2002-03-30’. This 9793 style is equivalent to ‘+%Y-%m-%d’. 9794 9795 You can specify the default value of the ‘--time-style’ option with 9796 the environment variable ‘TIME_STYLE’; if ‘TIME_STYLE’ is not set 9797 the default style is ‘long-iso’. For compatibility with ‘ls’, if 9798 ‘TIME_STYLE’ begins with ‘+’ and contains a newline, the newline 9799 and any later characters are ignored; if ‘TIME_STYLE’ begins with 9800 ‘posix-’ the ‘posix-’ is ignored; and if ‘TIME_STYLE’ is ‘locale’ 9801 it is ignored. 9802 9803‘-X FILE’ 9804‘--exclude-from=FILE’ 9805 Like ‘--exclude’, except take the patterns to exclude from FILE, 9806 one per line. If FILE is ‘-’, take the patterns from standard 9807 input. 9808 9809‘--exclude=PATTERN’ 9810 When recursing, skip subdirectories or files matching PATTERN. For 9811 example, ‘du --exclude='*.o'’ excludes files whose names end in 9812 ‘.o’. 9813 9814‘-x’ 9815‘--one-file-system’ 9816 Skip directories that are on different file systems from the one 9817 that the argument being processed is on. 9818 9819 On BSD systems, ‘du’ reports sizes that are half the correct values 9820for files that are NFS-mounted from HP-UX systems. On HP-UX systems, it 9821reports sizes that are twice the correct values for files that are 9822NFS-mounted from BSD systems. This is due to a flaw in HP-UX; it also 9823affects the HP-UX ‘du’ program. 9824 9825 An exit status of zero indicates success, and a nonzero value 9826indicates failure. 9827 9828 9829File: coreutils.info, Node: stat invocation, Next: sync invocation, Prev: du invocation, Up: Disk usage 9830 983114.3 ‘stat’: Report file or file system status 9832============================================== 9833 9834‘stat’ displays information about the specified file(s). Synopsis: 9835 9836 stat [OPTION]... [FILE]... 9837 9838 With no option, ‘stat’ reports all information about the given files. 9839But it also can be used to report the information of the file systems 9840the given files are located on. If the files are links, ‘stat’ can also 9841give information about the files the links point to. 9842 9843 Due to shell aliases and built-in ‘stat’ functions, using an 9844unadorned ‘stat’ interactively or in a script may get you different 9845functionality than that described here. Invoke it via ‘env’ (i.e., ‘env 9846stat ...’) to avoid interference from the shell. 9847 9848‘-L’ 9849‘--dereference’ 9850 Change how ‘stat’ treats symbolic links. With this option, ‘stat’ 9851 acts on the file referenced by each symbolic link argument. 9852 Without it, ‘stat’ acts on any symbolic link argument directly. 9853 9854‘-f’ 9855‘--file-system’ 9856 Report information about the file systems where the given files are 9857 located instead of information about the files themselves. This 9858 option implies the ‘-L’ option. 9859 9860‘--cached=MODE’ 9861 Control how attributes are read from the file system; if supported 9862 by the system. This allows one to control the trade-off between 9863 freshness and efficiency of attribute access, especially useful 9864 with remote file systems. MODE can be: 9865 9866 ‘always’ 9867 Always read the already cached attributes if available. 9868 9869 ‘never’ 9870 Always sychronize with the latest file system attributes. 9871 9872 ‘default’ 9873 Leave the caching behavior to the underlying file system. 9874 9875‘-c’ 9876‘--format=FORMAT’ 9877 Use FORMAT rather than the default format. FORMAT is automatically 9878 newline-terminated, so running a command like the following with 9879 two or more FILE operands produces a line of output for each 9880 operand: 9881 $ stat --format=%d:%i / /usr 9882 2050:2 9883 2057:2 9884 9885‘--printf=FORMAT’ 9886 Use FORMAT rather than the default format. Like ‘--format’, but 9887 interpret backslash escapes, and do not output a mandatory trailing 9888 newline. If you want a newline, include ‘\n’ in the FORMAT. 9889 Here’s how you would use ‘--printf’ to print the device and inode 9890 numbers of ‘/’ and ‘/usr’: 9891 $ stat --printf='%d:%i\n' / /usr 9892 2050:2 9893 2057:2 9894 9895‘-t’ 9896‘--terse’ 9897 Print the information in terse form, suitable for parsing by other 9898 programs. 9899 9900 The output of the following commands are identical and the 9901 ‘--format’ also identifies the items printed (in fuller form) in 9902 the default format. Note the format string would include another 9903 ‘%C’ at the end with an active SELinux security context. 9904 $ stat --format="%n %s %b %f %u %g %D %i %h %t %T %X %Y %Z %W %o" ... 9905 $ stat --terse ... 9906 9907 The same illustrating terse output in ‘--file-system’ mode: 9908 $ stat -f --format="%n %i %l %t %s %S %b %f %a %c %d" ... 9909 $ stat -f --terse ... 9910 9911 The valid FORMAT directives for files with ‘--format’ and ‘--printf’ 9912are: 9913 9914 • %a - Permission bits in octal (note ‘#’ and ‘0’ printf flags) 9915 • %A - Permission bits in symbolic form (similar to ‘ls -ld’) 9916 • %b - Number of blocks allocated (see ‘%B’) 9917 • %B - The size in bytes of each block reported by ‘%b’ 9918 • %C - The SELinux security context of a file, if available 9919 • %d - Device number in decimal 9920 • %D - Device number in hex 9921 • %f - Raw mode in hex 9922 • %F - File type 9923 • %g - Group ID of owner 9924 • %G - Group name of owner 9925 • %h - Number of hard links 9926 • %i - Inode number 9927 • %m - Mount point (See note below) 9928 • %n - File name 9929 • %N - Quoted file name with dereference if symbolic link (see below) 9930 • %o - Optimal I/O transfer size hint 9931 • %s - Total size, in bytes 9932 • %t - Major device type in hex (see below) 9933 • %T - Minor device type in hex (see below) 9934 • %u - User ID of owner 9935 • %U - User name of owner 9936 • %w - Time of file birth, or ‘-’ if unknown 9937 • %W - Time of file birth as seconds since Epoch, or ‘0’ 9938 • %x - Time of last access 9939 • %X - Time of last access as seconds since Epoch 9940 • %y - Time of last data modification 9941 • %Y - Time of last data modification as seconds since Epoch 9942 • %z - Time of last status change 9943 • %Z - Time of last status change as seconds since Epoch 9944 9945 The ‘%a’ format prints the octal mode, and so it is useful to control 9946the zero padding of the output with the ‘#’ and ‘0’ printf flags. For 9947example to pad to at least 3 wide while making larger numbers 9948unambiguously octal, you can use ‘%#03a’. 9949 9950 The ‘%N’ format can be set with the environment variable 9951‘QUOTING_STYLE’. If that environment variable is not set, the default 9952value is ‘shell-escape-always’. Valid quoting styles are: 9953‘literal’ 9954 Output strings as-is; this is the same as the ‘-N’ or ‘--literal’ 9955 option. 9956‘shell’ 9957 Quote strings for the shell if they contain shell metacharacters or 9958 would cause ambiguous output. The quoting is suitable for 9959 POSIX-compatible shells like ‘bash’, but it does not always work 9960 for incompatible shells like ‘csh’. 9961‘shell-always’ 9962 Quote strings for the shell, even if they would normally not 9963 require quoting. 9964‘shell-escape’ 9965 Like ‘shell’, but also quoting non-printable characters using the 9966 POSIX proposed ‘$''’ syntax suitable for most shells. 9967‘shell-escape-always’ 9968 Like ‘shell-escape’, but quote strings even if they would normally 9969 not require quoting. 9970‘c’ 9971 Quote strings as for C character string literals, including the 9972 surrounding double-quote characters; this is the same as the ‘-Q’ 9973 or ‘--quote-name’ option. 9974‘escape’ 9975 Quote strings as for C character string literals, except omit the 9976 surrounding double-quote characters; this is the same as the ‘-b’ 9977 or ‘--escape’ option. 9978‘clocale’ 9979 Quote strings as for C character string literals, except use 9980 surrounding quotation marks appropriate for the locale. 9981‘locale’ 9982 Quote strings as for C character string literals, except use 9983 surrounding quotation marks appropriate for the locale, and quote 9984 'like this' instead of "like this" in the default C locale. This 9985 looks nicer on many displays. 9986 9987 The ‘%t’ and ‘%T’ formats operate on the st_rdev member of the 9988stat(2) structure, and are only defined for character and block special 9989files. On some systems or file types, st_rdev may be used to represent 9990other quantities. 9991 9992 The ‘%W’, ‘%X’, ‘%Y’, and ‘%Z’ formats accept a precision preceded by 9993a period to specify the number of digits to print after the decimal 9994point. For example, ‘%.3X’ outputs the access timestamp to millisecond 9995precision. If a period is given but no precision, ‘stat’ uses 9 digits, 9996so ‘%.X’ is equivalent to ‘%.9X’. When discarding excess precision, 9997timestamps are truncated toward minus infinity. 9998 9999 zero pad: 10000 $ stat -c '[%015Y]' /usr 10001 [000001288929712] 10002 space align: 10003 $ stat -c '[%15Y]' /usr 10004 [ 1288929712] 10005 $ stat -c '[%-15Y]' /usr 10006 [1288929712 ] 10007 precision: 10008 $ stat -c '[%.3Y]' /usr 10009 [1288929712.114] 10010 $ stat -c '[%.Y]' /usr 10011 [1288929712.114951834] 10012 10013 The mount point printed by ‘%m’ is similar to that output by ‘df’, 10014except that: 10015 • stat does not dereference symlinks by default (unless ‘-L’ is 10016 specified) 10017 • stat does not search for specified device nodes in the file system 10018 list, instead operating on them directly 10019 • stat outputs the alias for a bind mounted file, rather than the 10020 initial mount point of its backing device. One can recursively 10021 call stat until there is no change in output, to get the current 10022 base mount point 10023 10024 When listing file system information (‘--file-system’ (‘-f’)), you 10025must use a different set of FORMAT directives: 10026 10027 • %a - Free blocks available to non-super-user 10028 • %b - Total data blocks in file system 10029 • %c - Total file nodes in file system 10030 • %d - Free file nodes in file system 10031 • %f - Free blocks in file system 10032 • %i - File System ID in hex 10033 • %l - Maximum length of file names 10034 • %n - File name 10035 • %s - Block size (for faster transfers) 10036 • %S - Fundamental block size (for block counts) 10037 • %t - Type in hex 10038 • %T - Type in human readable form 10039 10040 Timestamps are listed according to the time zone rules specified by 10041the ‘TZ’ environment variable, or by the system default rules if ‘TZ’ is 10042not set. *Note Specifying the Time Zone with ‘TZ’: (libc)TZ Variable. 10043 10044 An exit status of zero indicates success, and a nonzero value 10045indicates failure. 10046 10047 10048File: coreutils.info, Node: sync invocation, Next: truncate invocation, Prev: stat invocation, Up: Disk usage 10049 1005014.4 ‘sync’: Synchronize cached writes to persistent storage 10051============================================================ 10052 10053‘sync’ synchronizes in memory files or file systems to persistent 10054storage. Synopsis: 10055 10056 sync [OPTION] [FILE]... 10057 10058 ‘sync’ writes any data buffered in memory out to disk. This can 10059include (but is not limited to) modified superblocks, modified inodes, 10060and delayed reads and writes. This must be implemented by the kernel; 10061The ‘sync’ program does nothing but exercise the ‘sync’, ‘syncfs’, 10062‘fsync’, and ‘fdatasync’ system calls. 10063 10064 The kernel keeps data in memory to avoid doing (relatively slow) disk 10065reads and writes. This improves performance, but if the computer 10066crashes, data may be lost or the file system corrupted as a result. The 10067‘sync’ command instructs the kernel to write data in memory to 10068persistent storage. 10069 10070 If any argument is specified then only those files will be 10071synchronized using the fsync(2) syscall by default. 10072 10073 If at least one file is specified, it is possible to change the 10074synchronization method with the following options. Also see *note 10075Common options::. 10076 10077‘-d’ 10078‘--data’ 10079 Use fdatasync(2) to sync only the data for the file, and any 10080 metadata required to maintain file system consistency. 10081 10082‘-f’ 10083‘--file-system’ 10084 Synchronize all the I/O waiting for the file systems that contain 10085 the file, using the syscall syncfs(2). Note you would usually 10086 _not_ specify this option if passing a device node like ‘/dev/sda’ 10087 for example, as that would sync the containing file system rather 10088 than the referenced one. Note also that depending on the system, 10089 passing individual device nodes or files may have different sync 10090 characteristics than using no arguments. I.e., arguments passed to 10091 fsync(2) may provide greater guarantees through write barriers, 10092 than a global sync(2) used when no arguments are provided. 10093 10094 An exit status of zero indicates success, and a nonzero value 10095indicates failure. 10096 10097 10098File: coreutils.info, Node: truncate invocation, Prev: sync invocation, Up: Disk usage 10099 1010014.5 ‘truncate’: Shrink or extend the size of a file 10101==================================================== 10102 10103‘truncate’ shrinks or extends the size of each FILE to the specified 10104size. Synopsis: 10105 10106 truncate OPTION... FILE... 10107 10108 Any FILE that does not exist is created. 10109 10110 If a FILE is larger than the specified size, the extra data is lost. 10111If a FILE is shorter, it is extended and the sparse extended part (or 10112hole) reads as zero bytes. 10113 10114 The program accepts the following options. Also see *note Common 10115options::. 10116 10117‘-c’ 10118‘--no-create’ 10119 Do not create files that do not exist. 10120 10121‘-o’ 10122‘--io-blocks’ 10123 Treat SIZE as number of I/O blocks of the FILE rather than bytes. 10124 10125‘-r RFILE’ 10126‘--reference=RFILE’ 10127 Base the size of each FILE on the size of RFILE. 10128 10129‘-s SIZE’ 10130‘--size=SIZE’ 10131 Set or adjust the size of each FILE according to SIZE. SIZE is in 10132 bytes unless ‘--io-blocks’ is specified. SIZE may be, or may be an 10133 integer optionally followed by, one of the following multiplicative 10134 suffixes: 10135 ‘KB’ => 1000 (KiloBytes) 10136 ‘K’ => 1024 (KibiBytes) 10137 ‘MB’ => 1000*1000 (MegaBytes) 10138 ‘M’ => 1024*1024 (MebiBytes) 10139 ‘GB’ => 1000*1000*1000 (GigaBytes) 10140 ‘G’ => 1024*1024*1024 (GibiBytes) 10141 and so on for ‘T’, ‘P’, ‘E’, ‘Z’, and ‘Y’. Binary prefixes can be 10142 used, too: ‘KiB’=‘K’, ‘MiB’=‘M’, and so on. 10143 10144 SIZE may also be prefixed by one of the following to adjust the 10145 size of each FILE based on its current size: 10146 ‘+’ => extend by 10147 ‘-’ => reduce by 10148 ‘<’ => at most 10149 ‘>’ => at least 10150 ‘/’ => round down to multiple of 10151 ‘%’ => round up to multiple of 10152 10153 An exit status of zero indicates success, and a nonzero value 10154indicates failure. 10155 10156 10157File: coreutils.info, Node: Printing text, Next: Conditions, Prev: Disk usage, Up: Top 10158 1015915 Printing text 10160**************** 10161 10162This section describes commands that display text strings. 10163 10164* Menu: 10165 10166* echo invocation:: Print a line of text. 10167* printf invocation:: Format and print data. 10168* yes invocation:: Print a string until interrupted. 10169 10170 10171File: coreutils.info, Node: echo invocation, Next: printf invocation, Up: Printing text 10172 1017315.1 ‘echo’: Print a line of text 10174================================= 10175 10176‘echo’ writes each given STRING to standard output, with a space between 10177each and a newline after the last one. Synopsis: 10178 10179 echo [OPTION]... [STRING]... 10180 10181 Due to shell aliases and built-in ‘echo’ functions, using an 10182unadorned ‘echo’ interactively or in a script may get you different 10183functionality than that described here. Invoke it via ‘env’ (i.e., ‘env 10184echo ...’) to avoid interference from the shell. 10185 10186 The program accepts the following options. Also see *note Common 10187options::. Options must precede operands, and the normally-special 10188argument ‘--’ has no special meaning and is treated like any other 10189STRING. 10190 10191‘-n’ 10192 Do not output the trailing newline. 10193 10194‘-e’ 10195 Enable interpretation of the following backslash-escaped characters 10196 in each STRING: 10197 10198 ‘\a’ 10199 alert (bell) 10200 ‘\b’ 10201 backspace 10202 ‘\c’ 10203 produce no further output 10204 ‘\e’ 10205 escape 10206 ‘\f’ 10207 form feed 10208 ‘\n’ 10209 newline 10210 ‘\r’ 10211 carriage return 10212 ‘\t’ 10213 horizontal tab 10214 ‘\v’ 10215 vertical tab 10216 ‘\\’ 10217 backslash 10218 ‘\0NNN’ 10219 the eight-bit value that is the octal number NNN (zero to 10220 three octal digits), if NNN is a nine-bit value, the ninth bit 10221 is ignored 10222 ‘\NNN’ 10223 the eight-bit value that is the octal number NNN (one to three 10224 octal digits), if NNN is a nine-bit value, the ninth bit is 10225 ignored 10226 ‘\xHH’ 10227 the eight-bit value that is the hexadecimal number HH (one or 10228 two hexadecimal digits) 10229 10230‘-E’ 10231 Disable interpretation of backslash escapes in each STRING. This 10232 is the default. If ‘-e’ and ‘-E’ are both specified, the last one 10233 given takes effect. 10234 10235 If the ‘POSIXLY_CORRECT’ environment variable is set, then when 10236‘echo’’s first argument is not ‘-n’ it outputs option-like arguments 10237instead of treating them as options. For example, ‘echo -ne hello’ 10238outputs ‘-ne hello’ instead of plain ‘hello’. Also backslash escapes 10239are always enabled. 10240 10241 POSIX does not require support for any options, and says that the 10242behavior of ‘echo’ is implementation-defined if any STRING contains a 10243backslash or if the first argument is ‘-n’. Portable programs can use 10244the ‘printf’ command if they need to omit trailing newlines or output 10245control characters or backslashes. *Note printf invocation::. 10246 10247 An exit status of zero indicates success, and a nonzero value 10248indicates failure. 10249 10250 10251File: coreutils.info, Node: printf invocation, Next: yes invocation, Prev: echo invocation, Up: Printing text 10252 1025315.2 ‘printf’: Format and print data 10254==================================== 10255 10256‘printf’ does formatted printing of text. Synopsis: 10257 10258 printf FORMAT [ARGUMENT]... 10259 10260 ‘printf’ prints the FORMAT string, interpreting ‘%’ directives and 10261‘\’ escapes to format numeric and string arguments in a way that is 10262mostly similar to the C ‘printf’ function. *Note ‘printf’ format 10263directives: (libc)Output Conversion Syntax, for details. The 10264differences are listed below. 10265 10266 Due to shell aliases and built-in ‘printf’ functions, using an 10267unadorned ‘printf’ interactively or in a script may get you different 10268functionality than that described here. Invoke it via ‘env’ (i.e., ‘env 10269printf ...’) to avoid interference from the shell. 10270 10271 • The FORMAT argument is reused as necessary to convert all the given 10272 ARGUMENTs. For example, the command ‘printf %s a b’ outputs ‘ab’. 10273 10274 • Missing ARGUMENTs are treated as null strings or as zeros, 10275 depending on whether the context expects a string or a number. For 10276 example, the command ‘printf %sx%d’ prints ‘x0’. 10277 10278 • An additional escape, ‘\c’, causes ‘printf’ to produce no further 10279 output. For example, the command ‘printf 'A%sC\cD%sF' B E’ prints 10280 ‘ABC’. 10281 10282 • The hexadecimal escape sequence ‘\xHH’ has at most two digits, as 10283 opposed to C where it can have an unlimited number of digits. For 10284 example, the command ‘printf '\x07e'’ prints two bytes, whereas the 10285 C statement ‘printf ("\x07e")’ prints just one. 10286 10287 • An additional directive ‘%b’, prints its argument string with ‘\’ 10288 escapes interpreted in the same way as in the FORMAT string, except 10289 that octal escapes are of the form ‘\0OOO’ where OOO is 0 to 3 10290 octal digits. If ‘\OOO’ is nine-bit value, ignore the ninth bit. 10291 If a precision is also given, it limits the number of bytes printed 10292 from the converted string. 10293 10294 • An additional directive ‘%q’, prints its argument string in a 10295 format that can be reused as input by most shells. Non-printable 10296 characters are escaped with the POSIX proposed ‘$''’ syntax, and 10297 shell metacharacters are quoted appropriately. This is an 10298 equivalent format to ‘ls --quoting=shell-escape’ output. 10299 10300 • Numeric arguments must be single C constants, possibly with leading 10301 ‘+’ or ‘-’. For example, ‘printf %.4d -3’ outputs ‘-0003’. 10302 10303 • If the leading character of a numeric argument is ‘"’ or ‘'’ then 10304 its value is the numeric value of the immediately following 10305 character. Any remaining characters are silently ignored if the 10306 ‘POSIXLY_CORRECT’ environment variable is set; otherwise, a warning 10307 is printed. For example, ‘printf "%d" "'a"’ outputs ‘97’ on hosts 10308 that use the ASCII character set, since ‘a’ has the numeric value 10309 97 in ASCII. 10310 10311 A floating point argument is interpreted according to the 10312‘LC_NUMERIC’ category of either the current or the C locale, and is 10313printed according to the current locale. For example, in a locale whose 10314decimal point character is a comma, the command ‘printf '%g %g' 2,5 2.5’ 10315outputs ‘2,5 2,5’. *Note Floating point::. 10316 10317 ‘printf’ interprets ‘\OOO’ in FORMAT as an octal number (if OOO is 1 10318to 3 octal digits) specifying a byte to print, and ‘\xHH’ as a 10319hexadecimal number (if HH is 1 to 2 hex digits) specifying a character 10320to print. Note however that when ‘\OOO’ specifies a number larger than 10321255, ‘printf’ ignores the ninth bit. For example, ‘printf '\400'’ is 10322equivalent to ‘printf '\0'’. 10323 10324 ‘printf’ interprets two character syntaxes introduced in ISO C 99: 10325‘\u’ for 16-bit Unicode (ISO/IEC 10646) characters, specified as four 10326hexadecimal digits HHHH, and ‘\U’ for 32-bit Unicode characters, 10327specified as eight hexadecimal digits HHHHHHHH. ‘printf’ outputs the 10328Unicode characters according to the ‘LC_CTYPE’ locale. Unicode 10329characters in the ranges U+0000...U+009F, U+D800...U+DFFF cannot be 10330specified by this syntax, except for U+0024 ($), U+0040 (@), and U+0060 10331()̀. 10332 10333 The processing of ‘\u’ and ‘\U’ requires a full-featured ‘iconv’ 10334facility. It is activated on systems with glibc 2.2 (or newer), or when 10335‘libiconv’ is installed prior to this package. Otherwise ‘\u’ and ‘\U’ 10336will print as-is. 10337 10338 The only options are a lone ‘--help’ or ‘--version’. *Note Common 10339options::. Options must precede operands. 10340 10341 The Unicode character syntaxes are useful for writing strings in a 10342locale independent way. For example, a string containing the Euro 10343currency symbol 10344 10345 $ env printf '\u20AC 14.95' 10346 10347will be output correctly in all locales supporting the Euro symbol 10348(ISO-8859-15, UTF-8, and others). Similarly, a Chinese string 10349 10350 $ env printf '\u4e2d\u6587' 10351 10352will be output correctly in all Chinese locales (GB2312, BIG5, UTF-8, 10353etc). 10354 10355 Note that in these examples, the ‘printf’ command has been invoked 10356via ‘env’ to ensure that we run the program found via your shell’s 10357search path, and not a shell alias or a built-in function. 10358 10359 For larger strings, you don’t need to look up the hexadecimal code 10360values of each character one by one. ASCII characters mixed with \u 10361escape sequences is also known as the JAVA source file encoding. You 10362can use GNU recode 3.5c (or newer) to convert strings to this encoding. 10363Here is how to convert a piece of text into a shell script which will 10364output this text in a locale-independent way: 10365 10366 $ LC_CTYPE=zh_CN.big5 /usr/local/bin/printf \ 10367 '\u4e2d\u6587\n' > sample.txt 10368 $ recode BIG5..JAVA < sample.txt \ 10369 | sed -e "s|^|/usr/local/bin/printf '|" -e "s|$|\\\\n'|" \ 10370 > sample.sh 10371 10372 An exit status of zero indicates success, and a nonzero value 10373indicates failure. 10374 10375 10376File: coreutils.info, Node: yes invocation, Prev: printf invocation, Up: Printing text 10377 1037815.3 ‘yes’: Print a string until interrupted 10379============================================ 10380 10381‘yes’ prints the command line arguments, separated by spaces and 10382followed by a newline, forever until it is killed. If no arguments are 10383given, it prints ‘y’ followed by a newline forever until killed. 10384 10385 Upon a write error, ‘yes’ exits with status ‘1’. 10386 10387 The only options are a lone ‘--help’ or ‘--version’. To output an 10388argument that begins with ‘-’, precede it with ‘--’, e.g., ‘yes -- 10389--help’. *Note Common options::. 10390 10391 10392File: coreutils.info, Node: Conditions, Next: Redirection, Prev: Printing text, Up: Top 10393 1039416 Conditions 10395************* 10396 10397This section describes commands that are primarily useful for their exit 10398status, rather than their output. Thus, they are often used as the 10399condition of shell ‘if’ statements, or as the last command in a 10400pipeline. 10401 10402* Menu: 10403 10404* false invocation:: Do nothing, unsuccessfully. 10405* true invocation:: Do nothing, successfully. 10406* test invocation:: Check file types and compare values. 10407* expr invocation:: Evaluate expressions. 10408 10409 10410File: coreutils.info, Node: false invocation, Next: true invocation, Up: Conditions 10411 1041216.1 ‘false’: Do nothing, unsuccessfully 10413======================================== 10414 10415‘false’ does nothing except return an exit status of 1, meaning 10416“failure”. It can be used as a place holder in shell scripts where an 10417unsuccessful command is needed. In most modern shells, ‘false’ is a 10418built-in command, so when you use ‘false’ in a script, you’re probably 10419using the built-in command, not the one documented here. 10420 10421 ‘false’ honors the ‘--help’ and ‘--version’ options. 10422 10423 This version of ‘false’ is implemented as a C program, and is thus 10424more secure and faster than a shell script implementation, and may 10425safely be used as a dummy shell for the purpose of disabling accounts. 10426 10427 Note that ‘false’ (unlike all other programs documented herein) exits 10428unsuccessfully, even when invoked with ‘--help’ or ‘--version’. 10429 10430 Portable programs should not assume that the exit status of ‘false’ 10431is 1, as it is greater than 1 on some non-GNU hosts. 10432 10433 10434File: coreutils.info, Node: true invocation, Next: test invocation, Prev: false invocation, Up: Conditions 10435 1043616.2 ‘true’: Do nothing, successfully 10437===================================== 10438 10439‘true’ does nothing except return an exit status of 0, meaning 10440“success”. It can be used as a place holder in shell scripts where a 10441successful command is needed, although the shell built-in command ‘:’ 10442(colon) may do the same thing faster. In most modern shells, ‘true’ is 10443a built-in command, so when you use ‘true’ in a script, you’re probably 10444using the built-in command, not the one documented here. 10445 10446 ‘true’ honors the ‘--help’ and ‘--version’ options. 10447 10448 Note, however, that it is possible to cause ‘true’ to exit with 10449nonzero status: with the ‘--help’ or ‘--version’ option, and with 10450standard output already closed or redirected to a file that evokes an 10451I/O error. For example, using a Bourne-compatible shell: 10452 10453 $ ./true --version >&- 10454 ./true: write error: Bad file number 10455 $ ./true --version > /dev/full 10456 ./true: write error: No space left on device 10457 10458 This version of ‘true’ is implemented as a C program, and is thus 10459more secure and faster than a shell script implementation, and may 10460safely be used as a dummy shell for the purpose of disabling accounts. 10461 10462 10463File: coreutils.info, Node: test invocation, Next: expr invocation, Prev: true invocation, Up: Conditions 10464 1046516.3 ‘test’: Check file types and compare values 10466================================================ 10467 10468‘test’ returns a status of 0 (true) or 1 (false) depending on the 10469evaluation of the conditional expression EXPR. Each part of the 10470expression must be a separate argument. 10471 10472 ‘test’ has file status checks, string operators, and numeric 10473comparison operators. 10474 10475 ‘test’ has an alternate form that uses opening and closing square 10476brackets instead a leading ‘test’. For example, instead of ‘test -d /’, 10477you can write ‘[ -d / ]’. The square brackets must be separate 10478arguments; for example, ‘[-d /]’ does not have the desired effect. 10479Since ‘test EXPR’ and ‘[ EXPR ]’ have the same meaning, only the former 10480form is discussed below. 10481 10482 Synopses: 10483 10484 test EXPRESSION 10485 test 10486 [ EXPRESSION ] 10487 [ ] 10488 [ OPTION 10489 10490 Due to shell aliases and built-in ‘test’ functions, using an 10491unadorned ‘test’ interactively or in a script may get you different 10492functionality than that described here. Invoke it via ‘env’ (i.e., ‘env 10493test ...’) to avoid interference from the shell. 10494 10495 If EXPRESSION is omitted, ‘test’ returns false. If EXPRESSION is a 10496single argument, ‘test’ returns false if the argument is null and true 10497otherwise. The argument can be any string, including strings like ‘-d’, 10498‘-1’, ‘--’, ‘--help’, and ‘--version’ that most other programs would 10499treat as options. To get help and version information, invoke the 10500commands ‘[ --help’ and ‘[ --version’, without the usual closing 10501brackets. *Note Common options::. 10502 10503 Exit status: 10504 10505 0 if the expression is true, 10506 1 if the expression is false, 10507 2 if an error occurred. 10508 10509* Menu: 10510 10511* File type tests:: -[bcdfhLpSt] 10512* Access permission tests:: -[gkruwxOG] 10513* File characteristic tests:: -e -s -nt -ot -ef 10514* String tests:: -z -n = == != 10515* Numeric tests:: -eq -ne -lt -le -gt -ge 10516* Connectives for test:: ! -a -o 10517 10518 10519File: coreutils.info, Node: File type tests, Next: Access permission tests, Up: test invocation 10520 1052116.3.1 File type tests 10522---------------------- 10523 10524These options test for particular types of files. (Everything’s a file, 10525but not all files are the same!) 10526 10527‘-b FILE’ 10528 True if FILE exists and is a block special device. 10529 10530‘-c FILE’ 10531 True if FILE exists and is a character special device. 10532 10533‘-d FILE’ 10534 True if FILE exists and is a directory. 10535 10536‘-f FILE’ 10537 True if FILE exists and is a regular file. 10538 10539‘-h FILE’ 10540‘-L FILE’ 10541 True if FILE exists and is a symbolic link. Unlike all other 10542 file-related tests, this test does not dereference FILE if it is a 10543 symbolic link. 10544 10545‘-p FILE’ 10546 True if FILE exists and is a named pipe. 10547 10548‘-S FILE’ 10549 True if FILE exists and is a socket. 10550 10551‘-t FD’ 10552 True if FD is a file descriptor that is associated with a terminal. 10553 10554 10555File: coreutils.info, Node: Access permission tests, Next: File characteristic tests, Prev: File type tests, Up: test invocation 10556 1055716.3.2 Access permission tests 10558------------------------------ 10559 10560These options test for particular access permissions. 10561 10562‘-g FILE’ 10563 True if FILE exists and has its set-group-ID bit set. 10564 10565‘-k FILE’ 10566 True if FILE exists and has its “sticky” bit set. 10567 10568‘-r FILE’ 10569 True if FILE exists and read permission is granted. 10570 10571‘-u FILE’ 10572 True if FILE exists and has its set-user-ID bit set. 10573 10574‘-w FILE’ 10575 True if FILE exists and write permission is granted. 10576 10577‘-x FILE’ 10578 True if FILE exists and execute permission is granted (or search 10579 permission, if it is a directory). 10580 10581‘-O FILE’ 10582 True if FILE exists and is owned by the current effective user ID. 10583 10584‘-G FILE’ 10585 True if FILE exists and is owned by the current effective group ID. 10586 10587 10588File: coreutils.info, Node: File characteristic tests, Next: String tests, Prev: Access permission tests, Up: test invocation 10589 1059016.3.3 File characteristic tests 10591-------------------------------- 10592 10593These options test other file characteristics. 10594 10595‘-e FILE’ 10596 True if FILE exists. 10597 10598‘-s FILE’ 10599 True if FILE exists and has a size greater than zero. 10600 10601‘FILE1 -nt FILE2’ 10602 True if FILE1 is newer (according to modification date) than FILE2, 10603 or if FILE1 exists and FILE2 does not. 10604 10605‘FILE1 -ot FILE2’ 10606 True if FILE1 is older (according to modification date) than FILE2, 10607 or if FILE2 exists and FILE1 does not. 10608 10609‘FILE1 -ef FILE2’ 10610 True if FILE1 and FILE2 have the same device and inode numbers, 10611 i.e., if they are hard links to each other. 10612 10613‘-N FILE’ 10614 True if FILE exists and has been modified (mtime) since it was last 10615 read (atime). 10616 10617 10618File: coreutils.info, Node: String tests, Next: Numeric tests, Prev: File characteristic tests, Up: test invocation 10619 1062016.3.4 String tests 10621------------------- 10622 10623These options test string characteristics. You may need to quote STRING 10624arguments for the shell. For example: 10625 10626 test -n "$V" 10627 10628 The quotes here prevent the wrong arguments from being passed to 10629‘test’ if ‘$V’ is empty or contains special characters. 10630 10631‘-z STRING’ 10632 True if the length of STRING is zero. 10633 10634‘-n STRING’ 10635‘STRING’ 10636 True if the length of STRING is nonzero. 10637 10638‘STRING1 = STRING2’ 10639 True if the strings are equal. 10640 10641‘STRING1 == STRING2’ 10642 True if the strings are equal (synonym for =). 10643 10644‘STRING1 != STRING2’ 10645 True if the strings are not equal. 10646 10647 10648File: coreutils.info, Node: Numeric tests, Next: Connectives for test, Prev: String tests, Up: test invocation 10649 1065016.3.5 Numeric tests 10651-------------------- 10652 10653Numeric relational operators. The arguments must be entirely numeric 10654(possibly negative), or the special expression ‘-l STRING’, which 10655evaluates to the length of STRING. 10656 10657‘ARG1 -eq ARG2’ 10658‘ARG1 -ne ARG2’ 10659‘ARG1 -lt ARG2’ 10660‘ARG1 -le ARG2’ 10661‘ARG1 -gt ARG2’ 10662‘ARG1 -ge ARG2’ 10663 These arithmetic binary operators return true if ARG1 is equal, 10664 not-equal, less-than, less-than-or-equal, greater-than, or 10665 greater-than-or-equal than ARG2, respectively. 10666 10667 For example: 10668 10669 test -1 -gt -2 && echo yes 10670 ⇒ yes 10671 test -l abc -gt 1 && echo yes 10672 ⇒ yes 10673 test 0x100 -eq 1 10674 error→ test: integer expression expected before -eq 10675 10676 10677File: coreutils.info, Node: Connectives for test, Prev: Numeric tests, Up: test invocation 10678 1067916.3.6 Connectives for ‘test’ 10680----------------------------- 10681 10682Note it’s preferred to use shell logical primitives rather than these 10683logical connectives internal to ‘test’, because an expression may become 10684ambiguous depending on the expansion of its parameters. 10685 10686 For example, this becomes ambiguous when ‘$1’ is set to ‘'!'’ and 10687‘$2’ to the empty string ‘''’: 10688 10689 test "$1" -a "$2" 10690 10691 and should be written as: 10692 10693 test "$1" && test "$2" 10694 10695 Note the shell logical primitives also benefit from short circuit 10696operation, which can be significant for file attribute tests. 10697 10698‘! EXPR’ 10699 True if EXPR is false. ‘!’ has lower precedence than all parts of 10700 EXPR. Note ‘!’ needs to be specified to the left of a binary 10701 expression, I.e., ‘'!' 1 -gt 2’ rather than ‘1 '!' -gt 2’. Also 10702 ‘!’ is often a shell special character and is best used quoted. 10703 10704‘EXPR1 -a EXPR2’ 10705 True if both EXPR1 and EXPR2 are true. ‘-a’ is left associative, 10706 and has a higher precedence than ‘-o’. 10707 10708‘EXPR1 -o EXPR2’ 10709 True if either EXPR1 or EXPR2 is true. ‘-o’ is left associative. 10710 10711 10712File: coreutils.info, Node: expr invocation, Prev: test invocation, Up: Conditions 10713 1071416.4 ‘expr’: Evaluate expressions 10715================================= 10716 10717‘expr’ evaluates an expression and writes the result on standard output. 10718Each token of the expression must be a separate argument. 10719 10720 Operands are either integers or strings. Integers consist of one or 10721more decimal digits, with an optional leading ‘-’. ‘expr’ converts 10722anything appearing in an operand position to an integer or a string 10723depending on the operation being applied to it. 10724 10725 Strings are not quoted for ‘expr’ itself, though you may need to 10726quote them to protect characters with special meaning to the shell, 10727e.g., spaces. However, regardless of whether it is quoted, a string 10728operand should not be a parenthesis or any of ‘expr’’s operators like 10729‘+’, so you cannot safely pass an arbitrary string ‘$str’ to expr merely 10730by quoting it to the shell. One way to work around this is to use the 10731GNU extension ‘+’, (e.g., ‘+ "$str" = foo’); a more portable way is to 10732use ‘" $str"’ and to adjust the rest of the expression to take the 10733leading space into account (e.g., ‘" $str" = " foo"’). 10734 10735 You should not pass a negative integer or a string with leading ‘-’ 10736as ‘expr’’s first argument, as it might be misinterpreted as an option; 10737this can be avoided by parenthesization. Also, portable scripts should 10738not use a string operand that happens to take the form of an integer; 10739this can be worked around by inserting leading spaces as mentioned 10740above. 10741 10742 Operators may be given as infix symbols or prefix keywords. 10743Parentheses may be used for grouping in the usual manner. You must 10744quote parentheses and many operators to avoid the shell evaluating them, 10745however. 10746 10747 When built with support for the GNU MP library, ‘expr’ uses 10748arbitrary-precision arithmetic; otherwise, it uses native arithmetic 10749types and may fail due to arithmetic overflow. 10750 10751 The only options are ‘--help’ and ‘--version’. *Note Common 10752options::. Options must precede operands. 10753 10754 Exit status: 10755 10756 0 if the expression is neither null nor 0, 10757 1 if the expression is null or 0, 10758 2 if the expression is invalid, 10759 3 if an internal error occurred (e.g., arithmetic overflow). 10760 10761* Menu: 10762 10763* String expressions:: + : match substr index length 10764* Numeric expressions:: + - * / % 10765* Relations for expr:: | & < <= = == != >= > 10766* Examples of expr:: Examples. 10767 10768 10769File: coreutils.info, Node: String expressions, Next: Numeric expressions, Up: expr invocation 10770 1077116.4.1 String expressions 10772------------------------- 10773 10774‘expr’ supports pattern matching and other string operators. These have 10775higher precedence than both the numeric and relational operators (in the 10776next sections). 10777 10778‘STRING : REGEX’ 10779 Perform pattern matching. The arguments are converted to strings 10780 and the second is considered to be a (basic, a la GNU ‘grep’) 10781 regular expression, with a ‘^’ implicitly prepended. The first 10782 argument is then matched against this regular expression. 10783 10784 If the match succeeds and REGEX uses ‘\(’ and ‘\)’, the ‘:’ 10785 expression returns the part of STRING that matched the 10786 subexpression; otherwise, it returns the number of characters 10787 matched. 10788 10789 If the match fails, the ‘:’ operator returns the null string if 10790 ‘\(’ and ‘\)’ are used in REGEX, otherwise 0. 10791 10792 Only the first ‘\( ... \)’ pair is relevant to the return value; 10793 additional pairs are meaningful only for grouping the regular 10794 expression operators. 10795 10796 In the regular expression, ‘\+’, ‘\?’, and ‘\|’ are operators which 10797 respectively match one or more, zero or one, or separate 10798 alternatives. SunOS and other ‘expr’’s treat these as regular 10799 characters. (POSIX allows either behavior.) *Note Regular 10800 Expression Library: (regex)Top, for details of regular expression 10801 syntax. Some examples are in *note Examples of expr::. 10802 10803‘match STRING REGEX’ 10804 An alternative way to do pattern matching. This is the same as 10805 ‘STRING : REGEX’. 10806 10807‘substr STRING POSITION LENGTH’ 10808 Returns the substring of STRING beginning at POSITION with length 10809 at most LENGTH. If either POSITION or LENGTH is negative, zero, or 10810 non-numeric, returns the null string. 10811 10812‘index STRING CHARSET’ 10813 Returns the first position in STRING where the first character in 10814 CHARSET was found. If no character in CHARSET is found in STRING, 10815 return 0. 10816 10817‘length STRING’ 10818 Returns the length of STRING. 10819 10820‘+ TOKEN’ 10821 Interpret TOKEN as a string, even if it is a keyword like MATCH or 10822 an operator like ‘/’. This makes it possible to test ‘expr length 10823 + "$x"’ or ‘expr + "$x" : '.*/\(.\)'’ and have it do the right 10824 thing even if the value of $X happens to be (for example) ‘/’ or 10825 ‘index’. This operator is a GNU extension. Portable shell scripts 10826 should use ‘" $token" : ' \(.*\)'’ instead of ‘+ "$token"’. 10827 10828 To make ‘expr’ interpret keywords as strings, you must use the 10829‘quote’ operator. 10830 10831 10832File: coreutils.info, Node: Numeric expressions, Next: Relations for expr, Prev: String expressions, Up: expr invocation 10833 1083416.4.2 Numeric expressions 10835-------------------------- 10836 10837‘expr’ supports the usual numeric operators, in order of increasing 10838precedence. These numeric operators have lower precedence than the 10839string operators described in the previous section, and higher 10840precedence than the connectives (next section). 10841 10842‘+ -’ 10843 Addition and subtraction. Both arguments are converted to 10844 integers; an error occurs if this cannot be done. 10845 10846‘* / %’ 10847 Multiplication, division, remainder. Both arguments are converted 10848 to integers; an error occurs if this cannot be done. 10849 10850 10851File: coreutils.info, Node: Relations for expr, Next: Examples of expr, Prev: Numeric expressions, Up: expr invocation 10852 1085316.4.3 Relations for ‘expr’ 10854--------------------------- 10855 10856‘expr’ supports the usual logical connectives and relations. These have 10857lower precedence than the string and numeric operators (previous 10858sections). Here is the list, lowest-precedence operator first. 10859 10860‘|’ 10861 Returns its first argument if that is neither null nor zero, 10862 otherwise its second argument if it is neither null nor zero, 10863 otherwise 0. It does not evaluate its second argument if its first 10864 argument is neither null nor zero. 10865 10866‘&’ 10867 Return its first argument if neither argument is null or zero, 10868 otherwise 0. It does not evaluate its second argument if its first 10869 argument is null or zero. 10870 10871‘< <= = == != >= >’ 10872 Compare the arguments and return 1 if the relation is true, 0 10873 otherwise. ‘==’ is a synonym for ‘=’. ‘expr’ first tries to 10874 convert both arguments to integers and do a numeric comparison; if 10875 either conversion fails, it does a lexicographic comparison using 10876 the character collating sequence specified by the ‘LC_COLLATE’ 10877 locale. 10878 10879 10880File: coreutils.info, Node: Examples of expr, Prev: Relations for expr, Up: expr invocation 10881 1088216.4.4 Examples of using ‘expr’ 10883------------------------------- 10884 10885Here are a few examples, including quoting for shell metacharacters. 10886 10887 To add 1 to the shell variable ‘foo’, in Bourne-compatible shells: 10888 10889 foo=$(expr $foo + 1) 10890 10891 To print the non-directory part of the file name stored in ‘$fname’, 10892which need not contain a ‘/’: 10893 10894 expr $fname : '.*/\(.*\)' '|' $fname 10895 10896 An example showing that ‘\+’ is an operator: 10897 10898 expr aaa : 'a\+' 10899 ⇒ 3 10900 10901 expr abc : 'a\(.\)c' 10902 ⇒ b 10903 expr index abcdef cz 10904 ⇒ 3 10905 expr index index a 10906 error→ expr: syntax error 10907 expr index + index a 10908 ⇒ 0 10909 10910 10911File: coreutils.info, Node: Redirection, Next: File name manipulation, Prev: Conditions, Up: Top 10912 1091317 Redirection 10914************** 10915 10916Unix shells commonly provide several forms of “redirection”—ways to 10917change the input source or output destination of a command. But one 10918useful redirection is performed by a separate command, not by the shell; 10919it’s described here. 10920 10921* Menu: 10922 10923* tee invocation:: Redirect output to multiple files or processes. 10924 10925 10926File: coreutils.info, Node: tee invocation, Up: Redirection 10927 1092817.1 ‘tee’: Redirect output to multiple files or processes 10929========================================================== 10930 10931The ‘tee’ command copies standard input to standard output and also to 10932any files given as arguments. This is useful when you want not only to 10933send some data down a pipe, but also to save a copy. Synopsis: 10934 10935 tee [OPTION]... [FILE]... 10936 10937 If a file being written to does not already exist, it is created. If 10938a file being written to already exists, the data it previously contained 10939is overwritten unless the ‘-a’ option is used. 10940 10941 In previous versions of GNU coreutils (v5.3.0 - v8.23), a FILE of ‘-’ 10942caused ‘tee’ to send another copy of input to standard output. However, 10943as the interleaved output was not very useful, ‘tee’ now conforms to 10944POSIX which explicitly mandates it to treat ‘-’ as a file with such 10945name. 10946 10947 The program accepts the following options. Also see *note Common 10948options::. 10949 10950‘-a’ 10951‘--append’ 10952 Append standard input to the given files rather than overwriting 10953 them. 10954 10955‘-i’ 10956‘--ignore-interrupts’ 10957 Ignore interrupt signals. 10958 10959‘-p’ 10960‘--output-error[=MODE]’ 10961 Adjust the behavior with errors on the outputs, with the long form 10962 option supporting selection between the following MODEs: 10963 10964 ‘warn’ 10965 Warn on error opening or writing any output, including pipes. 10966 Writing is continued to still open files/pipes. Exit status 10967 indicates failure if any output has an error. 10968 10969 ‘warn-nopipe’ 10970 This is the default MODE when not specified, or when the short 10971 form ‘-p’ is used. Warn on error opening or writing any 10972 output, except pipes. Writing is continued to still open 10973 files/pipes. Exit status indicates failure if any non pipe 10974 output had an error. 10975 10976 ‘exit’ 10977 Exit on error opening or writing any output, including pipes. 10978 10979 ‘exit-nopipe’ 10980 Exit on error opening or writing any output, except pipes. 10981 10982 The ‘tee’ command is useful when you happen to be transferring a 10983large amount of data and also want to summarize that data without 10984reading it a second time. For example, when you are downloading a DVD 10985image, you often want to verify its signature or checksum right away. 10986The inefficient way to do it is simply: 10987 10988 wget https://example.com/some.iso && sha1sum some.iso 10989 10990 One problem with the above is that it makes you wait for the download 10991to complete before starting the time-consuming SHA1 computation. 10992Perhaps even more importantly, the above requires reading the DVD image 10993a second time (the first was from the network). 10994 10995 The efficient way to do it is to interleave the download and SHA1 10996computation. Then, you’ll get the checksum for free, because the entire 10997process parallelizes so well: 10998 10999 # slightly contrived, to demonstrate process substitution 11000 wget -O - https://example.com/dvd.iso \ 11001 | tee >(sha1sum > dvd.sha1) > dvd.iso 11002 11003 That makes ‘tee’ write not just to the expected output file, but also 11004to a pipe running ‘sha1sum’ and saving the final checksum in a file 11005named ‘dvd.sha1’. 11006 11007 Note, however, that this example relies on a feature of modern shells 11008called “process substitution” (the ‘>(command)’ syntax, above; *Note 11009Process Substitution: (bash)Process Substitution.), so it works with 11010‘zsh’, ‘bash’, and ‘ksh’, but not with ‘/bin/sh’. So if you write code 11011like this in a shell script, be sure to start the script with 11012‘#!/bin/bash’. 11013 11014 Note also that if any of the process substitutions (or piped stdout) 11015might exit early without consuming all the data, the ‘-p’ option is 11016needed to allow ‘tee’ to continue to process the input to any remaining 11017outputs. 11018 11019 Since the above example writes to one file and one process, a more 11020conventional and portable use of ‘tee’ is even better: 11021 11022 wget -O - https://example.com/dvd.iso \ 11023 | tee dvd.iso | sha1sum > dvd.sha1 11024 11025 You can extend this example to make ‘tee’ write to two processes, 11026computing MD5 and SHA1 checksums in parallel. In this case, process 11027substitution is required: 11028 11029 wget -O - https://example.com/dvd.iso \ 11030 | tee >(sha1sum > dvd.sha1) \ 11031 >(md5sum > dvd.md5) \ 11032 > dvd.iso 11033 11034 This technique is also useful when you want to make a _compressed_ 11035copy of the contents of a pipe. Consider a tool to graphically 11036summarize disk usage data from ‘du -ak’. For a large hierarchy, ‘du 11037-ak’ can run for a long time, and can easily produce terabytes of data, 11038so you won’t want to rerun the command unnecessarily. Nor will you want 11039to save the uncompressed output. 11040 11041 Doing it the inefficient way, you can’t even start the GUI until 11042after you’ve compressed all of the ‘du’ output: 11043 11044 du -ak | gzip -9 > /tmp/du.gz 11045 gzip -d /tmp/du.gz | xdiskusage -a 11046 11047 With ‘tee’ and process substitution, you start the GUI right away and 11048eliminate the decompression completely: 11049 11050 du -ak | tee >(gzip -9 > /tmp/du.gz) | xdiskusage -a 11051 11052 Finally, if you regularly create more than one type of compressed 11053tarball at once, for example when ‘make dist’ creates both 11054‘gzip’-compressed and ‘bzip2’-compressed tarballs, there may be a better 11055way. Typical ‘automake’-generated ‘Makefile’ rules create the two 11056compressed tar archives with commands in sequence, like this (slightly 11057simplified): 11058 11059 tardir=your-pkg-M.N 11060 tar chof - "$tardir" | gzip -9 -c > your-pkg-M.N.tar.gz 11061 tar chof - "$tardir" | bzip2 -9 -c > your-pkg-M.N.tar.bz2 11062 11063 However, if the hierarchy you are archiving and compressing is larger 11064than a couple megabytes, and especially if you are using a 11065multi-processor system with plenty of memory, then you can do much 11066better by reading the directory contents only once and running the 11067compression programs in parallel: 11068 11069 tardir=your-pkg-M.N 11070 tar chof - "$tardir" \ 11071 | tee >(gzip -9 -c > your-pkg-M.N.tar.gz) \ 11072 | bzip2 -9 -c > your-pkg-M.N.tar.bz2 11073 11074 If you want to further process the output from process substitutions, 11075and those processes write atomically (i.e., write less than the system’s 11076PIPE_BUF size at a time), that’s possible with a construct like: 11077 11078 tardir=your-pkg-M.N 11079 tar chof - "$tardir" \ 11080 | tee >(md5sum --tag) > >(sha256sum --tag) \ 11081 | sort | gpg --clearsign > your-pkg-M.N.tar.sig 11082 11083 An exit status of zero indicates success, and a nonzero value 11084indicates failure. 11085 11086 11087File: coreutils.info, Node: File name manipulation, Next: Working context, Prev: Redirection, Up: Top 11088 1108918 File name manipulation 11090************************* 11091 11092This section describes commands that manipulate file names. 11093 11094* Menu: 11095 11096* basename invocation:: Strip directory and suffix from a file name. 11097* dirname invocation:: Strip last file name component. 11098* pathchk invocation:: Check file name validity and portability. 11099* mktemp invocation:: Create temporary file or directory. 11100* realpath invocation:: Print resolved file names. 11101 11102 11103File: coreutils.info, Node: basename invocation, Next: dirname invocation, Up: File name manipulation 11104 1110518.1 ‘basename’: Strip directory and suffix from a file name 11106============================================================ 11107 11108‘basename’ removes any leading directory components from NAME. 11109Synopsis: 11110 11111 basename NAME [SUFFIX] 11112 basename OPTION... NAME... 11113 11114 If SUFFIX is specified and is identical to the end of NAME, it is 11115removed from NAME as well. Note that since trailing slashes are removed 11116prior to suffix matching, SUFFIX will do nothing if it contains slashes. 11117‘basename’ prints the result on standard output. 11118 11119 Together, ‘basename’ and ‘dirname’ are designed such that if ‘ls 11120"$name"’ succeeds, then the command sequence ‘cd "$(dirname "$name")"; 11121ls "$(basename "$name")"’ will, too. This works for everything except 11122file names containing a trailing newline. 11123 11124 POSIX allows the implementation to define the results if NAME is 11125empty or ‘//’. In the former case, GNU ‘basename’ returns the empty 11126string. In the latter case, the result is ‘//’ on platforms where // is 11127distinct from /, and ‘/’ on platforms where there is no difference. 11128 11129 The program accepts the following options. Also see *note Common 11130options::. Options must precede operands. 11131 11132‘-a’ 11133‘--multiple’ 11134 Support more than one argument. Treat every argument as a NAME. 11135 With this, an optional SUFFIX must be specified using the ‘-s’ 11136 option. 11137 11138‘-s SUFFIX’ 11139‘--suffix=SUFFIX’ 11140 Remove a trailing SUFFIX. This option implies the ‘-a’ option. 11141 11142‘-z’ 11143‘--zero’ 11144 Output a zero byte (ASCII NUL) at the end of each line, rather than 11145 a newline. This option enables other programs to parse the output 11146 even when that output would contain data with embedded newlines. 11147 11148 An exit status of zero indicates success, and a nonzero value 11149indicates failure. 11150 11151 Examples: 11152 11153 # Output "sort". 11154 basename /usr/bin/sort 11155 11156 # Output "stdio". 11157 basename include/stdio.h .h 11158 11159 # Output "stdio". 11160 basename -s .h include/stdio.h 11161 11162 # Output "stdio" followed by "stdlib" 11163 basename -a -s .h include/stdio.h include/stdlib.h 11164 11165 11166File: coreutils.info, Node: dirname invocation, Next: pathchk invocation, Prev: basename invocation, Up: File name manipulation 11167 1116818.2 ‘dirname’: Strip last file name component 11169============================================== 11170 11171‘dirname’ prints all but the final slash-delimited component of each 11172NAME. Slashes on either side of the final component are also removed. 11173If the string contains no slash, ‘dirname’ prints ‘.’ (meaning the 11174current directory). Synopsis: 11175 11176 dirname [OPTION] NAME... 11177 11178 NAME need not be a file name, but if it is, this operation 11179effectively lists the directory that contains the final component, 11180including the case when the final component is itself a directory. 11181 11182 Together, ‘basename’ and ‘dirname’ are designed such that if ‘ls 11183"$name"’ succeeds, then the command sequence ‘cd "$(dirname "$name")"; 11184ls "$(basename "$name")"’ will, too. This works for everything except 11185file names containing a trailing newline. 11186 11187 POSIX allows the implementation to define the results if NAME is 11188‘//’. With GNU ‘dirname’, the result is ‘//’ on platforms where // is 11189distinct from /, and ‘/’ on platforms where there is no difference. 11190 11191 The program accepts the following option. Also see *note Common 11192options::. 11193 11194‘-z’ 11195‘--zero’ 11196 Output a zero byte (ASCII NUL) at the end of each line, rather than 11197 a newline. This option enables other programs to parse the output 11198 even when that output would contain data with embedded newlines. 11199 11200 An exit status of zero indicates success, and a nonzero value 11201indicates failure. 11202 11203 Examples: 11204 11205 # Output "/usr/bin". 11206 dirname /usr/bin/sort 11207 dirname /usr/bin//.// 11208 11209 # Output "dir1" followed by "dir2" 11210 dirname dir1/str dir2/str 11211 11212 # Output ".". 11213 dirname stdio.h 11214 11215 11216File: coreutils.info, Node: pathchk invocation, Next: mktemp invocation, Prev: dirname invocation, Up: File name manipulation 11217 1121818.3 ‘pathchk’: Check file name validity and portability 11219======================================================== 11220 11221‘pathchk’ checks validity and portability of file names. Synopsis: 11222 11223 pathchk [OPTION]... NAME... 11224 11225 For each NAME, ‘pathchk’ prints an error message if any of these 11226conditions is true: 11227 11228 1. One of the existing directories in NAME does not have search 11229 (execute) permission, 11230 2. The length of NAME is larger than the maximum supported by the 11231 operating system. 11232 3. The length of one component of NAME is longer than its file 11233 system’s maximum. 11234 11235 A nonexistent NAME is not an error, so long a file with that name 11236could be created under the above conditions. 11237 11238 The program accepts the following options. Also see *note Common 11239options::. Options must precede operands. 11240 11241‘-p’ 11242 Instead of performing checks based on the underlying file system, 11243 print an error message if any of these conditions is true: 11244 11245 1. A file name is empty. 11246 11247 2. A file name contains a character outside the POSIX portable 11248 file name character set, namely, the ASCII letters and digits, 11249 ‘.’, ‘_’, ‘-’, and ‘/’. 11250 11251 3. The length of a file name or one of its components exceeds the 11252 POSIX minimum limits for portability. 11253 11254‘-P’ 11255 Print an error message if a file name is empty, or if it contains a 11256 component that begins with ‘-’. 11257 11258‘--portability’ 11259 Print an error message if a file name is not portable to all POSIX 11260 hosts. This option is equivalent to ‘-p -P’. 11261 11262 Exit status: 11263 11264 0 if all specified file names passed all checks, 11265 1 otherwise. 11266 11267 11268File: coreutils.info, Node: mktemp invocation, Next: realpath invocation, Prev: pathchk invocation, Up: File name manipulation 11269 1127018.4 ‘mktemp’: Create temporary file or directory 11271================================================= 11272 11273‘mktemp’ manages the creation of temporary files and directories. 11274Synopsis: 11275 11276 mktemp [OPTION]... [TEMPLATE] 11277 11278 Safely create a temporary file or directory based on TEMPLATE, and 11279print its name. If given, TEMPLATE must include at least three 11280consecutive ‘X’s in the last component. If omitted, the template 11281‘tmp.XXXXXXXXXX’ is used, and option ‘--tmpdir’ is implied. The final 11282run of ‘X’s in the TEMPLATE will be replaced by alpha-numeric 11283characters; thus, on a case-sensitive file system, and with a TEMPLATE 11284including a run of N instances of ‘X’, there are ‘62**N’ potential file 11285names. 11286 11287 Older scripts used to create temporary files by simply joining the 11288name of the program with the process id (‘$$’) as a suffix. However, 11289that naming scheme is easily predictable, and suffers from a race 11290condition where the attacker can create an appropriately named symbolic 11291link, such that when the script then opens a handle to what it thought 11292was an unused file, it is instead modifying an existing file. Using the 11293same scheme to create a directory is slightly safer, since the ‘mkdir’ 11294will fail if the target already exists, but it is still inferior because 11295it allows for denial of service attacks. Therefore, modern scripts 11296should use the ‘mktemp’ command to guarantee that the generated name 11297will be unpredictable, and that knowledge of the temporary file name 11298implies that the file was created by the current script and cannot be 11299modified by other users. 11300 11301 When creating a file, the resulting file has read and write 11302permissions for the current user, but no permissions for the group or 11303others; these permissions are reduced if the current umask is more 11304restrictive. 11305 11306 Here are some examples (although note that if you repeat them, you 11307will most likely get different file names): 11308 11309 • Create a temporary file in the current directory. 11310 $ mktemp file.XXXX 11311 file.H47c 11312 11313 • Create a temporary file with a known suffix. 11314 $ mktemp --suffix=.txt file-XXXX 11315 file-H08W.txt 11316 $ mktemp file-XXXX-XXXX.txt 11317 file-XXXX-eI9L.txt 11318 11319 • Create a secure fifo relative to the user’s choice of ‘TMPDIR’, but 11320 falling back to the current directory rather than ‘/tmp’. Note 11321 that ‘mktemp’ does not create fifos, but can create a secure 11322 directory in which the fifo can live. Exit the shell if the 11323 directory or fifo could not be created. 11324 $ dir=$(mktemp -p "${TMPDIR:-.}" -d dir-XXXX) || exit 1 11325 $ fifo=$dir/fifo 11326 $ mkfifo "$fifo" || { rmdir "$dir"; exit 1; } 11327 11328 • Create and use a temporary file if possible, but ignore failure. 11329 The file will reside in the directory named by ‘TMPDIR’, if 11330 specified, or else in ‘/tmp’. 11331 $ file=$(mktemp -q) && { 11332 > # Safe to use $file only within this block. Use quotes, 11333 > # since $TMPDIR, and thus $file, may contain whitespace. 11334 > echo ... > "$file" 11335 > rm "$file" 11336 > } 11337 11338 • Act as a semi-random character generator (it is not fully random, 11339 since it is impacted by the contents of the current directory). To 11340 avoid security holes, do not use the resulting names to create a 11341 file. 11342 $ mktemp -u XXX 11343 Gb9 11344 $ mktemp -u XXX 11345 nzC 11346 11347 The program accepts the following options. Also see *note Common 11348options::. 11349 11350‘-d’ 11351‘--directory’ 11352 Create a directory rather than a file. The directory will have 11353 read, write, and search permissions for the current user, but no 11354 permissions for the group or others; these permissions are reduced 11355 if the current umask is more restrictive. 11356 11357‘-q’ 11358‘--quiet’ 11359 Suppress diagnostics about failure to create a file or directory. 11360 The exit status will still reflect whether a file was created. 11361 11362‘-u’ 11363‘--dry-run’ 11364 Generate a temporary name that does not name an existing file, 11365 without changing the file system contents. Using the output of 11366 this command to create a new file is inherently unsafe, as there is 11367 a window of time between generating the name and using it where 11368 another process can create an object by the same name. 11369 11370‘-p DIR’ 11371‘--tmpdir[=DIR]’ 11372 Treat TEMPLATE relative to the directory DIR. If DIR is not 11373 specified (only possible with the long option ‘--tmpdir’) or is the 11374 empty string, use the value of ‘TMPDIR’ if available, otherwise use 11375 ‘/tmp’. If this is specified, TEMPLATE must not be absolute. 11376 However, TEMPLATE can still contain slashes, although intermediate 11377 directories must already exist. 11378 11379‘--suffix=SUFFIX’ 11380 Append SUFFIX to the TEMPLATE. SUFFIX must not contain slash. If 11381 ‘--suffix’ is specified, TEMPLATE must end in ‘X’; if it is not 11382 specified, then an appropriate ‘--suffix’ is inferred by finding 11383 the last ‘X’ in TEMPLATE. This option exists for use with the 11384 default TEMPLATE and for the creation of a SUFFIX that starts with 11385 ‘X’. 11386 11387‘-t’ 11388 Treat TEMPLATE as a single file relative to the value of ‘TMPDIR’ 11389 if available, or to the directory specified by ‘-p’, otherwise to 11390 ‘/tmp’. TEMPLATE must not contain slashes. This option is 11391 deprecated; the use of ‘-p’ without ‘-t’ offers better defaults (by 11392 favoring the command line over ‘TMPDIR’) and more flexibility (by 11393 allowing intermediate directories). 11394 11395 Exit status: 11396 11397 0 if the file was created, 11398 1 otherwise. 11399 11400 11401File: coreutils.info, Node: realpath invocation, Prev: mktemp invocation, Up: File name manipulation 11402 1140318.5 ‘realpath’: Print the resolved file name. 11404============================================== 11405 11406‘realpath’ expands all symbolic links and resolves references to ‘/./’, 11407‘/../’ and extra ‘/’ characters. By default, all but the last component 11408of the specified files must exist. Synopsis: 11409 11410 realpath [OPTION]... FILE... 11411 11412 The file name canonicalization functionality overlaps with that of 11413the ‘readlink’ command. This is the preferred command for 11414canonicalization as it’s a more suitable and standard name. In addition 11415this command supports relative file name processing functionality. 11416 11417 The program accepts the following options. Also see *note Common 11418options::. 11419 11420‘-e’ 11421‘--canonicalize-existing’ 11422 Ensure that all components of the specified file names exist. If 11423 any component is missing or unavailable, ‘realpath’ will output a 11424 diagnostic unless the ‘-q’ option is specified, and exit with a 11425 nonzero exit code. A trailing slash requires that the name resolve 11426 to a directory. 11427 11428‘-m’ 11429‘--canonicalize-missing’ 11430 If any component of a specified file name is missing or 11431 unavailable, treat it as a directory. 11432 11433‘-L’ 11434‘--logical’ 11435 Symbolic links are resolved in the specified file names, but they 11436 are resolved after any subsequent ‘..’ components are processed. 11437 11438‘-P’ 11439‘--physical’ 11440 Symbolic links are resolved in the specified file names, and they 11441 are resolved before any subsequent ‘..’ components are processed. 11442 This is the default mode of operation. 11443 11444‘-q’ 11445‘--quiet’ 11446 Suppress diagnostic messages for specified file names. 11447 11448‘--relative-to=DIR’ 11449 Print the resolved file names relative to the specified directory. 11450 Note this option honors the ‘-m’ and ‘-e’ options pertaining to 11451 file existence. 11452 11453‘--relative-base=DIR’ 11454 Print the resolved file names as relative _if_ the files are 11455 descendants of DIR. Otherwise, print the resolved file names as 11456 absolute. Note this option honors the ‘-m’ and ‘-e’ options 11457 pertaining to file existence. For details about combining 11458 ‘--relative-to’ and ‘--relative-base’, *note Realpath usage 11459 examples::. 11460 11461‘-s’ 11462‘--strip’ 11463‘--no-symlinks’ 11464 Do not resolve symbolic links. Only resolve references to ‘/./’, 11465 ‘/../’ and remove extra ‘/’ characters. When combined with the 11466 ‘-m’ option, realpath operates only on the file name, and does not 11467 touch any actual file. 11468 11469‘-z’ 11470‘--zero’ 11471 Output a zero byte (ASCII NUL) at the end of each line, rather than 11472 a newline. This option enables other programs to parse the output 11473 even when that output would contain data with embedded newlines. 11474 11475 Exit status: 11476 11477 0 if all file names were printed without issue. 11478 1 otherwise. 11479 11480* Menu: 11481 11482* Realpath usage examples:: Realpath usage examples. 11483 11484 11485File: coreutils.info, Node: Realpath usage examples, Up: realpath invocation 11486 1148718.5.1 Realpath usage examples 11488------------------------------ 11489 11490By default, ‘realpath’ prints the absolute file name of given files 11491(symlinks are resolved, ‘words’ is resolved to ‘american-english’): 11492 11493 cd /home/user 11494 realpath /usr/bin/sort /tmp/foo /usr/share/dict/words 1.txt 11495 ⇒ /usr/bin/sort 11496 ⇒ /tmp/foo 11497 ⇒ /usr/share/dict/american-english 11498 ⇒ /home/user/1.txt 11499 11500 With ‘--relative-to’, file names are printed relative to the given 11501directory: 11502 11503 realpath --relative-to=/usr/bin \ 11504 /usr/bin/sort /tmp/foo /usr/share/dict/words 1.txt 11505 ⇒ sort 11506 ⇒ ../../tmp/foo 11507 ⇒ ../share/dict/american-english 11508 ⇒ ../../home/user/1.txt 11509 11510 With ‘--relative-base’, relative file names are printed _if_ the 11511resolved file name is below the given base directory. For files outside 11512the base directory absolute file names are printed: 11513 11514 realpath --relative-base=/usr \ 11515 /usr/bin/sort /tmp/foo /usr/share/dict/words 1.txt 11516 ⇒ bin/sort 11517 ⇒ /tmp/foo 11518 ⇒ share/dict/american-english 11519 ⇒ /home/user/1.txt 11520 11521 When both ‘--relative-to=DIR1’ and ‘--relative-base=DIR2’ are used, 11522file names are printed relative to DIR1 _if_ they are located below 11523DIR2. If the files are not below DIR2, they are printed as absolute 11524file names: 11525 11526 realpath --relative-to=/usr/bin --relative-base=/usr \ 11527 /usr/bin/sort /tmp/foo /usr/share/dict/words 1.txt 11528 ⇒ sort 11529 ⇒ /tmp/foo 11530 ⇒ ../share/dict/american-english 11531 ⇒ /home/user/1.txt 11532 11533 When both ‘--relative-to=DIR1’ and ‘--relative-base=DIR2’ are used, 11534DIR1 _must_ be a subdirectory of DIR2. Otherwise, ‘realpath’ prints 11535absolutes file names. 11536 11537 11538File: coreutils.info, Node: Working context, Next: User information, Prev: File name manipulation, Up: Top 11539 1154019 Working context 11541****************** 11542 11543This section describes commands that display or alter the context in 11544which you are working: the current directory, the terminal settings, and 11545so forth. See also the user-related commands in the next section. 11546 11547* Menu: 11548 11549* pwd invocation:: Print working directory. 11550* stty invocation:: Print or change terminal characteristics. 11551* printenv invocation:: Print environment variables. 11552* tty invocation:: Print file name of terminal on standard input. 11553 11554 11555File: coreutils.info, Node: pwd invocation, Next: stty invocation, Up: Working context 11556 1155719.1 ‘pwd’: Print working directory 11558=================================== 11559 11560‘pwd’ prints the name of the current directory. Synopsis: 11561 11562 pwd [OPTION]... 11563 11564 The program accepts the following options. Also see *note Common 11565options::. 11566 11567‘-L’ 11568‘--logical’ 11569 If the contents of the environment variable ‘PWD’ provide an 11570 absolute name of the current directory with no ‘.’ or ‘..’ 11571 components, but possibly with symbolic links, then output those 11572 contents. Otherwise, fall back to default ‘-P’ handling. 11573 11574‘-P’ 11575‘--physical’ 11576 Print a fully resolved name for the current directory. That is, 11577 all components of the printed name will be actual directory 11578 names—none will be symbolic links. 11579 11580 If ‘-L’ and ‘-P’ are both given, the last one takes precedence. If 11581neither option is given, then this implementation uses ‘-P’ as the 11582default unless the ‘POSIXLY_CORRECT’ environment variable is set. 11583 11584 Due to shell aliases and built-in ‘pwd’ functions, using an unadorned 11585‘pwd’ interactively or in a script may get you different functionality 11586than that described here. Invoke it via ‘env’ (i.e., ‘env pwd ...’) to 11587avoid interference from the shell. 11588 11589 An exit status of zero indicates success, and a nonzero value 11590indicates failure. 11591 11592 11593File: coreutils.info, Node: stty invocation, Next: printenv invocation, Prev: pwd invocation, Up: Working context 11594 1159519.2 ‘stty’: Print or change terminal characteristics 11596===================================================== 11597 11598‘stty’ prints or changes terminal characteristics, such as baud rate. 11599Synopses: 11600 11601 stty [OPTION] [SETTING]... 11602 stty [OPTION] 11603 11604 If given no line settings, ‘stty’ prints the baud rate, line 11605discipline number (on systems that support it), and line settings that 11606have been changed from the values set by ‘stty sane’. By default, mode 11607reading and setting are performed on the tty line connected to standard 11608input, although this can be modified by the ‘--file’ option. 11609 11610 ‘stty’ accepts many non-option arguments that change aspects of the 11611terminal line operation, as described below. 11612 11613 The program accepts the following options. Also see *note Common 11614options::. 11615 11616‘-a’ 11617‘--all’ 11618 Print all current settings in human-readable form. This option may 11619 not be used in combination with any line settings. 11620 11621‘-F DEVICE’ 11622‘--file=DEVICE’ 11623 Set the line opened by the file name specified in DEVICE instead of 11624 the tty line connected to standard input. This option is necessary 11625 because opening a POSIX tty requires use of the ‘O_NONDELAY’ flag 11626 to prevent a POSIX tty from blocking until the carrier detect line 11627 is high if the ‘clocal’ flag is not set. Hence, it is not always 11628 possible to allow the shell to open the device in the traditional 11629 manner. 11630 11631‘-g’ 11632‘--save’ 11633 Print all current settings in a form that can be used as an 11634 argument to another ‘stty’ command to restore the current settings. 11635 This option may not be used in combination with any line settings. 11636 11637 Many settings can be turned off by preceding them with a ‘-’. Such 11638arguments are marked below with “May be negated” in their description. 11639The descriptions themselves refer to the positive case, that is, when 11640_not_ negated (unless stated otherwise, of course). 11641 11642 Some settings are not available on all POSIX systems, since they use 11643extensions. Such arguments are marked below with “Non-POSIX” in their 11644description. On non-POSIX systems, those or other settings also may not 11645be available, but it’s not feasible to document all the variations: just 11646try it and see. 11647 11648 ‘stty’ is installed only on platforms with the POSIX terminal 11649interface, so portable scripts should not rely on its existence on 11650non-POSIX platforms. 11651 11652 An exit status of zero indicates success, and a nonzero value 11653indicates failure. 11654 11655* Menu: 11656 11657* Control:: Control settings 11658* Input:: Input settings 11659* Output:: Output settings 11660* Local:: Local settings 11661* Combination:: Combination settings 11662* Characters:: Special characters 11663* Special:: Special settings 11664 11665 11666File: coreutils.info, Node: Control, Next: Input, Up: stty invocation 11667 1166819.2.1 Control settings 11669----------------------- 11670 11671Control settings: 11672 11673‘parenb’ 11674 Generate parity bit in output and expect parity bit in input. May 11675 be negated. 11676 11677‘parodd’ 11678 Set odd parity (even if negated). May be negated. 11679 11680‘cmspar’ 11681 Use "stick" (mark/space) parity. If parodd is set, the parity bit 11682 is always 1; if parodd is not set, the parity bit is always zero. 11683 Non-POSIX. May be negated. 11684 11685‘cs5’ 11686‘cs6’ 11687‘cs7’ 11688‘cs8’ 11689 Set character size to 5, 6, 7, or 8 bits. 11690 11691‘hup’ 11692‘hupcl’ 11693 Send a hangup signal when the last process closes the tty. May be 11694 negated. 11695 11696‘cstopb’ 11697 Use two stop bits per character (one if negated). May be negated. 11698 11699‘cread’ 11700 Allow input to be received. May be negated. 11701 11702‘clocal’ 11703 Disable modem control signals. May be negated. 11704 11705‘crtscts’ 11706 Enable RTS/CTS flow control. Non-POSIX. May be negated. 11707 11708‘cdtrdsr’ 11709 Enable DTR/DSR flow control. Non-POSIX. May be negated. 11710 11711 11712File: coreutils.info, Node: Input, Next: Output, Prev: Control, Up: stty invocation 11713 1171419.2.2 Input settings 11715--------------------- 11716 11717These settings control operations on data received from the terminal. 11718 11719‘ignbrk’ 11720 Ignore break characters. May be negated. 11721 11722‘brkint’ 11723 Make breaks cause an interrupt signal. May be negated. 11724 11725‘ignpar’ 11726 Ignore characters with parity errors. May be negated. 11727 11728‘parmrk’ 11729 Mark parity errors (with a 255-0-character sequence). May be 11730 negated. 11731 11732‘inpck’ 11733 Enable input parity checking. May be negated. 11734 11735‘istrip’ 11736 Clear high (8th) bit of input characters. May be negated. 11737 11738‘inlcr’ 11739 Translate newline to carriage return. May be negated. 11740 11741‘igncr’ 11742 Ignore carriage return. May be negated. 11743 11744‘icrnl’ 11745 Translate carriage return to newline. May be negated. 11746 11747‘iutf8’ 11748 Assume input characters are UTF-8 encoded. May be negated. 11749 11750‘ixon’ 11751 Enable XON/XOFF flow control (that is, ‘Ctrl-S’/‘Ctrl-Q’). May be 11752 negated. 11753 11754‘ixoff’ 11755‘tandem’ 11756 Enable sending of ‘stop’ character when the system input buffer is 11757 almost full, and ‘start’ character when it becomes almost empty 11758 again. May be negated. 11759 11760‘iuclc’ 11761 Translate uppercase characters to lowercase. Non-POSIX. May be 11762 negated. Note ilcuc is not implemented, as one would not be able 11763 to issue almost any (lowercase) Unix command, after invoking it. 11764 11765‘ixany’ 11766 Allow any character to restart output (only the start character if 11767 negated). Non-POSIX. May be negated. 11768 11769‘imaxbel’ 11770 Enable beeping and not flushing input buffer if a character arrives 11771 when the input buffer is full. Non-POSIX. May be negated. 11772 11773 11774File: coreutils.info, Node: Output, Next: Local, Prev: Input, Up: stty invocation 11775 1177619.2.3 Output settings 11777---------------------- 11778 11779These settings control operations on data sent to the terminal. 11780 11781‘opost’ 11782 Postprocess output. May be negated. 11783 11784‘olcuc’ 11785 Translate lowercase characters to uppercase. Non-POSIX. May be 11786 negated. (Note ouclc is not currently implemented.) 11787 11788‘ocrnl’ 11789 Translate carriage return to newline. Non-POSIX. May be negated. 11790 11791‘onlcr’ 11792 Translate newline to carriage return-newline. Non-POSIX. May be 11793 negated. 11794 11795‘onocr’ 11796 Do not print carriage returns in the first column. Non-POSIX. May 11797 be negated. 11798 11799‘onlret’ 11800 Newline performs a carriage return. Non-POSIX. May be negated. 11801 11802‘ofill’ 11803 Use fill (padding) characters instead of timing for delays. 11804 Non-POSIX. May be negated. 11805 11806‘ofdel’ 11807 Use ASCII DEL characters for fill instead of ASCII NUL characters. 11808 Non-POSIX. May be negated. 11809 11810‘nl1’ 11811‘nl0’ 11812 Newline delay style. Non-POSIX. 11813 11814‘cr3’ 11815‘cr2’ 11816‘cr1’ 11817‘cr0’ 11818 Carriage return delay style. Non-POSIX. 11819 11820‘tab3’ 11821‘tab2’ 11822‘tab1’ 11823‘tab0’ 11824 Horizontal tab delay style. Non-POSIX. 11825 11826‘bs1’ 11827‘bs0’ 11828 Backspace delay style. Non-POSIX. 11829 11830‘vt1’ 11831‘vt0’ 11832 Vertical tab delay style. Non-POSIX. 11833 11834‘ff1’ 11835‘ff0’ 11836 Form feed delay style. Non-POSIX. 11837 11838 11839File: coreutils.info, Node: Local, Next: Combination, Prev: Output, Up: stty invocation 11840 1184119.2.4 Local settings 11842--------------------- 11843 11844‘isig’ 11845 Enable ‘interrupt’, ‘quit’, and ‘suspend’ special characters. May 11846 be negated. 11847 11848‘icanon’ 11849 Enable ‘erase’, ‘kill’, ‘werase’, and ‘rprnt’ special characters. 11850 May be negated. 11851 11852‘iexten’ 11853 Enable non-POSIX special characters. May be negated. 11854 11855‘echo’ 11856 Echo input characters. May be negated. 11857 11858‘echoe’ 11859‘crterase’ 11860 Echo ‘erase’ characters as backspace-space-backspace. May be 11861 negated. 11862 11863‘echok’ 11864 Echo a newline after a ‘kill’ character. May be negated. 11865 11866‘echonl’ 11867 Echo newline even if not echoing other characters. May be negated. 11868 11869‘noflsh’ 11870 Disable flushing after ‘interrupt’ and ‘quit’ special characters. 11871 May be negated. 11872 11873‘xcase’ 11874 Enable input and output of uppercase characters by preceding their 11875 lowercase equivalents with ‘\’, when ‘icanon’ is set. Non-POSIX. 11876 May be negated. 11877 11878‘tostop’ 11879 Stop background jobs that try to write to the terminal. Non-POSIX. 11880 May be negated. 11881 11882‘echoprt’ 11883‘prterase’ 11884 Echo erased characters backward, between ‘\’ and ‘/’. Non-POSIX. 11885 May be negated. 11886 11887‘echoctl’ 11888‘ctlecho’ 11889 Echo control characters in hat notation (‘^C’) instead of 11890 literally. Non-POSIX. May be negated. 11891 11892‘echoke’ 11893‘crtkill’ 11894 Echo the ‘kill’ special character by erasing each character on the 11895 line as indicated by the ‘echoprt’ and ‘echoe’ settings, instead of 11896 by the ‘echoctl’ and ‘echok’ settings. Non-POSIX. May be negated. 11897 11898‘extproc’ 11899 Enable ‘LINEMODE’, which is used to avoid echoing each character 11900 over high latency links. See also Internet RFC 1116 11901 (https://tools.ietf.org/search/rfc1116). Non-POSIX. May be 11902 negated. 11903 11904‘flusho’ 11905 Discard output. Note this setting is currently ignored on 11906 GNU/Linux systems. Non-POSIX. May be negated. 11907 11908 11909File: coreutils.info, Node: Combination, Next: Characters, Prev: Local, Up: stty invocation 11910 1191119.2.5 Combination settings 11912--------------------------- 11913 11914Combination settings: 11915 11916‘evenp’ 11917‘parity’ 11918 Same as ‘parenb -parodd cs7’. May be negated. If negated, same as 11919 ‘-parenb cs8’. 11920 11921‘oddp’ 11922 Same as ‘parenb parodd cs7’. May be negated. If negated, same as 11923 ‘-parenb cs8’. 11924 11925‘nl’ 11926 Same as ‘-icrnl -onlcr’. May be negated. If negated, same as 11927 ‘icrnl -inlcr -igncr onlcr -ocrnl -onlret’. 11928 11929‘ek’ 11930 Reset the ‘erase’ and ‘kill’ special characters to their default 11931 values. 11932 11933‘sane’ 11934 Same as: 11935 11936 cread -ignbrk brkint -inlcr -igncr icrnl 11937 icanon iexten echo echoe echok -echonl -noflsh 11938 -ixoff -iutf8 -iuclc -ixany imaxbel -xcase -olcuc -ocrnl 11939 opost -ofill onlcr -onocr -onlret nl0 cr0 tab0 bs0 vt0 ff0 11940 isig -tostop -ofdel -echoprt echoctl echoke -extproc 11941 11942 and also sets all special characters to their default values. 11943 11944‘cooked’ 11945 Same as ‘brkint ignpar istrip icrnl ixon opost isig icanon’, plus 11946 sets the ‘eof’ and ‘eol’ characters to their default values if they 11947 are the same as the ‘min’ and ‘time’ characters. May be negated. 11948 If negated, same as ‘raw’. 11949 11950‘raw’ 11951 Same as: 11952 11953 -ignbrk -brkint -ignpar -parmrk -inpck -istrip 11954 -inlcr -igncr -icrnl -ixon -ixoff -icanon -opost 11955 -isig -iuclc -ixany -imaxbel -xcase min 1 time 0 11956 11957 May be negated. If negated, same as ‘cooked’. 11958 11959‘cbreak’ 11960 Same as ‘-icanon’. May be negated. If negated, same as ‘icanon’. 11961 11962‘pass8’ 11963 Same as ‘-parenb -istrip cs8’. May be negated. If negated, same 11964 as ‘parenb istrip cs7’. 11965 11966‘litout’ 11967 Same as ‘-parenb -istrip -opost cs8’. May be negated. If negated, 11968 same as ‘parenb istrip opost cs7’. 11969 11970‘decctlq’ 11971 Same as ‘-ixany’. Non-POSIX. May be negated. 11972 11973‘tabs’ 11974 Same as ‘tab0’. Non-POSIX. May be negated. If negated, same as 11975 ‘tab3’. 11976 11977‘lcase’ 11978‘LCASE’ 11979 Same as ‘xcase iuclc olcuc’. Non-POSIX. May be negated. (Used 11980 for terminals with uppercase characters only.) 11981 11982‘crt’ 11983 Same as ‘echoe echoctl echoke’. 11984 11985‘dec’ 11986 Same as ‘echoe echoctl echoke -ixany intr ^C erase ^? kill C-u’. 11987 11988 11989File: coreutils.info, Node: Characters, Next: Special, Prev: Combination, Up: stty invocation 11990 1199119.2.6 Special characters 11992------------------------- 11993 11994The special characters’ default values vary from system to system. They 11995are set with the syntax ‘name value’, where the names are listed below 11996and the value can be given either literally, in hat notation (‘^C’), or 11997as an integer which may start with ‘0x’ to indicate hexadecimal, ‘0’ to 11998indicate octal, or any other digit to indicate decimal. 11999 12000 For GNU stty, giving a value of ‘^-’ or ‘undef’ disables that special 12001character. (This is incompatible with Ultrix ‘stty’, which uses a value 12002of ‘u’ to disable a special character. GNU ‘stty’ treats a value ‘u’ 12003like any other, namely to set that special character to <U>.) 12004 12005‘intr’ 12006 Send an interrupt signal. 12007 12008‘quit’ 12009 Send a quit signal. 12010 12011‘erase’ 12012 Erase the last character typed. 12013 12014‘kill’ 12015 Erase the current line. 12016 12017‘eof’ 12018 Send an end of file (terminate the input). 12019 12020‘eol’ 12021 End the line. 12022 12023‘eol2’ 12024 Alternate character to end the line. Non-POSIX. 12025 12026‘discard’ 12027 Alternate character to toggle discarding of output. Non-POSIX. 12028 12029‘swtch’ 12030 Switch to a different shell layer. Non-POSIX. 12031 12032‘status’ 12033 Send an info signal. Not currently supported on Linux. Non-POSIX. 12034 12035‘start’ 12036 Restart the output after stopping it. 12037 12038‘stop’ 12039 Stop the output. 12040 12041‘susp’ 12042 Send a terminal stop signal. 12043 12044‘dsusp’ 12045 Send a terminal stop signal after flushing the input. Non-POSIX. 12046 12047‘rprnt’ 12048 Redraw the current line. Non-POSIX. 12049 12050‘werase’ 12051 Erase the last word typed. Non-POSIX. 12052 12053‘lnext’ 12054 Enter the next character typed literally, even if it is a special 12055 character. Non-POSIX. 12056 12057 12058File: coreutils.info, Node: Special, Prev: Characters, Up: stty invocation 12059 1206019.2.7 Special settings 12061----------------------- 12062 12063‘min N’ 12064 Set the minimum number of characters that will satisfy a read until 12065 the time value has expired, when ‘-icanon’ is set. 12066 12067‘time N’ 12068 Set the number of tenths of a second before reads time out if the 12069 minimum number of characters have not been read, when ‘-icanon’ is 12070 set. 12071 12072‘ispeed N’ 12073 Set the input speed to N. 12074 12075‘ospeed N’ 12076 Set the output speed to N. 12077 12078‘rows N’ 12079 Tell the tty kernel driver that the terminal has N rows. 12080 Non-POSIX. 12081 12082‘cols N’ 12083‘columns N’ 12084 Tell the kernel that the terminal has N columns. Non-POSIX. 12085 12086‘drain’ 12087 Apply settings after first waiting for pending output to be 12088 transmitted. This is enabled by default for GNU ‘stty’. It is 12089 useful to disable this option in cases where the system may be in a 12090 state where serial transmission is not possible. For example, if 12091 the system has received the ‘DC3’ character with ‘ixon’ (software 12092 flow control) enabled, then ‘stty’ would block without ‘-drain’ 12093 being specified. May be negated. Non-POSIX. 12094 12095‘size’ 12096 Print the number of rows and columns that the kernel thinks the 12097 terminal has. (Systems that don’t support rows and columns in the 12098 kernel typically use the environment variables ‘LINES’ and 12099 ‘COLUMNS’ instead; however, GNU ‘stty’ does not know anything about 12100 them.) Non-POSIX. 12101 12102‘line N’ 12103 Use line discipline N. Non-POSIX. 12104 12105‘speed’ 12106 Print the terminal speed. 12107 12108‘N’ 12109 Set the input and output speeds to N. N can be one of: 0 50 75 110 12110 134 134.5 150 200 300 600 1200 1800 2400 4800 9600 19200 38400 12111 ‘exta’ ‘extb’. ‘exta’ is the same as 19200; ‘extb’ is the same as 12112 38400. Many systems, including GNU/Linux, support higher speeds. 12113 The ‘stty’ command includes support for speeds of 57600, 115200, 12114 230400, 460800, 500000, 576000, 921600, 1000000, 1152000, 1500000, 12115 2000000, 2500000, 3000000, 3500000, or 4000000 where the system 12116 supports these. 0 hangs up the line if ‘-clocal’ is set. 12117 12118 12119File: coreutils.info, Node: printenv invocation, Next: tty invocation, Prev: stty invocation, Up: Working context 12120 1212119.3 ‘printenv’: Print all or some environment variables 12122======================================================== 12123 12124‘printenv’ prints environment variable values. Synopsis: 12125 12126 printenv [OPTION] [VARIABLE]... 12127 12128 If no VARIABLEs are specified, ‘printenv’ prints the value of every 12129environment variable. Otherwise, it prints the value of each VARIABLE 12130that is set, and nothing for those that are not set. 12131 12132 The program accepts the following option. Also see *note Common 12133options::. 12134 12135‘-0’ 12136‘--null’ 12137 Output a zero byte (ASCII NUL) at the end of each line, rather than 12138 a newline. This option enables other programs to parse the output 12139 even when that output would contain data with embedded newlines. 12140 12141 Exit status: 12142 12143 0 if all variables specified were found 12144 1 if at least one specified variable was not found 12145 2 if a write error occurred 12146 12147 12148File: coreutils.info, Node: tty invocation, Prev: printenv invocation, Up: Working context 12149 1215019.4 ‘tty’: Print file name of terminal on standard input 12151========================================================= 12152 12153‘tty’ prints the file name of the terminal connected to its standard 12154input. It prints ‘not a tty’ if standard input is not a terminal. 12155Synopsis: 12156 12157 tty [OPTION]... 12158 12159 The program accepts the following option. Also see *note Common 12160options::. 12161 12162‘-s’ 12163‘--silent’ 12164‘--quiet’ 12165 Print nothing; only return an exit status. 12166 12167 Exit status: 12168 12169 0 if standard input is a terminal 12170 1 if standard input is a non-terminal file 12171 2 if given incorrect arguments 12172 3 if a write error occurs 12173 12174 12175File: coreutils.info, Node: User information, Next: System context, Prev: Working context, Up: Top 12176 1217720 User information 12178******************* 12179 12180This section describes commands that print user-related information: 12181logins, groups, and so forth. 12182 12183* Menu: 12184 12185* id invocation:: Print user identity. 12186* logname invocation:: Print current login name. 12187* whoami invocation:: Print effective user ID. 12188* groups invocation:: Print group names a user is in. 12189* users invocation:: Print login names of users currently logged in. 12190* who invocation:: Print who is currently logged in. 12191 12192 12193File: coreutils.info, Node: id invocation, Next: logname invocation, Up: User information 12194 1219520.1 ‘id’: Print user identity 12196============================== 12197 12198‘id’ prints information about the given user, or the process running it 12199if no user is specified. Synopsis: 12200 12201 id [OPTION]... [USER]... 12202 12203 USER can be either a user ID or a name, with name look-up taking 12204precedence unless the ID is specified with a leading ‘+’. *Note 12205Disambiguating names and IDs::. 12206 12207 By default, it prints the real user ID, real group ID, effective user 12208ID if different from the real user ID, effective group ID if different 12209from the real group ID, and supplemental group IDs. In addition, if 12210SELinux is enabled and the ‘POSIXLY_CORRECT’ environment variable is not 12211set, then print ‘context=C’, where C is the security context. 12212 12213 Each of these numeric values is preceded by an identifying string and 12214followed by the corresponding user or group name in parentheses. 12215 12216 The options cause ‘id’ to print only part of the above information. 12217Also see *note Common options::. 12218 12219‘-g’ 12220‘--group’ 12221 Print only the group ID. 12222 12223‘-G’ 12224‘--groups’ 12225 Print only the group ID and the supplementary groups. 12226 12227‘-n’ 12228‘--name’ 12229 Print the user or group name instead of the ID number. Requires 12230 ‘-u’, ‘-g’, or ‘-G’. 12231 12232‘-r’ 12233‘--real’ 12234 Print the real, instead of effective, user or group ID. Requires 12235 ‘-u’, ‘-g’, or ‘-G’. 12236 12237‘-u’ 12238‘--user’ 12239 Print only the user ID. 12240 12241‘-Z’ 12242‘--context’ 12243 Print only the security context of the process, which is generally 12244 the user’s security context inherited from the parent process. If 12245 neither SELinux or SMACK is enabled then print a warning and set 12246 the exit status to 1. 12247 12248‘-z’ 12249‘--zero’ 12250 Delimit output items with ASCII NUL characters. This option is not 12251 permitted when using the default format. When multiple users are 12252 specified, and the ‘--groups’ option is also in effect, groups are 12253 delimited with a single NUL character, while users are delimited 12254 with two NUL characters. 12255 12256 Example: 12257 $ id -Gn --zero 12258 users <NUL> devs <NUL> 12259 12260 Primary and supplementary groups for a process are normally inherited 12261from its parent and are usually unchanged since login. This means that 12262if you change the group database after logging in, ‘id’ will not reflect 12263your changes within your existing login session. Running ‘id’ with a 12264user argument causes the user and group database to be consulted afresh, 12265and so will give a different result. 12266 12267 An exit status of zero indicates success, and a nonzero value 12268indicates failure. 12269 12270 12271File: coreutils.info, Node: logname invocation, Next: whoami invocation, Prev: id invocation, Up: User information 12272 1227320.2 ‘logname’: Print current login name 12274======================================== 12275 12276‘logname’ prints the calling user’s name, as found in a 12277system-maintained file (often ‘/var/run/utmp’ or ‘/etc/utmp’), and exits 12278with a status of 0. If there is no entry for the calling process, 12279‘logname’ prints an error message and exits with a status of 1. 12280 12281 The only options are ‘--help’ and ‘--version’. *Note Common 12282options::. 12283 12284 An exit status of zero indicates success, and a nonzero value 12285indicates failure. 12286 12287 12288File: coreutils.info, Node: whoami invocation, Next: groups invocation, Prev: logname invocation, Up: User information 12289 1229020.3 ‘whoami’: Print effective user ID 12291====================================== 12292 12293‘whoami’ prints the user name associated with the current effective user 12294ID. It is equivalent to the command ‘id -un’. 12295 12296 The only options are ‘--help’ and ‘--version’. *Note Common 12297options::. 12298 12299 An exit status of zero indicates success, and a nonzero value 12300indicates failure. 12301 12302 12303File: coreutils.info, Node: groups invocation, Next: users invocation, Prev: whoami invocation, Up: User information 12304 1230520.4 ‘groups’: Print group names a user is in 12306============================================= 12307 12308‘groups’ prints the names of the primary and any supplementary groups 12309for each given USERNAME, or the current process if no names are given. 12310If more than one name is given, the name of each user is printed before 12311the list of that user’s groups and the user name is separated from the 12312group list by a colon. Synopsis: 12313 12314 groups [USERNAME]... 12315 12316 The group lists are equivalent to the output of the command ‘id -Gn’. 12317 12318 The only options are ‘--help’ and ‘--version’. *Note Common 12319options::. 12320 12321 Primary and supplementary groups for a process are normally inherited 12322from its parent and are usually unchanged since login. This means that 12323if you change the group database after logging in, ‘groups’ will not 12324reflect your changes within your existing login session. Running 12325‘groups’ with a list of users causes the user and group database to be 12326consulted afresh, and so will give a different result. 12327 12328 An exit status of zero indicates success, and a nonzero value 12329indicates failure. 12330 12331 12332File: coreutils.info, Node: users invocation, Next: who invocation, Prev: groups invocation, Up: User information 12333 1233420.5 ‘users’: Print login names of users currently logged in 12335============================================================ 12336 12337‘users’ prints on a single line a blank-separated list of user names of 12338users currently logged in to the current host. Each user name 12339corresponds to a login session, so if a user has more than one login 12340session, that user’s name will appear the same number of times in the 12341output. Synopsis: 12342 12343 users [FILE] 12344 12345 With no FILE argument, ‘users’ extracts its information from a 12346system-maintained file (often ‘/var/run/utmp’ or ‘/etc/utmp’). If a 12347file argument is given, ‘users’ uses that file instead. A common choice 12348is ‘/var/log/wtmp’. 12349 12350 The only options are ‘--help’ and ‘--version’. *Note Common 12351options::. 12352 12353 The ‘users’ command is installed only on platforms with the POSIX 12354‘<utmpx.h>’ include file or equivalent, so portable scripts should not 12355rely on its existence on non-POSIX platforms. 12356 12357 An exit status of zero indicates success, and a nonzero value 12358indicates failure. 12359 12360 12361File: coreutils.info, Node: who invocation, Prev: users invocation, Up: User information 12362 1236320.6 ‘who’: Print who is currently logged in 12364============================================ 12365 12366‘who’ prints information about users who are currently logged on. 12367Synopsis: 12368 12369 who [OPTION] [FILE] [am i] 12370 12371 If given no non-option arguments, ‘who’ prints the following 12372information for each user currently logged on: login name, terminal 12373line, login time, and remote hostname or X display. 12374 12375 If given one non-option argument, ‘who’ uses that instead of a 12376default system-maintained file (often ‘/var/run/utmp’ or ‘/etc/utmp’) as 12377the name of the file containing the record of users logged on. 12378‘/var/log/wtmp’ is commonly given as an argument to ‘who’ to look at who 12379has previously logged on. 12380 12381 If given two non-option arguments, ‘who’ prints only the entry for 12382the user running it (determined from its standard input), preceded by 12383the hostname. Traditionally, the two arguments given are ‘am i’, as in 12384‘who am i’. 12385 12386 Timestamps are listed according to the time zone rules specified by 12387the ‘TZ’ environment variable, or by the system default rules if ‘TZ’ is 12388not set. *Note Specifying the Time Zone with ‘TZ’: (libc)TZ Variable. 12389 12390 The program accepts the following options. Also see *note Common 12391options::. 12392 12393‘-a’ 12394‘--all’ 12395 Same as ‘-b -d --login -p -r -t -T -u’. 12396 12397‘-b’ 12398‘--boot’ 12399 Print the date and time of last system boot. 12400 12401‘-d’ 12402‘--dead’ 12403 Print information corresponding to dead processes. 12404 12405‘-H’ 12406‘--heading’ 12407 Print a line of column headings. 12408 12409‘-l’ 12410‘--login’ 12411 List only the entries that correspond to processes via which the 12412 system is waiting for a user to login. The user name is always 12413 ‘LOGIN’. 12414 12415‘--lookup’ 12416 Attempt to canonicalize hostnames found in utmp through a DNS 12417 lookup. This is not the default because it can cause significant 12418 delays on systems with automatic dial-up internet access. 12419 12420‘-m’ 12421 Same as ‘who am i’. 12422 12423‘-p’ 12424‘--process’ 12425 List active processes spawned by init. 12426 12427‘-q’ 12428‘--count’ 12429 Print only the login names and the number of users logged on. 12430 Overrides all other options. 12431 12432‘-r’ 12433‘--runlevel’ 12434 Print the current (and maybe previous) run-level of the init 12435 process. 12436 12437‘-s’ 12438 Ignored; for compatibility with other versions of ‘who’. 12439 12440‘-t’ 12441‘--time’ 12442 Print last system clock change. 12443 12444‘-u’ 12445 After the login time, print the number of hours and minutes that 12446 the user has been idle. ‘.’ means the user was active in the last 12447 minute. ‘old’ means the user has been idle for more than 24 hours. 12448 12449‘-w’ 12450‘-T’ 12451‘--mesg’ 12452‘--message’ 12453‘--writable’ 12454 After each login name print a character indicating the user’s 12455 message status: 12456 12457 ‘+’ allowing ‘write’ messages 12458 ‘-’ disallowing ‘write’ messages 12459 ‘?’ cannot find terminal device 12460 12461 The ‘who’ command is installed only on platforms with the POSIX 12462‘<utmpx.h>’ include file or equivalent, so portable scripts should not 12463rely on its existence on non-POSIX platforms. 12464 12465 An exit status of zero indicates success, and a nonzero value 12466indicates failure. 12467 12468 12469File: coreutils.info, Node: System context, Next: SELinux context, Prev: User information, Up: Top 12470 1247121 System context 12472***************** 12473 12474This section describes commands that print or change system-wide 12475information. 12476 12477* Menu: 12478 12479* date invocation:: Print or set system date and time. 12480* arch invocation:: Print machine hardware name. 12481* nproc invocation:: Print the number of processors. 12482* uname invocation:: Print system information. 12483* hostname invocation:: Print or set system name. 12484* hostid invocation:: Print numeric host identifier. 12485* uptime invocation:: Print system uptime and load. 12486 12487 12488File: coreutils.info, Node: date invocation, Next: arch invocation, Up: System context 12489 1249021.1 ‘date’: Print or set system date and time 12491============================================== 12492 12493Synopses: 12494 12495 date [OPTION]... [+FORMAT] 12496 date [-u|--utc|--universal] [ MMDDhhmm[[CC]YY][.ss] ] 12497 12498 Invoking ‘date’ with no FORMAT argument is equivalent to invoking it 12499with a default format that depends on the ‘LC_TIME’ locale category. In 12500the default C locale, this format is ‘'+%a %b %e %H:%M:%S %Z %Y'’, so 12501the output looks like ‘Thu Mar 3 13:47:51 PST 2005’. 12502 12503 Normally, ‘date’ uses the time zone rules indicated by the ‘TZ’ 12504environment variable, or the system default rules if ‘TZ’ is not set. 12505*Note Specifying the Time Zone with ‘TZ’: (libc)TZ Variable. 12506 12507 If given an argument that starts with a ‘+’, ‘date’ prints the 12508current date and time (or the date and time specified by the ‘--date’ 12509option, see below) in the format defined by that argument, which is 12510similar to that of the ‘strftime’ function. Except for conversion 12511specifiers, which start with ‘%’, characters in the format string are 12512printed unchanged. The conversion specifiers are described below. 12513 12514 An exit status of zero indicates success, and a nonzero value 12515indicates failure. 12516 12517* Menu: 12518 12519* Time conversion specifiers:: %[HIklMNpPrRsSTXzZ] 12520* Date conversion specifiers:: %[aAbBcCdDeFgGhjmuUVwWxyY] 12521* Literal conversion specifiers:: %[%nt] 12522* Padding and other flags:: Pad with zeros, spaces, etc. 12523* Setting the time:: Changing the system clock. 12524* Options for date:: Instead of the current time. 12525* Date input formats:: Specifying date strings. 12526* Examples of date:: Examples. 12527 12528 12529File: coreutils.info, Node: Time conversion specifiers, Next: Date conversion specifiers, Up: date invocation 12530 1253121.1.1 Time conversion specifiers 12532--------------------------------- 12533 12534‘date’ conversion specifiers related to times. 12535 12536‘%H’ 12537 hour (‘00’...‘23’) 12538‘%I’ 12539 hour (‘01’...‘12’) 12540‘%k’ 12541 hour, space padded (‘ 0’...‘23’); equivalent to ‘%_H’. This is a 12542 GNU extension. 12543‘%l’ 12544 hour, space padded (‘ 1’...‘12’); equivalent to ‘%_I’. This is a 12545 GNU extension. 12546‘%M’ 12547 minute (‘00’...‘59’) 12548‘%N’ 12549 nanoseconds (‘000000000’...‘999999999’). This is a GNU extension. 12550‘%p’ 12551 locale’s equivalent of either ‘AM’ or ‘PM’; blank in many locales. 12552 Noon is treated as ‘PM’ and midnight as ‘AM’. 12553‘%P’ 12554 like ‘%p’, except lower case. This is a GNU extension. 12555‘%r’ 12556 locale’s 12-hour clock time (e.g., ‘11:11:04 PM’) 12557‘%R’ 12558 24-hour hour and minute. Same as ‘%H:%M’. 12559‘%s’ 12560 seconds since the epoch, i.e., since 1970-01-01 00:00:00 UTC. Leap 12561 seconds are not counted unless leap second support is available. 12562 *Note %s-examples::, for examples. This is a GNU extension. 12563‘%S’ 12564 second (‘00’...‘60’). This may be ‘60’ if leap seconds are 12565 supported. 12566‘%T’ 12567 24-hour hour, minute, and second. Same as ‘%H:%M:%S’. 12568‘%X’ 12569 locale’s time representation (e.g., ‘23:13:48’) 12570‘%z’ 12571 Four-digit numeric time zone, e.g., ‘-0600’ or ‘+0530’, or ‘-0000’ 12572 if no time zone is determinable. This value reflects the numeric 12573 time zone appropriate for the current time, using the time zone 12574 rules specified by the ‘TZ’ environment variable. A time zone is 12575 not determinable if its numeric offset is zero and its abbreviation 12576 begins with ‘-’. The time (and optionally, the time zone rules) 12577 can be overridden by the ‘--date’ option. 12578‘%:z’ 12579 Numeric time zone with ‘:’, e.g., ‘-06:00’ or ‘+05:30’), or 12580 ‘-00:00’ if no time zone is determinable. This is a GNU extension. 12581‘%::z’ 12582 Numeric time zone to the nearest second with ‘:’ (e.g., ‘-06:00:00’ 12583 or ‘+05:30:00’), or ‘-00:00:00’ if no time zone is determinable. 12584 This is a GNU extension. 12585‘%:::z’ 12586 Numeric time zone with ‘:’ using the minimum necessary precision 12587 (e.g., ‘-06’, ‘+05:30’, or ‘-04:56:02’), or ‘-00’ if no time zone 12588 is determinable. This is a GNU extension. 12589‘%Z’ 12590 alphabetic time zone abbreviation (e.g., ‘EDT’), or nothing if no 12591 time zone is determinable. See ‘%z’ for how it is determined. 12592 12593 12594File: coreutils.info, Node: Date conversion specifiers, Next: Literal conversion specifiers, Prev: Time conversion specifiers, Up: date invocation 12595 1259621.1.2 Date conversion specifiers 12597--------------------------------- 12598 12599‘date’ conversion specifiers related to dates. 12600 12601‘%a’ 12602 locale’s abbreviated weekday name (e.g., ‘Sun’) 12603‘%A’ 12604 locale’s full weekday name, variable length (e.g., ‘Sunday’) 12605‘%b’ 12606 locale’s abbreviated month name (e.g., ‘Jan’) 12607‘%B’ 12608 locale’s full month name, variable length (e.g., ‘January’) 12609‘%c’ 12610 locale’s date and time (e.g., ‘Thu Mar 3 23:05:25 2005’) 12611‘%C’ 12612 century. This is like ‘%Y’, except the last two digits are 12613 omitted. For example, it is ‘20’ if ‘%Y’ is ‘2000’, and is ‘-0’ if 12614 ‘%Y’ is ‘-001’. It is normally at least two characters, but it may 12615 be more. 12616‘%d’ 12617 day of month (e.g., ‘01’) 12618‘%D’ 12619 date; same as ‘%m/%d/%y’ 12620‘%e’ 12621 day of month, space padded; same as ‘%_d’ 12622‘%F’ 12623 full date in ISO 8601 format; like ‘%+4Y-%m-%d’ except that any 12624 flags or field width override the ‘+’ and (after subtracting 6) the 12625 ‘4’. This is a good choice for a date format, as it is standard 12626 and is easy to sort in the usual case where years are in the range 12627 0000...9999. 12628‘%g’ 12629 year corresponding to the ISO week number, but without the century 12630 (range ‘00’ through ‘99’). This has the same format and value as 12631 ‘%y’, except that if the ISO week number (see ‘%V’) belongs to the 12632 previous or next year, that year is used instead. 12633‘%G’ 12634 year corresponding to the ISO week number. This has the same 12635 format and value as ‘%Y’, except that if the ISO week number (see 12636 ‘%V’) belongs to the previous or next year, that year is used 12637 instead. It is normally useful only if ‘%V’ is also used; for 12638 example, the format ‘%G-%m-%d’ is probably a mistake, since it 12639 combines the ISO week number year with the conventional month and 12640 day. 12641‘%h’ 12642 same as ‘%b’ 12643‘%j’ 12644 day of year (‘001’...‘366’) 12645‘%m’ 12646 month (‘01’...‘12’) 12647‘%q’ 12648 quarter of year (‘1’...‘4’) 12649‘%u’ 12650 day of week (‘1’...‘7’) with ‘1’ corresponding to Monday 12651‘%U’ 12652 week number of year, with Sunday as the first day of the week 12653 (‘00’...‘53’). Days in a new year preceding the first Sunday are 12654 in week zero. 12655‘%V’ 12656 ISO week number, that is, the week number of year, with Monday as 12657 the first day of the week (‘01’...‘53’). If the week containing 12658 January 1 has four or more days in the new year, then it is 12659 considered week 1; otherwise, it is week 53 of the previous year, 12660 and the next week is week 1. (See the ISO 8601 standard.) 12661‘%w’ 12662 day of week (‘0’...‘6’) with 0 corresponding to Sunday 12663‘%W’ 12664 week number of year, with Monday as first day of week 12665 (‘00’...‘53’). Days in a new year preceding the first Monday are 12666 in week zero. 12667‘%x’ 12668 locale’s date representation (e.g., ‘12/31/99’) 12669‘%y’ 12670 last two digits of year (‘00’...‘99’) 12671‘%Y’ 12672 year. This is normally at least four characters, but it may be 12673 more. Year ‘0000’ precedes year ‘0001’, and year ‘-001’ precedes 12674 year ‘0000’. 12675 12676 12677File: coreutils.info, Node: Literal conversion specifiers, Next: Padding and other flags, Prev: Date conversion specifiers, Up: date invocation 12678 1267921.1.3 Literal conversion specifiers 12680------------------------------------ 12681 12682‘date’ conversion specifiers that produce literal strings. 12683 12684‘%%’ 12685 a literal % 12686‘%n’ 12687 a newline 12688‘%t’ 12689 a horizontal tab 12690 12691 12692File: coreutils.info, Node: Padding and other flags, Next: Setting the time, Prev: Literal conversion specifiers, Up: date invocation 12693 1269421.1.4 Padding and other flags 12695------------------------------ 12696 12697Unless otherwise specified, ‘date’ normally pads numeric fields with 12698zeros, so that, for example, numeric months are always output as two 12699digits. Seconds since the epoch are not padded, though, since there is 12700no natural width for them. 12701 12702 The following optional flags can appear after the ‘%’: 12703 12704‘-’ 12705 (hyphen) Do not pad the field; useful if the output is intended for 12706 human consumption. This is a GNU extension. 12707‘_’ 12708 (underscore) Pad with spaces; useful if you need a fixed number of 12709 characters in the output, but zeros are too distracting. This is a 12710 GNU extension. 12711‘0’ 12712 (zero) Pad with zeros even if the conversion specifier would 12713 normally pad with spaces. 12714‘+’ 12715 Pad with zeros, like ‘0’. In addition, precede any year number 12716 with ‘+’ if it exceeds 9999 or if its field width exceeds 4; 12717 similarly, precede any century number with ‘+’ if it exceeds 99 or 12718 if its field width exceeds 2. This supports ISO 8601 formats for 12719 dates far in the future; for example, the command ‘date 12720 --date=12019-02-25 +%+13F’ outputs the string ‘+012019-02-25’. 12721‘^’ 12722 Use upper case characters if possible. This is a GNU extension. 12723‘#’ 12724 Use opposite case characters if possible. A field that is normally 12725 upper case becomes lower case, and vice versa. This is a GNU 12726 extension. 12727 12728Here are some examples of padding: 12729 12730 date +%d/%m -d "Feb 1" 12731 ⇒ 01/02 12732 date +%-d/%-m -d "Feb 1" 12733 ⇒ 1/2 12734 date +%_d/%_m -d "Feb 1" 12735 ⇒ 1/ 2 12736 12737 You can optionally specify the field width (after any flag, if 12738present) as a decimal number. If the natural size of the output of the 12739field has less than the specified number of characters, the result is 12740written right adjusted and padded to the given size. For example, ‘%9B’ 12741prints the right adjusted month name in a field of width 9. 12742 12743 An optional modifier can follow the optional flag and width 12744specification. The modifiers are: 12745 12746‘E’ 12747 Use the locale’s alternate representation for date and time. This 12748 modifier applies to the ‘%c’, ‘%C’, ‘%x’, ‘%X’, ‘%y’ and ‘%Y’ 12749 conversion specifiers. In a Japanese locale, for example, ‘%Ex’ 12750 might yield a date format based on the Japanese Emperors’ reigns. 12751 12752‘O’ 12753 Use the locale’s alternate numeric symbols for numbers. This 12754 modifier applies only to numeric conversion specifiers. 12755 12756 If the format supports the modifier but no alternate representation 12757is available, it is ignored. 12758 12759 POSIX specifies the behavior of flags and field widths only for ‘%C’, 12760‘%F’, ‘%G’, and ‘%Y’ (all without modifiers), and requires a flag to be 12761present if and only if a field width is also present. Other 12762combinations of flags, field widths and modifiers are GNU extensions. 12763 12764 12765File: coreutils.info, Node: Setting the time, Next: Options for date, Prev: Padding and other flags, Up: date invocation 12766 1276721.1.5 Setting the time 12768----------------------- 12769 12770If given an argument that does not start with ‘+’, ‘date’ sets the 12771system clock to the date and time specified by that argument (as 12772described below). You must have appropriate privileges to set the 12773system clock. Note for changes to persist across a reboot, the hardware 12774clock may need to be updated from the system clock, which might not 12775happen automatically on your system. 12776 12777 The argument must consist entirely of digits, which have the 12778following meaning: 12779 12780‘MM’ 12781 month 12782‘DD’ 12783 day within month 12784‘hh’ 12785 hour 12786‘mm’ 12787 minute 12788‘CC’ 12789 first two digits of year (optional) 12790‘YY’ 12791 last two digits of year (optional) 12792‘ss’ 12793 second (optional) 12794 12795 Note, the ‘--date’ and ‘--set’ options may not be used with an 12796argument in the above format. The ‘--universal’ option may be used with 12797such an argument to indicate that the specified date and time are 12798relative to Universal Time rather than to the local time zone. 12799 12800 12801File: coreutils.info, Node: Options for date, Next: Examples of date, Prev: Setting the time, Up: date invocation 12802 1280321.1.6 Options for ‘date’ 12804------------------------- 12805 12806The program accepts the following options. Also see *note Common 12807options::. 12808 12809‘-d DATESTR’ 12810‘--date=DATESTR’ 12811 Display the date and time specified in DATESTR instead of the 12812 current date and time. DATESTR can be in almost any common format. 12813 It can contain month names, time zones, ‘am’ and ‘pm’, ‘yesterday’, 12814 etc. For example, ‘--date="2004-02-27 14:19:13.489392193 +0530"’ 12815 specifies the instant of time that is 489,392,193 nanoseconds after 12816 February 27, 2004 at 2:19:13 PM in a time zone that is 5 hours and 12817 30 minutes east of UTC. 12818 Note: input currently must be in locale independent format. E.g., 12819 the LC_TIME=C below is needed to print back the correct date in 12820 many locales: 12821 date -d "$(LC_TIME=C date)" 12822 *Note Date input formats::. 12823 12824‘--debug’ 12825 Annotate the parsed date, display the effective time zone, and warn 12826 about potential misuse. 12827 12828‘-f DATEFILE’ 12829‘--file=DATEFILE’ 12830 Parse each line in DATEFILE as with ‘-d’ and display the resulting 12831 date and time. If DATEFILE is ‘-’, use standard input. This is 12832 useful when you have many dates to process, because the system 12833 overhead of starting up the ‘date’ executable many times can be 12834 considerable. 12835 12836‘-I[TIMESPEC]’ 12837‘--iso-8601[=TIMESPEC]’ 12838 Display the date using an ISO 8601 format, ‘%Y-%m-%d’. 12839 12840 The argument TIMESPEC specifies the number of additional terms of 12841 the time to include. It can be one of the following: 12842 ‘auto’ 12843 Print just the date. This is the default if TIMESPEC is 12844 omitted. 12845 12846 ‘hours’ 12847 Append the hour of the day to the date. 12848 12849 ‘minutes’ 12850 Append the hours and minutes. 12851 12852 ‘seconds’ 12853 Append the hours, minutes and seconds. 12854 12855 ‘ns’ 12856 Append the hours, minutes, seconds and nanoseconds. 12857 12858 If showing any time terms, then include the time zone using the 12859 format ‘%:z’. This format is always suitable as input for the 12860 ‘--date’ (‘-d’) and ‘--file’ (‘-f’) options, regardless of the 12861 current locale. 12862 12863‘-r FILE’ 12864‘--reference=FILE’ 12865 Display the date and time of the last modification of FILE, instead 12866 of the current date and time. 12867 12868‘-R’ 12869‘--rfc-email’ 12870 Display the date and time using the format ‘%a, %d %b %Y %H:%M:%S 12871 %z’, evaluated in the C locale so abbreviations are always in 12872 English. For example: 12873 12874 Fri, 09 Sep 2005 13:51:39 -0700 12875 12876 This format conforms to Internet RFCs 5322 12877 (https://tools.ietf.org/search/rfc5322), 2822 12878 (https://tools.ietf.org/search/rfc2822) and 822 12879 (https://tools.ietf.org/search/rfc822), the current and previous 12880 standards for Internet email. For compatibility with older 12881 versions of ‘date’, ‘--rfc-2822’ and ‘--rfc-822’ are aliases for 12882 ‘--rfc-email’. 12883 12884‘--rfc-3339=TIMESPEC’ 12885 Display the date using a format specified by Internet RFC 3339 12886 (https://tools.ietf.org/search/rfc3339). This is like 12887 ‘--iso-8601’, except that a space rather than a ‘T’ separates dates 12888 from times. This format is always suitable as input for the 12889 ‘--date’ (‘-d’) and ‘--file’ (‘-f’) options, regardless of the 12890 current locale. 12891 12892 The argument TIMESPEC specifies how much of the time to include. 12893 It can be one of the following: 12894 12895 ‘date’ 12896 Print just the full-date, e.g., ‘2005-09-14’. This is 12897 equivalent to the format ‘%Y-%m-%d’. 12898 12899 ‘seconds’ 12900 Print the full-date and full-time separated by a space, e.g., 12901 ‘2005-09-14 00:56:06+05:30’. The output ends with a numeric 12902 time-offset; here the ‘+05:30’ means that local time is five 12903 hours and thirty minutes east of UTC. This is equivalent to 12904 the format ‘%Y-%m-%d %H:%M:%S%:z’. 12905 12906 ‘ns’ 12907 Like ‘seconds’, but also print nanoseconds, e.g., ‘2005-09-14 12908 00:56:06.998458565+05:30’. This is equivalent to the format 12909 ‘%Y-%m-%d %H:%M:%S.%N%:z’. 12910 12911‘-s DATESTR’ 12912‘--set=DATESTR’ 12913 Set the date and time to DATESTR. See ‘-d’ above. See also *note 12914 Setting the time::. 12915 12916‘-u’ 12917‘--utc’ 12918‘--universal’ 12919 Use Universal Time by operating as if the ‘TZ’ environment variable 12920 were set to the string ‘UTC0’. UTC stands for Coordinated 12921 Universal Time, established in 1960. Universal Time is often 12922 called “Greenwich Mean Time” (GMT) for historical reasons. 12923 Typically, systems ignore leap seconds and thus implement an 12924 approximation to UTC rather than true UTC. 12925 12926 12927File: coreutils.info, Node: Examples of date, Prev: Options for date, Up: date invocation 12928 1292921.1.7 Examples of ‘date’ 12930------------------------- 12931 12932Here are a few examples. Also see the documentation for the ‘-d’ option 12933in the previous section. 12934 12935 • To print the date of the day before yesterday: 12936 12937 date --date='2 days ago' 12938 12939 • To print the date of the day three months and one day hence: 12940 12941 date --date='3 months 1 day' 12942 12943 • To print the day of year of Christmas in the current year: 12944 12945 date --date='25 Dec' +%j 12946 12947 • To print the current full month name and the day of the month: 12948 12949 date '+%B %d' 12950 12951 But this may not be what you want because for the first nine days 12952 of the month, the ‘%d’ expands to a zero-padded two-digit field, 12953 for example ‘date -d 1may '+%B %d'’ will print ‘May 01’. 12954 12955 • To print a date without the leading zero for one-digit days of the 12956 month, you can use the (GNU extension) ‘-’ flag to suppress the 12957 padding altogether: 12958 12959 date -d 1may '+%B %-d' 12960 12961 • To print the current date and time in the format required by many 12962 non-GNU versions of ‘date’ when setting the system clock: 12963 12964 date +%m%d%H%M%Y.%S 12965 12966 • To set the system clock forward by two minutes: 12967 12968 date --set='+2 minutes' 12969 12970 • To print the date in Internet RFC 5322 format, use ‘date 12971 --rfc-email’. Here is some example output: 12972 12973 Fri, 09 Sep 2005 13:51:39 -0700 12974 12975 • To convert a date string to the number of seconds since the epoch 12976 (which is 1970-01-01 00:00:00 UTC), use the ‘--date’ option with 12977 the ‘%s’ format. That can be useful in sorting and/or graphing 12978 and/or comparing data by date. The following command outputs the 12979 number of the seconds since the epoch for the time two minutes 12980 after the epoch: 12981 12982 date --date='1970-01-01 00:02:00 +0000' +%s 12983 120 12984 12985 If you do not specify time zone information in the date string, 12986 ‘date’ uses your computer’s idea of the time zone when interpreting 12987 the string. For example, if your computer’s time zone is that of 12988 Cambridge, Massachusetts, which was then 5 hours (i.e., 18,000 12989 seconds) behind UTC: 12990 12991 # local time zone used 12992 date --date='1970-01-01 00:02:00' +%s 12993 18120 12994 12995 • If you’re sorting or graphing dated data, your raw date values may 12996 be represented as seconds since the epoch. But few people can look 12997 at the date ‘946684800’ and casually note “Oh, that’s the first 12998 second of the year 2000 in Greenwich, England.” 12999 13000 date --date='2000-01-01 UTC' +%s 13001 946684800 13002 13003 An alternative is to use the ‘--utc’ (‘-u’) option. Then you may 13004 omit ‘UTC’ from the date string. Although this produces the same 13005 result for ‘%s’ and many other format sequences, with a time zone 13006 offset different from zero, it would give a different result for 13007 zone-dependent formats like ‘%z’. 13008 13009 date -u --date=2000-01-01 +%s 13010 946684800 13011 13012 To convert such an unwieldy number of seconds back to a more 13013 readable form, use a command like this: 13014 13015 # local time zone used 13016 date -d '1970-01-01 UTC 946684800 seconds' +"%Y-%m-%d %T %z" 13017 1999-12-31 19:00:00 -0500 13018 13019 Or if you do not mind depending on the ‘@’ feature present since 13020 coreutils 5.3.0, you could shorten this to: 13021 13022 date -d @946684800 +"%F %T %z" 13023 1999-12-31 19:00:00 -0500 13024 13025 Often it is better to output UTC-relative date and time: 13026 13027 date -u -d '1970-01-01 946684800 seconds' +"%Y-%m-%d %T %z" 13028 2000-01-01 00:00:00 +0000 13029 13030 • Typically the seconds count omits leap seconds, but some systems 13031 are exceptions. Because leap seconds are not predictable, the 13032 mapping between the seconds count and a future timestamp is not 13033 reliable on the atypical systems that include leap seconds in their 13034 counts. 13035 13036 Here is how the two kinds of systems handle the leap second at 13037 2012-06-30 23:59:60 UTC: 13038 13039 # Typical systems ignore leap seconds: 13040 date --date='2012-06-30 23:59:59 +0000' +%s 13041 1341100799 13042 date --date='2012-06-30 23:59:60 +0000' +%s 13043 date: invalid date '2012-06-30 23:59:60 +0000' 13044 date --date='2012-07-01 00:00:00 +0000' +%s 13045 1341100800 13046 13047 # Atypical systems count leap seconds: 13048 date --date='2012-06-30 23:59:59 +0000' +%s 13049 1341100823 13050 date --date='2012-06-30 23:59:60 +0000' +%s 13051 1341100824 13052 date --date='2012-07-01 00:00:00 +0000' +%s 13053 1341100825 13054 13055 13056File: coreutils.info, Node: arch invocation, Next: nproc invocation, Prev: date invocation, Up: System context 13057 1305821.2 ‘arch’: Print machine hardware name 13059======================================== 13060 13061‘arch’ prints the machine hardware name, and is equivalent to ‘uname 13062-m’. Synopsis: 13063 13064 arch [OPTION] 13065 13066 The program accepts the *note Common options:: only. 13067 13068 ‘arch’ is not installed by default, so portable scripts should not 13069rely on its existence. 13070 13071 An exit status of zero indicates success, and a nonzero value 13072indicates failure. 13073 13074 13075File: coreutils.info, Node: nproc invocation, Next: uname invocation, Prev: arch invocation, Up: System context 13076 1307721.3 ‘nproc’: Print the number of available processors 13078====================================================== 13079 13080Print the number of processing units available to the current process, 13081which may be less than the number of online processors. If this 13082information is not accessible, then print the number of processors 13083installed. If the ‘OMP_NUM_THREADS’ or ‘OMP_THREAD_LIMIT’ environment 13084variables are set, then they will determine the minimum and maximum 13085returned value respectively. The result is guaranteed to be greater 13086than zero. Synopsis: 13087 13088 nproc [OPTION] 13089 13090 The program accepts the following options. Also see *note Common 13091options::. 13092 13093‘--all’ 13094 Print the number of installed processors on the system, which may 13095 be greater than the number online or available to the current 13096 process. The ‘OMP_NUM_THREADS’ or ‘OMP_THREAD_LIMIT’ environment 13097 variables are not honored in this case. 13098 13099‘--ignore=NUMBER’ 13100 If possible, exclude this NUMBER of processing units. 13101 13102 An exit status of zero indicates success, and a nonzero value 13103indicates failure. 13104 13105 13106File: coreutils.info, Node: uname invocation, Next: hostname invocation, Prev: nproc invocation, Up: System context 13107 1310821.4 ‘uname’: Print system information 13109====================================== 13110 13111‘uname’ prints information about the machine and operating system it is 13112run on. If no options are given, ‘uname’ acts as if the ‘-s’ option 13113were given. Synopsis: 13114 13115 uname [OPTION]... 13116 13117 If multiple options or ‘-a’ are given, the selected information is 13118printed in this order: 13119 13120 KERNEL-NAME NODENAME KERNEL-RELEASE KERNEL-VERSION 13121 MACHINE PROCESSOR HARDWARE-PLATFORM OPERATING-SYSTEM 13122 13123 The information may contain internal spaces, so such output cannot be 13124parsed reliably. In the following example, RELEASE is 13125‘2.2.18ss.e820-bda652a #4 SMP Tue Jun 5 11:24:08 PDT 2001’: 13126 13127 uname -a 13128 ⇒ Linux dumdum 2.2.18 #4 SMP Tue Jun 5 11:24:08 PDT 2001 i686 unknown unknown GNU/Linux 13129 13130 The program accepts the following options. Also see *note Common 13131options::. 13132 13133‘-a’ 13134‘--all’ 13135 Print all of the below information, except omit the processor type 13136 and the hardware platform name if they are unknown. 13137 13138‘-i’ 13139‘--hardware-platform’ 13140 Print the hardware platform name (sometimes called the hardware 13141 implementation). Print ‘unknown’ if this information is not 13142 available. Note this is non-portable (even across GNU/Linux 13143 distributions). 13144 13145‘-m’ 13146‘--machine’ 13147 Print the machine hardware name (sometimes called the hardware 13148 class or hardware type). 13149 13150‘-n’ 13151‘--nodename’ 13152 Print the network node hostname. 13153 13154‘-p’ 13155‘--processor’ 13156 Print the processor type (sometimes called the instruction set 13157 architecture or ISA). Print ‘unknown’ if this information is not 13158 available. Note this is non-portable (even across GNU/Linux 13159 distributions). 13160 13161‘-o’ 13162‘--operating-system’ 13163 Print the name of the operating system. 13164 13165‘-r’ 13166‘--kernel-release’ 13167 Print the kernel release. 13168 13169‘-s’ 13170‘--kernel-name’ 13171 Print the kernel name. POSIX 1003.1-2001 (*note Standards 13172 conformance::) calls this “the implementation of the operating 13173 system”, because the POSIX specification itself has no notion of 13174 “kernel”. The kernel name might be the same as the operating 13175 system name printed by the ‘-o’ or ‘--operating-system’ option, but 13176 it might differ. Some operating systems (e.g., FreeBSD, HP-UX) 13177 have the same name as their underlying kernels; others (e.g., 13178 GNU/Linux, Solaris) do not. 13179 13180‘-v’ 13181‘--kernel-version’ 13182 Print the kernel version. 13183 13184 An exit status of zero indicates success, and a nonzero value 13185indicates failure. 13186 13187 13188File: coreutils.info, Node: hostname invocation, Next: hostid invocation, Prev: uname invocation, Up: System context 13189 1319021.5 ‘hostname’: Print or set system name 13191========================================= 13192 13193With no arguments, ‘hostname’ prints the name of the current host 13194system. With one argument, it sets the current host name to the 13195specified string. You must have appropriate privileges to set the host 13196name. Synopsis: 13197 13198 hostname [NAME] 13199 13200 The only options are ‘--help’ and ‘--version’. *Note Common 13201options::. 13202 13203 ‘hostname’ is not installed by default, and other packages also 13204supply a ‘hostname’ command, so portable scripts should not rely on its 13205existence or on the exact behavior documented above. 13206 13207 An exit status of zero indicates success, and a nonzero value 13208indicates failure. 13209 13210 13211File: coreutils.info, Node: hostid invocation, Next: uptime invocation, Prev: hostname invocation, Up: System context 13212 1321321.6 ‘hostid’: Print numeric host identifier 13214============================================ 13215 13216‘hostid’ prints the numeric identifier of the current host in 13217hexadecimal. This command accepts no arguments. The only options are 13218‘--help’ and ‘--version’. *Note Common options::. 13219 13220 For example, here’s what it prints on one system I use: 13221 13222 $ hostid 13223 1bac013d 13224 13225 On that system, the 32-bit quantity happens to be closely related to 13226the system’s Internet address, but that isn’t always the case. 13227 13228 ‘hostid’ is installed only on systems that have the ‘gethostid’ 13229function, so portable scripts should not rely on its existence. 13230 13231 An exit status of zero indicates success, and a nonzero value 13232indicates failure. 13233 13234 13235File: coreutils.info, Node: uptime invocation, Prev: hostid invocation, Up: System context 13236 1323721.7 ‘uptime’: Print system uptime and load 13238=========================================== 13239 13240‘uptime’ prints the current time, the system’s uptime, the number of 13241logged-in users and the current load average. 13242 13243 If an argument is specified, it is used as the file to be read to 13244discover how many users are logged in. If no argument is specified, a 13245system default is used (‘uptime --help’ indicates the default setting). 13246 13247 The only options are ‘--help’ and ‘--version’. *Note Common 13248options::. 13249 13250 For example, here’s what it prints right now on one system I use: 13251 13252 $ uptime 13253 14:07 up 3:35, 3 users, load average: 1.39, 1.15, 1.04 13254 13255 The precise method of calculation of load average varies somewhat 13256between systems. Some systems calculate it as the average number of 13257runnable processes over the last 1, 5 and 15 minutes, but some systems 13258also include processes in the uninterruptible sleep state (that is, 13259those processes which are waiting for disk I/O). The Linux kernel 13260includes uninterruptible processes. 13261 13262 ‘uptime’ is installed only on platforms with infrastructure for 13263obtaining the boot time, and other packages also supply an ‘uptime’ 13264command, so portable scripts should not rely on its existence or on the 13265exact behavior documented above. 13266 13267 An exit status of zero indicates success, and a nonzero value 13268indicates failure. 13269 13270 13271File: coreutils.info, Node: SELinux context, Next: Modified command invocation, Prev: System context, Up: Top 13272 1327322 SELinux context 13274****************** 13275 13276This section describes commands for operations with SELinux contexts. 13277 13278* Menu: 13279 13280* chcon invocation:: Change SELinux context of file 13281* runcon invocation:: Run a command in specified SELinux context 13282 13283 13284File: coreutils.info, Node: chcon invocation, Next: runcon invocation, Up: SELinux context 13285 1328622.1 ‘chcon’: Change SELinux context of file 13287============================================ 13288 13289‘chcon’ changes the SELinux security context of the selected files. 13290Synopses: 13291 13292 chcon [OPTION]... CONTEXT FILE... 13293 chcon [OPTION]... [-u USER] [-r ROLE] [-l RANGE] [-t TYPE] FILE... 13294 chcon [OPTION]... --reference=RFILE FILE... 13295 13296 Change the SELinux security context of each FILE to CONTEXT. With 13297‘--reference’, change the security context of each FILE to that of 13298RFILE. 13299 13300 The program accepts the following options. Also see *note Common 13301options::. 13302 13303‘--dereference’ 13304 Do not affect symbolic links but what they refer to; this is the 13305 default. 13306 13307‘-h’ 13308‘--no-dereference’ 13309 Affect the symbolic links themselves instead of any referenced 13310 file. 13311 13312‘--reference=RFILE’ 13313 Use RFILE’s security context rather than specifying a CONTEXT 13314 value. 13315 13316‘-R’ 13317‘--recursive’ 13318 Operate on files and directories recursively. 13319 13320‘--preserve-root’ 13321 Refuse to operate recursively on the root directory, ‘/’, when used 13322 together with the ‘--recursive’ option. *Note Treating / 13323 specially::. 13324 13325‘--no-preserve-root’ 13326 Do not treat the root directory, ‘/’, specially when operating 13327 recursively; this is the default. *Note Treating / specially::. 13328 13329‘-H’ 13330 If ‘--recursive’ (‘-R’) is specified and a command line argument is 13331 a symbolic link to a directory, traverse it. *Note Traversing 13332 symlinks::. 13333 13334‘-L’ 13335 In a recursive traversal, traverse every symbolic link to a 13336 directory that is encountered. *Note Traversing symlinks::. 13337 13338‘-P’ 13339 Do not traverse any symbolic links. This is the default if none of 13340 ‘-H’, ‘-L’, or ‘-P’ is specified. *Note Traversing symlinks::. 13341 13342‘-v’ 13343‘--verbose’ 13344 Output a diagnostic for every file processed. 13345 13346‘-u USER’ 13347‘--user=USER’ 13348 Set user USER in the target security context. 13349 13350‘-r ROLE’ 13351‘--role=ROLE’ 13352 Set role ROLE in the target security context. 13353 13354‘-t TYPE’ 13355‘--type=TYPE’ 13356 Set type TYPE in the target security context. 13357 13358‘-l RANGE’ 13359‘--range=RANGE’ 13360 Set range RANGE in the target security context. 13361 13362 An exit status of zero indicates success, and a nonzero value 13363indicates failure. 13364 13365 13366File: coreutils.info, Node: runcon invocation, Prev: chcon invocation, Up: SELinux context 13367 1336822.2 ‘runcon’: Run a command in specified SELinux context 13369========================================================= 13370 13371‘runcon’ runs file in specified SELinux security context. 13372 13373 Synopses: 13374 runcon CONTEXT COMMAND [ARGS] 13375 runcon [ -c ] [-u USER] [-r ROLE] [-t TYPE] [-l RANGE] COMMAND [ARGS] 13376 13377 Run COMMAND with completely-specified CONTEXT, or with current or 13378transitioned security context modified by one or more of LEVEL, ROLE, 13379TYPE and USER. 13380 13381 If none of ‘-c’, ‘-t’, ‘-u’, ‘-r’, or ‘-l’ is specified, the first 13382argument is used as the complete context. Any additional arguments 13383after COMMAND are interpreted as arguments to the command. 13384 13385 With neither CONTEXT nor COMMAND, print the current security context. 13386 13387 Note also the ‘setpriv’ command which can be used to set the 13388NO_NEW_PRIVS bit using ‘setpriv --no-new-privs runcon ...’, thus 13389disallowing usage of a security context with more privileges than the 13390process would normally have. 13391 13392 ‘runcon’ accepts the following options. Also see *note Common 13393options::. 13394 13395‘-c’ 13396‘--compute’ 13397 Compute process transition context before modifying. 13398 13399‘-u USER’ 13400‘--user=USER’ 13401 Set user USER in the target security context. 13402 13403‘-r ROLE’ 13404‘--role=ROLE’ 13405 Set role ROLE in the target security context. 13406 13407‘-t TYPE’ 13408‘--type=TYPE’ 13409 Set type TYPE in the target security context. 13410 13411‘-l RANGE’ 13412‘--range=RANGE’ 13413 Set range RANGE in the target security context. 13414 13415 Exit status: 13416 13417 126 if COMMAND is found but cannot be invoked 13418 127 if ‘runcon’ itself fails or if COMMAND cannot be found 13419 the exit status of COMMAND otherwise 13420 13421 13422File: coreutils.info, Node: Modified command invocation, Next: Process control, Prev: SELinux context, Up: Top 13423 1342423 Modified command invocation 13425****************************** 13426 13427This section describes commands that run other commands in some context 13428different than the current one: a modified environment, as a different 13429user, etc. 13430 13431* Menu: 13432 13433* chroot invocation:: Modify the root directory. 13434* env invocation:: Modify environment variables. 13435* nice invocation:: Modify niceness. 13436* nohup invocation:: Immunize to hangups. 13437* stdbuf invocation:: Modify buffering of standard streams. 13438* timeout invocation:: Run with time limit. 13439 13440 13441File: coreutils.info, Node: chroot invocation, Next: env invocation, Up: Modified command invocation 13442 1344323.1 ‘chroot’: Run a command with a different root directory 13444============================================================ 13445 13446‘chroot’ runs a command with a specified root directory. On many 13447systems, only the super-user can do this.(1). Synopses: 13448 13449 chroot OPTION NEWROOT [COMMAND [ARGS]...] 13450 chroot OPTION 13451 13452 Ordinarily, file names are looked up starting at the root of the 13453directory structure, i.e., ‘/’. ‘chroot’ changes the root to the 13454directory NEWROOT (which must exist), then changes the working directory 13455to ‘/’, and finally runs COMMAND with optional ARGS. If COMMAND is not 13456specified, the default is the value of the ‘SHELL’ environment variable 13457or ‘/bin/sh’ if not set, invoked with the ‘-i’ option. COMMAND must not 13458be a special built-in utility (*note Special built-in utilities::). 13459 13460 The program accepts the following options. Also see *note Common 13461options::. Options must precede operands. 13462 13463‘--groups=GROUPS’ 13464 Use this option to override the supplementary GROUPS to be used by 13465 the new process. The items in the list (names or numeric IDs) must 13466 be separated by commas. Use ‘--groups=''’ to disable the 13467 supplementary group look-up implicit in the ‘--userspec’ option. 13468 13469‘--userspec=USER[:GROUP]’ 13470 By default, COMMAND is run with the same credentials as the 13471 invoking process. Use this option to run it as a different USER 13472 and/or with a different primary GROUP. If a USER is specified then 13473 the supplementary groups are set according to the system defined 13474 list for that user, unless overridden with the ‘--groups’ option. 13475 13476‘--skip-chdir’ 13477 Use this option to not change the working directory to ‘/’ after 13478 changing the root directory to NEWROOT, i.e., inside the chroot. 13479 This option is only permitted when NEWROOT is the old ‘/’ 13480 directory, and therefore is mostly useful together with the 13481 ‘--groups’ and ‘--userspec’ options to retain the previous working 13482 directory. 13483 13484 The user and group name look-up performed by the ‘--userspec’ and 13485‘--groups’ options, is done both outside and inside the chroot, with 13486successful look-ups inside the chroot taking precedence. If the 13487specified user or group items are intended to represent a numeric ID, 13488then a name to ID resolving step is avoided by specifying a leading ‘+’. 13489*Note Disambiguating names and IDs::. 13490 13491 Here are a few tips to help avoid common problems in using chroot. 13492To start with a simple example, make COMMAND refer to a statically 13493linked binary. If you were to use a dynamically linked executable, then 13494you’d have to arrange to have the shared libraries in the right place 13495under your new root directory. 13496 13497 For example, if you create a statically linked ‘ls’ executable, and 13498put it in ‘/tmp/empty’, you can run this command as root: 13499 13500 $ chroot /tmp/empty /ls -Rl / 13501 13502 Then you’ll see output like this: 13503 13504 /: 13505 total 1023 13506 -rwxr-xr-x 1 0 0 1041745 Aug 16 11:17 ls 13507 13508 If you want to use a dynamically linked executable, say ‘bash’, then 13509first run ‘ldd bash’ to see what shared objects it needs. Then, in 13510addition to copying the actual binary, also copy the listed files to the 13511required positions under your intended new root directory. Finally, if 13512the executable requires any other files (e.g., data, state, device 13513files), copy them into place, too. 13514 13515 ‘chroot’ is installed only on systems that have the ‘chroot’ 13516function, so portable scripts should not rely on its existence. 13517 13518 Exit status: 13519 13520 125 if ‘chroot’ itself fails 13521 126 if COMMAND is found but cannot be invoked 13522 127 if COMMAND cannot be found 13523 the exit status of COMMAND otherwise 13524 13525 ---------- Footnotes ---------- 13526 13527 (1) However, some systems (e.g., FreeBSD) can be configured to allow 13528certain regular users to use the ‘chroot’ system call, and hence to run 13529this program. Also, on Cygwin, anyone can run the ‘chroot’ command, 13530because the underlying function is non-privileged due to lack of support 13531in MS-Windows. Furthermore, the ‘chroot’ command avoids the ‘chroot’ 13532system call when NEWROOT is identical to the old ‘/’ directory for 13533consistency with systems where this is allowed for non-privileged users. 13534 13535 13536File: coreutils.info, Node: env invocation, Next: nice invocation, Prev: chroot invocation, Up: Modified command invocation 13537 1353823.2 ‘env’: Run a command in a modified environment 13539=================================================== 13540 13541‘env’ runs a command with a modified environment. Synopses: 13542 13543 env [OPTION]... [NAME=VALUE]... [COMMAND [ARGS]...] 13544 env -[v]S'[OPTION]... [NAME=VALUE]... [COMMAND [ARGS]...]' 13545 env 13546 13547 ‘env’ is commonly used on first line of scripts (shebang line): 13548 #!/usr/bin/env COMMAND 13549 #!/usr/bin/env -[v]S[OPTION]... [NAME=VALUE]... COMMAND [ARGS]... 13550 13551 Operands of the form ‘VARIABLE=VALUE’ set the environment variable 13552VARIABLE to value VALUE. VALUE may be empty (‘VARIABLE=’). Setting a 13553variable to an empty value is different from unsetting it. These 13554operands are evaluated left-to-right, so if two operands mention the 13555same variable the earlier is ignored. 13556 13557 Environment variable names can be empty, and can contain any 13558characters other than ‘=’ and ASCII NUL. However, it is wise to limit 13559yourself to names that consist solely of underscores, digits, and ASCII 13560letters, and that begin with a non-digit, as applications like the shell 13561do not work well with other names. 13562 13563 The first operand that does not contain the character ‘=’ specifies 13564the program to invoke; it is searched for according to the ‘PATH’ 13565environment variable. Any remaining arguments are passed as arguments 13566to that program. The program should not be a special built-in utility 13567(*note Special built-in utilities::). 13568 13569 Modifications to ‘PATH’ take effect prior to searching for COMMAND. 13570Use caution when reducing ‘PATH’; behavior is not portable when ‘PATH’ 13571is undefined or omits key directories such as ‘/bin’. 13572 13573 In the rare case that a utility contains a ‘=’ in the name, the only 13574way to disambiguate it from a variable assignment is to use an 13575intermediate command for COMMAND, and pass the problematic program name 13576via ARGS. For example, if ‘./prog=’ is an executable in the current 13577‘PATH’: 13578 13579 env prog= true # runs 'true', with prog= in environment 13580 env ./prog= true # runs 'true', with ./prog= in environment 13581 env -- prog= true # runs 'true', with prog= in environment 13582 env sh -c '\prog= true' # runs 'prog=' with argument 'true' 13583 env sh -c 'exec "$@"' sh prog= true # also runs 'prog=' 13584 13585 If no command name is specified following the environment 13586specifications, the resulting environment is printed. This is like 13587specifying the ‘printenv’ program. 13588 13589 For some examples, suppose the environment passed to ‘env’ contains 13590‘LOGNAME=rms’, ‘EDITOR=emacs’, and ‘PATH=.:/gnubin:/hacks’: 13591 13592 • Output the current environment. 13593 $ env | LC_ALL=C sort 13594 EDITOR=emacs 13595 LOGNAME=rms 13596 PATH=.:/gnubin:/hacks 13597 13598 • Run ‘foo’ with a reduced environment, preserving only the original 13599 ‘PATH’ to avoid problems in locating ‘foo’. 13600 env - PATH="$PATH" foo 13601 13602 • Run ‘foo’ with the environment containing ‘LOGNAME=rms’, 13603 ‘EDITOR=emacs’, and ‘PATH=.:/gnubin:/hacks’, and guarantees that 13604 ‘foo’ was found in the file system rather than as a shell built-in. 13605 env foo 13606 13607 • Run ‘nemacs’ with the environment containing ‘LOGNAME=foo’, 13608 ‘EDITOR=emacs’, ‘PATH=.:/gnubin:/hacks’, and ‘DISPLAY=gnu:0’. 13609 env DISPLAY=gnu:0 LOGNAME=foo nemacs 13610 13611 • Attempt to run the program ‘/energy/--’ (as that is the only 13612 possible path search result); if the command exists, the 13613 environment will contain ‘LOGNAME=rms’ and ‘PATH=/energy’, and the 13614 arguments will be ‘e=mc2’, ‘bar’, and ‘baz’. 13615 env -u EDITOR PATH=/energy -- e=mc2 bar baz 13616 1361723.2.1 General options 13618---------------------- 13619 13620The program accepts the following options. Also see *note Common 13621options::. Options must precede operands. 13622 13623‘-0’ 13624‘--null’ 13625 Output a zero byte (ASCII NUL) at the end of each line, rather than 13626 a newline. This option enables other programs to parse the output 13627 even when that output would contain data with embedded newlines. 13628 13629‘-u NAME’ 13630‘--unset=NAME’ 13631 Remove variable NAME from the environment, if it was in the 13632 environment. 13633 13634‘-’ 13635‘-i’ 13636‘--ignore-environment’ 13637 Start with an empty environment, ignoring the inherited 13638 environment. 13639 13640‘-C DIR’ 13641‘--chdir=DIR’ 13642 Change the working directory to DIR before invoking COMMAND. This 13643 differs from the shell built-in ‘cd’ in that it starts COMMAND as a 13644 subprocess rather than altering the shell’s own working directory; 13645 this allows it to be chained with other commands that run commands 13646 in a different context. For example: 13647 13648 # Run 'true' with /chroot as its root directory and /srv as its working 13649 # directory. 13650 chroot /chroot env --chdir=/srv true 13651 # Run 'true' with /build as its working directory, FOO=bar in its 13652 # environment, and a time limit of five seconds. 13653 env --chdir=/build FOO=bar timeout 5 true 13654 13655‘--default-signal[=SIG]’ 13656 Unblock and reset signal SIG to its default signal handler. 13657 Without SIG all known signals are unblocked and reset to their 13658 defaults. Multiple signals can be comma-separated. The following 13659 command runs ‘seq’ with SIGINT and SIGPIPE set to their default 13660 (which is to terminate the program): 13661 13662 env --default-signal=PIPE,INT seq 1000 | head -n1 13663 13664 In the following example, we see how this is not possible to do 13665 with traditional shells. Here the first trap command sets SIGPIPE 13666 to ignore. The second trap command ostensibly sets it back to its 13667 default, but POSIX mandates that the shell must not change 13668 inherited state of the signal - so it is a no-op. 13669 13670 trap '' PIPE && sh -c 'trap - PIPE ; seq inf | head -n1' 13671 13672 Using ‘--default-signal=PIPE’ we can ensure the signal handling is 13673 set to its default behavior: 13674 13675 trap '' PIPE && sh -c 'env --default-signal=PIPE seq inf | head -n1' 13676 13677‘--ignore-signal[=SIG]’ 13678 Ignore signal SIG when running a program. Without SIG all known 13679 signals are set to ignore. Multiple signals can be 13680 comma-separated. The following command runs ‘seq’ with SIGINT set 13681 to be ignored - pressing ‘Ctrl-C’ will not terminate it: 13682 13683 env --ignore-signal=INT seq inf > /dev/null 13684 13685 ‘SIGCHLD’ is special, in that ‘--ignore-signal=CHLD’ might have no 13686 effect (POSIX says it’s unspecified). 13687 13688 Most operating systems do not allow ignoring ‘SIGKILL’, ‘SIGSTOP’ 13689 (and possibly other signals). Attempting to ignore these signals 13690 will fail. 13691 13692 Multiple (and contradictory) ‘--default-signal=SIG’ and 13693 ‘--ignore-signal=SIG’ options are processed left-to-right, with the 13694 latter taking precedence. In the following example, ‘SIGPIPE’ is 13695 set to default while ‘SIGINT’ is ignored: 13696 13697 env --default-signal=INT,PIPE --ignore-signal=INT 13698 13699‘--block-signal[=SIG]’ 13700 Block signal(s) SIG from being delivered. 13701 13702‘--list-signal-handling’ 13703 List blocked or ignored signals to stderr, before executing a 13704 command. 13705 13706‘-v’ 13707‘--debug’ 13708 Show verbose information for each processing step. 13709 13710 $ env -v -uTERM A=B uname -s 13711 unset: TERM 13712 setenv: A=B 13713 executing: uname 13714 arg[0]= 'uname' 13715 arg[1]= '-s' 13716 Linux 13717 13718 When combined with ‘-S’ it is recommended to list ‘-v’ first, e.g. 13719 ‘env -vS'string'’. 13720 13721‘-S STRING’ 13722‘--split-string=STRING’ 13723 process and split STRING into separate arguments used to pass 13724 multiple arguments on shebang lines. ‘env’ supports FreeBSD’s 13725 syntax of several escape sequences and environment variable 13726 expansions. See below for details and examples. 13727 13728 Exit status: 13729 13730 0 if no COMMAND is specified and the environment is output 13731 125 if ‘env’ itself fails 13732 126 if COMMAND is found but cannot be invoked 13733 127 if COMMAND cannot be found 13734 the exit status of COMMAND otherwise 13735 1373623.2.2 ‘-S’/‘--split-string’ usage in scripts 13737--------------------------------------------- 13738 13739The ‘-S’/‘--split-string’ options enable using multiple arguments on the 13740first one of scripts (shebang line, ‘#!’). 13741 13742 When a script’s interpreter is in a known location, scripts typically 13743contain the absolute file name in their first line: 13744 13745Shell script: #!/bin/sh 13746 echo hello 13747 13748Perl script: #!/usr/bin/perl 13749 print "hello\n"; 13750 13751Python script: #!/usr/bin/python3 13752 print("hello") 13753 13754 13755 When a script’s interpreter is in a non-standard location in the 13756‘PATH’ environment variable, it is recommended to use ‘env’ on the first 13757line of the script to find the executable and run it: 13758 13759Shell script: #!/usr/bin/env bash 13760 echo hello 13761 13762Perl script: #!/usr/bin/env perl 13763 print "hello\n"; 13764 13765Python script: #!/usr/bin/env python3 13766 print("hello") 13767 13768 13769 Most operating systems (e.g. GNU/Linux, BSDs) treat all text after 13770the first space as a single argument. When using ‘env’ in a script it 13771is thus not possible to specify multiple arguments. 13772 13773 In the following example: 13774 #!/usr/bin/env perl -T -w 13775 print "hello\n"; 13776 13777 The operating system treats ‘perl -T -w’ as one argument (the 13778program’s name), and executing the script fails with: 13779 13780 /usr/bin/env: 'perl -T -w': No such file or directory 13781 13782 The ‘-S’ option instructs ‘env’ to split the single string into 13783multiple arguments. The following example works as expected: 13784 13785 $ cat hello.pl 13786 #!/usr/bin/env -S perl -T -w 13787 print "hello\n"; 13788 13789 $ chmod a+x hello.pl 13790 $ ./hello.pl 13791 hello 13792 13793 And is equivalent to running ‘perl -T -w hello.pl’ on the command 13794line prompt. 13795 13796Testing and troubleshooting 13797........................... 13798 13799To test ‘env -S’ on the command line, use single quotes for the ‘-S’ 13800string to emulate a single paramter. Single quotes are not needed when 13801using ‘env -S’ in a shebang line on the first line of a script (the 13802operating system already treats it as one argument). 13803 13804 The following command is equivalent to the ‘hello.pl’ script above: 13805 13806 $ env -S'perl -T -w' hello.pl 13807 13808 To troubleshoot ‘-S’ usage add the ‘-v’ as the first argument (before 13809‘-S’). 13810 13811 Using ‘-vS’ on a shebang line in a script: 13812 13813 $ cat hello-debug.pl 13814 #!/usr/bin/env -vS perl -T -w 13815 print "hello\n"; 13816 13817 $ chmod a+x hello-debug.pl 13818 $ ./hello-debug.pl 13819 split -S: 'perl -T -w' 13820 into: 'perl' 13821 & '-T' 13822 & '-w' 13823 executing: perl 13824 arg[0]= 'perl' 13825 arg[1]= '-T' 13826 arg[2]= '-w' 13827 arg[3]= './hello-debug.pl' 13828 hello 13829 13830 Using ‘-vS’ on the command line prompt (adding single quotes): 13831 13832 $ env -vS'perl -T -w' hello-debug.pl 13833 split -S: 'perl -T -w' 13834 into: 'perl' 13835 & '-T' 13836 & '-w' 13837 executing: perl 13838 arg[0]= 'perl' 13839 arg[1]= '-T' 13840 arg[2]= '-w' 13841 arg[3]= 'hello-debug.pl' 13842 hello 13843 1384423.2.3 ‘-S’/‘--split-string’ syntax 13845----------------------------------- 13846 13847Splitting arguments by whitespace 13848................................. 13849 13850Running ‘env -Sstring’ splits the STRING into arguments based on 13851unquoted spaces or tab characters. 13852 13853 In the following contrived example the ‘awk’ variable ‘OFS’ will be 13854‘<space>xyz<space>’ as these spaces are inside double quotes. The other 13855space characters are used as argument separators: 13856 13857 $ cat one.awk 13858 #!/usr/bin/env -S awk -v OFS=" xyz " -f 13859 BEGIN {print 1,2,3} 13860 13861 $ chmod a+x one.awk 13862 $ ./one.awk 13863 1 xyz 2 xyz 3 13864 13865 When using ‘-S’ on the command line prompt, remember to add single 13866quotes around the entire string: 13867 13868 $ env -S'awk -v OFS=" xyz " -f' one.awk 13869 1 xyz 2 xyz 3 13870 13871Escape sequences 13872................ 13873 13874‘env’ supports several escape sequences. These sequences are processed 13875when unquoted or inside double quotes (unless otherwise noted). Single 13876quotes disable escape sequences except ‘\'’ and ‘\\’. 13877 13878‘\c’ Ignore the remaining characters in the string. Cannot be used 13879 inside double quotes. 13880 13881‘\f’ form-feed character (ASCII 0x0C) 13882 13883‘\n’ new-line character (ASCII 0x0A) 13884 13885‘\r’ carriage-return character (ASCII 0x0D) 13886 13887‘\t’ tab character (ASCII 0x09) 13888 13889‘\v’ vertical tab character (ASCII 0x0B) 13890 13891‘\#’ A hash ‘#’ character. Used when a ‘#’ character is needed as 13892 the first character of an argument (see ’comments’ section 13893 below). 13894 13895‘\$’ A dollar-sign character ‘$’. Unescaped ‘$’ characters are used 13896 to expand environment variables (see ’variables’ section 13897 below). 13898 13899‘\_’ Inside double-quotes, replaced with a single space character. 13900 Outside quotes, treated as an argument separator. ‘\_’ can be 13901 used to avoid space characters in a shebang line (see examples 13902 below). 13903 13904‘\"’ A double-quote character. 13905 13906‘\'’ A single-quote character. This escape sequence works inside 13907 single-quoted strings. 13908 13909‘\\’ A backslash character. This escape sequence works inside 13910 single-quoted strings. 13911 13912 13913 The following ‘awk’ script will use tab character as input and output 13914field separator (instead of spaces and tabs): 13915 13916 $ cat tabs.awk 13917 #!/usr/bin/env -S awk -v FS="\t" -v OFS="\t" -f 13918 ... 13919 13920Comments 13921........ 13922 13923The escape sequence ‘\c’ (used outside single/double quotes) causes 13924‘env’ to ignore the rest of the string. 13925 13926 The ‘#’ character causes ‘env’ to ignore the rest of the string when 13927it appears as the first character of an argument. Use ‘\#’ to reverse 13928this behavior. 13929 13930 $ env -S'printf %s\n A B C' 13931 A 13932 B 13933 C 13934 13935 $ env -S'printf %s\n A# B C' 13936 A# 13937 B 13938 C 13939 13940 $ env -S'printf %s\n A #B C' 13941 A 13942 13943 $ env -S'printf %s\n A \#B C' 13944 A 13945 #B 13946 C 13947 13948 $ env -S'printf %s\n A\cB C' 13949 A 13950 13951 NOTE: The above examples use single quotes as they are executed on 13952the command-line. 13953 13954Environment variable expansion 13955.............................. 13956 13957The pattern ‘${VARNAME}’ is used to substitute a value from the 13958environment variable. The pattern must include the curly braces 13959(‘{’,‘}’). Without them ‘env’ will reject the string. Special shell 13960variables (such as ‘$@’, ‘$*’, ‘$$’) are not supported. 13961 13962 If the environment variable is empty or not set, the pattern will be 13963replaced by an empty string. The value of ‘${VARNAME}’ will be that of 13964the executed ‘env’, before any modifications using 13965‘-i’/‘--ignore-environment’/‘-u’/‘--unset’ or setting new values using 13966‘VAR=VALUE’. 13967 13968 The following python script prepends ‘/opt/custom/modules’ to the 13969python module search path environment variable (‘PYTHONPATH’): 13970 13971 $ cat custom.py 13972 #!/usr/bin/env -S PYTHONPATH=/opt/custom/modules/:${PYTHONPATH} python 13973 print "hello" 13974 ... 13975 13976 The expansion of ‘${PYTHONPATH}’ is performed by ‘env’, not by a 13977shell. If the curly braces are omitted, ‘env’ will fail: 13978 13979 $ cat custom.py 13980 #!/usr/bin/env -S PYTHONPATH=/opt/custom/modules/:$PYTHONPATH python 13981 print "hello" 13982 ... 13983 13984 $ chmod a+x custom.py 13985 $ custom.py 13986 /usr/bin/env: only ${VARNAME} expansion is supported, error at: $PYTHONPATH python 13987 13988 Environment variable expansion happens before clearing the 13989environment (with ‘-i’) or unsetting specific variables (with ‘-u’): 13990 13991 $ env -S'-i OLDUSER=${USER} env' 13992 OLDUSER=gordon 13993 13994 Use ‘-v’ to diagnose the operations step-by-step: 13995 13996 $ env -vS'-i OLDUSER=${USER} env' 13997 expanding ${USER} into 'gordon' 13998 split -S: '-i OLDUSER=${USER} env' 13999 into: '-i' 14000 & 'OLDUSER=gordon' 14001 & 'env' 14002 cleaning environ 14003 setenv: OLDUSER=gordon 14004 executing: env 14005 arg[0]= 'env' 14006 OLDUSER=gordon 14007 14008 14009File: coreutils.info, Node: nice invocation, Next: nohup invocation, Prev: env invocation, Up: Modified command invocation 14010 1401123.3 ‘nice’: Run a command with modified niceness 14012================================================= 14013 14014‘nice’ prints a process’s “niceness”, or runs a command with modified 14015niceness. “niceness” affects how favorably the process is scheduled in 14016the system. Synopsis: 14017 14018 nice [OPTION]... [COMMAND [ARG]...] 14019 14020 If no arguments are given, ‘nice’ prints the current niceness. 14021Otherwise, ‘nice’ runs the given COMMAND with its niceness adjusted. By 14022default, its niceness is incremented by 10. 14023 14024 Niceness values range at least from −20 (process has high priority 14025and gets more resources, thus slowing down other processes) through 19 14026(process has lower priority and runs slowly itself, but has less impact 14027on the speed of other running processes). Some systems may have a wider 14028range of niceness values; conversely, other systems may enforce more 14029restrictive limits. An attempt to set the niceness outside the 14030supported range is treated as an attempt to use the minimum or maximum 14031supported value. 14032 14033 A niceness should not be confused with a scheduling priority, which 14034lets applications determine the order in which threads are scheduled to 14035run. Unlike a priority, a niceness is merely advice to the scheduler, 14036which the scheduler is free to ignore. Also, as a point of terminology, 14037POSIX defines the behavior of ‘nice’ in terms of a “nice value”, which 14038is the non-negative difference between a niceness and the minimum 14039niceness. Though ‘nice’ conforms to POSIX, its documentation and 14040diagnostics use the term “niceness” for compatibility with historical 14041practice. 14042 14043 COMMAND must not be a special built-in utility (*note Special 14044built-in utilities::). 14045 14046 Due to shell aliases and built-in ‘nice’ functions, using an 14047unadorned ‘nice’ interactively or in a script may get you different 14048functionality than that described here. Invoke it via ‘env’ (i.e., ‘env 14049nice ...’) to avoid interference from the shell. 14050 14051 Note to change the “niceness” of an existing process, one needs to 14052use the ‘renice’ command. 14053 14054 The program accepts the following option. Also see *note Common 14055options::. Options must precede operands. 14056 14057‘-n ADJUSTMENT’ 14058‘--adjustment=ADJUSTMENT’ 14059 Add ADJUSTMENT instead of 10 to the command’s niceness. If 14060 ADJUSTMENT is negative and you lack appropriate privileges, ‘nice’ 14061 issues a warning but otherwise acts as if you specified a zero 14062 adjustment. 14063 14064 For compatibility ‘nice’ also supports an obsolete option syntax 14065 ‘-ADJUSTMENT’. New scripts should use ‘-n ADJUSTMENT’ instead. 14066 14067 ‘nice’ is installed only on systems that have the POSIX ‘setpriority’ 14068function, so portable scripts should not rely on its existence on 14069non-POSIX platforms. 14070 14071 Exit status: 14072 14073 0 if no COMMAND is specified and the niceness is output 14074 125 if ‘nice’ itself fails 14075 126 if COMMAND is found but cannot be invoked 14076 127 if COMMAND cannot be found 14077 the exit status of COMMAND otherwise 14078 14079 It is sometimes useful to run a non-interactive program with reduced 14080niceness. 14081 14082 $ nice factor 4611686018427387903 14083 14084 Since ‘nice’ prints the current niceness, you can invoke it through 14085itself to demonstrate how it works. 14086 14087 The default behavior is to increase the niceness by ‘10’: 14088 14089 $ nice 14090 0 14091 $ nice nice 14092 10 14093 $ nice -n 10 nice 14094 10 14095 14096 The ADJUSTMENT is relative to the current niceness. In the next 14097example, the first ‘nice’ invocation runs the second one with niceness 1409810, and it in turn runs the final one with a niceness that is 3 more: 14099 14100 $ nice nice -n 3 nice 14101 13 14102 14103 Specifying a niceness larger than the supported range is the same as 14104specifying the maximum supported value: 14105 14106 $ nice -n 10000000000 nice 14107 19 14108 14109 Only a privileged user may run a process with lower niceness: 14110 14111 $ nice -n -1 nice 14112 nice: cannot set niceness: Permission denied 14113 0 14114 $ sudo nice -n -1 nice 14115 -1 14116 14117 14118File: coreutils.info, Node: nohup invocation, Next: stdbuf invocation, Prev: nice invocation, Up: Modified command invocation 14119 1412023.4 ‘nohup’: Run a command immune to hangups 14121============================================= 14122 14123‘nohup’ runs the given COMMAND with hangup signals ignored, so that the 14124command can continue running in the background after you log out. 14125Synopsis: 14126 14127 nohup COMMAND [ARG]... 14128 14129 If standard input is a terminal, redirect it so that terminal 14130sessions do not mistakenly consider the terminal to be used by the 14131command. Make the substitute file descriptor unreadable, so that 14132commands that mistakenly attempt to read from standard input can report 14133an error. This redirection is a GNU extension; programs intended to be 14134portable to non-GNU hosts can use ‘nohup COMMAND [ARG]... 0>/dev/null’ 14135instead. 14136 14137 If standard output is a terminal, the command’s standard output is 14138appended to the file ‘nohup.out’; if that cannot be written to, it is 14139appended to the file ‘$HOME/nohup.out’; and if that cannot be written 14140to, the command is not run. Any ‘nohup.out’ or ‘$HOME/nohup.out’ file 14141created by ‘nohup’ is made readable and writable only to the user, 14142regardless of the current umask settings. 14143 14144 If standard error is a terminal, it is normally redirected to the 14145same file descriptor as the (possibly-redirected) standard output. 14146However, if standard output is closed, standard error terminal output is 14147instead appended to the file ‘nohup.out’ or ‘$HOME/nohup.out’ as above. 14148 14149 To capture the command’s output to a file other than ‘nohup.out’ you 14150can redirect it. For example, to capture the output of ‘make’: 14151 14152 nohup make > make.log 14153 14154 ‘nohup’ does not automatically put the command it runs in the 14155background; you must do that explicitly, by ending the command line with 14156an ‘&’. Also, ‘nohup’ does not alter the niceness of COMMAND; use 14157‘nice’ for that, e.g., ‘nohup nice COMMAND’. 14158 14159 COMMAND must not be a special built-in utility (*note Special 14160built-in utilities::). 14161 14162 The only options are ‘--help’ and ‘--version’. *Note Common 14163options::. Options must precede operands. 14164 14165 Exit status: 14166 14167 125 if ‘nohup’ itself fails, and ‘POSIXLY_CORRECT’ is not set 14168 126 if COMMAND is found but cannot be invoked 14169 127 if COMMAND cannot be found 14170 the exit status of COMMAND otherwise 14171 14172 If ‘POSIXLY_CORRECT’ is set, internal failures give status 127 14173instead of 125. 14174 14175 14176File: coreutils.info, Node: stdbuf invocation, Next: timeout invocation, Prev: nohup invocation, Up: Modified command invocation 14177 1417823.5 ‘stdbuf’: Run a command with modified I/O stream buffering 14179=============================================================== 14180 14181‘stdbuf’ allows one to modify the buffering operations of the three 14182standard I/O streams associated with a program. Synopsis: 14183 14184 stdbuf OPTION... COMMAND 14185 14186 COMMAND must start with the name of a program that 14187 1. uses the ISO C ‘FILE’ streams for input/output (note the programs 14188 ‘dd’ and ‘cat’ don’t do that), 14189 14190 2. does not adjust the buffering of its standard streams (note the 14191 program ‘tee’ is not in this category). 14192 14193 Any additional ARGs are passed as additional arguments to the 14194COMMAND. 14195 14196 The program accepts the following options. Also see *note Common 14197options::. 14198 14199‘-i MODE’ 14200‘--input=MODE’ 14201 Adjust the standard input stream buffering. 14202 14203‘-o MODE’ 14204‘--output=MODE’ 14205 Adjust the standard output stream buffering. 14206 14207‘-e MODE’ 14208‘--error=MODE’ 14209 Adjust the standard error stream buffering. 14210 14211 The MODE can be specified as follows: 14212 14213‘L’ 14214 Set the stream to line buffered mode. In this mode data is 14215 coalesced until a newline is output or input is read from any 14216 stream attached to a terminal device. This option is invalid with 14217 standard input. 14218 14219‘0’ 14220 Disable buffering of the selected stream. In this mode, data is 14221 output immediately and only the amount of data requested is read 14222 from input. Note the difference in function for input and output. 14223 Disabling buffering for input will not influence the responsiveness 14224 or blocking behavior of the stream input functions. For example 14225 ‘fread’ will still block until ‘EOF’ or error, even if the 14226 underlying ‘read’ returns less data than requested. 14227 14228‘SIZE’ 14229 Specify the size of the buffer to use in fully buffered mode. SIZE 14230 may be, or may be an integer optionally followed by, one of the 14231 following multiplicative suffixes: 14232 ‘KB’ => 1000 (KiloBytes) 14233 ‘K’ => 1024 (KibiBytes) 14234 ‘MB’ => 1000*1000 (MegaBytes) 14235 ‘M’ => 1024*1024 (MebiBytes) 14236 ‘GB’ => 1000*1000*1000 (GigaBytes) 14237 ‘G’ => 1024*1024*1024 (GibiBytes) 14238 and so on for ‘T’, ‘P’, ‘E’, ‘Z’, and ‘Y’. Binary prefixes can be 14239 used, too: ‘KiB’=‘K’, ‘MiB’=‘M’, and so on. 14240 14241 ‘stdbuf’ is installed only on platforms that use the Executable and 14242Linkable Format (ELF) and support the ‘constructor’ attribute, so 14243portable scripts should not rely on its existence. 14244 14245 Exit status: 14246 14247 125 if ‘stdbuf’ itself fails 14248 126 if COMMAND is found but cannot be invoked 14249 127 if COMMAND cannot be found 14250 the exit status of COMMAND otherwise 14251 14252 14253File: coreutils.info, Node: timeout invocation, Prev: stdbuf invocation, Up: Modified command invocation 14254 1425523.6 ‘timeout’: Run a command with a time limit 14256=============================================== 14257 14258‘timeout’ runs the given COMMAND and kills it if it is still running 14259after the specified time interval. Synopsis: 14260 14261 timeout [OPTION] DURATION COMMAND [ARG]... 14262 14263 COMMAND must not be a special built-in utility (*note Special 14264built-in utilities::). 14265 14266 The program accepts the following options. Also see *note Common 14267options::. Options must precede operands. 14268 14269‘--preserve-status’ 14270 Return the exit status of the managed COMMAND on timeout, rather 14271 than a specific exit status indicating a timeout. This is useful 14272 if the managed COMMAND supports running for an indeterminate amount 14273 of time. 14274 14275‘--foreground’ 14276 Don’t create a separate background program group, so that the 14277 managed COMMAND can use the foreground TTY normally. This is 14278 needed to support timing out commands not started directly from an 14279 interactive shell, in two situations. 14280 1. COMMAND is interactive and needs to read from the terminal for 14281 example 14282 2. the user wants to support sending signals directly to COMMAND 14283 from the terminal (like Ctrl-C for example) 14284 14285 Note in this mode of operation, any children of COMMAND will not be 14286 timed out. Also SIGCONT will not be sent to COMMAND, as it’s 14287 generally not needed with foreground processes, and can cause 14288 intermittent signal delivery issues with programs that are monitors 14289 themselves (like GDB for example). 14290 14291‘-k DURATION’ 14292‘--kill-after=DURATION’ 14293 Ensure the monitored COMMAND is killed by also sending a ‘KILL’ 14294 signal, after the specified DURATION. Without this option, if the 14295 selected signal proves not to be fatal, ‘timeout’ does not kill the 14296 COMMAND. 14297 14298‘-s SIGNAL’ 14299‘--signal=SIGNAL’ 14300 Send this SIGNAL to COMMAND on timeout, rather than the default 14301 ‘TERM’ signal. SIGNAL may be a name like ‘HUP’ or a number. *Note 14302 Signal specifications::. 14303 14304‘-v’ 14305‘--verbose’ 14306 Diagnose to stderr, any signal sent upon timeout. 14307 14308 DURATION is a floating point number in either the current or the C 14309locale (*note Floating point::) followed by an optional unit: 14310 ‘s’ for seconds (the default) 14311 ‘m’ for minutes 14312 ‘h’ for hours 14313 ‘d’ for days 14314 A duration of 0 disables the associated timeout. Note that the 14315actual timeout duration is dependent on system conditions, which should 14316be especially considered when specifying sub-second timeouts. 14317 14318 Exit status: 14319 14320 124 if COMMAND times out 14321 125 if ‘timeout’ itself fails 14322 126 if COMMAND is found but cannot be invoked 14323 127 if COMMAND cannot be found 14324 137 if COMMAND is sent the KILL(9) signal (128+9) 14325 the exit status of COMMAND otherwise 14326 14327 14328File: coreutils.info, Node: Process control, Next: Delaying, Prev: Modified command invocation, Up: Top 14329 1433024 Process control 14331****************** 14332 14333* Menu: 14334 14335* kill invocation:: Sending a signal to processes. 14336 14337 14338File: coreutils.info, Node: kill invocation, Up: Process control 14339 1434024.1 ‘kill’: Send a signal to processes 14341======================================= 14342 14343The ‘kill’ command sends a signal to processes, causing them to 14344terminate or otherwise act upon receiving the signal in some way. 14345Alternatively, it lists information about signals. Synopses: 14346 14347 kill [-s SIGNAL | --signal SIGNAL | -SIGNAL] PID... 14348 kill [-l | --list | -t | --table] [SIGNAL]... 14349 14350 Due to shell aliases and built-in ‘kill’ functions, using an 14351unadorned ‘kill’ interactively or in a script may get you different 14352functionality than that described here. Invoke it via ‘env’ (i.e., ‘env 14353kill ...’) to avoid interference from the shell. 14354 14355 The first form of the ‘kill’ command sends a signal to all PID 14356arguments. The default signal to send if none is specified is ‘TERM’. 14357The special signal number ‘0’ does not denote a valid signal, but can be 14358used to test whether the PID arguments specify processes to which a 14359signal could be sent. 14360 14361 If PID is positive, the signal is sent to the process with the 14362process ID PID. If PID is zero, the signal is sent to all processes in 14363the process group of the current process. If PID is −1, the signal is 14364sent to all processes for which the user has permission to send a 14365signal. If PID is less than −1, the signal is sent to all processes in 14366the process group that equals the absolute value of PID. 14367 14368 If PID is not positive, a system-dependent set of system processes is 14369excluded from the list of processes to which the signal is sent. 14370 14371 If a negative PID argument is desired as the first one, it should be 14372preceded by ‘--’. However, as a common extension to POSIX, ‘--’ is not 14373required with ‘kill -SIGNAL -PID’. The following commands are 14374equivalent: 14375 14376 kill -15 -1 14377 kill -TERM -1 14378 kill -s TERM -- -1 14379 kill -- -1 14380 14381 The first form of the ‘kill’ command succeeds if every PID argument 14382specifies at least one process that the signal was sent to. 14383 14384 The second form of the ‘kill’ command lists signal information. 14385Either the ‘-l’ or ‘--list’ option, or the ‘-t’ or ‘--table’ option must 14386be specified. Without any SIGNAL argument, all supported signals are 14387listed. The output of ‘-l’ or ‘--list’ is a list of the signal names, 14388one per line; if SIGNAL is already a name, the signal number is printed 14389instead. The output of ‘-t’ or ‘--table’ is a table of signal numbers, 14390names, and descriptions. This form of the ‘kill’ command succeeds if 14391all SIGNAL arguments are valid and if there is no output error. 14392 14393 The ‘kill’ command also supports the ‘--help’ and ‘--version’ 14394options. *Note Common options::. 14395 14396 A SIGNAL may be a signal name like ‘HUP’, or a signal number like 14397‘1’, or an exit status of a process terminated by the signal. A signal 14398name can be given in canonical form or prefixed by ‘SIG’. The case of 14399the letters is ignored, except for the ‘-SIGNAL’ option which must use 14400upper case to avoid ambiguity with lower case option letters. *Note 14401Signal specifications::, for a list of supported signal names and 14402numbers. 14403 14404 14405File: coreutils.info, Node: Delaying, Next: Numeric operations, Prev: Process control, Up: Top 14406 1440725 Delaying 14408*********** 14409 14410* Menu: 14411 14412* sleep invocation:: Delay for a specified time. 14413 14414 14415File: coreutils.info, Node: sleep invocation, Up: Delaying 14416 1441725.1 ‘sleep’: Delay for a specified time 14418======================================== 14419 14420‘sleep’ pauses for an amount of time specified by the sum of the values 14421of the command line arguments. Synopsis: 14422 14423 sleep NUMBER[smhd]... 14424 14425 Each argument is a non-negative number followed by an optional unit; 14426the default is seconds. The units are: 14427 14428‘s’ 14429 seconds 14430‘m’ 14431 minutes 14432‘h’ 14433 hours 14434‘d’ 14435 days 14436 14437 Although portable POSIX scripts must give ‘sleep’ a single 14438non-negative integer argument without a suffix, GNU ‘sleep’ also accepts 14439two or more arguments, unit suffixes, and floating-point numbers in 14440either the current or the C locale. *Note Floating point::. 14441 14442 For instance, the following could be used to ‘sleep’ for 1 second, 14443234 milli-, 567 micro- and 890 nanoseconds: 14444 14445 sleep 1234e-3 567.89e-6 14446 14447 The only options are ‘--help’ and ‘--version’. *Note Common 14448options::. 14449 14450 Due to shell aliases and built-in ‘sleep’ functions, using an 14451unadorned ‘sleep’ interactively or in a script may get you different 14452functionality than that described here. Invoke it via ‘env’ (i.e., ‘env 14453sleep ...’) to avoid interference from the shell. 14454 14455 An exit status of zero indicates success, and a nonzero value 14456indicates failure. 14457 14458 14459File: coreutils.info, Node: Numeric operations, Next: File permissions, Prev: Delaying, Up: Top 14460 1446126 Numeric operations 14462********************* 14463 14464These programs do numerically-related operations. 14465 14466* Menu: 14467 14468* factor invocation:: Show factors of numbers. 14469* numfmt invocation:: Reformat numbers. 14470* seq invocation:: Print sequences of numbers. 14471 14472 14473File: coreutils.info, Node: factor invocation, Next: numfmt invocation, Up: Numeric operations 14474 1447526.1 ‘factor’: Print prime factors 14476================================== 14477 14478‘factor’ prints prime factors. Synopses: 14479 14480 factor [NUMBER]... 14481 factor OPTION 14482 14483 If no NUMBER is specified on the command line, ‘factor’ reads numbers 14484from standard input, delimited by newlines, tabs, or spaces. 14485 14486 The ‘factor’ command supports only a small number of options: 14487 14488‘--help’ 14489 Print a short help on standard output, then exit without further 14490 processing. 14491 14492‘--version’ 14493 Print the program version on standard output, then exit without 14494 further processing. 14495 14496 Factoring the product of the eighth and ninth Mersenne primes takes 14497about 30 milliseconds of CPU time on a 2.2 GHz Athlon. 14498 14499 M8=$(echo 2^31-1|bc) 14500 M9=$(echo 2^61-1|bc) 14501 n=$(echo "$M8 * $M9" | bc) 14502 /usr/bin/time -f %U factor $n 14503 4951760154835678088235319297: 2147483647 2305843009213693951 14504 0.03 14505 14506 Similarly, factoring the eighth Fermat number 2^{256}+1 takes about 1450720 seconds on the same machine. 14508 14509 Factoring large numbers is, in general, hard. The Pollard-Brent rho 14510algorithm used by ‘factor’ is particularly effective for numbers with 14511relatively small factors. If you wish to factor large numbers which do 14512not have small factors (for example, numbers which are the product of 14513two large primes), other methods are far better. 14514 14515 If ‘factor’ is built without using GNU MP, only single-precision 14516arithmetic is available, and so large numbers (typically 2^{128} and 14517above) will not be supported. The single-precision code uses an 14518algorithm which is designed for factoring smaller numbers. 14519 14520 An exit status of zero indicates success, and a nonzero value 14521indicates failure. 14522 14523 14524File: coreutils.info, Node: numfmt invocation, Next: seq invocation, Prev: factor invocation, Up: Numeric operations 14525 1452626.2 ‘numfmt’: Reformat numbers 14527=============================== 14528 14529‘numfmt’ reads numbers in various representations and reformats them as 14530requested. The most common usage is converting numbers to/from _human_ 14531representation (e.g. ‘4G’ ↦ ‘4,000,000,000’). 14532 14533 numfmt [OPTION]... [NUMBER] 14534 14535 ‘numfmt’ converts each NUMBER on the command-line according to the 14536specified options (see below). If no NUMBERs are given, it reads 14537numbers from standard input. ‘numfmt’ can optionally extract numbers 14538from specific columns, maintaining proper line padding and alignment. 14539 14540 An exit status of zero indicates success, and a nonzero value 14541indicates failure. 14542 14543 See ‘--invalid’ for additional information regarding exit status. 14544 1454526.2.1 General options 14546---------------------- 14547 14548The program accepts the following options. Also see *note Common 14549options::. 14550 14551‘--debug’ 14552 Print (to standard error) warning messages about possible erroneous 14553 usage. 14554 14555‘-d D’ 14556‘--delimiter=D’ 14557 Use the character D as input field separator (default: whitespace). 14558 _Note_: Using non-default delimiter turns off automatic padding. 14559 14560‘--field=FIELDS’ 14561 Convert the number in input field FIELDS (default: 1). FIELDS 14562 supports ‘cut’ style field ranges: 14563 14564 N N'th field, counted from 1 14565 N- from N'th field, to end of line 14566 N-M from N'th to M'th field (inclusive) 14567 -M from first to M'th field (inclusive) 14568 - all fields 14569 14570‘--format=FORMAT’ 14571 Use printf-style floating FORMAT string. The FORMAT string must 14572 contain one ‘%f’ directive, optionally with ‘'’, ‘-’, ‘0’, width or 14573 precision modifiers. The ‘'’ modifier will enable ‘--grouping’, 14574 the ‘-’ modifier will enable left-aligned ‘--padding’ and the width 14575 modifier will enable right-aligned ‘--padding’. The ‘0’ width 14576 modifier (without the ‘-’ modifier) will generate leading zeros on 14577 the number, up to the specified width. A precision specification 14578 like ‘%.1f’ will override the precision determined from the input 14579 data or set due to ‘--to’ option auto scaling. 14580 14581‘--from=UNIT’ 14582 Auto-scales input numbers according to UNIT. See UNITS below. The 14583 default is no scaling, meaning suffixes (e.g. ‘M’, ‘G’) will 14584 trigger an error. 14585 14586‘--from-unit=N’ 14587 Specify the input unit size (instead of the default 1). Use this 14588 option when the input numbers represent other units (e.g. if the 14589 input number ‘10’ represents 10 units of 512 bytes, use 14590 ‘--from-unit=512’). Suffixes are handled as with ‘--from=auto’. 14591 14592‘--grouping’ 14593 Group digits in output numbers according to the current locale’s 14594 grouping rules (e.g _Thousands Separator_ character, commonly ‘.’ 14595 (dot) or ‘,’ comma). This option has no effect in ‘POSIX/C’ 14596 locale. 14597 14598‘--header[=N]’ 14599 Print the first N (default: 1) lines without any conversion. 14600 14601‘--invalid=MODE’ 14602 The default action on input errors is to exit immediately with 14603 status code 2. ‘--invalid=‘abort’’ explicitly specifies this 14604 default mode. With a MODE of ‘fail’, print a warning for _each_ 14605 conversion error, and exit with status 2. With a MODE of ‘warn’, 14606 exit with status 0, even in the presence of conversion errors, and 14607 with a MODE of ‘ignore’ do not even print diagnostics. 14608 14609‘--padding=N’ 14610 Pad the output numbers to N characters, by adding spaces. If N is 14611 a positive number, numbers will be right-aligned. If N is a 14612 negative number, numbers will be left-aligned. By default, numbers 14613 are automatically aligned based on the input line’s width (only 14614 with the default delimiter). 14615 14616‘--round=METHOD’ 14617 When converting number representations, round the number according 14618 to METHOD, which can be ‘up’, ‘down’, ‘from-zero’ (the default), 14619 ‘towards-zero’, ‘nearest’. 14620 14621‘--suffix=SUFFIX’ 14622 Add ‘SUFFIX’ to the output numbers, and accept optional ‘SUFFIX’ in 14623 input numbers. 14624 14625‘--to=UNIT’ 14626 Auto-scales output numbers according to UNIT. See _Units_ below. 14627 The default is no scaling, meaning all the digits of the number are 14628 printed. 14629 14630‘--to-unit=N’ 14631 Specify the output unit size (instead of the default 1). Use this 14632 option when the output numbers represent other units (e.g. to 14633 represent ‘4,000,000’ bytes in blocks of 1KB, use ‘--to=si 14634 --to-unit=1000’). Suffixes are handled as with ‘--from=auto’. 14635 14636‘-z’ 14637‘--zero-terminated’ 14638 Delimit items with a zero byte rather than a newline (ASCII LF). 14639 I.e., treat input as items separated by ASCII NUL and terminate 14640 output items with ASCII NUL. This option can be useful in 14641 conjunction with ‘perl -0’ or ‘find -print0’ and ‘xargs -0’ which 14642 do the same in order to reliably handle arbitrary file names (even 14643 those containing blanks or other special characters). Note with 14644 ‘-z’ the newline character is treated as a field separator. 14645 1464626.2.2 Possible UNITs: 14647---------------------- 14648 14649The following are the possible UNIT options with ‘--from=UNITS’ and 14650‘--to=UNITS’: 14651 14652NONE 14653 No scaling is performed. For input numbers, no suffixes are 14654 accepted, and any trailing characters following the number will 14655 trigger an error. For output numbers, all digits of the numbers 14656 will be printed. 14657 14658SI 14659 Auto-scale numbers according to the _International System of Units 14660 (SI)_ standard. For input numbers, accept one of the following 14661 suffixes. For output numbers, values larger than 1000 will be 14662 rounded, and printed with one of the following suffixes: 14663 14664 ‘K’ => 1000^1 = 10^3 (Kilo) 14665 ‘M’ => 1000^2 = 10^6 (Mega) 14666 ‘G’ => 1000^3 = 10^9 (Giga) 14667 ‘T’ => 1000^4 = 10^{12} (Tera) 14668 ‘P’ => 1000^5 = 10^{15} (Peta) 14669 ‘E’ => 1000^6 = 10^{18} (Exa) 14670 ‘Z’ => 1000^7 = 10^{21} (Zetta) 14671 ‘Y’ => 1000^8 = 10^{24} (Yotta) 14672 14673IEC 14674 Auto-scale numbers according to the _International Electrotechnical 14675 Commission (IEC)_ standard. For input numbers, accept one of the 14676 following suffixes. For output numbers, values larger than 1024 14677 will be rounded, and printed with one of the following suffixes: 14678 14679 ‘K’ => 1024^1 = 2^{10} (Kibi) 14680 ‘M’ => 1024^2 = 2^{20} (Mebi) 14681 ‘G’ => 1024^3 = 2^{30} (Gibi) 14682 ‘T’ => 1024^4 = 2^{40} (Tebi) 14683 ‘P’ => 1024^5 = 2^{50} (Pebi) 14684 ‘E’ => 1024^6 = 2^{60} (Exbi) 14685 ‘Z’ => 1024^7 = 2^{70} (Zebi) 14686 ‘Y’ => 1024^8 = 2^{80} (Yobi) 14687 14688 The ‘iec’ option uses a single letter suffix (e.g. ‘G’), which is 14689 not fully standard, as the _iec_ standard recommends a two-letter 14690 symbol (e.g ‘Gi’) - but in practice, this method common. Compare 14691 with the ‘iec-i’ option. 14692 14693IEC-I 14694 Auto-scale numbers according to the _International Electrotechnical 14695 Commission (IEC)_ standard. For input numbers, accept one of the 14696 following suffixes. For output numbers, values larger than 1024 14697 will be rounded, and printed with one of the following suffixes: 14698 14699 ‘Ki’ => 1024^1 = 2^{10} (Kibi) 14700 ‘Mi’ => 1024^2 = 2^{20} (Mebi) 14701 ‘Gi’ => 1024^3 = 2^{30} (Gibi) 14702 ‘Ti’ => 1024^4 = 2^{40} (Tebi) 14703 ‘Pi’ => 1024^5 = 2^{50} (Pebi) 14704 ‘Ei’ => 1024^6 = 2^{60} (Exbi) 14705 ‘Zi’ => 1024^7 = 2^{70} (Zebi) 14706 ‘Yi’ => 1024^8 = 2^{80} (Yobi) 14707 14708 The ‘iec-i’ option uses a two-letter suffix symbol (e.g. ‘Gi’), as 14709 the _iec_ standard recommends, but this is not always common in 14710 practice. Compare with the ‘iec’ option. 14711 14712AUTO 14713 ‘auto’ can only be used with ‘--from’. With this method, numbers 14714 with ‘K’,‘M’,‘G’,‘T’,‘P’,‘E’,‘Z’,‘Y’ suffixes are interpreted as 14715 _SI_ values, and numbers with ‘Ki’, 14716 ‘Mi’,‘Gi’,‘Ti’,‘Pi’,‘Ei’,‘Zi’,‘Yi’ suffixes are interpreted as 14717 _IEC_ values. 14718 1471926.2.3 Examples of using ‘numfmt’ 14720--------------------------------- 14721 14722Converting a single number from/to _human_ representation: 14723 $ numfmt --to=si 500000 14724 500K 14725 14726 $ numfmt --to=iec 500000 14727 489K 14728 14729 $ numfmt --to=iec-i 500000 14730 489Ki 14731 14732 $ numfmt --from=si 1M 14733 1000000 14734 14735 $ numfmt --from=iec 1M 14736 1048576 14737 14738 # with '--from=auto', M=Mega, Mi=Mebi 14739 $ numfmt --from=auto 1M 14740 1000000 14741 $ numfmt --from=auto 1Mi 14742 1048576 14743 14744 Converting from ‘SI’ to ‘IEC’ scales (e.g. when a harddisk capacity 14745is advertised as ‘1TB’, while checking the drive’s capacity gives lower 14746values): 14747 14748 $ numfmt --from=si --to=iec 1T 14749 932G 14750 14751 Converting a single field from an input file / piped input (these 14752contrived examples are for demonstration purposes only, as both ‘ls’ and 14753‘df’ support the ‘--human-readable’ option to output sizes in 14754human-readable format): 14755 14756 # Third field (file size) will be shown in SI representation 14757 $ ls -log | numfmt --field 3 --header --to=si | head -n4 14758 -rw-r--r-- 1 94K Aug 23 2011 ABOUT-NLS 14759 -rw-r--r-- 1 3.7K Jan 7 16:15 AUTHORS 14760 -rw-r--r-- 1 36K Jun 1 2011 COPYING 14761 -rw-r--r-- 1 0 Jan 7 15:15 ChangeLog 14762 14763 # Second field (size) will be shown in IEC representation 14764 $ df --block-size=1 | numfmt --field 2 --header --to=iec | head -n4 14765 File system 1B-blocks Used Available Use% Mounted on 14766 rootfs 132G 104741408 26554036 80% / 14767 tmpfs 794M 7580 804960 1% /run/shm 14768 /dev/sdb1 694G 651424756 46074696 94% /home 14769 14770 Output can be tweaked using ‘--padding’ or ‘--format’: 14771 14772 # Pad to 10 characters, right-aligned 14773 $ du -s * | numfmt --to=si --padding=10 14774 2.5K config.log 14775 108 config.status 14776 1.7K configure 14777 20 configure.ac 14778 14779 # Pad to 10 characters, left-aligned 14780 $ du -s * | numfmt --to=si --padding=-10 14781 2.5K config.log 14782 108 config.status 14783 1.7K configure 14784 20 configure.ac 14785 14786 # Pad to 10 characters, left-aligned, using 'format' 14787 $ du -s * | numfmt --to=si --format="%10f" 14788 2.5K config.log 14789 108 config.status 14790 1.7K configure 14791 20 configure.ac 14792 14793 # Pad to 10 characters, left-aligned, using 'format' 14794 $ du -s * | numfmt --to=si --padding="%-10f" 14795 2.5K config.log 14796 108 config.status 14797 1.7K configure 14798 20 configure.ac 14799 14800 With locales that support grouping digits, using ‘--grouping’ or 14801‘--format’ enables grouping. In ‘POSIX’ locale, grouping is silently 14802ignored: 14803 14804 $ LC_ALL=C numfmt --from=iec --grouping 2G 14805 2147483648 14806 14807 $ LC_ALL=en_US.utf8 numfmt --from=iec --grouping 2G 14808 2,147,483,648 14809 14810 $ LC_ALL=ta_IN numfmt --from=iec --grouping 2G 14811 2,14,74,83,648 14812 14813 $ LC_ALL=C ./src/numfmt --from=iec --format="==%'15f==" 2G 14814 == 2147483648== 14815 14816 $ LC_ALL=en_US.utf8 ./src/numfmt --from=iec --format="==%'15f==" 2G 14817 == 2,147,483,648== 14818 14819 $ LC_ALL=en_US.utf8 ./src/numfmt --from=iec --format="==%'-15f==" 2G 14820 ==2,147,483,648 == 14821 14822 $ LC_ALL=ta_IN ./src/numfmt --from=iec --format="==%'15f==" 2G 14823 == 2,14,74,83,648== 14824 14825 14826File: coreutils.info, Node: seq invocation, Prev: numfmt invocation, Up: Numeric operations 14827 1482826.3 ‘seq’: Print numeric sequences 14829=================================== 14830 14831‘seq’ prints a sequence of numbers to standard output. Synopses: 14832 14833 seq [OPTION]... LAST 14834 seq [OPTION]... FIRST LAST 14835 seq [OPTION]... FIRST INCREMENT LAST 14836 14837 ‘seq’ prints the numbers from FIRST to LAST by INCREMENT. By 14838default, each number is printed on a separate line. When INCREMENT is 14839not specified, it defaults to ‘1’, even when FIRST is larger than LAST. 14840FIRST also defaults to ‘1’. So ‘seq 1’ prints ‘1’, but ‘seq 0’ and ‘seq 1484110 5’ produce no output. The sequence of numbers ends when the sum of 14842the current number and INCREMENT would become greater than LAST, so ‘seq 148431 10 10’ only produces ‘1’. INCREMENT must not be ‘0’; use the tool 14844‘yes’ to get repeated output of a constant number. FIRST, INCREMENT and 14845LAST must not be ‘NaN’. Floating-point numbers may be specified in 14846either the current or the C locale. *Note Floating point::. 14847 14848 The program accepts the following options. Also see *note Common 14849options::. Options must precede operands. 14850 14851‘-f FORMAT’ 14852‘--format=FORMAT’ 14853 Print all numbers using FORMAT. FORMAT must contain exactly one of 14854 the ‘printf’-style floating point conversion specifications ‘%a’, 14855 ‘%e’, ‘%f’, ‘%g’, ‘%A’, ‘%E’, ‘%F’, ‘%G’. The ‘%’ may be followed 14856 by zero or more flags taken from the set ‘-+#0 '’, then an optional 14857 width containing one or more digits, then an optional precision 14858 consisting of a ‘.’ followed by zero or more digits. FORMAT may 14859 also contain any number of ‘%%’ conversion specifications. All 14860 conversion specifications have the same meaning as with ‘printf’. 14861 14862 The default format is derived from FIRST, STEP, and LAST. If these 14863 all use a fixed point decimal representation, the default format is 14864 ‘%.Pf’, where P is the minimum precision that can represent the 14865 output numbers exactly. Otherwise, the default format is ‘%g’. 14866 14867‘-s STRING’ 14868‘--separator=STRING’ 14869 Separate numbers with STRING; default is a newline. The output 14870 always terminates with a newline. 14871 14872‘-w’ 14873‘--equal-width’ 14874 Print all numbers with the same width, by padding with leading 14875 zeros. FIRST, STEP, and LAST should all use a fixed point decimal 14876 representation. (To have other kinds of padding, use ‘--format’). 14877 14878 You can get finer-grained control over output with ‘-f’: 14879 14880 $ seq -f '(%9.2E)' -9e5 1.1e6 1.3e6 14881 (-9.00E+05) 14882 ( 2.00E+05) 14883 ( 1.30E+06) 14884 14885 If you want hexadecimal integer output, you can use ‘printf’ to 14886perform the conversion: 14887 14888 $ printf '%x\n' $(seq 1048575 1024 1050623) 14889 fffff 14890 1003ff 14891 1007ff 14892 14893 For very long lists of numbers, use xargs to avoid system limitations 14894on the length of an argument list: 14895 14896 $ seq 1000000 | xargs printf '%x\n' | tail -n 3 14897 f423e 14898 f423f 14899 f4240 14900 14901 To generate octal output, use the printf ‘%o’ format instead of ‘%x’. 14902 14903 On most systems, seq can produce whole-number output for values up to 14904at least 2^{53}. Larger integers are approximated. The details differ 14905depending on your floating-point implementation. *Note Floating 14906point::. A common case is that ‘seq’ works with integers through 149072^{64}, and larger integers may not be numerically correct: 14908 14909 $ seq 50000000000000000000 2 50000000000000000004 14910 50000000000000000000 14911 50000000000000000000 14912 50000000000000000004 14913 14914 However, note that when limited to non-negative whole numbers, an 14915increment of 1 and no format-specifying option, seq can print 14916arbitrarily large numbers. 14917 14918 Be careful when using ‘seq’ with outlandish values: otherwise you may 14919see surprising results, as ‘seq’ uses floating point internally. For 14920example, on the x86 platform, where the internal representation uses a 1492164-bit fraction, the command: 14922 14923 seq 1 0.0000000000000000001 1.0000000000000000009 14924 14925 outputs 1.0000000000000000007 twice and skips 1.0000000000000000008. 14926 14927 An exit status of zero indicates success, and a nonzero value 14928indicates failure. 14929 14930 14931File: coreutils.info, Node: File permissions, Next: File timestamps, Prev: Numeric operations, Up: Top 14932 1493327 File permissions 14934******************* 14935 14936Each file has a set of “file mode bits” that control the kinds of access 14937that users have to that file. They can be represented either in 14938symbolic form or as an octal number. 14939 14940* Menu: 14941 14942* Mode Structure:: Structure of file mode bits. 14943* Symbolic Modes:: Mnemonic representation of file mode bits. 14944* Numeric Modes:: File mode bits as octal numbers. 14945* Operator Numeric Modes:: ANDing, ORing, and setting modes octally. 14946* Directory Setuid and Setgid:: Set-user-ID and set-group-ID on directories. 14947 14948 14949File: coreutils.info, Node: Mode Structure, Next: Symbolic Modes, Up: File permissions 14950 1495127.1 Structure of File Mode Bits 14952================================ 14953 14954The file mode bits have two parts: the “file permission bits”, which 14955control ordinary access to the file, and “special mode bits”, which 14956affect only some files. 14957 14958 There are three kinds of permissions that a user can have for a file: 14959 14960 1. permission to read the file. For directories, this means 14961 permission to list the contents of the directory. 14962 2. permission to write to (change) the file. For directories, this 14963 means permission to create and remove files in the directory. 14964 3. permission to execute the file (run it as a program). For 14965 directories, this means permission to access files in the 14966 directory. 14967 14968 There are three categories of users who may have different 14969permissions to perform any of the above operations on a file: 14970 14971 1. the file’s owner; 14972 2. other users who are in the file’s group; 14973 3. everyone else. 14974 14975 Files are given an owner and group when they are created. Usually 14976the owner is the current user and the group is the group of the 14977directory the file is in, but this varies with the operating system, the 14978file system the file is created on, and the way the file is created. 14979You can change the owner and group of a file by using the ‘chown’ and 14980‘chgrp’ commands. 14981 14982 In addition to the three sets of three permissions listed above, the 14983file mode bits have three special components, which affect only 14984executable files (programs) and, on most systems, directories: 14985 14986The “set-user-ID bit” (“setuid bit”). 14987 On execution, set the process’s effective user ID to that of the 14988 file. For directories on a few systems, give files created in the 14989 directory the same owner as the directory, no matter who creates 14990 them, and set the set-user-ID bit of newly-created subdirectories. 14991 14992The “set-group-ID bit” (“setgid bit”). 14993 On execution, set the process’s effective group ID to that of the 14994 file. For directories on most systems, give files created in the 14995 directory the same group as the directory, no matter what group the 14996 user who creates them is in, and set the set-group-ID bit of 14997 newly-created subdirectories. 14998 14999The “restricted deletion flag” or “sticky bit”. 15000 Prevent unprivileged users from removing or renaming a file in a 15001 directory unless they own the file or the directory; this is 15002 commonly found on world-writable directories like ‘/tmp’. For 15003 regular files on some older systems, save the program’s text image 15004 on the swap device so it will load more quickly when run, so that 15005 the image is “sticky”. 15006 15007 In addition to the file mode bits listed above, there may be file 15008attributes specific to the file system, e.g., access control lists 15009(ACLs), whether a file is compressed, whether a file can be modified 15010(immutability), and whether a file can be dumped. These are usually set 15011using programs specific to the file system. For example: 15012 15013ext2 15014 On GNU and GNU/Linux the file attributes specific to the ext2 file 15015 system are set using ‘chattr’. 15016 15017FFS 15018 On FreeBSD the file flags specific to the FFS file system are set 15019 using ‘chflags’. 15020 15021 Even if a file’s mode bits allow an operation on that file, that 15022operation may still fail, because: 15023 15024 • the file-system-specific attributes or flags do not permit it; or 15025 15026 • the file system is mounted as read-only. 15027 15028 For example, if the immutable attribute is set on a file, it cannot 15029be modified, regardless of the fact that you may have just run ‘chmod 15030a+w FILE’. 15031 15032 15033File: coreutils.info, Node: Symbolic Modes, Next: Numeric Modes, Prev: Mode Structure, Up: File permissions 15034 1503527.2 Symbolic Modes 15036=================== 15037 15038“Symbolic modes” represent changes to files’ mode bits as operations on 15039single-character symbols. They allow you to modify either all or 15040selected parts of files’ mode bits, optionally based on their previous 15041values, and perhaps on the current ‘umask’ as well (*note Umask and 15042Protection::). 15043 15044 The format of symbolic modes is: 15045 15046 [ugoa...][-+=]PERMS...[,...] 15047 15048where PERMS is either zero or more letters from the set ‘rwxXst’, or a 15049single letter from the set ‘ugo’. 15050 15051 The following sections describe the operators and other details of 15052symbolic modes. 15053 15054* Menu: 15055 15056* Setting Permissions:: Basic operations on permissions. 15057* Copying Permissions:: Copying existing permissions. 15058* Changing Special Mode Bits:: Special mode bits. 15059* Conditional Executability:: Conditionally affecting executability. 15060* Multiple Changes:: Making multiple changes. 15061* Umask and Protection:: The effect of the umask. 15062 15063 15064File: coreutils.info, Node: Setting Permissions, Next: Copying Permissions, Up: Symbolic Modes 15065 1506627.2.1 Setting Permissions 15067-------------------------- 15068 15069The basic symbolic operations on a file’s permissions are adding, 15070removing, and setting the permission that certain users have to read, 15071write, and execute or search the file. These operations have the 15072following format: 15073 15074 USERS OPERATION PERMISSIONS 15075 15076The spaces between the three parts above are shown for readability only; 15077symbolic modes cannot contain spaces. 15078 15079 The USERS part tells which users’ access to the file is changed. It 15080consists of one or more of the following letters (or it can be empty; 15081*note Umask and Protection::, for a description of what happens then). 15082When more than one of these letters is given, the order that they are in 15083does not matter. 15084 15085‘u’ 15086 the user who owns the file; 15087‘g’ 15088 other users who are in the file’s group; 15089‘o’ 15090 all other users; 15091‘a’ 15092 all users; the same as ‘ugo’. 15093 15094 The OPERATION part tells how to change the affected users’ access to 15095the file, and is one of the following symbols: 15096 15097‘+’ 15098 to add the PERMISSIONS to whatever permissions the USERS already 15099 have for the file; 15100‘-’ 15101 to remove the PERMISSIONS from whatever permissions the USERS 15102 already have for the file; 15103‘=’ 15104 to make the PERMISSIONS the only permissions that the USERS have 15105 for the file. 15106 15107 The PERMISSIONS part tells what kind of access to the file should be 15108changed; it is normally zero or more of the following letters. As with 15109the USERS part, the order does not matter when more than one letter is 15110given. Omitting the PERMISSIONS part is useful only with the ‘=’ 15111operation, where it gives the specified USERS no access at all to the 15112file. 15113 15114‘r’ 15115 the permission the USERS have to read the file; 15116‘w’ 15117 the permission the USERS have to write to the file; 15118‘x’ 15119 the permission the USERS have to execute the file, or search it if 15120 it is a directory. 15121 15122 For example, to give everyone permission to read and write a regular 15123file, but not to execute it, use: 15124 15125 a=rw 15126 15127 To remove write permission for all users other than the file’s owner, 15128use: 15129 15130 go-w 15131 15132The above command does not affect the access that the owner of the file 15133has to it, nor does it affect whether other users can read or execute 15134the file. 15135 15136 To give everyone except a file’s owner no permission to do anything 15137with that file, use the mode below. Other users could still remove the 15138file, if they have write permission on the directory it is in. 15139 15140 go= 15141 15142Another way to specify the same thing is: 15143 15144 og-rwx 15145 15146 15147File: coreutils.info, Node: Copying Permissions, Next: Changing Special Mode Bits, Prev: Setting Permissions, Up: Symbolic Modes 15148 1514927.2.2 Copying Existing Permissions 15150----------------------------------- 15151 15152You can base a file’s permissions on its existing permissions. To do 15153this, instead of using a series of ‘r’, ‘w’, or ‘x’ letters after the 15154operator, you use the letter ‘u’, ‘g’, or ‘o’. For example, the mode 15155 15156 o+g 15157 15158adds the permissions for users who are in a file’s group to the 15159permissions that other users have for the file. Thus, if the file 15160started out as mode 664 (‘rw-rw-r--’), the above mode would change it to 15161mode 666 (‘rw-rw-rw-’). If the file had started out as mode 741 15162(‘rwxr----x’), the above mode would change it to mode 745 (‘rwxr--r-x’). 15163The ‘-’ and ‘=’ operations work analogously. 15164 15165 15166File: coreutils.info, Node: Changing Special Mode Bits, Next: Conditional Executability, Prev: Copying Permissions, Up: Symbolic Modes 15167 1516827.2.3 Changing Special Mode Bits 15169--------------------------------- 15170 15171In addition to changing a file’s read, write, and execute/search 15172permissions, you can change its special mode bits. *Note Mode 15173Structure::, for a summary of these special mode bits. 15174 15175 To change the file mode bits to set the user ID on execution, use ‘u’ 15176in the USERS part of the symbolic mode and ‘s’ in the PERMISSIONS part. 15177 15178 To change the file mode bits to set the group ID on execution, use 15179‘g’ in the USERS part of the symbolic mode and ‘s’ in the PERMISSIONS 15180part. 15181 15182 To set both user and group ID on execution, omit the USERS part of 15183the symbolic mode (or use ‘a’) and use ‘s’ in the PERMISSIONS part. 15184 15185 To change the file mode bits to set the restricted deletion flag or 15186sticky bit, omit the USERS part of the symbolic mode (or use ‘a’) and 15187use ‘t’ in the PERMISSIONS part. 15188 15189 For example, to set the set-user-ID mode bit of a program, you can 15190use the mode: 15191 15192 u+s 15193 15194 To remove both set-user-ID and set-group-ID mode bits from it, you 15195can use the mode: 15196 15197 a-s 15198 15199 To set the restricted deletion flag or sticky bit, you can use the 15200mode: 15201 15202 +t 15203 15204 The combination ‘o+s’ has no effect. On GNU systems the combinations 15205‘u+t’ and ‘g+t’ have no effect, and ‘o+t’ acts like plain ‘+t’. 15206 15207 The ‘=’ operator is not very useful with special mode bits. For 15208example, the mode: 15209 15210 o=t 15211 15212does set the restricted deletion flag or sticky bit, but it also removes 15213all read, write, and execute/search permissions that users not in the 15214file’s group might have had for it. 15215 15216 *Note Directory Setuid and Setgid::, for additional rules concerning 15217set-user-ID and set-group-ID bits and directories. 15218 15219 15220File: coreutils.info, Node: Conditional Executability, Next: Multiple Changes, Prev: Changing Special Mode Bits, Up: Symbolic Modes 15221 1522227.2.4 Conditional Executability 15223-------------------------------- 15224 15225There is one more special type of symbolic permission: if you use ‘X’ 15226instead of ‘x’, execute/search permission is affected only if the file 15227is a directory or already had execute permission. 15228 15229 For example, this mode: 15230 15231 a+X 15232 15233gives all users permission to search directories, or to execute files if 15234anyone could execute them before. 15235 15236 15237File: coreutils.info, Node: Multiple Changes, Next: Umask and Protection, Prev: Conditional Executability, Up: Symbolic Modes 15238 1523927.2.5 Making Multiple Changes 15240------------------------------ 15241 15242The format of symbolic modes is actually more complex than described 15243above (*note Setting Permissions::). It provides two ways to make 15244multiple changes to files’ mode bits. 15245 15246 The first way is to specify multiple OPERATION and PERMISSIONS parts 15247after a USERS part in the symbolic mode. 15248 15249 For example, the mode: 15250 15251 og+rX-w 15252 15253gives users other than the owner of the file read permission and, if it 15254is a directory or if someone already had execute permission to it, gives 15255them execute/search permission; and it also denies them write permission 15256to the file. It does not affect the permission that the owner of the 15257file has for it. The above mode is equivalent to the two modes: 15258 15259 og+rX 15260 og-w 15261 15262 The second way to make multiple changes is to specify more than one 15263simple symbolic mode, separated by commas. For example, the mode: 15264 15265 a+r,go-w 15266 15267gives everyone permission to read the file and removes write permission 15268on it for all users except its owner. Another example: 15269 15270 u=rwx,g=rx,o= 15271 15272sets all of the permission bits for the file explicitly. (It gives 15273users who are not in the file’s group no permission at all for it.) 15274 15275 The two methods can be combined. The mode: 15276 15277 a+r,g+x-w 15278 15279gives all users permission to read the file, and gives users who are in 15280the file’s group permission to execute/search it as well, but not 15281permission to write to it. The above mode could be written in several 15282different ways; another is: 15283 15284 u+r,g+rx,o+r,g-w 15285 15286 15287File: coreutils.info, Node: Umask and Protection, Prev: Multiple Changes, Up: Symbolic Modes 15288 1528927.2.6 The Umask and Protection 15290------------------------------- 15291 15292If the USERS part of a symbolic mode is omitted, it defaults to ‘a’ 15293(affect all users), except that any permissions that are _set_ in the 15294system variable ‘umask’ are _not affected_. The value of ‘umask’ can be 15295set using the ‘umask’ command. Its default value varies from system to 15296system. 15297 15298 Omitting the USERS part of a symbolic mode is generally not useful 15299with operations other than ‘+’. It is useful with ‘+’ because it allows 15300you to use ‘umask’ as an easily customizable protection against giving 15301away more permission to files than you intended to. 15302 15303 As an example, if ‘umask’ has the value 2, which removes write 15304permission for users who are not in the file’s group, then the mode: 15305 15306 +w 15307 15308adds permission to write to the file to its owner and to other users who 15309are in the file’s group, but _not_ to other users. In contrast, the 15310mode: 15311 15312 a+w 15313 15314ignores ‘umask’, and _does_ give write permission for the file to all 15315users. 15316 15317 15318File: coreutils.info, Node: Numeric Modes, Next: Operator Numeric Modes, Prev: Symbolic Modes, Up: File permissions 15319 1532027.3 Numeric Modes 15321================== 15322 15323As an alternative to giving a symbolic mode, you can give an octal (base 153248) number that represents the mode. 15325 15326 The permissions granted to the user, to other users in the file’s 15327group, and to other users not in the file’s group each require three 15328bits: one bit for read, one for write, and one for execute/search 15329permission. These three bits are represented as one octal digit; for 15330example, if all three are present, the resulting 111 (in binary) is 15331represented as the digit 7 (in octal). The three special mode bits also 15332require one bit each, and they are as a group represented as another 15333octal digit. Here is how the bits are arranged, starting with the 15334highest valued bit: 15335 15336 Value in Corresponding 15337 Mode Mode Bit 15338 15339 Special mode bits: 15340 4000 Set user ID 15341 2000 Set group ID 15342 1000 Restricted deletion flag or sticky bit 15343 15344 The file's owner: 15345 400 Read 15346 200 Write 15347 100 Execute/search 15348 15349 Other users in the file's group: 15350 40 Read 15351 20 Write 15352 10 Execute/search 15353 15354 Other users not in the file's group: 15355 4 Read 15356 2 Write 15357 1 Execute/search 15358 15359 For example, numeric mode ‘4751’ corresponds to symbolic mode 15360‘u=srwx,g=rx,o=x’, and numeric mode ‘664’ corresponds to symbolic mode 15361‘ug=rw,o=r’. Numeric mode ‘0’ corresponds to symbolic mode ‘a=’. 15362 15363 A numeric mode is usually shorter than the corresponding symbolic 15364mode, but it is limited in that normally it cannot take into account the 15365previous file mode bits; it can only set them absolutely. The 15366set-user-ID and set-group-ID bits of directories are an exception to 15367this general limitation. *Note Directory Setuid and Setgid::. Also, 15368operator numeric modes can take previous file mode bits into account. 15369*Note Operator Numeric Modes::. 15370 15371 Numeric modes are always interpreted in octal; you do not have to add 15372a leading ‘0’, as you do in C. Mode ‘0055’ is the same as mode ‘55’. 15373However, modes of five digits or more, such as ‘00055’, are sometimes 15374special (*note Directory Setuid and Setgid::). 15375 15376 15377File: coreutils.info, Node: Operator Numeric Modes, Next: Directory Setuid and Setgid, Prev: Numeric Modes, Up: File permissions 15378 1537927.4 Operator Numeric Modes 15380=========================== 15381 15382An operator numeric mode is a numeric mode that is prefixed by a ‘-’, 15383‘+’, or ‘=’ operator, which has the same interpretation as in symbolic 15384modes. For example, ‘+440’ enables read permission for the file’s owner 15385and group, ‘-1’ disables execute permission for other users, and ‘=600’ 15386clears all permissions except for enabling read-write permissions for 15387the file’s owner. Operator numeric modes can be combined with symbolic 15388modes by separating them with a comma; for example, ‘=0,u+r’ clears all 15389permissions except for enabling read permission for the file’s owner. 15390 15391 The commands ‘chmod =755 DIR’ and ‘chmod 755 DIR’ differ in that the 15392former clears the directory DIR’s setuid and setgid bits, whereas the 15393latter preserves them. *Note Directory Setuid and Setgid::. 15394 15395 Operator numeric modes are a GNU extension. 15396 15397 15398File: coreutils.info, Node: Directory Setuid and Setgid, Prev: Operator Numeric Modes, Up: File permissions 15399 1540027.5 Directories and the Set-User-ID and Set-Group-ID Bits 15401========================================================== 15402 15403On most systems, if a directory’s set-group-ID bit is set, newly created 15404subfiles inherit the same group as the directory, and newly created 15405subdirectories inherit the set-group-ID bit of the parent directory. On 15406a few systems, a directory’s set-user-ID bit has a similar effect on the 15407ownership of new subfiles and the set-user-ID bits of new 15408subdirectories. These mechanisms let users share files more easily, by 15409lessening the need to use ‘chmod’ or ‘chown’ to share new files. 15410 15411 These convenience mechanisms rely on the set-user-ID and set-group-ID 15412bits of directories. If commands like ‘chmod’ and ‘mkdir’ routinely 15413cleared these bits on directories, the mechanisms would be less 15414convenient and it would be harder to share files. Therefore, a command 15415like ‘chmod’ does not affect the set-user-ID or set-group-ID bits of a 15416directory unless the user specifically mentions them in a symbolic mode, 15417or uses an operator numeric mode such as ‘=755’, or sets them in a 15418numeric mode, or clears them in a numeric mode that has five or more 15419octal digits. For example, on systems that support set-group-ID 15420inheritance: 15421 15422 # These commands leave the set-user-ID and 15423 # set-group-ID bits of the subdirectories alone, 15424 # so that they retain their default values. 15425 mkdir A B C 15426 chmod 755 A 15427 chmod 0755 B 15428 chmod u=rwx,go=rx C 15429 mkdir -m 755 D 15430 mkdir -m 0755 E 15431 mkdir -m u=rwx,go=rx F 15432 15433 If you want to try to set these bits, you must mention them 15434explicitly in the symbolic or numeric modes, e.g.: 15435 15436 # These commands try to set the set-user-ID 15437 # and set-group-ID bits of the subdirectories. 15438 mkdir G 15439 chmod 6755 G 15440 chmod +6000 G 15441 chmod u=rwx,go=rx,a+s G 15442 mkdir -m 6755 H 15443 mkdir -m +6000 I 15444 mkdir -m u=rwx,go=rx,a+s J 15445 15446 If you want to try to clear these bits, you must mention them 15447explicitly in a symbolic mode, or use an operator numeric mode, or 15448specify a numeric mode with five or more octal digits, e.g.: 15449 15450 # These commands try to clear the set-user-ID 15451 # and set-group-ID bits of the directory D. 15452 chmod a-s D 15453 chmod -6000 D 15454 chmod =755 D 15455 chmod 00755 D 15456 15457 This behavior is a GNU extension. Portable scripts should not rely 15458on requests to set or clear these bits on directories, as POSIX allows 15459implementations to ignore these requests. The GNU behavior with numeric 15460modes of four or fewer digits is intended for scripts portable to 15461systems that preserve these bits; the behavior with numeric modes of 15462five or more digits is for scripts portable to systems that do not 15463preserve the bits. 15464 15465 15466File: coreutils.info, Node: File timestamps, Next: Date input formats, Prev: File permissions, Up: Top 15467 1546828 File timestamps 15469****************** 15470 15471Standard POSIX files have three timestamps: the access timestamp (atime) 15472of the last read, the modification timestamp (mtime) of the last write, 15473and the status change timestamp (ctime) of the last change to the file’s 15474meta-information. Some file systems support a fourth time: the birth 15475timestamp (birthtime) of when the file was created; by definition, 15476birthtime never changes. 15477 15478 One common example of a ctime change is when the permissions of a 15479file change. Changing the permissions doesn’t access the file, so atime 15480doesn’t change, nor does it modify the file, so the mtime doesn’t 15481change. Yet, something about the file itself has changed, and this must 15482be noted somewhere. This is the job of the ctime field. This is 15483necessary, so that, for example, a backup program can make a fresh copy 15484of the file, including the new permissions value. Another operation 15485that modifies a file’s ctime without affecting the others is renaming. 15486 15487 Naively, a file’s atime, mtime, and ctime are set to the current time 15488whenever you read, write, or change the attributes of the file 15489respectively, and searching a directory counts as reading it. A file’s 15490atime and mtime can also be set directly, via the ‘touch’ command (*note 15491touch invocation::). In practice, though, timestamps are not updated 15492quite that way. 15493 15494 For efficiency reasons, many systems are lazy about updating atimes: 15495when a program accesses a file, they may delay updating the file’s 15496atime, or may not update the file’s atime if the file has been accessed 15497recently, or may not update the atime at all. Similar laziness, though 15498typically not quite so extreme, applies to mtimes and ctimes. 15499 15500 Some systems emulate timestamps instead of supporting them directly, 15501and these emulations may disagree with the naive interpretation. For 15502example, a system may fake an atime or ctime by using the mtime. 15503 15504 The determination of what time is “current” depends on the platform. 15505Platforms with network file systems often use different clocks for the 15506operating system and for file systems; because updates typically uses 15507file systems’ clocks by default, clock skew can cause the resulting file 15508timestamps to appear to be in a program’s “future” or “past”. 15509 15510 When the system updates a file timestamp to a desired time T (which 15511is either the current time, or a time specified via the ‘touch’ 15512command), there are several reasons the file’s timestamp may be set to a 15513value that differs from T. First, T may have a higher resolution than 15514supported. Second, a file system may use different resolutions for 15515different types of times. Third, file timestamps may use a different 15516resolution than operating system timestamps. Fourth, the operating 15517system primitives used to update timestamps may employ yet a different 15518resolution. For example, in theory a file system might use 1551910-microsecond resolution for access timestamp and 100-nanosecond 15520resolution for modification timestamp, and the operating system might 15521use nanosecond resolution for the current time and microsecond 15522resolution for the primitive that ‘touch’ uses to set a file’s timestamp 15523to an arbitrary value. 15524 15525 15526File: coreutils.info, Node: Date input formats, Next: Version sort ordering, Prev: File timestamps, Up: Top 15527 1552829 Date input formats 15529********************* 15530 15531First, a quote: 15532 15533 Our units of temporal measurement, from seconds on up to months, 15534 are so complicated, asymmetrical and disjunctive so as to make 15535 coherent mental reckoning in time all but impossible. Indeed, had 15536 some tyrannical god contrived to enslave our minds to time, to make 15537 it all but impossible for us to escape subjection to sodden 15538 routines and unpleasant surprises, he could hardly have done better 15539 than handing down our present system. It is like a set of 15540 trapezoidal building blocks, with no vertical or horizontal 15541 surfaces, like a language in which the simplest thought demands 15542 ornate constructions, useless particles and lengthy 15543 circumlocutions. Unlike the more successful patterns of language 15544 and science, which enable us to face experience boldly or at least 15545 level-headedly, our system of temporal calculation silently and 15546 persistently encourages our terror of time. 15547 15548 ... It is as though architects had to measure length in feet, width 15549 in meters and height in ells; as though basic instruction manuals 15550 demanded a knowledge of five different languages. It is no wonder 15551 then that we often look into our own immediate past or future, last 15552 Tuesday or a week from Sunday, with feelings of helpless confusion. 15553 ... 15554 15555 —Robert Grudin, ‘Time and the Art of Living’. 15556 15557 This section describes the textual date representations that GNU 15558programs accept. These are the strings you, as a user, can supply as 15559arguments to the various programs. The C interface (via the 15560‘parse_datetime’ function) is not described here. 15561 15562* Menu: 15563 15564* General date syntax:: Common rules. 15565* Calendar date items:: 19 Dec 1994. 15566* Time of day items:: 9:20pm. 15567* Time zone items:: EST, PDT, UTC, ... 15568* Combined date and time of day items:: 1972-09-24T20:02:00,000000-0500. 15569* Day of week items:: Monday and others. 15570* Relative items in date strings:: next tuesday, 2 years ago. 15571* Pure numbers in date strings:: 19931219, 1440. 15572* Seconds since the Epoch:: @1078100502. 15573* Specifying time zone rules:: TZ="America/New_York", TZ="UTC0". 15574* Authors of parse_datetime:: Bellovin, Eggert, Salz, Berets, et al. 15575 15576 15577File: coreutils.info, Node: General date syntax, Next: Calendar date items, Up: Date input formats 15578 1557929.1 General date syntax 15580======================== 15581 15582A “date” is a string, possibly empty, containing many items separated by 15583whitespace. The whitespace may be omitted when no ambiguity arises. 15584The empty string means the beginning of today (i.e., midnight). Order 15585of the items is immaterial. A date string may contain many flavors of 15586items: 15587 15588 • calendar date items 15589 • time of day items 15590 • time zone items 15591 • combined date and time of day items 15592 • day of the week items 15593 • relative items 15594 • pure numbers. 15595 15596We describe each of these item types in turn, below. 15597 15598 A few ordinal numbers may be written out in words in some contexts. 15599This is most useful for specifying day of the week items or relative 15600items (see below). Among the most commonly used ordinal numbers, the 15601word ‘last’ stands for -1, ‘this’ stands for 0, and ‘first’ and ‘next’ 15602both stand for 1. Because the word ‘second’ stands for the unit of time 15603there is no way to write the ordinal number 2, but for convenience 15604‘third’ stands for 3, ‘fourth’ for 4, ‘fifth’ for 5, ‘sixth’ for 6, 15605‘seventh’ for 7, ‘eighth’ for 8, ‘ninth’ for 9, ‘tenth’ for 10, 15606‘eleventh’ for 11 and ‘twelfth’ for 12. 15607 15608 When a month is written this way, it is still considered to be 15609written numerically, instead of being “spelled in full”; this changes 15610the allowed strings. 15611 15612 In the current implementation, only English is supported for words 15613and abbreviations like ‘AM’, ‘DST’, ‘EST’, ‘first’, ‘January’, ‘Sunday’, 15614‘tomorrow’, and ‘year’. 15615 15616 The output of the ‘date’ command is not always acceptable as a date 15617string, not only because of the language problem, but also because there 15618is no standard meaning for time zone items like ‘IST’. When using 15619‘date’ to generate a date string intended to be parsed later, specify a 15620date format that is independent of language and that does not use time 15621zone items other than ‘UTC’ and ‘Z’. Here are some ways to do this: 15622 15623 $ LC_ALL=C TZ=UTC0 date 15624 Mon Mar 1 00:21:42 UTC 2004 15625 $ TZ=UTC0 date +'%Y-%m-%d %H:%M:%SZ' 15626 2004-03-01 00:21:42Z 15627 $ date --rfc-3339=ns # --rfc-3339 is a GNU extension. 15628 2004-02-29 16:21:42.692722128-08:00 15629 $ date --rfc-2822 # a GNU extension 15630 Sun, 29 Feb 2004 16:21:42 -0800 15631 $ date +'%Y-%m-%d %H:%M:%S %z' # %z is a GNU extension. 15632 2004-02-29 16:21:42 -0800 15633 $ date +'@%s.%N' # %s and %N are GNU extensions. 15634 @1078100502.692722128 15635 15636 Alphabetic case is completely ignored in dates. Comments may be 15637introduced between round parentheses, as long as included parentheses 15638are properly nested. Hyphens not followed by a digit are currently 15639ignored. Leading zeros on numbers are ignored. 15640 15641 Invalid dates like ‘2005-02-29’ or times like ‘24:00’ are rejected. 15642In the typical case of a host that does not support leap seconds, a time 15643like ‘23:59:60’ is rejected even if it corresponds to a valid leap 15644second. 15645 15646 15647File: coreutils.info, Node: Calendar date items, Next: Time of day items, Prev: General date syntax, Up: Date input formats 15648 1564929.2 Calendar date items 15650======================== 15651 15652A “calendar date item” specifies a day of the year. It is specified 15653differently, depending on whether the month is specified numerically or 15654literally. All these strings specify the same calendar date: 15655 15656 1972-09-24 # ISO 8601. 15657 72-9-24 # Assume 19xx for 69 through 99, 15658 # 20xx for 00 through 68. 15659 72-09-24 # Leading zeros are ignored. 15660 9/24/72 # Common U.S. writing. 15661 24 September 1972 15662 24 Sept 72 # September has a special abbreviation. 15663 24 Sep 72 # Three-letter abbreviations always allowed. 15664 Sep 24, 1972 15665 24-sep-72 15666 24sep72 15667 15668 The year can also be omitted. In this case, the last specified year 15669is used, or the current year if none. For example: 15670 15671 9/24 15672 sep 24 15673 15674 Here are the rules. 15675 15676 For numeric months, the ISO 8601 format ‘YEAR-MONTH-DAY’ is allowed, 15677where YEAR is any positive number, MONTH is a number between 01 and 12, 15678and DAY is a number between 01 and 31. A leading zero must be present 15679if a number is less than ten. If YEAR is 68 or smaller, then 2000 is 15680added to it; otherwise, if YEAR is less than 100, then 1900 is added to 15681it. The construct ‘MONTH/DAY/YEAR’, popular in the United States, is 15682accepted. Also ‘MONTH/DAY’, omitting the year. 15683 15684 Literal months may be spelled out in full: ‘January’, ‘February’, 15685‘March’, ‘April’, ‘May’, ‘June’, ‘July’, ‘August’, ‘September’, 15686‘October’, ‘November’ or ‘December’. Literal months may be abbreviated 15687to their first three letters, possibly followed by an abbreviating dot. 15688It is also permitted to write ‘Sept’ instead of ‘September’. 15689 15690 When months are written literally, the calendar date may be given as 15691any of the following: 15692 15693 DAY MONTH YEAR 15694 DAY MONTH 15695 MONTH DAY YEAR 15696 DAY-MONTH-YEAR 15697 15698 Or, omitting the year: 15699 15700 MONTH DAY 15701 15702 15703File: coreutils.info, Node: Time of day items, Next: Time zone items, Prev: Calendar date items, Up: Date input formats 15704 1570529.3 Time of day items 15706====================== 15707 15708A “time of day item” in date strings specifies the time on a given day. 15709Here are some examples, all of which represent the same time: 15710 15711 20:02:00.000000 15712 20:02 15713 8:02pm 15714 20:02-0500 # In EST (U.S. Eastern Standard Time). 15715 15716 More generally, the time of day may be given as ‘HOUR:MINUTE:SECOND’, 15717where HOUR is a number between 0 and 23, MINUTE is a number between 0 15718and 59, and SECOND is a number between 0 and 59 possibly followed by ‘.’ 15719or ‘,’ and a fraction containing one or more digits. Alternatively, 15720‘:SECOND’ can be omitted, in which case it is taken to be zero. On the 15721rare hosts that support leap seconds, SECOND may be 60. 15722 15723 If the time is followed by ‘am’ or ‘pm’ (or ‘a.m.’ or ‘p.m.’), HOUR 15724is restricted to run from 1 to 12, and ‘:MINUTE’ may be omitted (taken 15725to be zero). ‘am’ indicates the first half of the day, ‘pm’ indicates 15726the second half of the day. In this notation, 12 is the predecessor of 157271: midnight is ‘12am’ while noon is ‘12pm’. (This is the zero-oriented 15728interpretation of ‘12am’ and ‘12pm’, as opposed to the old tradition 15729derived from Latin which uses ‘12m’ for noon and ‘12pm’ for midnight.) 15730 15731 The time may alternatively be followed by a time zone correction, 15732expressed as ‘SHHMM’, where S is ‘+’ or ‘-’, HH is a number of zone 15733hours and MM is a number of zone minutes. The zone minutes term, MM, 15734may be omitted, in which case the one- or two-digit correction is 15735interpreted as a number of hours. You can also separate HH from MM with 15736a colon. When a time zone correction is given this way, it forces 15737interpretation of the time relative to Coordinated Universal Time (UTC), 15738overriding any previous specification for the time zone or the local 15739time zone. For example, ‘+0530’ and ‘+05:30’ both stand for the time 15740zone 5.5 hours ahead of UTC (e.g., India). This is the best way to 15741specify a time zone correction by fractional parts of an hour. The 15742maximum zone correction is 24 hours. 15743 15744 Either ‘am’/‘pm’ or a time zone correction may be specified, but not 15745both. 15746 15747 15748File: coreutils.info, Node: Time zone items, Next: Combined date and time of day items, Prev: Time of day items, Up: Date input formats 15749 1575029.4 Time zone items 15751==================== 15752 15753A “time zone item” specifies an international time zone, indicated by a 15754small set of letters, e.g., ‘UTC’ or ‘Z’ for Coordinated Universal Time. 15755Any included periods are ignored. By following a non-daylight-saving 15756time zone by the string ‘DST’ in a separate word (that is, separated by 15757some white space), the corresponding daylight saving time zone may be 15758specified. Alternatively, a non-daylight-saving time zone can be 15759followed by a time zone correction, to add the two values. This is 15760normally done only for ‘UTC’; for example, ‘UTC+05:30’ is equivalent to 15761‘+05:30’. 15762 15763 Time zone items other than ‘UTC’ and ‘Z’ are obsolescent and are not 15764recommended, because they are ambiguous; for example, ‘EST’ has a 15765different meaning in Australia than in the United States, and ‘A’ has 15766different meaning as a military time zone than as an obsolescent RFC 822 15767time zone. Instead, it’s better to use unambiguous numeric time zone 15768corrections like ‘-0500’, as described in the previous section. 15769 15770 If neither a time zone item nor a time zone correction is supplied, 15771timestamps are interpreted using the rules of the default time zone 15772(*note Specifying time zone rules::). 15773 15774 15775File: coreutils.info, Node: Combined date and time of day items, Next: Day of week items, Prev: Time zone items, Up: Date input formats 15776 1577729.5 Combined date and time of day items 15778======================================== 15779 15780The ISO 8601 date and time of day extended format consists of an ISO 157818601 date, a ‘T’ character separator, and an ISO 8601 time of day. This 15782format is also recognized if the ‘T’ is replaced by a space. 15783 15784 In this format, the time of day should use 24-hour notation. 15785Fractional seconds are allowed, with either comma or period preceding 15786the fraction. ISO 8601 fractional minutes and hours are not supported. 15787Typically, hosts support nanosecond timestamp resolution; excess 15788precision is silently discarded. 15789 15790 Here are some examples: 15791 15792 2012-09-24T20:02:00.052-05:00 15793 2012-12-31T23:59:59,999999999+11:00 15794 1970-01-01 00:00Z 15795 15796 15797File: coreutils.info, Node: Day of week items, Next: Relative items in date strings, Prev: Combined date and time of day items, Up: Date input formats 15798 1579929.6 Day of week items 15800====================== 15801 15802The explicit mention of a day of the week will forward the date (only if 15803necessary) to reach that day of the week in the future. 15804 15805 Days of the week may be spelled out in full: ‘Sunday’, ‘Monday’, 15806‘Tuesday’, ‘Wednesday’, ‘Thursday’, ‘Friday’ or ‘Saturday’. Days may be 15807abbreviated to their first three letters, optionally followed by a 15808period. The special abbreviations ‘Tues’ for ‘Tuesday’, ‘Wednes’ for 15809‘Wednesday’ and ‘Thur’ or ‘Thurs’ for ‘Thursday’ are also allowed. 15810 15811 A number may precede a day of the week item to move forward 15812supplementary weeks. It is best used in expression like ‘third monday’. 15813In this context, ‘last DAY’ or ‘next DAY’ is also acceptable; they move 15814one week before or after the day that DAY by itself would represent. 15815 15816 A comma following a day of the week item is ignored. 15817 15818 15819File: coreutils.info, Node: Relative items in date strings, Next: Pure numbers in date strings, Prev: Day of week items, Up: Date input formats 15820 1582129.7 Relative items in date strings 15822=================================== 15823 15824“Relative items” adjust a date (or the current date if none) forward or 15825backward. The effects of relative items accumulate. Here are some 15826examples: 15827 15828 1 year 15829 1 year ago 15830 3 years 15831 2 days 15832 15833 The unit of time displacement may be selected by the string ‘year’ or 15834‘month’ for moving by whole years or months. These are fuzzy units, as 15835years and months are not all of equal duration. More precise units are 15836‘fortnight’ which is worth 14 days, ‘week’ worth 7 days, ‘day’ worth 24 15837hours, ‘hour’ worth 60 minutes, ‘minute’ or ‘min’ worth 60 seconds, and 15838‘second’ or ‘sec’ worth one second. An ‘s’ suffix on these units is 15839accepted and ignored. 15840 15841 The unit of time may be preceded by a multiplier, given as an 15842optionally signed number. Unsigned numbers are taken as positively 15843signed. No number at all implies 1 for a multiplier. Following a 15844relative item by the string ‘ago’ is equivalent to preceding the unit by 15845a multiplier with value -1. 15846 15847 The string ‘tomorrow’ is worth one day in the future (equivalent to 15848‘day’), the string ‘yesterday’ is worth one day in the past (equivalent 15849to ‘day ago’). 15850 15851 The strings ‘now’ or ‘today’ are relative items corresponding to 15852zero-valued time displacement, these strings come from the fact a 15853zero-valued time displacement represents the current time when not 15854otherwise changed by previous items. They may be used to stress other 15855items, like in ‘12:00 today’. The string ‘this’ also has the meaning of 15856a zero-valued time displacement, but is preferred in date strings like 15857‘this thursday’. 15858 15859 When a relative item causes the resulting date to cross a boundary 15860where the clocks were adjusted, typically for daylight saving time, the 15861resulting date and time are adjusted accordingly. 15862 15863 The fuzz in units can cause problems with relative items. For 15864example, ‘2003-07-31 -1 month’ might evaluate to 2003-07-01, because 158652003-06-31 is an invalid date. To determine the previous month more 15866reliably, you can ask for the month before the 15th of the current 15867month. For example: 15868 15869 $ date -R 15870 Thu, 31 Jul 2003 13:02:39 -0700 15871 $ date --date='-1 month' +'Last month was %B?' 15872 Last month was July? 15873 $ date --date="$(date +%Y-%m-15) -1 month" +'Last month was %B!' 15874 Last month was June! 15875 15876 Also, take care when manipulating dates around clock changes such as 15877daylight saving leaps. In a few cases these have added or subtracted as 15878much as 24 hours from the clock, so it is often wise to adopt universal 15879time by setting the ‘TZ’ environment variable to ‘UTC0’ before embarking 15880on calendrical calculations. 15881 15882 15883File: coreutils.info, Node: Pure numbers in date strings, Next: Seconds since the Epoch, Prev: Relative items in date strings, Up: Date input formats 15884 1588529.8 Pure numbers in date strings 15886================================= 15887 15888The precise interpretation of a pure decimal number depends on the 15889context in the date string. 15890 15891 If the decimal number is of the form YYYYMMDD and no other calendar 15892date item (*note Calendar date items::) appears before it in the date 15893string, then YYYY is read as the year, MM as the month number and DD as 15894the day of the month, for the specified calendar date. 15895 15896 If the decimal number is of the form HHMM and no other time of day 15897item appears before it in the date string, then HH is read as the hour 15898of the day and MM as the minute of the hour, for the specified time of 15899day. MM can also be omitted. 15900 15901 If both a calendar date and a time of day appear to the left of a 15902number in the date string, but no relative item, then the number 15903overrides the year. 15904 15905 15906File: coreutils.info, Node: Seconds since the Epoch, Next: Specifying time zone rules, Prev: Pure numbers in date strings, Up: Date input formats 15907 1590829.9 Seconds since the Epoch 15909============================ 15910 15911If you precede a number with ‘@’, it represents an internal timestamp as 15912a count of seconds. The number can contain an internal decimal point 15913(either ‘.’ or ‘,’); any excess precision not supported by the internal 15914representation is truncated toward minus infinity. Such a number cannot 15915be combined with any other date item, as it specifies a complete 15916timestamp. 15917 15918 Internally, computer times are represented as a count of seconds 15919since an epoch—a well-defined point of time. On GNU and POSIX systems, 15920the epoch is 1970-01-01 00:00:00 UTC, so ‘@0’ represents this time, ‘@1’ 15921represents 1970-01-01 00:00:01 UTC, and so forth. GNU and most other 15922POSIX-compliant systems support such times as an extension to POSIX, 15923using negative counts, so that ‘@-1’ represents 1969-12-31 23:59:59 UTC. 15924 15925 Traditional Unix systems count seconds with 32-bit two’s-complement 15926integers and can represent times from 1901-12-13 20:45:52 through 159272038-01-19 03:14:07 UTC. More modern systems use 64-bit counts of 15928seconds with nanosecond subcounts, and can represent all the times in 15929the known lifetime of the universe to a resolution of 1 nanosecond. 15930 15931 On most hosts, these counts ignore the presence of leap seconds. For 15932example, on most hosts ‘@915148799’ represents 1998-12-31 23:59:59 UTC, 15933‘@915148800’ represents 1999-01-01 00:00:00 UTC, and there is no way to 15934represent the intervening leap second 1998-12-31 23:59:60 UTC. 15935 15936 15937File: coreutils.info, Node: Specifying time zone rules, Next: Authors of parse_datetime, Prev: Seconds since the Epoch, Up: Date input formats 15938 1593929.10 Specifying time zone rules 15940================================ 15941 15942Normally, dates are interpreted using the rules of the current time 15943zone, which in turn are specified by the ‘TZ’ environment variable, or 15944by a system default if ‘TZ’ is not set. To specify a different set of 15945default time zone rules that apply just to one date, start the date with 15946a string of the form ‘TZ="RULE"’. The two quote characters (‘"’) must 15947be present in the date, and any quotes or backslashes within RULE must 15948be escaped by a backslash. 15949 15950 For example, with the GNU ‘date’ command you can answer the question 15951“What time is it in New York when a Paris clock shows 6:30am on October 1595231, 2004?” by using a date beginning with ‘TZ="Europe/Paris"’ as shown 15953in the following shell transcript: 15954 15955 $ export TZ="America/New_York" 15956 $ date --date='TZ="Europe/Paris" 2004-10-31 06:30' 15957 Sun Oct 31 01:30:00 EDT 2004 15958 15959 In this example, the ‘--date’ operand begins with its own ‘TZ’ 15960setting, so the rest of that operand is processed according to 15961‘Europe/Paris’ rules, treating the string ‘2004-10-31 06:30’ as if it 15962were in Paris. However, since the output of the ‘date’ command is 15963processed according to the overall time zone rules, it uses New York 15964time. (Paris was normally six hours ahead of New York in 2004, but this 15965example refers to a brief Halloween period when the gap was five hours.) 15966 15967 A ‘TZ’ value is a rule that typically names a location in the ‘tz’ 15968database (https://www.iana.org/time-zones). A recent catalog of 15969location names appears in the TWiki Date and Time Gateway 15970(https://twiki.org/cgi-bin/xtra/tzdatepick.html). A few non-GNU hosts 15971require a colon before a location name in a ‘TZ’ setting, e.g., 15972‘TZ=":America/New_York"’. 15973 15974 The ‘tz’ database includes a wide variety of locations ranging from 15975‘Arctic/Longyearbyen’ to ‘Antarctica/South_Pole’, but if you are at sea 15976and have your own private time zone, or if you are using a non-GNU host 15977that does not support the ‘tz’ database, you may need to use a POSIX 15978rule instead. Simple POSIX rules like ‘UTC0’ specify a time zone 15979without daylight saving time; other rules can specify simple daylight 15980saving regimes. *Note Specifying the Time Zone with ‘TZ’: (libc)TZ 15981Variable. 15982 15983 15984File: coreutils.info, Node: Authors of parse_datetime, Prev: Specifying time zone rules, Up: Date input formats 15985 1598629.11 Authors of ‘parse_datetime’ 15987================================= 15988 15989‘parse_datetime’ started life as ‘getdate’, as originally implemented by 15990Steven M. Bellovin (<smb@research.att.com>) while at the University of 15991North Carolina at Chapel Hill. The code was later tweaked by a couple 15992of people on Usenet, then completely overhauled by Rich $alz 15993(<rsalz@bbn.com>) and Jim Berets (<jberets@bbn.com>) in August, 1990. 15994Various revisions for the GNU system were made by David MacKenzie, Jim 15995Meyering, Paul Eggert and others, including renaming it to ‘get_date’ to 15996avoid a conflict with the alternative Posix function ‘getdate’, and a 15997later rename to ‘parse_datetime’. The Posix function ‘getdate’ can 15998parse more locale-specific dates using ‘strptime’, but relies on an 15999environment variable and external file, and lacks the thread-safety of 16000‘parse_datetime’. 16001 16002 This chapter was originally produced by François Pinard 16003(<pinard@iro.umontreal.ca>) from the ‘parse_datetime.y’ source code, and 16004then edited by K. Berry (<kb@cs.umb.edu>). 16005 16006 16007File: coreutils.info, Node: Version sort ordering, Next: Opening the software toolbox, Prev: Date input formats, Up: Top 16008 1600930 Version sort ordering 16010************************ 16011 16012* Menu: 16013 16014* Version sort overview:: 16015* Implementation Details:: 16016* Differences from the official Debian Algorithm:: 16017* Advanced Topics:: 16018 16019 16020File: coreutils.info, Node: Version sort overview, Next: Implementation Details, Up: Version sort ordering 16021 1602230.1 Version sort overview 16023========================== 16024 16025“version sort” ordering (and similarly, “natural sort” ordering) is a 16026method to sort items such as file names and lines of text in an order 16027that feels more natural to people, when the text contains a mixture of 16028letters and digits. 16029 16030 Standard sorting usually does not produce the order that one expects 16031because comparisons are made on a character-by-character basis. 16032 16033 Compare the sorting of the following items: 16034 16035 Alphabetical sort: Version Sort: 16036 16037 a1 a1 16038 a120 a2 16039 a13 a13 16040 a2 a120 16041 16042 version sort functionality in GNU coreutils is available in the ‘ls 16043-v’, ‘ls --sort=version’, ‘sort -V’, ‘sort --version-sort’ commands. 16044 16045* Menu: 16046 16047* Using version sort in GNU coreutils:: 16048* Origin of version sort and differences from natural sort:: 16049* Correct/Incorrect ordering and Expected/Unexpected results:: 16050 16051 16052File: coreutils.info, Node: Using version sort in GNU coreutils, Next: Origin of version sort and differences from natural sort, Up: Version sort overview 16053 1605430.1.1 Using version sort in GNU coreutils 16055------------------------------------------ 16056 16057Two GNU coreutils programs use version sort: ‘ls’ and ‘sort’. 16058 16059 To list files in version sort order, use ‘ls’ with ‘-v’ or 16060‘--sort=version’ options: 16061 16062 default sort: version sort: 16063 16064 $ ls -1 $ ls -1 -v 16065 a1 a1 16066 a100 a1.4 16067 a1.13 a1.13 16068 a1.4 a1.40 16069 a1.40 a2 16070 a2 a100 16071 16072 To sort text files in version sort order, use ‘sort’ with the ‘-V’ 16073option: 16074 16075 $ cat input 16076 b3 16077 b11 16078 b1 16079 b20 16080 16081 16082 alphabetical order: version sort order: 16083 16084 $ sort input $ sort -V input 16085 b1 b1 16086 b11 b3 16087 b20 b11 16088 b3 b20 16089 16090 To sort a specific column in a file use ‘-k/--key’ with ‘V’ ordering 16091option: 16092 16093 $ cat input2 16094 1000 b3 apples 16095 2000 b11 oranges 16096 3000 b1 potatoes 16097 4000 b20 bananas 16098 16099 $ sort -k2V,2 input2 16100 3000 b1 potatoes 16101 1000 b3 apples 16102 2000 b11 oranges 16103 4000 b20 bananas 16104 16105 16106File: coreutils.info, Node: Origin of version sort and differences from natural sort, Next: Correct/Incorrect ordering and Expected/Unexpected results, Prev: Using version sort in GNU coreutils, Up: Version sort overview 16107 1610830.1.2 Origin of version sort and differences from natural sort 16109--------------------------------------------------------------- 16110 16111In GNU coreutils, the name “version sort” was chosen because it is based 16112on Debian GNU/Linux’s algorithm of sorting packages’ versions. 16113 16114 Its goal is to answer the question “which package is newer, 16115‘firefox-60.7.2’ or ‘firefox-60.12.3’ ?” 16116 16117 In coreutils this algorithm was slightly modified to work on more 16118general input such as textual strings and file names (see *note 16119Differences from the official Debian Algorithm::). 16120 16121 In other contexts, such as other programs and other programming 16122languages, a similar sorting functionality is called natural sort 16123(https://en.wikipedia.org/wiki/Natural_sort_order). 16124 16125 16126File: coreutils.info, Node: Correct/Incorrect ordering and Expected/Unexpected results, Prev: Origin of version sort and differences from natural sort, Up: Version sort overview 16127 1612830.1.3 Correct/Incorrect ordering and Expected/Unexpected results 16129----------------------------------------------------------------- 16130 16131Currently there is no standard for version/natural sort ordering. 16132 16133 That is: there is no one correct way or universally agreed-upon way 16134to order items. Each program and each programming language can decide 16135its own ordering algorithm and call it ’natural sort’ (or other various 16136names). 16137 16138 See *note Other version/natural sort implementations:: for many 16139examples of differing sorting possibilities, each with its own rules and 16140variations. 16141 16142 If you do suspect a bug in coreutils’ implementation of version-sort, 16143see *note Reporting bugs or incorrect results:: on how to report them. 16144 16145 16146File: coreutils.info, Node: Implementation Details, Next: Differences from the official Debian Algorithm, Prev: Version sort overview, Up: Version sort ordering 16147 1614830.2 Implementation Details 16149=========================== 16150 16151GNU coreutils’ version sort algorithm is based on Debian’s versioning 16152scheme 16153(https://www.debian.org/doc/debian-policy/ch-controlfields.html#version), 16154specifically on the "upstream version" part. 16155 16156 This section describes the ordering rules. 16157 16158 The next section (*note Differences from the official Debian 16159Algorithm::) describes some differences between GNU coreutils 16160implementation and Debian’s official algorithm. 16161 16162* Menu: 16163 16164* Version-sort ordering rules:: 16165* Version sort is not the same as numeric sort:: 16166* Punctuation Characters:: 16167* Punctuation Characters vs letters:: 16168* Tilde ~ character:: 16169* Version sort ignores locale:: 16170 16171 16172File: coreutils.info, Node: Version-sort ordering rules, Next: Version sort is not the same as numeric sort, Up: Implementation Details 16173 1617430.2.1 Version-sort ordering rules 16175---------------------------------- 16176 16177The version sort ordering rules are: 16178 16179 1. The strings are compared from left to right. 16180 16181 2. First the initial part of each string consisting entirely of 16182 non-digit characters is determined. 16183 16184 1. These two parts (one of which may be empty) are compared 16185 lexically. If a difference is found it is returned. 16186 16187 2. The lexical comparison is a comparison of ASCII values 16188 modified so that: 16189 16190 1. all the letters sort earlier than all the non-letters and 16191 2. so that a tilde sorts before anything, even the end of a 16192 part. 16193 16194 3. Then the initial part of the remainder of each string which 16195 consists entirely of digit characters is determined. The numerical 16196 values of these two parts are compared, and any difference found is 16197 returned as the result of the comparison. 16198 1. For these purposes an empty string (which can only occur at 16199 the end of one or both version strings being compared) counts 16200 as zero. 16201 16202 4. These two steps (comparing and removing initial non-digit strings 16203 and initial digit strings) are repeated until a difference is found 16204 or both strings are exhausted. 16205 16206 Consider the version-sort comparison of two file names: ‘foo07.7z’ 16207and ‘foo7a.7z’. The two strings will be broken down to the following 16208parts, and the parts compared respectively from each string: 16209 16210 foo vs foo (rule 2, non-digits characters) 16211 07 vs 7 (rule 3, digits characters) 16212 . vs a. (rule 2) 16213 7 vs 7 (rule 3) 16214 z vs z (rule 2) 16215 16216 Comparison flow based on above algorithm: 16217 16218 1. The first parts (‘foo’) are identical in both strings. 16219 16220 2. The second parts (‘07’ and ‘7’) are compared numerically, and are 16221 identical. 16222 16223 3. The third parts (‘‘.’’ vs ‘‘a.’’) are compared lexically by ASCII 16224 value (rule 2.2). 16225 16226 4. The first character of the first string (‘‘.’’) is compared to the 16227 first character of the second string (‘‘a’’). 16228 16229 5. Rule 2.2.1 dictates that "all letters sorts earlier than all 16230 non-letters". Hence, ‘‘a’’ comes before ‘‘.’’. 16231 16232 6. The returned result is that ‘foo7a.7z’ comes before ‘foo07.7z’. 16233 16234 Result when using sort: 16235 16236 $ cat input3 16237 foo07.7z 16238 foo7a.7z 16239 16240 $ sort -V input3 16241 foo7a.7z 16242 foo07.7z 16243 16244 See *note Differences from the official Debian Algorithm:: for 16245additional rules that extend the Debian algorithm in coreutils. 16246 16247 16248File: coreutils.info, Node: Version sort is not the same as numeric sort, Next: Punctuation Characters, Prev: Version-sort ordering rules, Up: Implementation Details 16249 1625030.2.2 Version sort is not the same as numeric sort 16251--------------------------------------------------- 16252 16253Consider the following text file: 16254 16255 $ cat input4 16256 8.10 16257 8.5 16258 8.1 16259 8.01 16260 8.010 16261 8.100 16262 8.49 16263 16264 16265 16266 Numerical Sort: Version Sort: 16267 16268 $ sort -n input4 $ sort -V input4 16269 8.01 8.01 16270 8.010 8.1 16271 8.1 8.5 16272 8.10 8.010 16273 8.100 8.10 16274 8.49 8.49 16275 8.5 8.100 16276 16277 Numeric sort (‘sort -n’) treats the entire string as a single numeric 16278value, and compares it to other values. For example, ‘8.1’, ‘8.10’ and 16279‘8.100’ are numerically equivalent, and are ordered together. 16280Similarly, ‘8.49’ is numerically smaller than ‘8.5’, and appears before 16281first. 16282 16283 Version sort (‘sort -V’) first breaks down the string into digits and 16284non-digits parts, and only then compares each part (see annotated 16285example in Version-sort ordering rules). 16286 16287 Comparing the string ‘8.1’ to ‘8.01’, first the ‘‘8’’ characters are 16288compared (and are identical), then the dots (‘‘.’’) are compared and are 16289identical, and lastly the remaining digits are compared numerically (‘1’ 16290and ‘01’) - which are numerically equivalent. Hence, ‘8.01’ and ‘8.1’ 16291are grouped together. 16292 16293 Similarly, comparing ‘8.5’ to ‘8.49’ - the ‘‘8’’ and ‘‘.’’ parts are 16294identical, then the numeric values ‘5’ and ‘49’ are compared. The 16295resulting ‘5’ appears before ‘49’. 16296 16297 This sorting order (where ‘8.5’ comes before ‘8.49’) is common when 16298assigning versions to computer programs (while perhaps not intuitive or 16299’natural’ for people). 16300 16301 16302File: coreutils.info, Node: Punctuation Characters, Next: Punctuation Characters vs letters, Prev: Version sort is not the same as numeric sort, Up: Implementation Details 16303 1630430.2.3 Punctuation Characters 16305----------------------------- 16306 16307Punctuation characters are sorted by ASCII order (rule 2.2). 16308 16309 $ touch 1.0.5_src.tar.gz 1.0_src.tar.gz 16310 16311 $ ls -v -1 16312 1.0.5_src.tar.gz 16313 1.0_src.tar.gz 16314 16315 Why is ‘1.0.5_src.tar.gz’ listed before ‘1.0_src.tar.gz’ ? 16316 16317 Based on the *note algorithm: Version-sort ordering rules. above, the 16318strings are broken down into the following parts: 16319 16320 1 vs 1 (rule 3, all digit characters) 16321 . vs . (rule 2, all non-digit characters) 16322 0 vs 0 (rule 3) 16323 . vs _src.tar.gz (rule 2) 16324 5 vs empty string (no more character in the file name) 16325 _src.tar.gz vs empty string 16326 16327 The fourth parts (‘‘.’’ and ‘_src.tar.gz’) are compared lexically by 16328ASCII order. The character ‘‘.’’ (ASCII value 46) is smaller than ‘‘_’’ 16329(ASCII value 95) - and should be listed before it. 16330 16331 Hence, ‘1.0.5_src.tar.gz’ is listed first. 16332 16333 If a different character appears instead of the underscore (for 16334example, percent sign ‘‘%’’ ASCII value 37, which is smaller than dot’s 16335ASCII value of 46), that file will be listed first: 16336 16337 $ touch 1.0.5_src.tar.gz 1.0%zzzzz.gz 16338 1.0%zzzzz.gz 16339 1.0.5_src.tar.gz 16340 16341 The same reasoning applies to the following example: The character 16342‘‘.’’ has ASCII value 46, and is smaller than slash character ‘‘/’’ 16343ASCII value 47: 16344 16345 $ cat input5 16346 3.0/ 16347 3.0.5 16348 16349 $ sort -V input5 16350 3.0.5 16351 3.0/ 16352 16353 16354File: coreutils.info, Node: Punctuation Characters vs letters, Next: Tilde ~ character, Prev: Punctuation Characters, Up: Implementation Details 16355 1635630.2.4 Punctuation Characters vs letters 16357---------------------------------------- 16358 16359Rule 2.2.1 dictates that letters sorts earlier than all non-letters 16360(after breaking down a string to digits and non-digits parts). 16361 16362 $ cat input6 16363 a% 16364 az 16365 16366 $ sort -V input6 16367 az 16368 a% 16369 16370 The input strings consist entirely of non-digits, and based on the 16371above algorithm have only one part, all non-digit characters (‘‘a%’’ vs 16372‘‘az’’). 16373 16374 Each part is then compared lexically, character-by-character. ‘‘a’’ 16375compares identically in both strings. 16376 16377 Rule 2.2.1 dictates that letters (‘‘z’’) sorts earlier than all 16378non-letters (‘‘%’’) - hence ‘‘az’’ appears first (despite ‘‘z’’ having 16379ASCII value of 122, much bigger than ‘‘%’’ with ASCII value 37). 16380 16381 16382File: coreutils.info, Node: Tilde ~ character, Next: Version sort ignores locale, Prev: Punctuation Characters vs letters, Up: Implementation Details 16383 1638430.2.5 Tilde ‘~’ character 16385-------------------------- 16386 16387Rule 2.2.2 dictates that tilde character ‘‘~’’ (ASCII 126) sorts before 16388all other non-digit characters, including an empty part. 16389 16390 $ cat input7 16391 1 16392 1% 16393 1.2 16394 1~ 16395 ~ 16396 16397 $ sort -V input7 16398 ~ 16399 1~ 16400 1 16401 1% 16402 1.2 16403 16404 The sorting algorithm starts by breaking down the string into 16405non-digits (rule 2) and digits parts (rule 3). 16406 16407 In the above input file, only the last line in the input file starts 16408with a non-digit (‘‘~’’). This is the first part. All other lines in 16409the input file start with a digit - their first non-digit part is empty. 16410 16411 Based on rule 2.2.2, tilde ‘‘~’’ sorts before all other non-digits 16412including the empty part - hence it comes before all other strings, and 16413is listed first in the sorted output. 16414 16415 The remaining lines (‘1’, ‘1%’, ‘1.2’, ‘1~’) follow similar logic: 16416The digit part is extracted (1 for all strings) and compares identical. 16417The following extracted parts for the remaining input lines are: empty 16418part, ‘%’, ‘.’, ‘~’. 16419 16420 Tilde sorts before all others, hence the line ‘1~’ appears next. 16421 16422 The remaining lines (‘1’, ‘1%’, ‘1.2’) are sorted based on previously 16423explained rules. 16424 16425 16426File: coreutils.info, Node: Version sort ignores locale, Prev: Tilde ~ character, Up: Implementation Details 16427 1642830.2.6 Version sort uses ASCII order, ignores locale, unicode characters 16429------------------------------------------------------------------------ 16430 16431In version sort, unicode characters are compared byte-by-byte according 16432to their binary representation, ignoring their unicode value or the 16433current locale. 16434 16435 Most commonly, unicode characters (e.g. Greek Small Letter Alpha 16436U+03B1 ‘α’) are encoded as UTF-8 bytes (e.g. ‘α’ is encoded as UTF-8 16437sequence ‘0xCE 0xB1’). The encoding will be compared byte-by-byte, e.g. 16438first ‘0xCE’ (decimal value 206) then ‘0xB1’ (decimal value 177). 16439 16440 $ touch aa az "a%" "aα" 16441 16442 $ ls -1 -v 16443 aa 16444 az 16445 a% 16446 aα 16447 16448 Ignoring the first letter (‘a’) which is identical in all strings, 16449the compared values are: 16450 16451 ‘‘a’’ and ‘‘z’’ are letters, and sort earlier than all other 16452non-digit characters. 16453 16454 Then, percent sign ‘‘%’’ (ASCII value 37) is compared to the first 16455byte of the UTF-8 sequence of ‘‘α’’, which is 0xCE or 206). The value 1645637 is smaller, hence ‘‘a%’’ is listed before ‘‘aα’’. 16457 16458 16459File: coreutils.info, Node: Differences from the official Debian Algorithm, Next: Advanced Topics, Prev: Implementation Details, Up: Version sort ordering 16460 1646130.3 Differences from the official Debian Algorithm 16462=================================================== 16463 16464The GNU coreutils’ version sort algorithm differs slightly from the 16465official Debian algorithm, in order to accommodate more general usage 16466and file name listing. 16467 16468* Menu: 16469 16470* Minus/Hyphen and Colon characters:: 16471* Additional hard-coded priorities in GNU coreutils' version sort:: 16472* Special handling of file extensions:: 16473 16474 16475File: coreutils.info, Node: Minus/Hyphen and Colon characters, Next: Additional hard-coded priorities in GNU coreutils' version sort, Up: Differences from the official Debian Algorithm 16476 1647730.3.1 Minus/Hyphen ‘-’ and Colon ‘:’ characters 16478------------------------------------------------ 16479 16480In Debian’s version string syntax the version consists of three parts: 16481 [epoch:]upstream_version[-debian_revision] 16482 The ‘epoch’ and ‘debian_revision’ parts are optional. 16483 16484 Example of such version strings: 16485 16486 60.7.2esr-1~deb9u1 16487 52.9.0esr-1~deb9u1 16488 1:2.3.4-1+b2 16489 327-2 16490 1:1.0.13-3 16491 2:1.19.2-1+deb9u5 16492 16493 If the ‘debian_revision part’ is not present, hyphen characters ‘-’ 16494are not allowed. If epoch is not present, colons ‘:’ are not allowed. 16495 16496 If these parts are present, hyphen and/or colons can appear only once 16497in valid Debian version strings. 16498 16499 In GNU coreutils, such restrictions are not reasonable (a file name 16500can have many hyphens, a line of text can have many colons). 16501 16502 As a result, in GNU coreutils hyphens and colons are treated exactly 16503like all other punctuation characters (i.e., they are sorted after 16504letters. See Punctuation Characters above). 16505 16506 In Debian, these characters are treated differently than in 16507coreutils: a version string with hyphen will sort before similar strings 16508without hyphens. 16509 16510 Compare: 16511 16512 $ touch abb ab-cd 16513 16514 $ ls -v -1 16515 abb 16516 ab-cd 16517 16518 With Debian’s ‘dpkg’ they will be listed as ‘ab-cd’ first and ‘abb’ 16519second. 16520 16521 For further technical details see bug35939 16522(https://bugs.gnu.org/35939). 16523 16524 16525File: coreutils.info, Node: Additional hard-coded priorities in GNU coreutils' version sort, Next: Special handling of file extensions, Prev: Minus/Hyphen and Colon characters, Up: Differences from the official Debian Algorithm 16526 1652730.3.2 Additional hard-coded priorities in GNU coreutils’ version sort 16528---------------------------------------------------------------------- 16529 16530In GNU coreutils’ version sort algorithm, the following items have 16531special priority and sort earlier than all other characters (listed in 16532order); 16533 16534 1. The empty string 16535 16536 2. The string ‘‘.’’ (a single dot character, ASCII 46) 16537 16538 3. The string ‘‘..’’ (two dot characters) 16539 16540 4. Strings start with a dot (‘‘.’’) sort earlier than strings starting 16541 with any other characters. 16542 16543 Example: 16544 16545 $ printf "%s\n" a "" b "." c ".." ".d20" ".d3" | sort -V 16546 16547 . 16548 .. 16549 .d3 16550 .d20 16551 a 16552 b 16553 c 16554 16555 These priorities make perfect sense for ‘ls -v’: The special files 16556dot ‘‘.’’ and dot-dot ‘‘..’’ will be listed first, followed by any 16557hidden files (files starting with a dot), followed by non-hidden files. 16558 16559 For ‘sort -V’ these priorities might seem arbitrary. However, 16560because the sorting code is shared between the ‘ls’ and ‘sort’ program, 16561the ordering rules are the same. 16562 16563 16564File: coreutils.info, Node: Special handling of file extensions, Prev: Additional hard-coded priorities in GNU coreutils' version sort, Up: Differences from the official Debian Algorithm 16565 1656630.3.3 Special handling of file extensions 16567------------------------------------------ 16568 16569GNU coreutils’ version sort algorithm implements specialized handling of 16570file extensions (or strings that look like file names with extensions). 16571 16572 This nuanced implementation enables slightly more natural ordering of 16573files. 16574 16575 The additional rules are: 16576 16577 1. A suffix (i.e., a file extension) is defined as: a dot, followed by 16578 a letter or tilde, followed by one or more letters, digits, or 16579 tildes (possibly repeated more than once), until the end of the 16580 string (technically, matching the regular expression 16581 ‘(\.[A-Za-z~][A-Za-z0-9~]*)*’). 16582 16583 2. If the strings contains suffixes, the suffixes are temporarily 16584 removed, and the strings are compared without them (using the *note 16585 algorithm: Version-sort ordering rules. above). 16586 16587 3. If the suffix-less strings are identical, the suffix is restored 16588 and the entire strings are compared. 16589 16590 4. If the non-suffixed strings differ, the result is returned and the 16591 suffix is effectively ignored. 16592 16593 Examples for rule 1: 16594 16595 • ‘hello-8.txt’: the suffix is ‘.txt’ 16596 16597 • ‘hello-8.2.txt’: the suffix is ‘.txt’ (‘‘.2’’ is not included 16598 because the dot is not followed by a letter) 16599 16600 • ‘hello-8.0.12.tar.gz’: the suffix is ‘.tar.gz’ (‘‘.0.12’’ is not 16601 included) 16602 16603 • ‘hello-8.2’: no suffix (suffix is an empty string) 16604 16605 • ‘hello.foobar65’: the suffix is ‘.foobar65’ 16606 16607 • ‘gcc-c++-10.8.12-0.7rc2.fc9.tar.bz2’: the suffix is ‘.fc9.tar.bz2’ 16608 (‘.7rc2’ is not included as it begins with a digit) 16609 16610 Examples for rule 2: 16611 16612 • Comparing ‘hello-8.txt’ to ‘hello-8.2.12.txt’, the ‘.txt’ suffix is 16613 temporarily removed from both strings. 16614 16615 • Comparing ‘foo-10.3.tar.gz’ to ‘foo-10.tar.xz’, the suffixes 16616 ‘.tar.gz’ and ‘.tar.xz’ are temporarily removed from the strings. 16617 16618 Example for rule 3: 16619 16620 • Comparing ‘hello.foobar65’ to ‘hello.foobar4’, the suffixes 16621 (‘.foobar65’ and ‘.foobar4’) are temporarily removed. The 16622 remaining strings are identical (‘hello’). The suffixes are then 16623 restored, and the entire strings are compared (‘hello.foobar4’ 16624 comes first). 16625 16626 Examples for rule 4: 16627 16628 • When comparing the strings ‘hello-8.2.txt’ and ‘hello-8.10.txt’, 16629 the suffixes (‘.txt’) are temporarily removed. The remaining 16630 strings (‘hello-8.2’ and ‘hello-8.10’) are compared as previously 16631 described (‘hello-8.2’ comes first). (In this case the suffix 16632 removal algorithm does not have a noticeable effect on the 16633 resulting order.) 16634 16635 How does the suffix-removal algorithm effect ordering results? 16636 16637 Consider the comparison of hello-8.txt and hello-8.2.txt. 16638 16639 Without the suffix-removal algorithm, the strings will be broken down 16640to the following parts: 16641 16642 hello- vs hello- (rule 2, all non-digit characters) 16643 8 vs 8 (rule 3, all digit characters) 16644 .txt vs . (rule 2) 16645 empty vs 2 16646 empty vs .txt 16647 16648 The comparison of the third parts (‘‘.’’ vs ‘‘.txt’’) will determine 16649that the shorter string comes first - resulting in ‘hello-8.2.txt’ 16650appearing first. 16651 16652 Indeed this is the order in which Debian’s ‘dpkg’ compares the 16653strings. 16654 16655 A more natural result is that ‘hello-8.txt’ should come before 16656‘hello-8.2.txt’, and this is where the suffix-removal comes into play: 16657 16658 The suffixes (‘.txt’) are removed, and the remaining strings are 16659broken down into the following parts: 16660 16661 hello- vs hello- (rule 2, all non-digit characters) 16662 8 vs 8 (rule 3, all digit characters) 16663 empty vs . (rule 2) 16664 empty vs 2 16665 16666 As empty strings sort before non-empty strings, the result is 16667‘hello-8’ being first. 16668 16669 A real-world example would be listing files such as: 16670‘gcc_10.fc9.tar.gz’ and ‘gcc_10.8.12.7rc2.fc9.tar.bz2’: Debian’s 16671algorithm would list ‘gcc_10.8.12.7rc2.fc9.tar.bz2’ first, while ‘ls -v’ 16672will list ‘gcc_10.fc9.tar.gz’ first. 16673 16674 These priorities make sense for ‘ls -v’: Versioned files will be 16675listed in a more natural order. 16676 16677 For ‘sort -V’ these priorities might seem arbitrary. However, 16678because the sorting code is shared between the ‘ls’ and ‘sort’ program, 16679the ordering rules are the same. 16680 16681 16682File: coreutils.info, Node: Advanced Topics, Prev: Differences from the official Debian Algorithm, Up: Version sort ordering 16683 1668430.4 Advanced Topics 16685==================== 16686 16687* Menu: 16688 16689* Comparing two strings using Debian's algorithm:: 16690* Reporting bugs or incorrect results:: 16691* Other version/natural sort implementations:: 16692* Related Source code:: 16693 16694 16695File: coreutils.info, Node: Comparing two strings using Debian's algorithm, Next: Reporting bugs or incorrect results, Up: Advanced Topics 16696 1669730.4.1 Comparing two strings using Debian’s algorithm 16698----------------------------------------------------- 16699 16700The Debian program ‘dpkg’ (available on all Debian and Ubuntu 16701installations) can compare two strings using the ‘--compare-versions’ 16702option. 16703 16704 To use it, create a helper shell function (simply copy & paste the 16705following snippet to your shell command-prompt): 16706 16707 compver() { 16708 dpkg --compare-versions "$1" lt "$2" \ 16709 && printf "%s\n" "$1" "$2" \ 16710 || printf "%s\n" "$2" "$1" ; \ 16711 } 16712 16713 Then compare two strings by calling compver: 16714 16715 $ compver 8.49 8.5 16716 8.5 16717 8.49 16718 16719 Note that ‘dpkg’ will warn if the strings have invalid syntax: 16720 16721 $ compver "foo07.7z" "foo7a.7z" 16722 dpkg: warning: version 'foo07.7z' has bad syntax: 16723 version number does not start with digit 16724 dpkg: warning: version 'foo7a.7z' has bad syntax: 16725 version number does not start with digit 16726 foo7a.7z 16727 foo07.7z 16728 16729 $ compver "3.0/" "3.0.5" 16730 dpkg: warning: version '3.0/' has bad syntax: 16731 invalid character in version number 16732 3.0.5 16733 3.0/ 16734 16735 To illustrate the different handling of hyphens between Debian and 16736coreutils’ algorithms (see *note Minus/Hyphen and Colon characters::): 16737 16738 $ compver abb ab-cd 2>/dev/null $ printf "abb\nab-cd\n" | sort -V 16739 ab-cd abb 16740 abb ab-cd 16741 16742 To illustrate the different handling of file extension: (see *note 16743Special handling of file extensions::): 16744 16745 $ compver hello-8.txt hello-8.2.txt 2>/dev/null 16746 hello-8.2.txt 16747 hello-8.txt 16748 16749 $ printf "%s\n" hello-8.txt hello-8.2.txt | sort -V 16750 hello-8.txt 16751 hello-8.2.txt 16752 16753 16754File: coreutils.info, Node: Reporting bugs or incorrect results, Next: Other version/natural sort implementations, Prev: Comparing two strings using Debian's algorithm, Up: Advanced Topics 16755 1675630.4.2 Reporting bugs or incorrect results 16757------------------------------------------ 16758 16759If you suspect a bug in GNU coreutils’ version sort (i.e., in the output 16760of ‘ls -v’ or ‘sort -V’), please first check the following: 16761 16762 1. Is the result consistent with Debian’s own ordering (using ‘dpkg’, 16763 see *note Comparing two strings using Debian's algorithm::) ? If 16764 it is, then this is not a bug - please do not report it. 16765 16766 2. If the result differs from Debian’s, is it explained by one of the 16767 sections in *note Differences from the official Debian Algorithm::? 16768 If it is, then this is not a bug - please do not report it. 16769 16770 3. If you have a question about specific ordering which is not 16771 explained here, please write to <coreutils@gnu.org>, and provide a 16772 concise example that will help us diagnose the issue. 16773 16774 4. If you still suspect a bug which is not explained by the above, 16775 please write to <bug-coreutils@gnu.org> with a concrete example of 16776 the suspected incorrect output, with details on why you think it is 16777 incorrect. 16778 16779 16780File: coreutils.info, Node: Other version/natural sort implementations, Next: Related Source code, Prev: Reporting bugs or incorrect results, Up: Advanced Topics 16781 1678230.4.3 Other version/natural sort implementations 16783------------------------------------------------- 16784 16785As previously mentioned, there are multiple variations on 16786version/natural sort, each with its own rules. Some examples are: 16787 16788 • Natural Sorting variants in Rosetta Code 16789 (https://rosettacode.org/wiki/Natural_sorting). 16790 16791 • Python’s natsort package (https://pypi.org/project/natsort/) 16792 (includes detailed description of their sorting rules: natsort - 16793 how it works 16794 (https://natsort.readthedocs.io/en/master/howitworks.html)). 16795 16796 • Ruby’s version_sorter (https://github.com/github/version_sorter). 16797 16798 • Perl has multiple packages for natual and version sorts (each 16799 likely with its own rules and nuances): Sort::Naturally 16800 (https://metacpan.org/pod/Sort::Naturally), Sort::Versions 16801 (https://metacpan.org/pod/Sort::Versions), CPAN::Version 16802 (https://metacpan.org/pod/CPAN::Version). 16803 16804 • PHP has a built-in function natsort 16805 (https://www.php.net/manual/en/function.natsort.php). 16806 16807 • NodeJS’s natural-sort package 16808 (https://www.npmjs.com/package/natural-sort). 16809 16810 • In zsh, the glob modifier 16811 (http://zsh.sourceforge.net/Doc/Release/Expansion.html#Glob-Qualifiers) 16812 ‘*(n)’ will expand to files in natural sort order. 16813 16814 • When writing ‘C’ programs, the GNU libc library (‘glibc’) provides 16815 the strvercmp(3) 16816 (http://man7.org/linux/man-pages/man3/strverscmp.3.html) function 16817 to compare two strings, and versionsort(3) 16818 (http://man7.org/linux/man-pages/man3/versionsort.3.html) function 16819 to compare two directory entries (despite the names, they are not 16820 identical to GNU coreutils’ version sort ordering). 16821 16822 • Using Debian’s sorting algorithm in: 16823 16824 • python: Stack Overflow Example #4957741 16825 (https://stackoverflow.com/a/4957741). 16826 16827 • NodeJS: deb-version-compare 16828 (https://www.npmjs.com/package/deb-version-compare). 16829 16830 16831File: coreutils.info, Node: Related Source code, Prev: Other version/natural sort implementations, Up: Advanced Topics 16832 1683330.4.4 Related Source code 16834-------------------------- 16835 16836 • Debian’s code which splits a version string into 16837 ‘epoch/upstream_version/debian_revision’ parts: 16838 parsehelp.c:parseversion() 16839 (https://git.dpkg.org/cgit/dpkg/dpkg.git/tree/lib/dpkg/parsehelp.c#n191). 16840 16841 • Debian’s code which performs the ‘upstream_version’ comparison: 16842 version.c 16843 (https://git.dpkg.org/cgit/dpkg/dpkg.git/tree/lib/dpkg/version.c#n140). 16844 16845 • GNULIB code (used by GNU coreutils) which performs the version 16846 comparison: filevercmp.c 16847 (https://git.savannah.gnu.org/cgit/gnulib.git/tree/lib/filevercmp.c). 16848 16849 16850File: coreutils.info, Node: Opening the software toolbox, Next: GNU Free Documentation License, Prev: Version sort ordering, Up: Top 16851 1685231 Opening the Software Toolbox 16853******************************* 16854 16855An earlier version of this chapter appeared in the ‘What’s GNU?’ column 16856of the June 1994 ‘Linux Journal’ 16857(https://www.linuxjournal.com/article.php?sid=2762). It was written by 16858Arnold Robbins. 16859 16860* Menu: 16861 16862* Toolbox introduction:: Toolbox introduction 16863* I/O redirection:: I/O redirection 16864* The who command:: The ‘who’ command 16865* The cut command:: The ‘cut’ command 16866* The sort command:: The ‘sort’ command 16867* The uniq command:: The ‘uniq’ command 16868* Putting the tools together:: Putting the tools together 16869 16870 16871File: coreutils.info, Node: Toolbox introduction, Next: I/O redirection, Up: Opening the software toolbox 16872 16873Toolbox Introduction 16874==================== 16875 16876This month’s column is only peripherally related to the GNU Project, in 16877that it describes a number of the GNU tools on your GNU/Linux system and 16878how they might be used. What it’s really about is the “Software Tools” 16879philosophy of program development and usage. 16880 16881 The software tools philosophy was an important and integral concept 16882in the initial design and development of Unix (of which Linux and GNU 16883are essentially clones). Unfortunately, in the modern day press of 16884Internetworking and flashy GUIs, it seems to have fallen by the wayside. 16885This is a shame, since it provides a powerful mental model for solving 16886many kinds of problems. 16887 16888 Many people carry a Swiss Army knife around in their pants pockets 16889(or purse). A Swiss Army knife is a handy tool to have: it has several 16890knife blades, a screwdriver, tweezers, toothpick, nail file, corkscrew, 16891and perhaps a number of other things on it. For the everyday, small 16892miscellaneous jobs where you need a simple, general purpose tool, it’s 16893just the thing. 16894 16895 On the other hand, an experienced carpenter doesn’t build a house 16896using a Swiss Army knife. Instead, he has a toolbox chock full of 16897specialized tools—a saw, a hammer, a screwdriver, a plane, and so on. 16898And he knows exactly when and where to use each tool; you won’t catch 16899him hammering nails with the handle of his screwdriver. 16900 16901 The Unix developers at Bell Labs were all professional programmers 16902and trained computer scientists. They had found that while a 16903one-size-fits-all program might appeal to a user because there’s only 16904one program to use, in practice such programs are 16905 16906 a. difficult to write, 16907 16908 b. difficult to maintain and debug, and 16909 16910 c. difficult to extend to meet new situations. 16911 16912 Instead, they felt that programs should be specialized tools. In 16913short, each program “should do one thing well.” No more and no less. 16914Such programs are simpler to design, write, and get right—they only do 16915one thing. 16916 16917 Furthermore, they found that with the right machinery for hooking 16918programs together, that the whole was greater than the sum of the parts. 16919By combining several special purpose programs, you could accomplish a 16920specific task that none of the programs was designed for, and accomplish 16921it much more quickly and easily than if you had to write a special 16922purpose program. We will see some (classic) examples of this further on 16923in the column. (An important additional point was that, if necessary, 16924take a detour and build any software tools you may need first, if you 16925don’t already have something appropriate in the toolbox.) 16926 16927 16928File: coreutils.info, Node: I/O redirection, Next: The who command, Prev: Toolbox introduction, Up: Opening the software toolbox 16929 16930I/O Redirection 16931=============== 16932 16933Hopefully, you are familiar with the basics of I/O redirection in the 16934shell, in particular the concepts of “standard input,” “standard 16935output,” and “standard error”. Briefly, “standard input” is a data 16936source, where data comes from. A program should not need to either know 16937or care if the data source is a disk file, a keyboard, a magnetic tape, 16938or even a punched card reader. Similarly, “standard output” is a data 16939sink, where data goes to. The program should neither know nor care 16940where this might be. Programs that only read their standard input, do 16941something to the data, and then send it on, are called “filters”, by 16942analogy to filters in a water pipeline. 16943 16944 With the Unix shell, it’s very easy to set up data pipelines: 16945 16946 program_to_create_data | filter1 | ... | filterN > final.pretty.data 16947 16948 We start out by creating the raw data; each filter applies some 16949successive transformation to the data, until by the time it comes out of 16950the pipeline, it is in the desired form. 16951 16952 This is fine and good for standard input and standard output. Where 16953does the standard error come in to play? Well, think about ‘filter1’ in 16954the pipeline above. What happens if it encounters an error in the data 16955it sees? If it writes an error message to standard output, it will just 16956disappear down the pipeline into ‘filter2’’s input, and the user will 16957probably never see it. So programs need a place where they can send 16958error messages so that the user will notice them. This is standard 16959error, and it is usually connected to your console or window, even if 16960you have redirected standard output of your program away from your 16961screen. 16962 16963 For filter programs to work together, the format of the data has to 16964be agreed upon. The most straightforward and easiest format to use is 16965simply lines of text. Unix data files are generally just streams of 16966bytes, with lines delimited by the ASCII LF (Line Feed) character, 16967conventionally called a “newline” in the Unix literature. (This is 16968‘'\n'’ if you’re a C programmer.) This is the format used by all the 16969traditional filtering programs. (Many earlier operating systems had 16970elaborate facilities and special purpose programs for managing binary 16971data. Unix has always shied away from such things, under the philosophy 16972that it’s easiest to simply be able to view and edit your data with a 16973text editor.) 16974 16975 OK, enough introduction. Let’s take a look at some of the tools, and 16976then we’ll see how to hook them together in interesting ways. In the 16977following discussion, we will only present those command line options 16978that interest us. As you should always do, double check your system 16979documentation for the full story. 16980 16981 16982File: coreutils.info, Node: The who command, Next: The cut command, Prev: I/O redirection, Up: Opening the software toolbox 16983 16984The ‘who’ Command 16985================= 16986 16987The first program is the ‘who’ command. By itself, it generates a list 16988of the users who are currently logged in. Although I’m writing this on 16989a single-user system, we’ll pretend that several people are logged in: 16990 16991 $ who 16992 ⊣ arnold console Jan 22 19:57 16993 ⊣ miriam ttyp0 Jan 23 14:19(:0.0) 16994 ⊣ bill ttyp1 Jan 21 09:32(:0.0) 16995 ⊣ arnold ttyp2 Jan 23 20:48(:0.0) 16996 16997 Here, the ‘$’ is the usual shell prompt, at which I typed ‘who’. 16998There are three people logged in, and I am logged in twice. On 16999traditional Unix systems, user names are never more than eight 17000characters long. This little bit of trivia will be useful later. The 17001output of ‘who’ is nice, but the data is not all that exciting. 17002 17003 17004File: coreutils.info, Node: The cut command, Next: The sort command, Prev: The who command, Up: Opening the software toolbox 17005 17006The ‘cut’ Command 17007================= 17008 17009The next program we’ll look at is the ‘cut’ command. This program cuts 17010out columns or fields of input data. For example, we can tell it to 17011print just the login name and full name from the ‘/etc/passwd’ file. 17012The ‘/etc/passwd’ file has seven fields, separated by colons: 17013 17014 arnold:xyzzy:2076:10:Arnold D. Robbins:/home/arnold:/bin/bash 17015 17016 To get the first and fifth fields, we would use ‘cut’ like this: 17017 17018 $ cut -d: -f1,5 /etc/passwd 17019 ⊣ root:Operator 17020 ... 17021 ⊣ arnold:Arnold D. Robbins 17022 ⊣ miriam:Miriam A. Robbins 17023 ... 17024 17025 With the ‘-c’ option, ‘cut’ will cut out specific characters (i.e., 17026columns) in the input lines. This is useful for input data that has 17027fixed width fields, and does not have a field separator. For example, 17028list the Monday dates for the current month: 17029 17030 $ cal | cut -c 3-5 17031 ⊣Mo 17032 ⊣ 17033 ⊣ 6 17034 ⊣ 13 17035 ⊣ 20 17036 ⊣ 27 17037 17038 17039File: coreutils.info, Node: The sort command, Next: The uniq command, Prev: The cut command, Up: Opening the software toolbox 17040 17041The ‘sort’ Command 17042================== 17043 17044Next we’ll look at the ‘sort’ command. This is one of the most powerful 17045commands on a Unix-style system; one that you will often find yourself 17046using when setting up fancy data plumbing. 17047 17048 The ‘sort’ command reads and sorts each file named on the command 17049line. It then merges the sorted data and writes it to standard output. 17050It will read standard input if no files are given on the command line 17051(thus making it into a filter). The sort is based on the character 17052collating sequence or based on user-supplied ordering criteria. 17053 17054 17055File: coreutils.info, Node: The uniq command, Next: Putting the tools together, Prev: The sort command, Up: Opening the software toolbox 17056 17057The ‘uniq’ Command 17058================== 17059 17060Finally (at least for now), we’ll look at the ‘uniq’ program. When 17061sorting data, you will often end up with duplicate lines, lines that are 17062identical. Usually, all you need is one instance of each line. This is 17063where ‘uniq’ comes in. The ‘uniq’ program reads its standard input. It 17064prints only one copy of each repeated line. It does have several 17065options. Later on, we’ll use the ‘-c’ option, which prints each unique 17066line, preceded by a count of the number of times that line occurred in 17067the input. 17068 17069 17070File: coreutils.info, Node: Putting the tools together, Prev: The uniq command, Up: Opening the software toolbox 17071 17072Putting the Tools Together 17073========================== 17074 17075Now, let’s suppose this is a large ISP server system with dozens of 17076users logged in. The management wants the system administrator to write 17077a program that will generate a sorted list of logged in users. 17078Furthermore, even if a user is logged in multiple times, his or her name 17079should only show up in the output once. 17080 17081 The administrator could sit down with the system documentation and 17082write a C program that did this. It would take perhaps a couple of 17083hundred lines of code and about two hours to write it, test it, and 17084debug it. However, knowing the software toolbox, the administrator can 17085instead start out by generating just a list of logged on users: 17086 17087 $ who | cut -c1-8 17088 ⊣ arnold 17089 ⊣ miriam 17090 ⊣ bill 17091 ⊣ arnold 17092 17093 Next, sort the list: 17094 17095 $ who | cut -c1-8 | sort 17096 ⊣ arnold 17097 ⊣ arnold 17098 ⊣ bill 17099 ⊣ miriam 17100 17101 Finally, run the sorted list through ‘uniq’, to weed out duplicates: 17102 17103 $ who | cut -c1-8 | sort | uniq 17104 ⊣ arnold 17105 ⊣ bill 17106 ⊣ miriam 17107 17108 The ‘sort’ command actually has a ‘-u’ option that does what ‘uniq’ 17109does. However, ‘uniq’ has other uses for which one cannot substitute 17110‘sort -u’. 17111 17112 The administrator puts this pipeline into a shell script, and makes 17113it available for all the users on the system (‘#’ is the system 17114administrator, or ‘root’, prompt): 17115 17116 # cat > /usr/local/bin/listusers 17117 who | cut -c1-8 | sort | uniq 17118 ^D 17119 # chmod +x /usr/local/bin/listusers 17120 17121 There are four major points to note here. First, with just four 17122programs, on one command line, the administrator was able to save about 17123two hours worth of work. Furthermore, the shell pipeline is just about 17124as efficient as the C program would be, and it is much more efficient in 17125terms of programmer time. People time is much more expensive than 17126computer time, and in our modern “there’s never enough time to do 17127everything” society, saving two hours of programmer time is no mean 17128feat. 17129 17130 Second, it is also important to emphasize that with the _combination_ 17131of the tools, it is possible to do a special purpose job never imagined 17132by the authors of the individual programs. 17133 17134 Third, it is also valuable to build up your pipeline in stages, as we 17135did here. This allows you to view the data at each stage in the 17136pipeline, which helps you acquire the confidence that you are indeed 17137using these tools correctly. 17138 17139 Finally, by bundling the pipeline in a shell script, other users can 17140use your command, without having to remember the fancy plumbing you set 17141up for them. In terms of how you run them, shell scripts and compiled 17142programs are indistinguishable. 17143 17144 After the previous warm-up exercise, we’ll look at two additional, 17145more complicated pipelines. For them, we need to introduce two more 17146tools. 17147 17148 The first is the ‘tr’ command, which stands for “transliterate.” The 17149‘tr’ command works on a character-by-character basis, changing 17150characters. Normally it is used for things like mapping upper case to 17151lower case: 17152 17153 $ echo ThIs ExAmPlE HaS MIXED case! | tr '[:upper:]' '[:lower:]' 17154 ⊣ this example has mixed case! 17155 17156 There are several options of interest: 17157 17158‘-c’ 17159 work on the complement of the listed characters, i.e., operations 17160 apply to characters not in the given set 17161 17162‘-d’ 17163 delete characters in the first set from the output 17164 17165‘-s’ 17166 squeeze repeated characters in the output into just one character. 17167 17168 We will be using all three options in a moment. 17169 17170 The other command we’ll look at is ‘comm’. The ‘comm’ command takes 17171two sorted input files as input data, and prints out the files’ lines in 17172three columns. The output columns are the data lines unique to the 17173first file, the data lines unique to the second file, and the data lines 17174that are common to both. The ‘-1’, ‘-2’, and ‘-3’ command line options 17175_omit_ the respective columns. (This is non-intuitive and takes a 17176little getting used to.) For example: 17177 17178 $ cat f1 17179 ⊣ 11111 17180 ⊣ 22222 17181 ⊣ 33333 17182 ⊣ 44444 17183 $ cat f2 17184 ⊣ 00000 17185 ⊣ 22222 17186 ⊣ 33333 17187 ⊣ 55555 17188 $ comm f1 f2 17189 ⊣ 00000 17190 ⊣ 11111 17191 ⊣ 22222 17192 ⊣ 33333 17193 ⊣ 44444 17194 ⊣ 55555 17195 17196 The file name ‘-’ tells ‘comm’ to read standard input instead of a 17197regular file. 17198 17199 Now we’re ready to build a fancy pipeline. The first application is 17200a word frequency counter. This helps an author determine if he or she 17201is over-using certain words. 17202 17203 The first step is to change the case of all the letters in our input 17204file to one case. “The” and “the” are the same word when doing 17205counting. 17206 17207 $ tr '[:upper:]' '[:lower:]' < whats.gnu | ... 17208 17209 The next step is to get rid of punctuation. Quoted words and 17210unquoted words should be treated identically; it’s easiest to just get 17211the punctuation out of the way. 17212 17213 $ tr '[:upper:]' '[:lower:]' < whats.gnu | tr -cd '[:alnum:]_ \n' | ... 17214 17215 The second ‘tr’ command operates on the complement of the listed 17216characters, which are all the letters, the digits, the underscore, and 17217the blank. The ‘\n’ represents the newline character; it has to be left 17218alone. (The ASCII tab character should also be included for good 17219measure in a production script.) 17220 17221 At this point, we have data consisting of words separated by blank 17222space. The words only contain alphanumeric characters (and the 17223underscore). The next step is break the data apart so that we have one 17224word per line. This makes the counting operation much easier, as we 17225will see shortly. 17226 17227 $ tr '[:upper:]' '[:lower:]' < whats.gnu | tr -cd '[:alnum:]_ \n' | 17228 > tr -s ' ' '\n' | ... 17229 17230 This command turns blanks into newlines. The ‘-s’ option squeezes 17231multiple newline characters in the output into just one, removing blank 17232lines. (The ‘>’ is the shell’s “secondary prompt.” This is what the 17233shell prints when it notices you haven’t finished typing in all of a 17234command.) 17235 17236 We now have data consisting of one word per line, no punctuation, all 17237one case. We’re ready to count each word: 17238 17239 $ tr '[:upper:]' '[:lower:]' < whats.gnu | tr -cd '[:alnum:]_ \n' | 17240 > tr -s ' ' '\n' | sort | uniq -c | ... 17241 17242 At this point, the data might look something like this: 17243 17244 60 a 17245 2 able 17246 6 about 17247 1 above 17248 2 accomplish 17249 1 acquire 17250 1 actually 17251 2 additional 17252 17253 The output is sorted by word, not by count! What we want is the most 17254frequently used words first. Fortunately, this is easy to accomplish, 17255with the help of two more ‘sort’ options: 17256 17257‘-n’ 17258 do a numeric sort, not a textual one 17259 17260‘-r’ 17261 reverse the order of the sort 17262 17263 The final pipeline looks like this: 17264 17265 $ tr '[:upper:]' '[:lower:]' < whats.gnu | tr -cd '[:alnum:]_ \n' | 17266 > tr -s ' ' '\n' | sort | uniq -c | sort -n -r 17267 ⊣ 156 the 17268 ⊣ 60 a 17269 ⊣ 58 to 17270 ⊣ 51 of 17271 ⊣ 51 and 17272 ... 17273 17274 Whew! That’s a lot to digest. Yet, the same principles apply. With 17275six commands, on two lines (really one long one split for convenience), 17276we’ve created a program that does something interesting and useful, in 17277much less time than we could have written a C program to do the same 17278thing. 17279 17280 A minor modification to the above pipeline can give us a simple 17281spelling checker! To determine if you’ve spelled a word correctly, all 17282you have to do is look it up in a dictionary. If it is not there, then 17283chances are that your spelling is incorrect. So, we need a dictionary. 17284The conventional location for a dictionary is ‘/usr/dict/words’. On my 17285GNU/Linux system,(1) this is a sorted, 45,402 word dictionary. 17286 17287 Now, how to compare our file with the dictionary? As before, we 17288generate a sorted list of words, one per line: 17289 17290 $ tr '[:upper:]' '[:lower:]' < whats.gnu | tr -cd '[:alnum:]_ \n' | 17291 > tr -s ' ' '\n' | sort -u | ... 17292 17293 Now, all we need is a list of words that are _not_ in the dictionary. 17294Here is where the ‘comm’ command comes in. 17295 17296 $ tr '[:upper:]' '[:lower:]' < whats.gnu | tr -cd '[:alnum:]_ \n' | 17297 > tr -s ' ' '\n' | sort -u | 17298 > comm -23 - /usr/dict/words 17299 17300 The ‘-2’ and ‘-3’ options eliminate lines that are only in the 17301dictionary (the second file), and lines that are in both files. Lines 17302only in the first file (standard input, our stream of words), are words 17303that are not in the dictionary. These are likely candidates for 17304spelling errors. This pipeline was the first cut at a production 17305spelling checker on Unix. 17306 17307 There are some other tools that deserve brief mention. 17308 17309‘grep’ 17310 search files for text that matches a regular expression 17311 17312‘wc’ 17313 count lines, words, characters 17314 17315‘tee’ 17316 a T-fitting for data pipes, copies data to files and to standard 17317 output 17318 17319‘sed’ 17320 the stream editor, an advanced tool 17321 17322‘awk’ 17323 a data manipulation language, another advanced tool 17324 17325 The software tools philosophy also espoused the following bit of 17326advice: “Let someone else do the hard part.” This means, take something 17327that gives you most of what you need, and then massage it the rest of 17328the way until it’s in the form that you want. 17329 17330 To summarize: 17331 17332 1. Each program should do one thing well. No more, no less. 17333 17334 2. Combining programs with appropriate plumbing leads to results where 17335 the whole is greater than the sum of the parts. It also leads to 17336 novel uses of programs that the authors might never have imagined. 17337 17338 3. Programs should never print extraneous header or trailer data, 17339 since these could get sent on down a pipeline. (A point we didn’t 17340 mention earlier.) 17341 17342 4. Let someone else do the hard part. 17343 17344 5. Know your toolbox! Use each program appropriately. If you don’t 17345 have an appropriate tool, build one. 17346 17347 All the programs discussed are available as described in GNU core 17348utilities (https://www.gnu.org/software/coreutils/coreutils.html). 17349 17350 None of what I have presented in this column is new. The Software 17351Tools philosophy was first introduced in the book ‘Software Tools’, by 17352Brian Kernighan and P.J. Plauger (Addison-Wesley, ISBN 0-201-03669-X). 17353This book showed how to write and use software tools. It was written in 173541976, using a preprocessor for FORTRAN named ‘ratfor’ (RATional 17355FORtran). At the time, C was not as ubiquitous as it is now; FORTRAN 17356was. The last chapter presented a ‘ratfor’ to FORTRAN processor, 17357written in ‘ratfor’. ‘ratfor’ looks an awful lot like C; if you know C, 17358you won’t have any problem following the code. 17359 17360 In 1981, the book was updated and made available as ‘Software Tools 17361in Pascal’ (Addison-Wesley, ISBN 0-201-10342-7). Both books are still 17362in print and are well worth reading if you’re a programmer. They 17363certainly made a major change in how I view programming. 17364 17365 The programs in both books are available from Brian Kernighan’s home 17366page (https://www.cs.princeton.edu/~bwk/). For a number of years, there 17367was an active Software Tools Users Group, whose members had ported the 17368original ‘ratfor’ programs to essentially every computer system with a 17369FORTRAN compiler. The popularity of the group waned in the middle 1980s 17370as Unix began to spread beyond universities. 17371 17372 With the current proliferation of GNU code and other clones of Unix 17373programs, these programs now receive little attention; modern C versions 17374are much more efficient and do more than these programs do. 17375Nevertheless, as exposition of good programming style, and evangelism 17376for a still-valuable philosophy, these books are unparalleled, and I 17377recommend them highly. 17378 17379 Acknowledgment: I would like to express my gratitude to Brian 17380Kernighan of Bell Labs, the original Software Toolsmith, for reviewing 17381this column. 17382 17383 ---------- Footnotes ---------- 17384 17385 (1) Redhat Linux 6.1, for the November 2000 revision of this article. 17386 17387 17388File: coreutils.info, Node: GNU Free Documentation License, Next: Concept index, Prev: Opening the software toolbox, Up: Top 17389 17390Appendix A GNU Free Documentation License 17391***************************************** 17392 17393 Version 1.3, 3 November 2008 17394 17395 Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc. 17396 <https://fsf.org/> 17397 17398 Everyone is permitted to copy and distribute verbatim copies 17399 of this license document, but changing it is not allowed. 17400 17401 0. PREAMBLE 17402 17403 The purpose of this License is to make a manual, textbook, or other 17404 functional and useful document “free” in the sense of freedom: to 17405 assure everyone the effective freedom to copy and redistribute it, 17406 with or without modifying it, either commercially or 17407 noncommercially. Secondarily, this License preserves for the 17408 author and publisher a way to get credit for their work, while not 17409 being considered responsible for modifications made by others. 17410 17411 This License is a kind of “copyleft”, which means that derivative 17412 works of the document must themselves be free in the same sense. 17413 It complements the GNU General Public License, which is a copyleft 17414 license designed for free software. 17415 17416 We have designed this License in order to use it for manuals for 17417 free software, because free software needs free documentation: a 17418 free program should come with manuals providing the same freedoms 17419 that the software does. But this License is not limited to 17420 software manuals; it can be used for any textual work, regardless 17421 of subject matter or whether it is published as a printed book. We 17422 recommend this License principally for works whose purpose is 17423 instruction or reference. 17424 17425 1. APPLICABILITY AND DEFINITIONS 17426 17427 This License applies to any manual or other work, in any medium, 17428 that contains a notice placed by the copyright holder saying it can 17429 be distributed under the terms of this License. Such a notice 17430 grants a world-wide, royalty-free license, unlimited in duration, 17431 to use that work under the conditions stated herein. The 17432 “Document”, below, refers to any such manual or work. Any member 17433 of the public is a licensee, and is addressed as “you”. You accept 17434 the license if you copy, modify or distribute the work in a way 17435 requiring permission under copyright law. 17436 17437 A “Modified Version” of the Document means any work containing the 17438 Document or a portion of it, either copied verbatim, or with 17439 modifications and/or translated into another language. 17440 17441 A “Secondary Section” is a named appendix or a front-matter section 17442 of the Document that deals exclusively with the relationship of the 17443 publishers or authors of the Document to the Document’s overall 17444 subject (or to related matters) and contains nothing that could 17445 fall directly within that overall subject. (Thus, if the Document 17446 is in part a textbook of mathematics, a Secondary Section may not 17447 explain any mathematics.) The relationship could be a matter of 17448 historical connection with the subject or with related matters, or 17449 of legal, commercial, philosophical, ethical or political position 17450 regarding them. 17451 17452 The “Invariant Sections” are certain Secondary Sections whose 17453 titles are designated, as being those of Invariant Sections, in the 17454 notice that says that the Document is released under this License. 17455 If a section does not fit the above definition of Secondary then it 17456 is not allowed to be designated as Invariant. The Document may 17457 contain zero Invariant Sections. If the Document does not identify 17458 any Invariant Sections then there are none. 17459 17460 The “Cover Texts” are certain short passages of text that are 17461 listed, as Front-Cover Texts or Back-Cover Texts, in the notice 17462 that says that the Document is released under this License. A 17463 Front-Cover Text may be at most 5 words, and a Back-Cover Text may 17464 be at most 25 words. 17465 17466 A “Transparent” copy of the Document means a machine-readable copy, 17467 represented in a format whose specification is available to the 17468 general public, that is suitable for revising the document 17469 straightforwardly with generic text editors or (for images composed 17470 of pixels) generic paint programs or (for drawings) some widely 17471 available drawing editor, and that is suitable for input to text 17472 formatters or for automatic translation to a variety of formats 17473 suitable for input to text formatters. A copy made in an otherwise 17474 Transparent file format whose markup, or absence of markup, has 17475 been arranged to thwart or discourage subsequent modification by 17476 readers is not Transparent. An image format is not Transparent if 17477 used for any substantial amount of text. A copy that is not 17478 “Transparent” is called “Opaque”. 17479 17480 Examples of suitable formats for Transparent copies include plain 17481 ASCII without markup, Texinfo input format, LaTeX input format, 17482 SGML or XML using a publicly available DTD, and standard-conforming 17483 simple HTML, PostScript or PDF designed for human modification. 17484 Examples of transparent image formats include PNG, XCF and JPG. 17485 Opaque formats include proprietary formats that can be read and 17486 edited only by proprietary word processors, SGML or XML for which 17487 the DTD and/or processing tools are not generally available, and 17488 the machine-generated HTML, PostScript or PDF produced by some word 17489 processors for output purposes only. 17490 17491 The “Title Page” means, for a printed book, the title page itself, 17492 plus such following pages as are needed to hold, legibly, the 17493 material this License requires to appear in the title page. For 17494 works in formats which do not have any title page as such, “Title 17495 Page” means the text near the most prominent appearance of the 17496 work’s title, preceding the beginning of the body of the text. 17497 17498 The “publisher” means any person or entity that distributes copies 17499 of the Document to the public. 17500 17501 A section “Entitled XYZ” means a named subunit of the Document 17502 whose title either is precisely XYZ or contains XYZ in parentheses 17503 following text that translates XYZ in another language. (Here XYZ 17504 stands for a specific section name mentioned below, such as 17505 “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) 17506 To “Preserve the Title” of such a section when you modify the 17507 Document means that it remains a section “Entitled XYZ” according 17508 to this definition. 17509 17510 The Document may include Warranty Disclaimers next to the notice 17511 which states that this License applies to the Document. These 17512 Warranty Disclaimers are considered to be included by reference in 17513 this License, but only as regards disclaiming warranties: any other 17514 implication that these Warranty Disclaimers may have is void and 17515 has no effect on the meaning of this License. 17516 17517 2. VERBATIM COPYING 17518 17519 You may copy and distribute the Document in any medium, either 17520 commercially or noncommercially, provided that this License, the 17521 copyright notices, and the license notice saying this License 17522 applies to the Document are reproduced in all copies, and that you 17523 add no other conditions whatsoever to those of this License. You 17524 may not use technical measures to obstruct or control the reading 17525 or further copying of the copies you make or distribute. However, 17526 you may accept compensation in exchange for copies. If you 17527 distribute a large enough number of copies you must also follow the 17528 conditions in section 3. 17529 17530 You may also lend copies, under the same conditions stated above, 17531 and you may publicly display copies. 17532 17533 3. COPYING IN QUANTITY 17534 17535 If you publish printed copies (or copies in media that commonly 17536 have printed covers) of the Document, numbering more than 100, and 17537 the Document’s license notice requires Cover Texts, you must 17538 enclose the copies in covers that carry, clearly and legibly, all 17539 these Cover Texts: Front-Cover Texts on the front cover, and 17540 Back-Cover Texts on the back cover. Both covers must also clearly 17541 and legibly identify you as the publisher of these copies. The 17542 front cover must present the full title with all words of the title 17543 equally prominent and visible. You may add other material on the 17544 covers in addition. Copying with changes limited to the covers, as 17545 long as they preserve the title of the Document and satisfy these 17546 conditions, can be treated as verbatim copying in other respects. 17547 17548 If the required texts for either cover are too voluminous to fit 17549 legibly, you should put the first ones listed (as many as fit 17550 reasonably) on the actual cover, and continue the rest onto 17551 adjacent pages. 17552 17553 If you publish or distribute Opaque copies of the Document 17554 numbering more than 100, you must either include a machine-readable 17555 Transparent copy along with each Opaque copy, or state in or with 17556 each Opaque copy a computer-network location from which the general 17557 network-using public has access to download using public-standard 17558 network protocols a complete Transparent copy of the Document, free 17559 of added material. If you use the latter option, you must take 17560 reasonably prudent steps, when you begin distribution of Opaque 17561 copies in quantity, to ensure that this Transparent copy will 17562 remain thus accessible at the stated location until at least one 17563 year after the last time you distribute an Opaque copy (directly or 17564 through your agents or retailers) of that edition to the public. 17565 17566 It is requested, but not required, that you contact the authors of 17567 the Document well before redistributing any large number of copies, 17568 to give them a chance to provide you with an updated version of the 17569 Document. 17570 17571 4. MODIFICATIONS 17572 17573 You may copy and distribute a Modified Version of the Document 17574 under the conditions of sections 2 and 3 above, provided that you 17575 release the Modified Version under precisely this License, with the 17576 Modified Version filling the role of the Document, thus licensing 17577 distribution and modification of the Modified Version to whoever 17578 possesses a copy of it. In addition, you must do these things in 17579 the Modified Version: 17580 17581 A. Use in the Title Page (and on the covers, if any) a title 17582 distinct from that of the Document, and from those of previous 17583 versions (which should, if there were any, be listed in the 17584 History section of the Document). You may use the same title 17585 as a previous version if the original publisher of that 17586 version gives permission. 17587 17588 B. List on the Title Page, as authors, one or more persons or 17589 entities responsible for authorship of the modifications in 17590 the Modified Version, together with at least five of the 17591 principal authors of the Document (all of its principal 17592 authors, if it has fewer than five), unless they release you 17593 from this requirement. 17594 17595 C. State on the Title page the name of the publisher of the 17596 Modified Version, as the publisher. 17597 17598 D. Preserve all the copyright notices of the Document. 17599 17600 E. Add an appropriate copyright notice for your modifications 17601 adjacent to the other copyright notices. 17602 17603 F. Include, immediately after the copyright notices, a license 17604 notice giving the public permission to use the Modified 17605 Version under the terms of this License, in the form shown in 17606 the Addendum below. 17607 17608 G. Preserve in that license notice the full lists of Invariant 17609 Sections and required Cover Texts given in the Document’s 17610 license notice. 17611 17612 H. Include an unaltered copy of this License. 17613 17614 I. Preserve the section Entitled “History”, Preserve its Title, 17615 and add to it an item stating at least the title, year, new 17616 authors, and publisher of the Modified Version as given on the 17617 Title Page. If there is no section Entitled “History” in the 17618 Document, create one stating the title, year, authors, and 17619 publisher of the Document as given on its Title Page, then add 17620 an item describing the Modified Version as stated in the 17621 previous sentence. 17622 17623 J. Preserve the network location, if any, given in the Document 17624 for public access to a Transparent copy of the Document, and 17625 likewise the network locations given in the Document for 17626 previous versions it was based on. These may be placed in the 17627 “History” section. You may omit a network location for a work 17628 that was published at least four years before the Document 17629 itself, or if the original publisher of the version it refers 17630 to gives permission. 17631 17632 K. For any section Entitled “Acknowledgements” or “Dedications”, 17633 Preserve the Title of the section, and preserve in the section 17634 all the substance and tone of each of the contributor 17635 acknowledgements and/or dedications given therein. 17636 17637 L. Preserve all the Invariant Sections of the Document, unaltered 17638 in their text and in their titles. Section numbers or the 17639 equivalent are not considered part of the section titles. 17640 17641 M. Delete any section Entitled “Endorsements”. Such a section 17642 may not be included in the Modified Version. 17643 17644 N. Do not retitle any existing section to be Entitled 17645 “Endorsements” or to conflict in title with any Invariant 17646 Section. 17647 17648 O. Preserve any Warranty Disclaimers. 17649 17650 If the Modified Version includes new front-matter sections or 17651 appendices that qualify as Secondary Sections and contain no 17652 material copied from the Document, you may at your option designate 17653 some or all of these sections as invariant. To do this, add their 17654 titles to the list of Invariant Sections in the Modified Version’s 17655 license notice. These titles must be distinct from any other 17656 section titles. 17657 17658 You may add a section Entitled “Endorsements”, provided it contains 17659 nothing but endorsements of your Modified Version by various 17660 parties—for example, statements of peer review or that the text has 17661 been approved by an organization as the authoritative definition of 17662 a standard. 17663 17664 You may add a passage of up to five words as a Front-Cover Text, 17665 and a passage of up to 25 words as a Back-Cover Text, to the end of 17666 the list of Cover Texts in the Modified Version. Only one passage 17667 of Front-Cover Text and one of Back-Cover Text may be added by (or 17668 through arrangements made by) any one entity. If the Document 17669 already includes a cover text for the same cover, previously added 17670 by you or by arrangement made by the same entity you are acting on 17671 behalf of, you may not add another; but you may replace the old 17672 one, on explicit permission from the previous publisher that added 17673 the old one. 17674 17675 The author(s) and publisher(s) of the Document do not by this 17676 License give permission to use their names for publicity for or to 17677 assert or imply endorsement of any Modified Version. 17678 17679 5. COMBINING DOCUMENTS 17680 17681 You may combine the Document with other documents released under 17682 this License, under the terms defined in section 4 above for 17683 modified versions, provided that you include in the combination all 17684 of the Invariant Sections of all of the original documents, 17685 unmodified, and list them all as Invariant Sections of your 17686 combined work in its license notice, and that you preserve all 17687 their Warranty Disclaimers. 17688 17689 The combined work need only contain one copy of this License, and 17690 multiple identical Invariant Sections may be replaced with a single 17691 copy. If there are multiple Invariant Sections with the same name 17692 but different contents, make the title of each such section unique 17693 by adding at the end of it, in parentheses, the name of the 17694 original author or publisher of that section if known, or else a 17695 unique number. Make the same adjustment to the section titles in 17696 the list of Invariant Sections in the license notice of the 17697 combined work. 17698 17699 In the combination, you must combine any sections Entitled 17700 “History” in the various original documents, forming one section 17701 Entitled “History”; likewise combine any sections Entitled 17702 “Acknowledgements”, and any sections Entitled “Dedications”. You 17703 must delete all sections Entitled “Endorsements.” 17704 17705 6. COLLECTIONS OF DOCUMENTS 17706 17707 You may make a collection consisting of the Document and other 17708 documents released under this License, and replace the individual 17709 copies of this License in the various documents with a single copy 17710 that is included in the collection, provided that you follow the 17711 rules of this License for verbatim copying of each of the documents 17712 in all other respects. 17713 17714 You may extract a single document from such a collection, and 17715 distribute it individually under this License, provided you insert 17716 a copy of this License into the extracted document, and follow this 17717 License in all other respects regarding verbatim copying of that 17718 document. 17719 17720 7. AGGREGATION WITH INDEPENDENT WORKS 17721 17722 A compilation of the Document or its derivatives with other 17723 separate and independent documents or works, in or on a volume of a 17724 storage or distribution medium, is called an “aggregate” if the 17725 copyright resulting from the compilation is not used to limit the 17726 legal rights of the compilation’s users beyond what the individual 17727 works permit. When the Document is included in an aggregate, this 17728 License does not apply to the other works in the aggregate which 17729 are not themselves derivative works of the Document. 17730 17731 If the Cover Text requirement of section 3 is applicable to these 17732 copies of the Document, then if the Document is less than one half 17733 of the entire aggregate, the Document’s Cover Texts may be placed 17734 on covers that bracket the Document within the aggregate, or the 17735 electronic equivalent of covers if the Document is in electronic 17736 form. Otherwise they must appear on printed covers that bracket 17737 the whole aggregate. 17738 17739 8. TRANSLATION 17740 17741 Translation is considered a kind of modification, so you may 17742 distribute translations of the Document under the terms of section 17743 4. Replacing Invariant Sections with translations requires special 17744 permission from their copyright holders, but you may include 17745 translations of some or all Invariant Sections in addition to the 17746 original versions of these Invariant Sections. You may include a 17747 translation of this License, and all the license notices in the 17748 Document, and any Warranty Disclaimers, provided that you also 17749 include the original English version of this License and the 17750 original versions of those notices and disclaimers. In case of a 17751 disagreement between the translation and the original version of 17752 this License or a notice or disclaimer, the original version will 17753 prevail. 17754 17755 If a section in the Document is Entitled “Acknowledgements”, 17756 “Dedications”, or “History”, the requirement (section 4) to 17757 Preserve its Title (section 1) will typically require changing the 17758 actual title. 17759 17760 9. TERMINATION 17761 17762 You may not copy, modify, sublicense, or distribute the Document 17763 except as expressly provided under this License. Any attempt 17764 otherwise to copy, modify, sublicense, or distribute it is void, 17765 and will automatically terminate your rights under this License. 17766 17767 However, if you cease all violation of this License, then your 17768 license from a particular copyright holder is reinstated (a) 17769 provisionally, unless and until the copyright holder explicitly and 17770 finally terminates your license, and (b) permanently, if the 17771 copyright holder fails to notify you of the violation by some 17772 reasonable means prior to 60 days after the cessation. 17773 17774 Moreover, your license from a particular copyright holder is 17775 reinstated permanently if the copyright holder notifies you of the 17776 violation by some reasonable means, this is the first time you have 17777 received notice of violation of this License (for any work) from 17778 that copyright holder, and you cure the violation prior to 30 days 17779 after your receipt of the notice. 17780 17781 Termination of your rights under this section does not terminate 17782 the licenses of parties who have received copies or rights from you 17783 under this License. If your rights have been terminated and not 17784 permanently reinstated, receipt of a copy of some or all of the 17785 same material does not give you any rights to use it. 17786 17787 10. FUTURE REVISIONS OF THIS LICENSE 17788 17789 The Free Software Foundation may publish new, revised versions of 17790 the GNU Free Documentation License from time to time. Such new 17791 versions will be similar in spirit to the present version, but may 17792 differ in detail to address new problems or concerns. See 17793 <https://www.gnu.org/copyleft/>. 17794 17795 Each version of the License is given a distinguishing version 17796 number. If the Document specifies that a particular numbered 17797 version of this License “or any later version” applies to it, you 17798 have the option of following the terms and conditions either of 17799 that specified version or of any later version that has been 17800 published (not as a draft) by the Free Software Foundation. If the 17801 Document does not specify a version number of this License, you may 17802 choose any version ever published (not as a draft) by the Free 17803 Software Foundation. If the Document specifies that a proxy can 17804 decide which future versions of this License can be used, that 17805 proxy’s public statement of acceptance of a version permanently 17806 authorizes you to choose that version for the Document. 17807 17808 11. RELICENSING 17809 17810 “Massive Multiauthor Collaboration Site” (or “MMC Site”) means any 17811 World Wide Web server that publishes copyrightable works and also 17812 provides prominent facilities for anybody to edit those works. A 17813 public wiki that anybody can edit is an example of such a server. 17814 A “Massive Multiauthor Collaboration” (or “MMC”) contained in the 17815 site means any set of copyrightable works thus published on the MMC 17816 site. 17817 17818 “CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 17819 license published by Creative Commons Corporation, a not-for-profit 17820 corporation with a principal place of business in San Francisco, 17821 California, as well as future copyleft versions of that license 17822 published by that same organization. 17823 17824 “Incorporate” means to publish or republish a Document, in whole or 17825 in part, as part of another Document. 17826 17827 An MMC is “eligible for relicensing” if it is licensed under this 17828 License, and if all works that were first published under this 17829 License somewhere other than this MMC, and subsequently 17830 incorporated in whole or in part into the MMC, (1) had no cover 17831 texts or invariant sections, and (2) were thus incorporated prior 17832 to November 1, 2008. 17833 17834 The operator of an MMC Site may republish an MMC contained in the 17835 site under CC-BY-SA on the same site at any time before August 1, 17836 2009, provided the MMC is eligible for relicensing. 17837 17838ADDENDUM: How to use this License for your documents 17839==================================================== 17840 17841To use this License in a document you have written, include a copy of 17842the License in the document and put the following copyright and license 17843notices just after the title page: 17844 17845 Copyright (C) YEAR YOUR NAME. 17846 Permission is granted to copy, distribute and/or modify this document 17847 under the terms of the GNU Free Documentation License, Version 1.3 17848 or any later version published by the Free Software Foundation; 17849 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover 17850 Texts. A copy of the license is included in the section entitled ``GNU 17851 Free Documentation License''. 17852 17853 If you have Invariant Sections, Front-Cover Texts and Back-Cover 17854Texts, replace the “with...Texts.” line with this: 17855 17856 with the Invariant Sections being LIST THEIR TITLES, with 17857 the Front-Cover Texts being LIST, and with the Back-Cover Texts 17858 being LIST. 17859 17860 If you have Invariant Sections without Cover Texts, or some other 17861combination of the three, merge those two alternatives to suit the 17862situation. 17863 17864 If your document contains nontrivial examples of program code, we 17865recommend releasing these examples in parallel under your choice of free 17866software license, such as the GNU General Public License, to permit 17867their use in free software. 17868 17869 17870File: coreutils.info, Node: Concept index, Prev: GNU Free Documentation License, Up: Top 17871 17872Index 17873***** 17874 17875�[index�] 17876* Menu: 17877 17878* !: Connectives for test. 17879 (line 23) 17880* !=: String tests. (line 28) 17881* %: Numeric expressions. (line 16) 17882* %b: printf invocation. (line 37) 17883* %q: printf invocation. (line 44) 17884* &: Relations for expr. (line 17) 17885* *: Numeric expressions. (line 16) 17886* +: String expressions. (line 53) 17887* + <1>: Numeric expressions. (line 12) 17888* +PAGE_RANGE: pr invocation. (line 39) 17889* -: Numeric expressions. (line 12) 17890* - <1>: env invocation. (line 102) 17891* - and Unix rm: rm invocation. (line 113) 17892* -, removing files beginning with: rm invocation. (line 101) 17893* --: Common options. (line 43) 17894* --across: pr invocation. (line 62) 17895* --additional-suffix: split invocation. (line 135) 17896* --address-radix: od invocation. (line 36) 17897* --adjustment: nice invocation. (line 51) 17898* --all: unexpand invocation. (line 51) 17899* --all <1>: Which files are listed. 17900 (line 13) 17901* --all <2>: df invocation. (line 42) 17902* --all <3>: du invocation. (line 32) 17903* --all <4>: stty invocation. (line 26) 17904* --all <5>: who invocation. (line 35) 17905* --all <6>: nproc invocation. (line 20) 17906* --all <7>: uname invocation. (line 30) 17907* --all-repeated: uniq invocation. (line 69) 17908* --almost-all: Which files are listed. 17909 (line 17) 17910* --apparent-size: du invocation. (line 35) 17911* --append: tee invocation. (line 27) 17912* --archive: cp invocation. (line 63) 17913* --attributes-only: cp invocation. (line 72) 17914* --author: What information is listed. 17915 (line 10) 17916* --auto-reference: Output formatting in ptx. 17917 (line 45) 17918* --backup: Backup options. (line 13) 17919* --backup <1>: cp invocation. (line 79) 17920* --backup <2>: install invocation. (line 41) 17921* --backup <3>: mv invocation. (line 59) 17922* --backup <4>: ln invocation. (line 82) 17923* --base16: basenc invocation. (line 49) 17924* --base2lsbf: basenc invocation. (line 55) 17925* --base2msbf: basenc invocation. (line 59) 17926* --base32: basenc invocation. (line 35) 17927* --base32hex: basenc invocation. (line 42) 17928* --base64: basenc invocation. (line 23) 17929* --base64url: basenc invocation. (line 29) 17930* --batch-size: sort invocation. (line 262) 17931* --before: tac invocation. (line 21) 17932* --binary: md5sum invocation. (line 41) 17933* --block-size: Block size. (line 121) 17934* --block-size <1>: df invocation. (line 54) 17935* --block-size <2>: du invocation. (line 52) 17936* --block-size=SIZE: Block size. (line 12) 17937* --body-numbering: nl invocation. (line 45) 17938* --boot: who invocation. (line 39) 17939* --bourne-shell: dircolors invocation. 17940 (line 34) 17941* --break-file: Input processing in ptx. 17942 (line 8) 17943* --buffer-size: sort invocation. (line 316) 17944* --bytes: fold invocation. (line 23) 17945* --bytes <1>: head invocation. (line 24) 17946* --bytes <2>: tail invocation. (line 39) 17947* --bytes <3>: split invocation. (line 41) 17948* --bytes <4>: wc invocation. (line 43) 17949* --bytes <5>: cut invocation. (line 26) 17950* --bytes <6>: du invocation. (line 57) 17951* --c-shell: dircolors invocation. 17952 (line 40) 17953* --cached=MODE: stat invocation. (line 33) 17954* --canonicalize: readlink invocation. (line 31) 17955* --canonicalize-existing: readlink invocation. (line 38) 17956* --canonicalize-existing <1>: realpath invocation. (line 22) 17957* --canonicalize-missing: readlink invocation. (line 45) 17958* --canonicalize-missing <1>: realpath invocation. (line 30) 17959* --changes: chown invocation. (line 73) 17960* --changes <1>: chgrp invocation. (line 24) 17961* --changes <2>: chmod invocation. (line 43) 17962* --characters: cut invocation. (line 34) 17963* --chars: wc invocation. (line 47) 17964* --chdir: env invocation. (line 107) 17965* --check: sort invocation. (line 39) 17966* --check <1>: sort invocation. (line 47) 17967* --check-chars: uniq invocation. (line 133) 17968* --classify: General output formatting. 17969 (line 46) 17970* --color: General output formatting. 17971 (line 22) 17972* --columns: pr invocation. (line 49) 17973* --compare: install invocation. (line 46) 17974* --complement: cut invocation. (line 86) 17975* --compute: runcon invocation. (line 32) 17976* --context: What information is listed. 17977 (line 259) 17978* --context <1>: cp invocation. (line 384) 17979* --context <2>: install invocation. (line 139) 17980* --context <3>: mv invocation. (line 117) 17981* --context <4>: mkdir invocation. (line 56) 17982* --context <5>: mkfifo invocation. (line 28) 17983* --context <6>: mknod invocation. (line 53) 17984* --context <7>: id invocation. (line 51) 17985* --count: uniq invocation. (line 55) 17986* --count <1>: who invocation. (line 69) 17987* --count-links: du invocation. (line 123) 17988* --crown-margin: fmt invocation. (line 34) 17989* --csh: dircolors invocation. 17990 (line 40) 17991* --data: sync invocation. (line 32) 17992* --date: touch invocation. (line 56) 17993* --date <1>: Options for date. (line 11) 17994* --dead: who invocation. (line 43) 17995* --debug: Options for date. (line 25) 17996* --debug <1>: env invocation. (line 173) 17997* --debug <2>: numfmt invocation. (line 29) 17998* --decode: base64 invocation. (line 30) 17999* --delimiter: cut invocation. (line 66) 18000* --delimiter <1>: numfmt invocation. (line 34) 18001* --delimiters: paste invocation. (line 61) 18002* --dereference: Which files are listed. 18003 (line 83) 18004* --dereference <1>: cp invocation. (line 149) 18005* --dereference <2>: chown invocation. (line 106) 18006* --dereference <3>: chgrp invocation. (line 34) 18007* --dereference <4>: du invocation. (line 117) 18008* --dereference <5>: stat invocation. (line 22) 18009* --dereference <6>: chcon invocation. (line 21) 18010* --dereference-args: du invocation. (line 67) 18011* --dereference-command-line: Which files are listed. 18012 (line 36) 18013* --dereference-command-line-symlink-to-dir: Which files are listed. 18014 (line 41) 18015* --dictionary-order: sort invocation. (line 87) 18016* --digits: csplit invocation. (line 81) 18017* --dir: rm invocation. (line 35) 18018* --directory: Which files are listed. 18019 (line 28) 18020* --directory <1>: install invocation. (line 67) 18021* --directory <2>: ln invocation. (line 88) 18022* --directory <3>: mktemp invocation. (line 85) 18023* --dired: What information is listed. 18024 (line 16) 18025* --double-space: pr invocation. (line 74) 18026* --dry-run: mktemp invocation. (line 97) 18027* --echo: shuf invocation. (line 19) 18028* --elide-empty-files: split invocation. (line 140) 18029* --elide-empty-files <1>: csplit invocation. (line 95) 18030* --endian: od invocation. (line 51) 18031* --equal-width: seq invocation. (line 49) 18032* --error: stdbuf invocation. (line 34) 18033* --escape: Formatting the file names. 18034 (line 11) 18035* --exact: shred invocation. (line 164) 18036* --exclude-from=FILE: du invocation. (line 252) 18037* --exclude-type: df invocation. (line 223) 18038* --exclude=PATTERN: du invocation. (line 257) 18039* --expand-tabs: pr invocation. (line 98) 18040* --field: numfmt invocation. (line 38) 18041* --field-separator: sort invocation. (line 332) 18042* --fields: cut invocation. (line 43) 18043* --file: stty invocation. (line 31) 18044* --file <1>: Options for date. (line 30) 18045* --file-system: stat invocation. (line 28) 18046* --file-system <1>: sync invocation. (line 37) 18047* --file-type: General output formatting. 18048 (line 57) 18049* --files0-from=FILE: wc invocation. (line 64) 18050* --files0-from=FILE <1>: sort invocation. (line 218) 18051* --files0-from=FILE <2>: du invocation. (line 79) 18052* --filter: split invocation. (line 63) 18053* --first-line-number: pr invocation. (line 174) 18054* --flag-truncation: Output formatting in ptx. 18055 (line 71) 18056* --follow: tail invocation. (line 56) 18057* --footer-numbering: nl invocation. (line 70) 18058* --force: cp invocation. (line 115) 18059* --force <1>: mv invocation. (line 64) 18060* --force <2>: rm invocation. (line 39) 18061* --force <3>: shred invocation. (line 123) 18062* --force <4>: ln invocation. (line 94) 18063* --foreground: timeout invocation. (line 24) 18064* --form-feed: pr invocation. (line 106) 18065* --format: od invocation. (line 90) 18066* --format <1>: What information is listed. 18067 (line 131) 18068* --format <2>: General output formatting. 18069 (line 10) 18070* --format <3>: General output formatting. 18071 (line 16) 18072* --format <4>: General output formatting. 18073 (line 103) 18074* --format <5>: General output formatting. 18075 (line 113) 18076* --format <6>: numfmt invocation. (line 48) 18077* --format <7>: seq invocation. (line 28) 18078* --format=FORMAT: stat invocation. (line 49) 18079* --format=roff: Output formatting in ptx. 18080 (line 100) 18081* --format=tex: Output formatting in ptx. 18082 (line 118) 18083* --from: chown invocation. (line 83) 18084* --from <1>: numfmt invocation. (line 59) 18085* --from-unit: numfmt invocation. (line 64) 18086* --full-time: What information is listed. 18087 (line 100) 18088* --gap-size: Output formatting in ptx. 18089 (line 26) 18090* --general-numeric-sort: sort invocation. (line 105) 18091* --goal: fmt invocation. (line 64) 18092* --group: uniq invocation. (line 100) 18093* --group <1>: install invocation. (line 73) 18094* --group <2>: id invocation. (line 29) 18095* --group-directories-first: Which files are listed. 18096 (line 50) 18097* --grouping: numfmt invocation. (line 70) 18098* --groups: id invocation. (line 33) 18099* --groups <1>: chroot invocation. (line 24) 18100* --hardware-platform: uname invocation. (line 35) 18101* --head-count: shuf invocation. (line 31) 18102* --header: pr invocation. (line 111) 18103* --header <1>: General options in join. 18104 (line 25) 18105* --header <2>: numfmt invocation. (line 76) 18106* --header-numbering: nl invocation. (line 74) 18107* --header=N: numfmt invocation. (line 76) 18108* --heading: who invocation. (line 47) 18109* --help: Common options. (line 36) 18110* --hex-suffixes: split invocation. (line 131) 18111* --hide-control-chars: Formatting the file names. 18112 (line 23) 18113* --hide=PATTERN: Which files are listed. 18114 (line 57) 18115* --human-numeric-sort: sort invocation. (line 126) 18116* --human-readable: Block size. (line 121) 18117* --human-readable <1>: What information is listed. 18118 (line 116) 18119* --human-readable <2>: df invocation. (line 59) 18120* --human-readable <3>: du invocation. (line 96) 18121* --hyperlink: General output formatting. 18122 (line 61) 18123* --ignore: nproc invocation. (line 26) 18124* --ignore-backups: Which files are listed. 18125 (line 23) 18126* --ignore-case: sort invocation. (line 94) 18127* --ignore-case <1>: uniq invocation. (line 59) 18128* --ignore-case <2>: Charset selection in ptx. 18129 (line 18) 18130* --ignore-case <3>: General options in join. 18131 (line 35) 18132* --ignore-environment: env invocation. (line 102) 18133* --ignore-fail-on-non-empty: rmdir invocation. (line 17) 18134* --ignore-file: Input processing in ptx. 18135 (line 26) 18136* --ignore-garbage: base64 invocation. (line 36) 18137* --ignore-interrupts: tee invocation. (line 32) 18138* --ignore-leading-blanks: sort invocation. (line 79) 18139* --ignore-missing: md5sum invocation. (line 76) 18140* --ignore-nonprinting: sort invocation. (line 143) 18141* --ignore=PATTERN: Which files are listed. 18142 (line 69) 18143* --indent: pr invocation. (line 180) 18144* --indicator-style: General output formatting. 18145 (line 46) 18146* --indicator-style <1>: General output formatting. 18147 (line 57) 18148* --indicator-style <2>: General output formatting. 18149 (line 70) 18150* --indicator-style <3>: General output formatting. 18151 (line 108) 18152* --initial: expand invocation. (line 46) 18153* --inode: What information is listed. 18154 (line 123) 18155* --inodes: df invocation. (line 69) 18156* --inodes <1>: du invocation. (line 102) 18157* --input: stdbuf invocation. (line 26) 18158* --input-range: shuf invocation. (line 23) 18159* --interactive: cp invocation. (line 139) 18160* --interactive <1>: mv invocation. (line 70) 18161* --interactive <2>: rm invocation. (line 54) 18162* --interactive <3>: ln invocation. (line 98) 18163* --invalid: numfmt invocation. (line 79) 18164* --io-blocks: truncate invocation. (line 26) 18165* --iso-8601[=TIMESPEC]: Options for date. (line 38) 18166* --iterations=NUMBER: shred invocation. (line 127) 18167* --join-blank-lines: nl invocation. (line 82) 18168* --join-lines: pr invocation. (line 124) 18169* --keep-files: csplit invocation. (line 86) 18170* --kernel-name: uname invocation. (line 66) 18171* --kernel-release: uname invocation. (line 62) 18172* --kernel-version: uname invocation. (line 77) 18173* --key: sort invocation. (line 231) 18174* --kibibytes: General output formatting. 18175 (line 89) 18176* --kill-after: timeout invocation. (line 41) 18177* --length: pr invocation. (line 133) 18178* --length <1>: b2sum invocation. (line 12) 18179* --line-bytes: split invocation. (line 56) 18180* --line-increment: nl invocation. (line 78) 18181* --lines: head invocation. (line 40) 18182* --lines <1>: tail invocation. (line 125) 18183* --lines <2>: split invocation. (line 33) 18184* --lines <3>: wc invocation. (line 55) 18185* --link: cp invocation. (line 145) 18186* --literal: Formatting the file names. 18187 (line 17) 18188* --local: df invocation. (line 80) 18189* --logical: ln invocation. (line 102) 18190* --logical <1>: realpath invocation. (line 35) 18191* --logical <2>: pwd invocation. (line 15) 18192* --login: who invocation. (line 51) 18193* --lookup: who invocation. (line 56) 18194* --machine: uname invocation. (line 42) 18195* --macro-name: Output formatting in ptx. 18196 (line 94) 18197* --max-depth=DEPTH: du invocation. (line 74) 18198* --max-line-length: wc invocation. (line 59) 18199* --max-unchanged-stats: tail invocation. (line 113) 18200* --merge: pr invocation. (line 140) 18201* --merge <1>: sort invocation. (line 53) 18202* --mesg: who invocation. (line 94) 18203* --message: who invocation. (line 94) 18204* --mode: install invocation. (line 79) 18205* --mode <1>: mkdir invocation. (line 19) 18206* --mode <2>: mkfifo invocation. (line 21) 18207* --mode <3>: mknod invocation. (line 47) 18208* --month-sort: sort invocation. (line 150) 18209* --multiple: basename invocation. (line 32) 18210* --name: id invocation. (line 37) 18211* --no-clobber: cp invocation. (line 156) 18212* --no-clobber <1>: mv invocation. (line 77) 18213* --no-create: touch invocation. (line 52) 18214* --no-create <1>: truncate invocation. (line 22) 18215* --no-dereference: cp invocation. (line 162) 18216* --no-dereference <1>: ln invocation. (line 108) 18217* --no-dereference <2>: chown invocation. (line 118) 18218* --no-dereference <3>: chgrp invocation. (line 46) 18219* --no-dereference <4>: touch invocation. (line 70) 18220* --no-dereference <5>: du invocation. (line 133) 18221* --no-dereference <6>: chcon invocation. (line 26) 18222* --no-file-warnings: pr invocation. (line 187) 18223* --no-group: What information is listed. 18224 (line 110) 18225* --no-newline: readlink invocation. (line 50) 18226* --no-preserve-root: rm invocation. (line 88) 18227* --no-preserve-root <1>: chown invocation. (line 131) 18228* --no-preserve-root <2>: chgrp invocation. (line 59) 18229* --no-preserve-root <3>: chmod invocation. (line 58) 18230* --no-preserve-root <4>: chcon invocation. (line 43) 18231* --no-renumber: nl invocation. (line 101) 18232* --no-symlinks: realpath invocation. (line 64) 18233* --no-sync: df invocation. (line 84) 18234* --no-target-directory: Target directory. (line 15) 18235* --no-target-directory <1>: cp invocation. (line 354) 18236* --no-target-directory <2>: install invocation. (line 130) 18237* --no-target-directory <3>: mv invocation. (line 112) 18238* --no-target-directory <4>: ln invocation. (line 175) 18239* --nodename: uname invocation. (line 47) 18240* --null: du invocation. (line 26) 18241* --null <1>: printenv invocation. (line 19) 18242* --null <2>: env invocation. (line 90) 18243* --number: cat invocation. (line 31) 18244* --number <1>: split invocation. (line 79) 18245* --number-format: nl invocation. (line 90) 18246* --number-lines: pr invocation. (line 153) 18247* --number-nonblank: cat invocation. (line 20) 18248* --number-separator: nl invocation. (line 105) 18249* --number-width: nl invocation. (line 115) 18250* --numeric-sort: sort invocation. (line 160) 18251* --numeric-suffixes: split invocation. (line 117) 18252* --numeric-uid-gid: What information is listed. 18253 (line 225) 18254* --omit-header: pr invocation. (line 210) 18255* --omit-pagination: pr invocation. (line 220) 18256* --one-file-system: cp invocation. (line 378) 18257* --one-file-system <1>: rm invocation. (line 65) 18258* --one-file-system <2>: du invocation. (line 263) 18259* --only-delimited: cut invocation. (line 74) 18260* --only-file: Input processing in ptx. 18261 (line 35) 18262* --operating-system: uname invocation. (line 58) 18263* --output: sort invocation. (line 288) 18264* --output <1>: shuf invocation. (line 36) 18265* --output <2>: df invocation. (line 91) 18266* --output <3>: stdbuf invocation. (line 30) 18267* --output-delimiter: cut invocation. (line 79) 18268* --output-duplicates: od invocation. (line 150) 18269* --output-error: tee invocation. (line 36) 18270* --output-tabs: pr invocation. (line 117) 18271* --owner: install invocation. (line 91) 18272* --padding: numfmt invocation. (line 87) 18273* --pages=PAGE_RANGE: pr invocation. (line 39) 18274* --page_width: pr invocation. (line 239) 18275* --parallel: sort invocation. (line 361) 18276* --parents: cp invocation. (line 239) 18277* --parents <1>: mkdir invocation. (line 34) 18278* --parents <2>: rmdir invocation. (line 22) 18279* --physical: ln invocation. (line 127) 18280* --physical <1>: realpath invocation. (line 40) 18281* --physical <2>: pwd invocation. (line 22) 18282* --pid: tail invocation. (line 131) 18283* --portability: df invocation. (line 148) 18284* --portability <1>: pathchk invocation. (line 44) 18285* --prefix: csplit invocation. (line 63) 18286* --preserve: cp invocation. (line 169) 18287* --preserve-context: install invocation. (line 96) 18288* --preserve-root: rm invocation. (line 81) 18289* --preserve-root <1>: chown invocation. (line 126) 18290* --preserve-root <2>: chgrp invocation. (line 54) 18291* --preserve-root <3>: chmod invocation. (line 53) 18292* --preserve-root <4>: chcon invocation. (line 38) 18293* --preserve-status: timeout invocation. (line 18) 18294* --preserve-timestamps: install invocation. (line 103) 18295* --print-database: dircolors invocation. 18296 (line 45) 18297* --print-type: df invocation. (line 200) 18298* --printf=FORMAT: stat invocation. (line 58) 18299* --process: who invocation. (line 65) 18300* --processor: uname invocation. (line 51) 18301* --quiet: head invocation. (line 47) 18302* --quiet <1>: tail invocation. (line 153) 18303* --quiet <2>: csplit invocation. (line 106) 18304* --quiet <3>: md5sum invocation. (line 82) 18305* --quiet <4>: readlink invocation. (line 57) 18306* --quiet <5>: chown invocation. (line 79) 18307* --quiet <6>: chgrp invocation. (line 30) 18308* --quiet <7>: chmod invocation. (line 49) 18309* --quiet <8>: mktemp invocation. (line 92) 18310* --quiet <9>: realpath invocation. (line 46) 18311* --quiet <10>: tty invocation. (line 18) 18312* --quote-name: Formatting the file names. 18313 (line 30) 18314* --quoting-style: Formatting the file names. 18315 (line 11) 18316* --quoting-style <1>: Formatting the file names. 18317 (line 17) 18318* --quoting-style <2>: Formatting the file names. 18319 (line 30) 18320* --quoting-style <3>: Formatting the file names. 18321 (line 34) 18322* --random-sort: sort invocation. (line 189) 18323* --random-source: sort invocation. (line 304) 18324* --random-source <1>: shuf invocation. (line 42) 18325* --random-source <2>: shred invocation. (line 133) 18326* --range: chcon invocation. (line 77) 18327* --range <1>: runcon invocation. (line 48) 18328* --read-bytes: od invocation. (line 76) 18329* --real: id invocation. (line 42) 18330* --recursive: Which files are listed. 18331 (line 90) 18332* --recursive <1>: cp invocation. (line 252) 18333* --recursive <2>: rm invocation. (line 95) 18334* --recursive <3>: chown invocation. (line 150) 18335* --recursive <4>: chgrp invocation. (line 77) 18336* --recursive <5>: chmod invocation. (line 73) 18337* --recursive <6>: chcon invocation. (line 35) 18338* --reference: chown invocation. (line 135) 18339* --reference <1>: chgrp invocation. (line 63) 18340* --reference <2>: chmod invocation. (line 66) 18341* --reference <3>: touch invocation. (line 89) 18342* --reference <4>: truncate invocation. (line 30) 18343* --reference <5>: Options for date. (line 65) 18344* --reference <6>: chcon invocation. (line 30) 18345* --references: Input processing in ptx. 18346 (line 48) 18347* --reflink[=WHEN]: cp invocation. (line 265) 18348* --regex: tac invocation. (line 26) 18349* --relative: ln invocation. (line 136) 18350* --relative-base: realpath invocation. (line 54) 18351* --relative-base <1>: Realpath usage examples. 18352 (line 6) 18353* --relative-to: realpath invocation. (line 49) 18354* --relative-to <1>: Realpath usage examples. 18355 (line 6) 18356* --remove: shred invocation. (line 144) 18357* --remove-destination: cp invocation. (line 295) 18358* --remove=unlink: shred invocation. (line 144) 18359* --remove=wipe: shred invocation. (line 144) 18360* --remove=wipesync: shred invocation. (line 144) 18361* --repeat: shuf invocation. (line 47) 18362* --repeated: uniq invocation. (line 63) 18363* --retry: tail invocation. (line 156) 18364* --reverse: sort invocation. (line 183) 18365* --reverse <1>: Sorting the output. (line 27) 18366* --rfc-2822: Options for date. (line 76) 18367* --rfc-3339=TIMESPEC: Options for date. (line 85) 18368* --rfc-822: Options for date. (line 76) 18369* --rfc-email: Options for date. (line 70) 18370* --right-side-refs: Output formatting in ptx. 18371 (line 56) 18372* --role: chcon invocation. (line 69) 18373* --role <1>: runcon invocation. (line 40) 18374* --round: numfmt invocation. (line 94) 18375* --round=down: numfmt invocation. (line 94) 18376* --round=from-zero: numfmt invocation. (line 94) 18377* --round=nearest: numfmt invocation. (line 94) 18378* --round=towards-zero: numfmt invocation. (line 94) 18379* --round=up: numfmt invocation. (line 94) 18380* --runlevel: who invocation. (line 74) 18381* --save: stty invocation. (line 41) 18382* --section-delimiter: nl invocation. (line 63) 18383* --sentence-regexp: Input processing in ptx. 18384 (line 65) 18385* --sep-string: pr invocation. (line 201) 18386* --separate-dirs: du invocation. (line 138) 18387* --separator: tac invocation. (line 30) 18388* --separator <1>: pr invocation. (line 192) 18389* --separator <2>: split invocation. (line 148) 18390* --separator <3>: seq invocation. (line 44) 18391* --serial: paste invocation. (line 52) 18392* --set: Options for date. (line 113) 18393* --sh: dircolors invocation. 18394 (line 34) 18395* --show-all: cat invocation. (line 16) 18396* --show-control-chars: pr invocation. (line 68) 18397* --show-control-chars <1>: Formatting the file names. 18398 (line 78) 18399* --show-ends: cat invocation. (line 27) 18400* --show-nonprinting: cat invocation. (line 51) 18401* --show-nonprinting <1>: pr invocation. (line 225) 18402* --show-tabs: cat invocation. (line 44) 18403* --si: Block size. (line 121) 18404* --si <1>: What information is listed. 18405 (line 251) 18406* --si <2>: df invocation. (line 167) 18407* --si <3>: du invocation. (line 145) 18408* --signal: timeout invocation. (line 48) 18409* --silent: head invocation. (line 47) 18410* --silent <1>: tail invocation. (line 153) 18411* --silent <2>: csplit invocation. (line 106) 18412* --silent <3>: readlink invocation. (line 57) 18413* --silent <4>: chown invocation. (line 79) 18414* --silent <5>: chgrp invocation. (line 30) 18415* --silent <6>: chmod invocation. (line 49) 18416* --silent <7>: tty invocation. (line 18) 18417* --size: What information is listed. 18418 (line 236) 18419* --size <1>: truncate invocation. (line 34) 18420* --size=BYTES: shred invocation. (line 138) 18421* --skip-bytes: od invocation. (line 59) 18422* --skip-chars: uniq invocation. (line 41) 18423* --skip-chdir: chroot invocation. (line 37) 18424* --skip-fields: uniq invocation. (line 31) 18425* --sleep-interval: tail invocation. (line 173) 18426* --sort: sort invocation. (line 105) 18427* --sort <1>: sort invocation. (line 126) 18428* --sort <2>: sort invocation. (line 150) 18429* --sort <3>: sort invocation. (line 160) 18430* --sort <4>: sort invocation. (line 189) 18431* --sort <5>: Sorting the output. (line 32) 18432* --sort <6>: Sorting the output. (line 36) 18433* --sort <7>: Sorting the output. (line 60) 18434* --sort <8>: Sorting the output. (line 67) 18435* --sort <9>: Sorting the output. (line 74) 18436* --spaces: fold invocation. (line 29) 18437* --sparse=WHEN: cp invocation. (line 299) 18438* --split-only: fmt invocation. (line 47) 18439* --split-string: env invocation. (line 188) 18440* --squeeze-blank: cat invocation. (line 36) 18441* --stable: sort invocation. (line 309) 18442* --starting-line-number: nl invocation. (line 110) 18443* --status: md5sum invocation. (line 90) 18444* --strict: md5sum invocation. (line 123) 18445* --strings: od invocation. (line 81) 18446* --strip: install invocation. (line 113) 18447* --strip <1>: realpath invocation. (line 64) 18448* --strip-program: install invocation. (line 116) 18449* --strip-trailing-slashes: cp invocation. (line 332) 18450* --strip-trailing-slashes <1>: mv invocation. (line 98) 18451* --suffix: Backup options. (line 49) 18452* --suffix <1>: cp invocation. (line 345) 18453* --suffix <2>: install invocation. (line 120) 18454* --suffix <3>: mv invocation. (line 103) 18455* --suffix <4>: ln invocation. (line 166) 18456* --suffix <5>: basename invocation. (line 38) 18457* --suffix <6>: mktemp invocation. (line 113) 18458* --suffix <7>: numfmt invocation. (line 99) 18459* --suffix-format: csplit invocation. (line 67) 18460* --suffix-length: split invocation. (line 109) 18461* --summarize: du invocation. (line 153) 18462* --suppress-matched: csplit invocation. (line 89) 18463* --symbolic: ln invocation. (line 160) 18464* --symbolic-link: cp invocation. (line 337) 18465* --sync: df invocation. (line 174) 18466* --sysv: sum invocation. (line 31) 18467* --tabs: expand invocation. (line 22) 18468* --tabs <1>: unexpand invocation. (line 24) 18469* --tabsize: General output formatting. 18470 (line 117) 18471* --tag: md5sum invocation. (line 99) 18472* --tagged-paragraph: fmt invocation. (line 40) 18473* --target-directory: Target directory. (line 31) 18474* --target-directory <1>: cp invocation. (line 350) 18475* --target-directory <2>: install invocation. (line 125) 18476* --target-directory <3>: mv invocation. (line 108) 18477* --target-directory <4>: ln invocation. (line 171) 18478* --temporary-directory: sort invocation. (line 353) 18479* --terse: stat invocation. (line 69) 18480* --text: md5sum invocation. (line 109) 18481* --threshold: du invocation. (line 157) 18482* --time: Sorting the output. (line 13) 18483* --time <1>: Sorting the output. (line 44) 18484* --time <2>: Sorting the output. (line 52) 18485* --time <3>: touch invocation. (line 48) 18486* --time <4>: touch invocation. (line 85) 18487* --time <5>: du invocation. (line 197) 18488* --time <6>: du invocation. (line 204) 18489* --time <7>: du invocation. (line 210) 18490* --time <8>: who invocation. (line 82) 18491* --time-style: Formatting file timestamps. 18492 (line 24) 18493* --time-style <1>: du invocation. (line 214) 18494* --tmpdir: mktemp invocation. (line 105) 18495* --to: numfmt invocation. (line 103) 18496* --to-unit: numfmt invocation. (line 108) 18497* --total: df invocation. (line 180) 18498* --total <1>: du invocation. (line 61) 18499* --traditional: od invocation. (line 200) 18500* --type: df invocation. (line 194) 18501* --type <1>: chcon invocation. (line 73) 18502* --type <2>: runcon invocation. (line 44) 18503* --unbuffered: split invocation. (line 155) 18504* --uniform-spacing: fmt invocation. (line 53) 18505* --unique: sort invocation. (line 369) 18506* --unique <1>: uniq invocation. (line 127) 18507* --universal: Options for date. (line 119) 18508* --unset: env invocation. (line 96) 18509* --update: cp invocation. (line 359) 18510* --update <1>: mv invocation. (line 84) 18511* --user: id invocation. (line 47) 18512* --user <1>: chcon invocation. (line 65) 18513* --user <2>: runcon invocation. (line 36) 18514* --userspec: chroot invocation. (line 30) 18515* --utc: Options for date. (line 119) 18516* --verbose: head invocation. (line 51) 18517* --verbose <1>: tail invocation. (line 184) 18518* --verbose <2>: split invocation. (line 159) 18519* --verbose <3>: cp invocation. (line 374) 18520* --verbose <4>: install invocation. (line 135) 18521* --verbose <5>: mv invocation. (line 95) 18522* --verbose <6>: rm invocation. (line 99) 18523* --verbose <7>: shred invocation. (line 159) 18524* --verbose <8>: ln invocation. (line 180) 18525* --verbose <9>: mkdir invocation. (line 51) 18526* --verbose <10>: readlink invocation. (line 61) 18527* --verbose <11>: rmdir invocation. (line 31) 18528* --verbose <12>: chown invocation. (line 142) 18529* --verbose <13>: chgrp invocation. (line 69) 18530* --verbose <14>: chmod invocation. (line 63) 18531* --verbose <15>: chcon invocation. (line 61) 18532* --verbose <16>: timeout invocation. (line 54) 18533* --version: Common options. (line 40) 18534* --version-sort: sort invocation. (line 177) 18535* --warn: md5sum invocation. (line 118) 18536* --width: od invocation. (line 157) 18537* --width <1>: fmt invocation. (line 59) 18538* --width <2>: pr invocation. (line 229) 18539* --width <3>: fold invocation. (line 35) 18540* --width <4>: Output formatting in ptx. 18541 (line 32) 18542* --width <5>: General output formatting. 18543 (line 128) 18544* --word-regexp: Input processing in ptx. 18545 (line 105) 18546* --words: wc invocation. (line 51) 18547* --wrap: base64 invocation. (line 22) 18548* --writable: who invocation. (line 94) 18549* --z85: basenc invocation. (line 63) 18550* --zero: md5sum invocation. (line 128) 18551* --zero <1>: shred invocation. (line 175) 18552* --zero <2>: readlink invocation. (line 65) 18553* --zero <3>: basename invocation. (line 42) 18554* --zero <4>: dirname invocation. (line 31) 18555* --zero <5>: realpath invocation. (line 71) 18556* --zero <6>: id invocation. (line 58) 18557* --zero-terminated: head invocation. (line 55) 18558* --zero-terminated <1>: tail invocation. (line 188) 18559* --zero-terminated <2>: sort invocation. (line 384) 18560* --zero-terminated <3>: shuf invocation. (line 55) 18561* --zero-terminated <4>: uniq invocation. (line 139) 18562* --zero-terminated <5>: comm invocation. (line 88) 18563* --zero-terminated <6>: cut invocation. (line 94) 18564* --zero-terminated <7>: paste invocation. (line 72) 18565* --zero-terminated <8>: General options in join. 18566 (line 93) 18567* --zero-terminated <9>: numfmt invocation. (line 115) 18568* -0: du invocation. (line 26) 18569* -0 <1>: printenv invocation. (line 19) 18570* -0 <2>: env invocation. (line 90) 18571* -1: comm invocation. (line 23) 18572* -1 <1>: General options in join. 18573 (line 40) 18574* -1 <2>: General output formatting. 18575 (line 10) 18576* -2: comm invocation. (line 23) 18577* -2 <1>: General options in join. 18578 (line 43) 18579* -3: comm invocation. (line 23) 18580* -A: cat invocation. (line 16) 18581* -A <1>: od invocation. (line 36) 18582* -a: od invocation. (line 169) 18583* -a <1>: pr invocation. (line 62) 18584* -a <2>: split invocation. (line 109) 18585* -A <2>: Output formatting in ptx. 18586 (line 45) 18587* -a <3>: General options in join. 18588 (line 10) 18589* -a <4>: unexpand invocation. (line 51) 18590* -a <5>: Which files are listed. 18591 (line 13) 18592* -A <3>: Which files are listed. 18593 (line 17) 18594* -a <6>: cp invocation. (line 63) 18595* -a <7>: touch invocation. (line 48) 18596* -a <8>: df invocation. (line 42) 18597* -a <9>: du invocation. (line 32) 18598* -a <10>: Connectives for test. 18599 (line 29) 18600* -a <11>: tee invocation. (line 27) 18601* -a <12>: basename invocation. (line 32) 18602* -a <13>: stty invocation. (line 26) 18603* -a <14>: who invocation. (line 35) 18604* -a <15>: uname invocation. (line 30) 18605* -b: Backup options. (line 13) 18606* -b <1>: cat invocation. (line 20) 18607* -b <2>: tac invocation. (line 21) 18608* -b <3>: nl invocation. (line 45) 18609* -b <4>: od invocation. (line 172) 18610* -b <5>: fold invocation. (line 23) 18611* -b <6>: split invocation. (line 41) 18612* -b <7>: csplit invocation. (line 67) 18613* -b <8>: md5sum invocation. (line 41) 18614* -b <9>: sort invocation. (line 79) 18615* -b <10>: Input processing in ptx. 18616 (line 8) 18617* -b <11>: cut invocation. (line 26) 18618* -B: Which files are listed. 18619 (line 23) 18620* -b <12>: Formatting the file names. 18621 (line 11) 18622* -b <13>: dircolors invocation. 18623 (line 34) 18624* -b <14>: cp invocation. (line 79) 18625* -b <15>: install invocation. (line 41) 18626* -b <16>: mv invocation. (line 59) 18627* -b <17>: ln invocation. (line 82) 18628* -B <1>: df invocation. (line 54) 18629* -B <2>: du invocation. (line 52) 18630* -b <18>: du invocation. (line 57) 18631* -b <19>: File type tests. (line 10) 18632* -b <20>: who invocation. (line 39) 18633* -c: od invocation. (line 175) 18634* -c <1>: fmt invocation. (line 34) 18635* -c <2>: pr invocation. (line 68) 18636* -c <3>: head invocation. (line 24) 18637* -c <4>: tail invocation. (line 39) 18638* -C: split invocation. (line 56) 18639* -c <5>: wc invocation. (line 43) 18640* -c <6>: sort invocation. (line 39) 18641* -c <7>: sort invocation. (line 47) 18642* -c <8>: shuf invocation. (line 19) 18643* -c <9>: uniq invocation. (line 55) 18644* -c <10>: cut invocation. (line 34) 18645* -c <11>: Sorting the output. (line 13) 18646* -C <1>: General output formatting. 18647 (line 16) 18648* -c <12>: dircolors invocation. 18649 (line 40) 18650* -C <2>: install invocation. (line 46) 18651* -c <13>: install invocation. (line 57) 18652* -c <14>: chown invocation. (line 73) 18653* -c <15>: chgrp invocation. (line 24) 18654* -c <16>: chmod invocation. (line 43) 18655* -c <17>: touch invocation. (line 52) 18656* -c <18>: du invocation. (line 61) 18657* -c <19>: stat invocation. (line 49) 18658* -c <20>: truncate invocation. (line 22) 18659* -c <21>: File type tests. (line 13) 18660* -c <22>: runcon invocation. (line 32) 18661* -C <3>: env invocation. (line 107) 18662* -COLUMN: pr invocation. (line 49) 18663* -d: nl invocation. (line 63) 18664* -d <1>: od invocation. (line 179) 18665* -d <2>: base64 invocation. (line 30) 18666* -d <3>: pr invocation. (line 74) 18667* -d <4>: split invocation. (line 117) 18668* -d <5>: sort invocation. (line 87) 18669* -d <6>: uniq invocation. (line 63) 18670* -D: uniq invocation. (line 69) 18671* -d <7>: cut invocation. (line 66) 18672* -d <8>: paste invocation. (line 61) 18673* -d <9>: Which files are listed. 18674 (line 28) 18675* -D <1>: What information is listed. 18676 (line 16) 18677* -d <10>: cp invocation. (line 109) 18678* -D <2>: install invocation. (line 60) 18679* -d <11>: install invocation. (line 67) 18680* -d <12>: rm invocation. (line 35) 18681* -d <13>: ln invocation. (line 88) 18682* -d <14>: touch invocation. (line 56) 18683* -D <3>: du invocation. (line 67) 18684* -d <15>: File type tests. (line 16) 18685* -d <16>: mktemp invocation. (line 85) 18686* -d <17>: who invocation. (line 43) 18687* -d <18>: Options for date. (line 11) 18688* -d <19>: numfmt invocation. (line 34) 18689* -d DEPTH: du invocation. (line 74) 18690* -e: cat invocation. (line 23) 18691* -E: cat invocation. (line 27) 18692* -e <1>: pr invocation. (line 98) 18693* -e <2>: split invocation. (line 140) 18694* -e <3>: General options in join. 18695 (line 21) 18696* -e <4>: readlink invocation. (line 38) 18697* -e <5>: echo invocation. (line 25) 18698* -E <1>: echo invocation. (line 61) 18699* -e <6>: File characteristic tests. 18700 (line 9) 18701* -e <7>: realpath invocation. (line 22) 18702* -e <8>: stdbuf invocation. (line 34) 18703* -ef: File characteristic tests. 18704 (line 23) 18705* -eq: Numeric tests. (line 17) 18706* -f: nl invocation. (line 70) 18707* -f <1>: od invocation. (line 182) 18708* -F: pr invocation. (line 106) 18709* -f <2>: pr invocation. (line 106) 18710* -f <3>: tail invocation. (line 56) 18711* -F <1>: tail invocation. (line 108) 18712* -f <4>: csplit invocation. (line 63) 18713* -f <5>: sort invocation. (line 94) 18714* -f <6>: uniq invocation. (line 31) 18715* -f <7>: Charset selection in ptx. 18716 (line 18) 18717* -F <2>: Output formatting in ptx. 18718 (line 71) 18719* -f <8>: cut invocation. (line 43) 18720* -f <9>: Sorting the output. (line 20) 18721* -F <3>: General output formatting. 18722 (line 46) 18723* -f <10>: cp invocation. (line 115) 18724* -f <11>: mv invocation. (line 64) 18725* -f <12>: rm invocation. (line 39) 18726* -f <13>: shred invocation. (line 123) 18727* -F <4>: ln invocation. (line 88) 18728* -f <14>: ln invocation. (line 94) 18729* -f <15>: readlink invocation. (line 31) 18730* -f <16>: chown invocation. (line 79) 18731* -f <17>: chgrp invocation. (line 30) 18732* -f <18>: chmod invocation. (line 49) 18733* -f <19>: touch invocation. (line 66) 18734* -f <20>: stat invocation. (line 28) 18735* -f <21>: File type tests. (line 19) 18736* -F <5>: stty invocation. (line 31) 18737* -f <22>: Options for date. (line 30) 18738* -f <23>: seq invocation. (line 28) 18739* -g: fmt invocation. (line 64) 18740* -g <1>: sort invocation. (line 105) 18741* -g <2>: Output formatting in ptx. 18742 (line 26) 18743* -g <3>: What information is listed. 18744 (line 105) 18745* -G: What information is listed. 18746 (line 110) 18747* -g <4>: install invocation. (line 73) 18748* -g <5>: Access permission tests. 18749 (line 9) 18750* -G <1>: Access permission tests. 18751 (line 31) 18752* -g <6>: stty invocation. (line 41) 18753* -g <7>: id invocation. (line 29) 18754* -G <2>: id invocation. (line 33) 18755* -ge: Numeric tests. (line 17) 18756* -gt: Numeric tests. (line 17) 18757* -h: Block size. (line 121) 18758* -H: Traversing symlinks. (line 18) 18759* -h <1>: nl invocation. (line 74) 18760* -h <2>: pr invocation. (line 111) 18761* -h <3>: sort invocation. (line 126) 18762* -H <1>: Which files are listed. 18763 (line 36) 18764* -h <4>: What information is listed. 18765 (line 116) 18766* -H <2>: cp invocation. (line 132) 18767* -h <5>: chown invocation. (line 118) 18768* -H <3>: chown invocation. (line 153) 18769* -h <6>: chgrp invocation. (line 46) 18770* -H <4>: chgrp invocation. (line 81) 18771* -h <7>: touch invocation. (line 70) 18772* -h <8>: df invocation. (line 59) 18773* -H <5>: df invocation. (line 65) 18774* -H <6>: du invocation. (line 92) 18775* -h <9>: du invocation. (line 96) 18776* -h <10>: File type tests. (line 23) 18777* -H <7>: who invocation. (line 47) 18778* -h <11>: chcon invocation. (line 26) 18779* -H <8>: chcon invocation. (line 47) 18780* -i: nl invocation. (line 78) 18781* -i <1>: od invocation. (line 185) 18782* -i <2>: base64 invocation. (line 36) 18783* -i <3>: pr invocation. (line 117) 18784* -i <4>: sort invocation. (line 143) 18785* -i <5>: shuf invocation. (line 23) 18786* -i <6>: uniq invocation. (line 59) 18787* -i <7>: Input processing in ptx. 18788 (line 26) 18789* -i <8>: General options in join. 18790 (line 35) 18791* -i <9>: expand invocation. (line 46) 18792* -I: Which files are listed. 18793 (line 69) 18794* -i <10>: What information is listed. 18795 (line 123) 18796* -i <11>: cp invocation. (line 139) 18797* -i <12>: mv invocation. (line 70) 18798* -i <13>: rm invocation. (line 43) 18799* -I <1>: rm invocation. (line 48) 18800* -i <14>: ln invocation. (line 98) 18801* -i <15>: df invocation. (line 69) 18802* -i <16>: tee invocation. (line 32) 18803* -i <17>: uname invocation. (line 35) 18804* -i <18>: env invocation. (line 102) 18805* -i <19>: stdbuf invocation. (line 26) 18806* -I[TIMESPEC]: Options for date. (line 38) 18807* -j: od invocation. (line 59) 18808* -J: pr invocation. (line 124) 18809* -k: Block size. (line 121) 18810* -k <1>: csplit invocation. (line 86) 18811* -k <2>: sort invocation. (line 231) 18812* -k <3>: General output formatting. 18813 (line 89) 18814* -k <4>: df invocation. (line 74) 18815* -k <5>: du invocation. (line 111) 18816* -k <6>: Access permission tests. 18817 (line 12) 18818* -k <7>: timeout invocation. (line 41) 18819* -L: Traversing symlinks. (line 22) 18820* -l: nl invocation. (line 82) 18821* -l <1>: od invocation. (line 188) 18822* -l <2>: pr invocation. (line 133) 18823* -l <3>: split invocation. (line 33) 18824* -l <4>: wc invocation. (line 55) 18825* -L <1>: wc invocation. (line 59) 18826* -l <5>: b2sum invocation. (line 12) 18827* -L <2>: Which files are listed. 18828 (line 83) 18829* -l <6>: What information is listed. 18830 (line 131) 18831* -l <7>: cp invocation. (line 145) 18832* -L <3>: cp invocation. (line 149) 18833* -L <4>: ln invocation. (line 102) 18834* -L <5>: chown invocation. (line 158) 18835* -L <6>: chgrp invocation. (line 86) 18836* -l <8>: df invocation. (line 80) 18837* -L <7>: du invocation. (line 117) 18838* -l <9>: du invocation. (line 123) 18839* -L <8>: stat invocation. (line 22) 18840* -L <9>: File type tests. (line 23) 18841* -L <10>: realpath invocation. (line 35) 18842* -L <11>: pwd invocation. (line 15) 18843* -l <10>: who invocation. (line 51) 18844* -L <12>: chcon invocation. (line 52) 18845* -l <11>: chcon invocation. (line 77) 18846* -l <12>: runcon invocation. (line 48) 18847* -le: Numeric tests. (line 17) 18848* -lt: Numeric tests. (line 17) 18849* -m: pr invocation. (line 140) 18850* -m <1>: wc invocation. (line 47) 18851* -m <2>: sort invocation. (line 53) 18852* -M: sort invocation. (line 150) 18853* -M <1>: Output formatting in ptx. 18854 (line 94) 18855* -m <3>: General output formatting. 18856 (line 103) 18857* -m <4>: install invocation. (line 79) 18858* -m <5>: mkdir invocation. (line 19) 18859* -m <6>: mkfifo invocation. (line 21) 18860* -m <7>: mknod invocation. (line 47) 18861* -m <8>: readlink invocation. (line 45) 18862* -m <9>: touch invocation. (line 85) 18863* -m <10>: du invocation. (line 127) 18864* -m <11>: realpath invocation. (line 30) 18865* -m <12>: who invocation. (line 61) 18866* -m <13>: uname invocation. (line 42) 18867* -n: cat invocation. (line 31) 18868* -n <1>: nl invocation. (line 90) 18869* -N: od invocation. (line 76) 18870* -n <2>: pr invocation. (line 153) 18871* -N <1>: pr invocation. (line 174) 18872* -n <3>: head invocation. (line 40) 18873* -n <4>: tail invocation. (line 125) 18874* -n <5>: split invocation. (line 79) 18875* -n <6>: csplit invocation. (line 81) 18876* -n <7>: sort invocation. (line 160) 18877* -n <8>: shuf invocation. (line 31) 18878* -n <9>: cut invocation. (line 70) 18879* -n <10>: What information is listed. 18880 (line 225) 18881* -N <2>: Formatting the file names. 18882 (line 17) 18883* -n <11>: cp invocation. (line 156) 18884* -n <12>: mv invocation. (line 77) 18885* -n <13>: ln invocation. (line 108) 18886* -n <14>: readlink invocation. (line 50) 18887* -n <15>: echo invocation. (line 22) 18888* -N <3>: File characteristic tests. 18889 (line 27) 18890* -n <16>: String tests. (line 19) 18891* -n <17>: id invocation. (line 37) 18892* -n <18>: uname invocation. (line 47) 18893* -n <19>: nice invocation. (line 51) 18894* -n NUMBER: shred invocation. (line 127) 18895* -ne: Numeric tests. (line 17) 18896* -nt: File characteristic tests. 18897 (line 15) 18898* -o: od invocation. (line 191) 18899* -o <1>: pr invocation. (line 180) 18900* -o <2>: sort invocation. (line 288) 18901* -o <3>: shuf invocation. (line 36) 18902* -o <4>: Input processing in ptx. 18903 (line 35) 18904* -O: Output formatting in ptx. 18905 (line 100) 18906* -o <5>: What information is listed. 18907 (line 230) 18908* -o <6>: install invocation. (line 91) 18909* -o <7>: truncate invocation. (line 26) 18910* -O <1>: Access permission tests. 18911 (line 28) 18912* -o <8>: Connectives for test. 18913 (line 33) 18914* -o <9>: uname invocation. (line 58) 18915* -o <10>: stdbuf invocation. (line 30) 18916* -ot: File characteristic tests. 18917 (line 19) 18918* -P: Traversing symlinks. (line 26) 18919* -p: nl invocation. (line 101) 18920* -p <1>: General output formatting. 18921 (line 108) 18922* -p <2>: dircolors invocation. 18923 (line 45) 18924* -P <1>: cp invocation. (line 162) 18925* -p <3>: cp invocation. (line 169) 18926* -p <4>: install invocation. (line 103) 18927* -P <2>: ln invocation. (line 127) 18928* -p <5>: mkdir invocation. (line 34) 18929* -p <6>: rmdir invocation. (line 22) 18930* -P <3>: chown invocation. (line 171) 18931* -P <4>: chgrp invocation. (line 99) 18932* -P <5>: df invocation. (line 148) 18933* -P <6>: du invocation. (line 133) 18934* -p <7>: File type tests. (line 28) 18935* -p <8>: tee invocation. (line 36) 18936* -p <9>: pathchk invocation. (line 27) 18937* -P <7>: pathchk invocation. (line 40) 18938* -p <10>: mktemp invocation. (line 105) 18939* -P <8>: realpath invocation. (line 40) 18940* -P <9>: pwd invocation. (line 22) 18941* -p <11>: who invocation. (line 65) 18942* -p <12>: uname invocation. (line 51) 18943* -P <10>: chcon invocation. (line 56) 18944* -q: head invocation. (line 47) 18945* -q <1>: tail invocation. (line 153) 18946* -q <2>: csplit invocation. (line 106) 18947* -q <3>: Formatting the file names. 18948 (line 23) 18949* -Q: Formatting the file names. 18950 (line 30) 18951* -q <4>: readlink invocation. (line 57) 18952* -q <5>: mktemp invocation. (line 92) 18953* -q <6>: realpath invocation. (line 46) 18954* -q <7>: who invocation. (line 69) 18955* -r: tac invocation. (line 26) 18956* -r <1>: pr invocation. (line 187) 18957* -r <2>: sum invocation. (line 25) 18958* -r <3>: sort invocation. (line 183) 18959* -R: sort invocation. (line 189) 18960* -r <4>: shuf invocation. (line 47) 18961* -r <5>: Input processing in ptx. 18962 (line 48) 18963* -R <1>: Output formatting in ptx. 18964 (line 56) 18965* -R <2>: Which files are listed. 18966 (line 90) 18967* -r <6>: Sorting the output. (line 27) 18968* -R <3>: cp invocation. (line 252) 18969* -r <7>: cp invocation. (line 252) 18970* -r <8>: rm invocation. (line 95) 18971* -R <4>: rm invocation. (line 95) 18972* -r <9>: ln invocation. (line 136) 18973* -R <5>: chown invocation. (line 150) 18974* -R <6>: chgrp invocation. (line 77) 18975* -R <7>: chmod invocation. (line 73) 18976* -r <10>: touch invocation. (line 89) 18977* -r <11>: truncate invocation. (line 30) 18978* -r <12>: Access permission tests. 18979 (line 15) 18980* -r <13>: id invocation. (line 42) 18981* -r <14>: who invocation. (line 74) 18982* -r <15>: Options for date. (line 65) 18983* -R <8>: Options for date. (line 70) 18984* -r <16>: uname invocation. (line 62) 18985* -R <9>: chcon invocation. (line 35) 18986* -r <17>: chcon invocation. (line 69) 18987* -r <18>: runcon invocation. (line 40) 18988* -S: Backup options. (line 49) 18989* -s: cat invocation. (line 36) 18990* -s <1>: tac invocation. (line 30) 18991* -s <2>: nl invocation. (line 105) 18992* -S <1>: od invocation. (line 81) 18993* -s <3>: od invocation. (line 194) 18994* -s <4>: fmt invocation. (line 47) 18995* -s <5>: pr invocation. (line 192) 18996* -S <2>: pr invocation. (line 201) 18997* -s <6>: fold invocation. (line 29) 18998* -s <7>: tail invocation. (line 173) 18999* -s <8>: csplit invocation. (line 106) 19000* -s <9>: sum invocation. (line 31) 19001* -s <10>: sort invocation. (line 309) 19002* -S <3>: sort invocation. (line 316) 19003* -s <11>: uniq invocation. (line 41) 19004* -S <4>: Input processing in ptx. 19005 (line 65) 19006* -s <12>: cut invocation. (line 74) 19007* -s <13>: paste invocation. (line 52) 19008* -s <14>: What information is listed. 19009 (line 236) 19010* -S <5>: Sorting the output. (line 32) 19011* -s <15>: cp invocation. (line 337) 19012* -S <6>: cp invocation. (line 345) 19013* -s <16>: install invocation. (line 113) 19014* -S <7>: install invocation. (line 120) 19015* -S <8>: mv invocation. (line 103) 19016* -s <17>: ln invocation. (line 160) 19017* -S <9>: ln invocation. (line 166) 19018* -s <18>: readlink invocation. (line 57) 19019* -S <10>: du invocation. (line 138) 19020* -s <19>: du invocation. (line 153) 19021* -s <20>: truncate invocation. (line 34) 19022* -S <11>: File type tests. (line 31) 19023* -s <21>: File characteristic tests. 19024 (line 12) 19025* -s <22>: basename invocation. (line 38) 19026* -s <23>: realpath invocation. (line 64) 19027* -s <24>: tty invocation. (line 18) 19028* -s <25>: who invocation. (line 78) 19029* -s <26>: Options for date. (line 113) 19030* -s <27>: uname invocation. (line 66) 19031* -S <12>: env invocation. (line 188) 19032* -s <28>: timeout invocation. (line 48) 19033* -s <29>: seq invocation. (line 44) 19034* -s BYTES: shred invocation. (line 138) 19035* -S, env and single quotes: env invocation. (line 264) 19036* -t: cat invocation. (line 40) 19037* -T: cat invocation. (line 44) 19038* -t <1>: od invocation. (line 90) 19039* -t <2>: fmt invocation. (line 40) 19040* -t <3>: pr invocation. (line 210) 19041* -T <1>: pr invocation. (line 220) 19042* -t <4>: split invocation. (line 148) 19043* -t <5>: md5sum invocation. (line 109) 19044* -t <6>: sort invocation. (line 332) 19045* -T <2>: sort invocation. (line 353) 19046* -T <3>: Output formatting in ptx. 19047 (line 118) 19048* -t <7>: expand invocation. (line 22) 19049* -t <8>: unexpand invocation. (line 24) 19050* -t <9>: Sorting the output. (line 36) 19051* -T <4>: General output formatting. 19052 (line 117) 19053* -t <10>: cp invocation. (line 350) 19054* -T <5>: cp invocation. (line 354) 19055* -t <11>: install invocation. (line 125) 19056* -T <6>: install invocation. (line 130) 19057* -t <12>: mv invocation. (line 108) 19058* -T <7>: mv invocation. (line 112) 19059* -t <13>: ln invocation. (line 171) 19060* -T <8>: ln invocation. (line 175) 19061* -t <14>: df invocation. (line 194) 19062* -T <9>: df invocation. (line 200) 19063* -t <15>: du invocation. (line 157) 19064* -t <16>: stat invocation. (line 69) 19065* -t <17>: File type tests. (line 34) 19066* -t <18>: mktemp invocation. (line 121) 19067* -t <19>: who invocation. (line 82) 19068* -T <10>: who invocation. (line 94) 19069* -t <20>: chcon invocation. (line 73) 19070* -t <21>: runcon invocation. (line 44) 19071* -u: cat invocation. (line 47) 19072* -u <1>: fmt invocation. (line 53) 19073* -u <2>: split invocation. (line 155) 19074* -u <3>: sort invocation. (line 369) 19075* -u <4>: uniq invocation. (line 127) 19076* -u <5>: Sorting the output. (line 44) 19077* -U: Sorting the output. (line 60) 19078* -u <6>: cp invocation. (line 359) 19079* -u <7>: mv invocation. (line 84) 19080* -u <8>: shred invocation. (line 144) 19081* -u <9>: Access permission tests. 19082 (line 18) 19083* -u <10>: mktemp invocation. (line 97) 19084* -u <11>: id invocation. (line 47) 19085* -u <12>: who invocation. (line 85) 19086* -u <13>: Options for date. (line 119) 19087* -u <14>: chcon invocation. (line 65) 19088* -u <15>: runcon invocation. (line 36) 19089* -u <16>: env invocation. (line 96) 19090* -v: cat invocation. (line 51) 19091* -v <1>: nl invocation. (line 110) 19092* -v <2>: od invocation. (line 150) 19093* -v <3>: pr invocation. (line 225) 19094* -v <4>: head invocation. (line 51) 19095* -v <5>: tail invocation. (line 184) 19096* -V: sort invocation. (line 177) 19097* -v <6>: Sorting the output. (line 67) 19098* -v <7>: cp invocation. (line 374) 19099* -v <8>: install invocation. (line 135) 19100* -v <9>: mv invocation. (line 95) 19101* -v <10>: rm invocation. (line 99) 19102* -v <11>: shred invocation. (line 159) 19103* -v <12>: ln invocation. (line 180) 19104* -v <13>: mkdir invocation. (line 51) 19105* -v <14>: readlink invocation. (line 61) 19106* -v <15>: rmdir invocation. (line 31) 19107* -v <16>: chown invocation. (line 142) 19108* -v <17>: chgrp invocation. (line 69) 19109* -v <18>: chmod invocation. (line 63) 19110* -v <19>: uname invocation. (line 77) 19111* -v <20>: chcon invocation. (line 61) 19112* -v <21>: env invocation. (line 173) 19113* -v <22>: timeout invocation. (line 54) 19114* -w: nl invocation. (line 115) 19115* -w <1>: od invocation. (line 157) 19116* -w <2>: base64 invocation. (line 22) 19117* -w <3>: fmt invocation. (line 59) 19118* -w <4>: pr invocation. (line 229) 19119* -W: pr invocation. (line 239) 19120* -w <5>: fold invocation. (line 35) 19121* -w <6>: wc invocation. (line 51) 19122* -w <7>: md5sum invocation. (line 118) 19123* -w <8>: uniq invocation. (line 133) 19124* -W <1>: Input processing in ptx. 19125 (line 105) 19126* -w <9>: Output formatting in ptx. 19127 (line 32) 19128* -w <10>: General output formatting. 19129 (line 128) 19130* -w <11>: Access permission tests. 19131 (line 21) 19132* -w <12>: who invocation. (line 94) 19133* -w <13>: seq invocation. (line 49) 19134* -WIDTH: fmt invocation. (line 59) 19135* -x: od invocation. (line 197) 19136* -x <1>: split invocation. (line 131) 19137* -X: Sorting the output. (line 74) 19138* -x <2>: General output formatting. 19139 (line 113) 19140* -x <3>: cp invocation. (line 378) 19141* -x <4>: shred invocation. (line 164) 19142* -x <5>: df invocation. (line 223) 19143* -x <6>: du invocation. (line 263) 19144* -x <7>: Access permission tests. 19145 (line 24) 19146* -X FILE: du invocation. (line 252) 19147* -z: head invocation. (line 55) 19148* -z <1>: tail invocation. (line 188) 19149* -z <2>: csplit invocation. (line 95) 19150* -z <3>: md5sum invocation. (line 128) 19151* -z <4>: sort invocation. (line 384) 19152* -z <5>: shuf invocation. (line 55) 19153* -z <6>: uniq invocation. (line 139) 19154* -z <7>: comm invocation. (line 88) 19155* -z <8>: cut invocation. (line 94) 19156* -z <9>: paste invocation. (line 72) 19157* -z <10>: General options in join. 19158 (line 93) 19159* -Z: What information is listed. 19160 (line 259) 19161* -Z <1>: cp invocation. (line 384) 19162* -Z <2>: install invocation. (line 139) 19163* -Z <3>: mv invocation. (line 117) 19164* -z <11>: shred invocation. (line 175) 19165* -Z <4>: mkdir invocation. (line 56) 19166* -Z <5>: mkfifo invocation. (line 28) 19167* -Z <6>: mknod invocation. (line 53) 19168* -z <12>: readlink invocation. (line 65) 19169* -z <13>: String tests. (line 15) 19170* -z <14>: basename invocation. (line 42) 19171* -z <15>: dirname invocation. (line 31) 19172* -z <16>: realpath invocation. (line 71) 19173* -Z <7>: id invocation. (line 51) 19174* -z <17>: id invocation. (line 58) 19175* -z <18>: numfmt invocation. (line 115) 19176* /: Numeric expressions. (line 16) 19177* 128-bit checksum: md5sum invocation. (line 6) 19178* 16-bit checksum: sum invocation. (line 6) 19179* 160-bit checksum: sha1sum invocation. (line 6) 19180* 224-bit checksum: sha2 utilities. (line 6) 19181* 256-bit checksum: sha2 utilities. (line 6) 19182* 384-bit checksum: sha2 utilities. (line 6) 19183* 512-bit checksum: b2sum invocation. (line 6) 19184* 512-bit checksum <1>: sha2 utilities. (line 6) 19185* <: Relations for expr. (line 22) 19186* <=: Relations for expr. (line 22) 19187* =: Relations for expr. (line 22) 19188* = <1>: String tests. (line 22) 19189* ==: Relations for expr. (line 22) 19190* == <1>: String tests. (line 25) 19191* >: Relations for expr. (line 22) 19192* >=: Relations for expr. (line 22) 19193* \( regexp operator: String expressions. (line 24) 19194* \+ regexp operator: String expressions. (line 28) 19195* \? regexp operator: String expressions. (line 28) 19196* \c: printf invocation. (line 28) 19197* \OOO: printf invocation. (line 67) 19198* \uhhhh: printf invocation. (line 74) 19199* \Uhhhhhhhh: printf invocation. (line 74) 19200* \xHH: printf invocation. (line 67) 19201* \| regexp operator: String expressions. (line 28) 19202* _POSIX2_VERSION: Standards conformance. 19203 (line 20) 19204* _POSIX2_VERSION <1>: tail invocation. (line 203) 19205* _POSIX2_VERSION <2>: sort invocation. (line 416) 19206* _POSIX2_VERSION <3>: uniq invocation. (line 46) 19207* _POSIX2_VERSION <4>: touch invocation. (line 107) 19208* |: Relations for expr. (line 11) 19209* abbreviations for months: Calendar date items. (line 38) 19210* access permission tests: Access permission tests. 19211 (line 6) 19212* access permissions, changing: chmod invocation. (line 6) 19213* access time, changing: touch invocation. (line 48) 19214* access timestamp: dd invocation. (line 278) 19215* access timestamp, printing or sorting files by: Sorting the output. 19216 (line 44) 19217* access timestamp, show the most recent: du invocation. (line 210) 19218* across columns: pr invocation. (line 62) 19219* across, listing files: General output formatting. 19220 (line 113) 19221* adding permissions: Setting Permissions. (line 35) 19222* addition: Numeric expressions. (line 12) 19223* ago in date strings: Relative items in date strings. 19224 (line 23) 19225* all lines, grouping: uniq invocation. (line 100) 19226* all repeated lines, outputting: uniq invocation. (line 69) 19227* alnum: Character sets. (line 88) 19228* alpha: Character sets. (line 90) 19229* alternate ebcdic, converting to: dd invocation. (line 117) 19230* always color option: General output formatting. 19231 (line 26) 19232* always hyperlink option: General output formatting. 19233 (line 65) 19234* always interactive option: rm invocation. (line 59) 19235* am i: who invocation. (line 21) 19236* am in date strings: Time of day items. (line 21) 19237* and operator: Connectives for test. 19238 (line 29) 19239* and operator <1>: Relations for expr. (line 17) 19240* append: dd invocation. (line 207) 19241* appending to the output file: dd invocation. (line 207) 19242* appropriate privileges: install invocation. (line 91) 19243* appropriate privileges <1>: Setting the time. (line 6) 19244* appropriate privileges <2>: hostname invocation. (line 6) 19245* appropriate privileges <3>: nice invocation. (line 6) 19246* arbitrary date strings, debugging: Options for date. (line 25) 19247* arbitrary date strings, parsing: Options for date. (line 11) 19248* arbitrary text, displaying: echo invocation. (line 6) 19249* arch: arch invocation. (line 6) 19250* arithmetic tests: Numeric tests. (line 6) 19251* ASCII dump of files: od invocation. (line 6) 19252* ascii, converting to: dd invocation. (line 106) 19253* atime: File timestamps. (line 6) 19254* atime, changing: touch invocation. (line 48) 19255* atime, printing or sorting files by: Sorting the output. (line 44) 19256* atime, show the most recent: du invocation. (line 210) 19257* attribute caching: stat invocation. (line 33) 19258* attributes, file: Changing file attributes. 19259 (line 6) 19260* authors of parse_datetime: Authors of parse_datetime. 19261 (line 6) 19262* auto color option: General output formatting. 19263 (line 25) 19264* auto hyperlink option: General output formatting. 19265 (line 64) 19266* b for block special file: mknod invocation. (line 31) 19267* b2sum: b2sum invocation. (line 6) 19268* background jobs, stopping at terminal write: Local. (line 41) 19269* backslash escapes: Character sets. (line 14) 19270* backslash escapes <1>: echo invocation. (line 25) 19271* backslash escapes <2>: echo invocation. (line 61) 19272* backslash sequences for file names: Formatting the file names. 19273 (line 11) 19274* backup files, ignoring: Which files are listed. 19275 (line 23) 19276* backup options: Backup options. (line 6) 19277* backup suffix: Backup options. (line 49) 19278* backups, making: Backup options. (line 13) 19279* backups, making <1>: cp invocation. (line 79) 19280* backups, making <2>: install invocation. (line 41) 19281* backups, making <3>: mv invocation. (line 59) 19282* backups, making <4>: ln invocation. (line 82) 19283* backups, making only: cp invocation. (line 51) 19284* base32: base32 invocation. (line 6) 19285* base32 encoding: base32 invocation. (line 6) 19286* base32 encoding <1>: basenc invocation. (line 6) 19287* base64: base64 invocation. (line 6) 19288* Base64 decoding: base64 invocation. (line 30) 19289* base64 encoding: base64 invocation. (line 6) 19290* basename: basename invocation. (line 6) 19291* basenc: basenc invocation. (line 6) 19292* baud rate, setting: Special. (line 52) 19293* beeping at input buffer full: Input. (line 59) 19294* beginning of time: Time conversion specifiers. 19295 (line 32) 19296* beginning of time, for POSIX: Seconds since the Epoch. 19297 (line 13) 19298* Bellovin, Steven M.: Authors of parse_datetime. 19299 (line 6) 19300* Berets, Jim: Authors of parse_datetime. 19301 (line 6) 19302* Berry, K.: Introduction. (line 29) 19303* Berry, K. <1>: Authors of parse_datetime. 19304 (line 19) 19305* binary: dd invocation. (line 295) 19306* binary I/O: dd invocation. (line 295) 19307* binary input files: md5sum invocation. (line 41) 19308* bind mount: rm invocation. (line 67) 19309* bind mount <1>: stat invocation. (line 191) 19310* birth time, printing or sorting files by: Sorting the output. 19311 (line 52) 19312* birthtime: File timestamps. (line 6) 19313* BLAKE2: b2sum invocation. (line 6) 19314* BLAKE2 hash length: b2sum invocation. (line 12) 19315* blank: Character sets. (line 92) 19316* blank lines, numbering: nl invocation. (line 82) 19317* blanks, ignoring leading: sort invocation. (line 79) 19318* block (space-padding): dd invocation. (line 127) 19319* block size: Block size. (line 6) 19320* block size <1>: dd invocation. (line 34) 19321* block size of conversion: dd invocation. (line 41) 19322* block size of input: dd invocation. (line 26) 19323* block size of output: dd invocation. (line 30) 19324* block special check: File type tests. (line 10) 19325* block special files: mknod invocation. (line 11) 19326* block special files, creating: mknod invocation. (line 6) 19327* BLOCKSIZE: Block size. (line 12) 19328* BLOCK_SIZE: Block size. (line 12) 19329* body, numbering: nl invocation. (line 17) 19330* Bourne shell syntax for color setup: dircolors invocation. 19331 (line 34) 19332* breaks, cause interrupts: Input. (line 12) 19333* breaks, ignoring: Input. (line 9) 19334* brkint: Input. (line 12) 19335* bs: dd invocation. (line 34) 19336* BSD output: md5sum invocation. (line 99) 19337* BSD sum: sum invocation. (line 25) 19338* BSD tail: tail invocation. (line 26) 19339* BSD touch compatibility: touch invocation. (line 66) 19340* bsN: Output. (line 55) 19341* btrfs file system type: df invocation. (line 211) 19342* bugs, reporting: Introduction. (line 12) 19343* built-in shell commands, conflicts with: mknod invocation. (line 20) 19344* built-in shell commands, conflicts with <1>: stat invocation. 19345 (line 15) 19346* built-in shell commands, conflicts with <2>: echo invocation. 19347 (line 11) 19348* built-in shell commands, conflicts with <3>: printf invocation. 19349 (line 16) 19350* built-in shell commands, conflicts with <4>: test invocation. 19351 (line 28) 19352* built-in shell commands, conflicts with <5>: pwd invocation. 19353 (line 30) 19354* built-in shell commands, conflicts with <6>: nice invocation. 19355 (line 38) 19356* built-in shell commands, conflicts with <7>: kill invocation. 19357 (line 13) 19358* built-in shell commands, conflicts with <8>: sleep invocation. 19359 (line 36) 19360* byte count: wc invocation. (line 6) 19361* byte-swapping: od invocation. (line 51) 19362* byte-swapping <1>: dd invocation. (line 159) 19363* c for character special file: mknod invocation. (line 34) 19364* C shell syntax for color setup: dircolors invocation. 19365 (line 40) 19366* C-s/C-q flow control: Input. (line 40) 19367* calendar date item: Calendar date items. (line 6) 19368* calling combined multi-call program: Multi-call invocation. 19369 (line 6) 19370* canonical file name: readlink invocation. (line 6) 19371* canonical file name <1>: realpath invocation. (line 6) 19372* canonicalize a file name: readlink invocation. (line 6) 19373* canonicalize a file name <1>: realpath invocation. (line 6) 19374* case folding: sort invocation. (line 94) 19375* case translation: Local. (line 36) 19376* case, ignored in dates: General date syntax. (line 60) 19377* cat: cat invocation. (line 6) 19378* cbreak: Combination. (line 52) 19379* cbs: dd invocation. (line 41) 19380* CD-ROM file system type: df invocation. (line 215) 19381* cdfs file system type: df invocation. (line 215) 19382* cdtrdsr: Control. (line 44) 19383* change or print terminal settings: stty invocation. (line 6) 19384* change SELinux context: chcon invocation. (line 6) 19385* changed files, verbosely describing: chgrp invocation. (line 24) 19386* changed owners, verbosely describing: chown invocation. (line 73) 19387* changing access permissions: chmod invocation. (line 6) 19388* changing file attributes: Changing file attributes. 19389 (line 6) 19390* changing file ownership: chown invocation. (line 6) 19391* changing file timestamps: touch invocation. (line 6) 19392* changing group ownership: chown invocation. (line 6) 19393* changing group ownership <1>: chgrp invocation. (line 6) 19394* changing security context: chcon invocation. (line 6) 19395* changing special mode bits: Changing Special Mode Bits. 19396 (line 6) 19397* character classes: Character sets. (line 74) 19398* character count: wc invocation. (line 6) 19399* character size: Control. (line 24) 19400* character special check: File type tests. (line 13) 19401* character special files: mknod invocation. (line 11) 19402* character special files, creating: mknod invocation. (line 6) 19403* characters, special: Characters. (line 6) 19404* chcon: chcon invocation. (line 6) 19405* check file types: test invocation. (line 6) 19406* checking for sortedness: sort invocation. (line 39) 19407* checking for sortedness <1>: sort invocation. (line 47) 19408* checksum, 128-bit: md5sum invocation. (line 6) 19409* checksum, 16-bit: sum invocation. (line 6) 19410* checksum, 160-bit: sha1sum invocation. (line 6) 19411* checksum, 224-bit: sha2 utilities. (line 6) 19412* checksum, 256-bit: sha2 utilities. (line 6) 19413* checksum, 384-bit: sha2 utilities. (line 6) 19414* checksum, 512-bit: b2sum invocation. (line 6) 19415* checksum, 512-bit <1>: sha2 utilities. (line 6) 19416* chgrp: chgrp invocation. (line 6) 19417* chmod: chmod invocation. (line 6) 19418* chown: chown invocation. (line 6) 19419* chroot: chroot invocation. (line 6) 19420* cio: dd invocation. (line 215) 19421* cksum: cksum invocation. (line 6) 19422* clocal: Control. (line 38) 19423* clock skew: Formatting file timestamps. 19424 (line 11) 19425* clock skew <1>: File timestamps. (line 39) 19426* clone: cp invocation. (line 265) 19427* cmspar: Control. (line 16) 19428* cntrl: Character sets. (line 94) 19429* color database, printing: dircolors invocation. 19430 (line 45) 19431* color setup: dircolors invocation. 19432 (line 6) 19433* color, distinguishing file types with: General output formatting. 19434 (line 22) 19435* cols: Special. (line 27) 19436* column to wrap data after: base64 invocation. (line 22) 19437* COLUMNS: General output formatting. 19438 (line 128) 19439* COLUMNS <1>: Special. (line 39) 19440* columns: Special. (line 27) 19441* combination settings: Combination. (line 6) 19442* combined: Multi-call invocation. 19443 (line 6) 19444* combined date and time of day item: Combined date and time of day items. 19445 (line 6) 19446* comm: comm invocation. (line 6) 19447* command-line operands to shuffle: shuf invocation. (line 19) 19448* commands for controlling processes: Process control. (line 6) 19449* commands for delaying: Delaying. (line 6) 19450* commands for exit status: Conditions. (line 6) 19451* commands for file name manipulation: File name manipulation. 19452 (line 6) 19453* commands for invoking other commands: Modified command invocation. 19454 (line 6) 19455* commands for printing text: Printing text. (line 6) 19456* commands for printing the working context: Working context. (line 6) 19457* commands for printing user information: User information. (line 6) 19458* commands for redirection: Redirection. (line 6) 19459* commands for SELinux context: SELinux context. (line 6) 19460* commands for system context: System context. (line 6) 19461* commas, outputting between files: General output formatting. 19462 (line 103) 19463* comments, in dates: General date syntax. (line 60) 19464* common field, joining on: join invocation. (line 6) 19465* common lines: comm invocation. (line 18) 19466* common options: Common options. (line 6) 19467* compare values: test invocation. (line 6) 19468* comparing sorted files: comm invocation. (line 6) 19469* comparison operators: Relations for expr. (line 22) 19470* concatenate and write files: cat invocation. (line 6) 19471* concurrent I/O: dd invocation. (line 215) 19472* conditional executability: Conditional Executability. 19473 (line 6) 19474* conditions: Conditions. (line 6) 19475* conflicts with shell built-ins: mknod invocation. (line 20) 19476* conflicts with shell built-ins <1>: stat invocation. (line 15) 19477* conflicts with shell built-ins <2>: echo invocation. (line 11) 19478* conflicts with shell built-ins <3>: printf invocation. (line 16) 19479* conflicts with shell built-ins <4>: test invocation. (line 28) 19480* conflicts with shell built-ins <5>: pwd invocation. (line 30) 19481* conflicts with shell built-ins <6>: nice invocation. (line 38) 19482* conflicts with shell built-ins <7>: kill invocation. (line 13) 19483* conflicts with shell built-ins <8>: sleep invocation. (line 36) 19484* connectives, logical: Connectives for test. 19485 (line 6) 19486* connectives, logical <1>: Relations for expr. (line 6) 19487* constant parity: Control. (line 16) 19488* context splitting: csplit invocation. (line 6) 19489* context, system: System context. (line 6) 19490* control characters, using ^C: Local. (line 51) 19491* control settings: Control. (line 6) 19492* controlling terminal: dd invocation. (line 284) 19493* conv: dd invocation. (line 100) 19494* conversion block size: dd invocation. (line 41) 19495* conversion specifiers, date: Date conversion specifiers. 19496 (line 6) 19497* conversion specifiers, literal: Literal conversion specifiers. 19498 (line 6) 19499* conversion specifiers, time: Time conversion specifiers. 19500 (line 6) 19501* converting tabs to spaces: expand invocation. (line 6) 19502* converting while copying a file: dd invocation. (line 6) 19503* cooked: Combination. (line 37) 19504* Coordinated Universal Time: Options for date. (line 119) 19505* copy on write: cp invocation. (line 265) 19506* copying directories recursively: cp invocation. (line 96) 19507* copying directories recursively <1>: cp invocation. (line 252) 19508* copying existing permissions: Copying Permissions. (line 6) 19509* copying files: cat invocation. (line 6) 19510* copying files and directories: cp invocation. (line 6) 19511* copying files and setting attributes: install invocation. (line 6) 19512* core utilities: Top. (line 18) 19513* count: dd invocation. (line 56) 19514* count_bytes: dd invocation. (line 313) 19515* COW: cp invocation. (line 265) 19516* cp: cp invocation. (line 6) 19517* crashes and corruption: sync invocation. (line 17) 19518* CRC checksum: cksum invocation. (line 6) 19519* cread: Control. (line 35) 19520* creating directories: mkdir invocation. (line 6) 19521* creating FIFOs (named pipes): mkfifo invocation. (line 6) 19522* creating links (hard only): link invocation. (line 6) 19523* creating links (hard or soft): ln invocation. (line 6) 19524* creating output file, avoiding: dd invocation. (line 176) 19525* creating output file, requiring: dd invocation. (line 172) 19526* creation timestamp, printing or sorting files by: Sorting the output. 19527 (line 52) 19528* crN: Output. (line 45) 19529* crown margin: fmt invocation. (line 34) 19530* crt: Combination. (line 75) 19531* crterase: Local. (line 22) 19532* crtkill: Local. (line 56) 19533* crtscts: Control. (line 41) 19534* csh syntax for color setup: dircolors invocation. 19535 (line 40) 19536* csN: Control. (line 24) 19537* csplit: csplit invocation. (line 6) 19538* cstopb: Control. (line 32) 19539* ctime: File timestamps. (line 6) 19540* ctime, printing or sorting by: Sorting the output. (line 13) 19541* ctime, show the most recent: du invocation. (line 204) 19542* ctlecho: Local. (line 51) 19543* current working directory, printing: pwd invocation. (line 6) 19544* cut: cut invocation. (line 6) 19545* cyclic redundancy check: cksum invocation. (line 6) 19546* data, erasing: shred invocation. (line 6) 19547* database for color setup, printing: dircolors invocation. 19548 (line 45) 19549* date: date invocation. (line 6) 19550* date and time of day format, ISO 8601: Combined date and time of day items. 19551 (line 6) 19552* date conversion specifiers: Date conversion specifiers. 19553 (line 6) 19554* date format, ISO 8601: Calendar date items. (line 30) 19555* date input formats: Date input formats. (line 6) 19556* date options: Options for date. (line 6) 19557* date strings, debugging: Options for date. (line 25) 19558* date strings, parsing: Options for date. (line 11) 19559* day in date strings: Relative items in date strings. 19560 (line 15) 19561* day in date strings <1>: Relative items in date strings. 19562 (line 29) 19563* day of week item: Day of week items. (line 6) 19564* dd: dd invocation. (line 6) 19565* ddrescue: dd invocation. (line 362) 19566* debugging date strings: Options for date. (line 25) 19567* debugging, env -S: env invocation. (line 273) 19568* dec: Combination. (line 78) 19569* decctlq: Combination. (line 63) 19570* Decode base64 data: base64 invocation. (line 30) 19571* delay for a specified time: sleep invocation. (line 6) 19572* delaying commands: Delaying. (line 6) 19573* deleting characters: Squeezing and deleting. 19574 (line 6) 19575* dereferencing symbolic links: ln invocation. (line 42) 19576* descriptor follow option: tail invocation. (line 56) 19577* destination directory: Target directory. (line 15) 19578* destination directory <1>: Target directory. (line 31) 19579* destination directory <2>: cp invocation. (line 350) 19580* destination directory <3>: cp invocation. (line 354) 19581* destination directory <4>: install invocation. (line 125) 19582* destination directory <5>: install invocation. (line 130) 19583* destination directory <6>: mv invocation. (line 108) 19584* destination directory <7>: mv invocation. (line 112) 19585* destination directory <8>: ln invocation. (line 171) 19586* destination directory <9>: ln invocation. (line 175) 19587* destinations, multiple output: tee invocation. (line 6) 19588* device file, disk: df invocation. (line 30) 19589* df: df invocation. (line 6) 19590* DF_BLOCK_SIZE: Block size. (line 12) 19591* diagnostic: chcon invocation. (line 61) 19592* dictionary order: sort invocation. (line 87) 19593* differing lines: comm invocation. (line 18) 19594* digit: Character sets. (line 96) 19595* dir: dir invocation. (line 6) 19596* dircolors: dircolors invocation. 19597 (line 6) 19598* direct: dd invocation. (line 221) 19599* direct I/O: dd invocation. (line 221) 19600* directories, copying: cp invocation. (line 6) 19601* directories, copying recursively: cp invocation. (line 96) 19602* directories, copying recursively <1>: cp invocation. (line 252) 19603* directories, creating: mkdir invocation. (line 6) 19604* directories, creating with given attributes: install invocation. 19605 (line 67) 19606* directories, removing: rm invocation. (line 35) 19607* directories, removing (recursively): rm invocation. (line 95) 19608* directories, removing empty: rmdir invocation. (line 6) 19609* directory: dd invocation. (line 229) 19610* directory check: File type tests. (line 16) 19611* directory components, printing: dirname invocation. (line 6) 19612* directory deletion, ignoring failures: rmdir invocation. (line 17) 19613* directory deletion, reporting: rmdir invocation. (line 31) 19614* directory I/O: dd invocation. (line 229) 19615* directory listing: ls invocation. (line 6) 19616* directory listing, brief: dir invocation. (line 6) 19617* directory listing, recursive: Which files are listed. 19618 (line 90) 19619* directory listing, verbose: vdir invocation. (line 6) 19620* directory order, listing by: Sorting the output. (line 20) 19621* directory, creating temporary: mktemp invocation. (line 6) 19622* directory, stripping from file names: basename invocation. (line 6) 19623* dired Emacs mode support: What information is listed. 19624 (line 16) 19625* dirname: dirname invocation. (line 6) 19626* disabling special characters: Characters. (line 12) 19627* disambiguating group names and IDs: Disambiguating names and IDs. 19628 (line 6) 19629* discard: Characters. (line 39) 19630* discarding file cache: dd invocation. (line 246) 19631* disk allocation: What information is listed. 19632 (line 236) 19633* disk device file: df invocation. (line 30) 19634* disk usage: Disk usage. (line 6) 19635* disk usage by file system: df invocation. (line 6) 19636* disk usage for files: du invocation. (line 6) 19637* disks, failing: dd invocation. (line 362) 19638* displacement of dates: Relative items in date strings. 19639 (line 6) 19640* displaying text: echo invocation. (line 6) 19641* displaying value of a symbolic link: readlink invocation. (line 6) 19642* division: Numeric expressions. (line 16) 19643* do nothing, successfully: true invocation. (line 6) 19644* do nothing, unsuccessfully: false invocation. (line 6) 19645* DOS file system: df invocation. (line 219) 19646* double spacing: pr invocation. (line 74) 19647* down columns: pr invocation. (line 49) 19648* drain: Special. (line 30) 19649* dsusp: Characters. (line 57) 19650* dsync: dd invocation. (line 235) 19651* DTR/DSR flow control: Control. (line 44) 19652* du: du invocation. (line 6) 19653* DU_BLOCK_SIZE: Block size. (line 12) 19654* DVD file system type: df invocation. (line 215) 19655* ebcdic, converting to: dd invocation. (line 112) 19656* echo: echo invocation. (line 6) 19657* echo <1>: Local. (line 18) 19658* echoctl: Local. (line 51) 19659* echoe: Local. (line 22) 19660* echok: Local. (line 26) 19661* echoke: Local. (line 56) 19662* echonl: Local. (line 29) 19663* echoprt: Local. (line 46) 19664* effective user and group IDs, printing: id invocation. (line 6) 19665* effective user ID, printing: whoami invocation. (line 6) 19666* Eggert, Paul: Authors of parse_datetime. 19667 (line 6) 19668* eight-bit characters: Control. (line 24) 19669* eight-bit characters <1>: Combination. (line 55) 19670* eight-bit input: Input. (line 25) 19671* ek: Combination. (line 22) 19672* empty files, creating: touch invocation. (line 11) 19673* empty lines, numbering: nl invocation. (line 82) 19674* endianness: od invocation. (line 51) 19675* entire files, output of: Output of entire files. 19676 (line 6) 19677* env: env invocation. (line 6) 19678* env -S, and single quotes: env invocation. (line 264) 19679* env -S, debugging: env invocation. (line 273) 19680* env in scripts: env invocation. (line 188) 19681* environment variables, printing: printenv invocation. (line 6) 19682* environment, printing: env invocation. (line 50) 19683* environment, running a program in a modified: env invocation. 19684 (line 6) 19685* eof: Characters. (line 30) 19686* eol: Characters. (line 33) 19687* eol2: Characters. (line 36) 19688* epoch, for POSIX: Seconds since the Epoch. 19689 (line 13) 19690* epoch, seconds since: Time conversion specifiers. 19691 (line 32) 19692* equal string check: String tests. (line 22) 19693* equal string check <1>: String tests. (line 25) 19694* equivalence classes: Character sets. (line 113) 19695* erase: Characters. (line 24) 19696* erasing data: shred invocation. (line 6) 19697* error messages, omitting: chown invocation. (line 79) 19698* error messages, omitting <1>: chgrp invocation. (line 30) 19699* error messages, omitting <2>: chmod invocation. (line 49) 19700* evaluation of expressions: expr invocation. (line 6) 19701* even parity: Control. (line 13) 19702* evenp: Combination. (line 9) 19703* exabyte, definition of: Block size. (line 106) 19704* examples of date: Examples of date. (line 6) 19705* examples of expr: Examples of expr. (line 6) 19706* exbibyte, definition of: Block size. (line 109) 19707* excl: dd invocation. (line 172) 19708* excluding files from du: du invocation. (line 252) 19709* excluding files from du <1>: du invocation. (line 257) 19710* executable file check: Access permission tests. 19711 (line 24) 19712* executables and file type, marking: General output formatting. 19713 (line 46) 19714* execute/search permission: Mode Structure. (line 16) 19715* execute/search permission, symbolic: Setting Permissions. (line 56) 19716* existence-of-file check: File characteristic tests. 19717 (line 9) 19718* existing backup method: Backup options. (line 39) 19719* exit status commands: Conditions. (line 6) 19720* exit status of chroot: chroot invocation. (line 78) 19721* exit status of env: env invocation. (line 193) 19722* exit status of expr: expr invocation. (line 43) 19723* exit status of false: false invocation. (line 6) 19724* exit status of ls: ls invocation. (line 29) 19725* exit status of mktemp: mktemp invocation. (line 128) 19726* exit status of nice: nice invocation. (line 63) 19727* exit status of nohup: nohup invocation. (line 48) 19728* exit status of pathchk: pathchk invocation. (line 47) 19729* exit status of printenv: printenv invocation. (line 23) 19730* exit status of realpath: realpath invocation. (line 75) 19731* exit status of runcon: runcon invocation. (line 50) 19732* exit status of sort: sort invocation. (line 58) 19733* exit status of stdbuf: stdbuf invocation. (line 70) 19734* exit status of test: test invocation. (line 41) 19735* exit status of timeout: timeout invocation. (line 66) 19736* exit status of true: true invocation. (line 6) 19737* exit status of tty: tty invocation. (line 20) 19738* expand: expand invocation. (line 6) 19739* expr: expr invocation. (line 6) 19740* expression evaluation: test invocation. (line 6) 19741* expression evaluation <1>: expr invocation. (line 6) 19742* expressions, numeric: Numeric expressions. (line 6) 19743* expressions, string: String expressions. (line 6) 19744* ext2 file system type: df invocation. (line 211) 19745* ext3 file system type: df invocation. (line 211) 19746* ext4 file system type: df invocation. (line 211) 19747* extended attributes, xattr: install invocation. (line 34) 19748* extended attributes, xattr <1>: mv invocation. (line 33) 19749* extension, sorting files by: Sorting the output. (line 74) 19750* extproc: Local. (line 61) 19751* factor: factor invocation. (line 6) 19752* failure exit status: false invocation. (line 6) 19753* false: false invocation. (line 6) 19754* fat file system file: df invocation. (line 219) 19755* fdatasync: dd invocation. (line 188) 19756* ffN: Output. (line 63) 19757* field separator character: sort invocation. (line 332) 19758* fields, padding numeric: Padding and other flags. 19759 (line 6) 19760* FIFOs, creating: mkfifo invocation. (line 6) 19761* file attributes, changing: Changing file attributes. 19762 (line 6) 19763* file characteristic tests: File characteristic tests. 19764 (line 6) 19765* file contents, dumping unambiguously: od invocation. (line 6) 19766* file information, preserving: cp invocation. (line 235) 19767* file information, preserving, extended attributes, xattr: cp invocation. 19768 (line 169) 19769* file mode bits, numeric: Numeric Modes. (line 6) 19770* file name manipulation: File name manipulation. 19771 (line 6) 19772* file names, canonicalization: realpath invocation. (line 6) 19773* file names, checking validity and portability: pathchk invocation. 19774 (line 6) 19775* file names, creating temporary: mktemp invocation. (line 6) 19776* file names, stripping directory and suffix: basename invocation. 19777 (line 6) 19778* file offset radix: od invocation. (line 36) 19779* file ownership, changing: chown invocation. (line 6) 19780* file sizes: du invocation. (line 52) 19781* file space usage: du invocation. (line 6) 19782* file status: stat invocation. (line 6) 19783* file system disk usage: df invocation. (line 6) 19784* file system sizes: df invocation. (line 54) 19785* file system space, retrieving current data more slowly: df invocation. 19786 (line 174) 19787* file system space, retrieving old data more quickly: df invocation. 19788 (line 84) 19789* file system status: stat invocation. (line 6) 19790* file system types, limiting output to certain: df invocation. 19791 (line 80) 19792* file system types, limiting output to certain <1>: df invocation. 19793 (line 194) 19794* file system types, printing: df invocation. (line 200) 19795* file systems: stat invocation. (line 28) 19796* file systems and hard links: ln invocation. (line 6) 19797* file systems, omitting copying to different: cp invocation. (line 378) 19798* file timestamp resolution: File timestamps. (line 45) 19799* file timestamps, changing: touch invocation. (line 6) 19800* file type and executables, marking: General output formatting. 19801 (line 46) 19802* file type tests: File type tests. (line 6) 19803* file type, marking: General output formatting. 19804 (line 57) 19805* file type, marking <1>: General output formatting. 19806 (line 108) 19807* file types: Special file types. (line 9) 19808* file types, special: Special file types. (line 6) 19809* file utilities: Top. (line 18) 19810* files beginning with -, removing: rm invocation. (line 101) 19811* files, copying: cp invocation. (line 6) 19812* files, creating: truncate invocation. (line 11) 19813* fingerprint, 128-bit: md5sum invocation. (line 6) 19814* fingerprint, 160-bit: sha1sum invocation. (line 6) 19815* fingerprint, 224-bit: sha2 utilities. (line 6) 19816* fingerprint, 256-bit: sha2 utilities. (line 6) 19817* fingerprint, 384-bit: sha2 utilities. (line 6) 19818* fingerprint, 512-bit: b2sum invocation. (line 6) 19819* fingerprint, 512-bit <1>: sha2 utilities. (line 6) 19820* first in date strings: General date syntax. (line 22) 19821* first part of files, outputting: head invocation. (line 6) 19822* fixed-length records, converting to variable-length: dd invocation. 19823 (line 41) 19824* floating point: Floating point. (line 6) 19825* flow control, hardware: Control. (line 41) 19826* flow control, hardware <1>: Control. (line 44) 19827* flow control, software: Input. (line 45) 19828* flush: Characters. (line 39) 19829* flushing, disabling: Local. (line 32) 19830* flusho: Local. (line 67) 19831* fmt: fmt invocation. (line 6) 19832* fold: fold invocation. (line 6) 19833* folding long input lines: fold invocation. (line 6) 19834* footers, numbering: nl invocation. (line 17) 19835* force deletion: shred invocation. (line 123) 19836* formatting file contents: Formatting file contents. 19837 (line 6) 19838* formatting of numbers in seq: seq invocation. (line 28) 19839* formatting times: pr invocation. (line 78) 19840* formatting times <1>: date invocation. (line 20) 19841* fortnight in date strings: Relative items in date strings. 19842 (line 15) 19843* fsync: dd invocation. (line 192) 19844* fullblock: dd invocation. (line 303) 19845* general date syntax: General date syntax. (line 6) 19846* general numeric sort: sort invocation. (line 105) 19847* gibibyte, definition of: Block size. (line 94) 19848* gigabyte, definition of: Block size. (line 91) 19849* giving away permissions: Umask and Protection. 19850 (line 12) 19851* GMT: Options for date. (line 119) 19852* grand total of disk size, usage and available space: df invocation. 19853 (line 180) 19854* grand total of disk space: du invocation. (line 61) 19855* graph: Character sets. (line 98) 19856* Greenwich Mean Time: Options for date. (line 119) 19857* group IDs, disambiguating: Disambiguating names and IDs. 19858 (line 6) 19859* group names, disambiguating: Disambiguating names and IDs. 19860 (line 6) 19861* group owner, default: Mode Structure. (line 27) 19862* group ownership of installed files, setting: install invocation. 19863 (line 73) 19864* group ownership, changing: chown invocation. (line 6) 19865* group ownership, changing <1>: chgrp invocation. (line 6) 19866* group, permissions for: Setting Permissions. (line 25) 19867* groups: groups invocation. (line 6) 19868* growing files: tail invocation. (line 56) 19869* hangups, immunity to: nohup invocation. (line 6) 19870* hard link check: File characteristic tests. 19871 (line 23) 19872* hard link, defined: ln invocation. (line 32) 19873* hard links: dd invocation. (line 292) 19874* hard links to directories: ln invocation. (line 88) 19875* hard links to symbolic links: ln invocation. (line 182) 19876* hard links, counting in du: du invocation. (line 123) 19877* hard links, creating: link invocation. (line 6) 19878* hard links, creating <1>: ln invocation. (line 6) 19879* hard links, preserving: cp invocation. (line 109) 19880* hardware class: uname invocation. (line 42) 19881* hardware flow control: Control. (line 41) 19882* hardware flow control <1>: Control. (line 44) 19883* hardware platform: uname invocation. (line 35) 19884* hardware type: uname invocation. (line 42) 19885* hat notation for control characters: Local. (line 51) 19886* head: head invocation. (line 6) 19887* head of output: shuf invocation. (line 31) 19888* headers, numbering: nl invocation. (line 17) 19889* help, online: Common options. (line 36) 19890* hex dump of files: od invocation. (line 6) 19891* holes, copying files with: cp invocation. (line 299) 19892* holes, creating files with: truncate invocation. (line 13) 19893* horizontal, listing files: General output formatting. 19894 (line 113) 19895* host processor type: uname invocation. (line 51) 19896* hostid: hostid invocation. (line 6) 19897* hostname: hostname invocation. (line 6) 19898* hostname <1>: uname invocation. (line 47) 19899* hour in date strings: Relative items in date strings. 19900 (line 15) 19901* human numeric sort: sort invocation. (line 126) 19902* human-readable output: Block size. (line 42) 19903* human-readable output <1>: What information is listed. 19904 (line 116) 19905* human-readable output <2>: df invocation. (line 59) 19906* human-readable output <3>: du invocation. (line 96) 19907* hup[cl]: Control. (line 28) 19908* hurd, author, printing: What information is listed. 19909 (line 10) 19910* hyperlink, linking to files: General output formatting. 19911 (line 61) 19912* ibs: dd invocation. (line 26) 19913* icanon: Local. (line 11) 19914* icrnl: Input. (line 34) 19915* id: id invocation. (line 6) 19916* idle time: who invocation. (line 85) 19917* IEEE floating point: Floating point. (line 6) 19918* iexten: Local. (line 15) 19919* if: dd invocation. (line 18) 19920* iflag: dd invocation. (line 196) 19921* ignbrk: Input. (line 9) 19922* igncr: Input. (line 31) 19923* ignore file systems: df invocation. (line 42) 19924* Ignore garbage in base64 stream: base64 invocation. (line 36) 19925* ignoring case: sort invocation. (line 94) 19926* ignpar: Input. (line 15) 19927* imaxbel: Input. (line 59) 19928* immunity to hangups: nohup invocation. (line 6) 19929* implementation, hardware: uname invocation. (line 35) 19930* indenting lines: pr invocation. (line 180) 19931* index: String expressions. (line 45) 19932* information, about current users: who invocation. (line 6) 19933* initial part of files, outputting: head invocation. (line 6) 19934* initial tabs, converting: expand invocation. (line 46) 19935* inlcr: Input. (line 28) 19936* inode number, printing: What information is listed. 19937 (line 123) 19938* inode usage: df invocation. (line 69) 19939* inode usage, dereferencing in du: du invocation. (line 102) 19940* inode, and hard links: ln invocation. (line 32) 19941* inodes, written buffered: sync invocation. (line 11) 19942* inpck: Input. (line 22) 19943* input block size: dd invocation. (line 26) 19944* input encoding, UTF-8: Input. (line 37) 19945* input range to shuffle: shuf invocation. (line 23) 19946* input settings: Input. (line 6) 19947* input tabs: pr invocation. (line 98) 19948* install: install invocation. (line 6) 19949* intr: Characters. (line 18) 19950* invocation of commands, modified: Modified command invocation. 19951 (line 6) 19952* isig: Local. (line 7) 19953* ISO 8601 date and time of day format: Combined date and time of day items. 19954 (line 6) 19955* ISO 8601 date format: Calendar date items. (line 30) 19956* ISO/IEC 10646: printf invocation. (line 74) 19957* ISO9660 file system type: df invocation. (line 215) 19958* iso9660 file system type: df invocation. (line 215) 19959* ispeed: Special. (line 16) 19960* istrip: Input. (line 25) 19961* items in date strings: General date syntax. (line 6) 19962* iterations, selecting the number of: shred invocation. (line 127) 19963* iuclc: Input. (line 50) 19964* iutf8: Input. (line 37) 19965* ixany: Input. (line 55) 19966* ixoff: Input. (line 45) 19967* ixon: Input. (line 40) 19968* join: join invocation. (line 6) 19969* kernel name: uname invocation. (line 66) 19970* kernel release: uname invocation. (line 62) 19971* kernel version: uname invocation. (line 77) 19972* kibibyte, definition of: Block size. (line 82) 19973* kibibytes for file sizes: du invocation. (line 111) 19974* kibibytes for file system sizes: df invocation. (line 74) 19975* kill: kill invocation. (line 6) 19976* kill <1>: Characters. (line 27) 19977* kilobyte, definition of: Block size. (line 78) 19978* Knuth, Donald E.: fmt invocation. (line 19) 19979* language, in dates: General date syntax. (line 36) 19980* language, in dates <1>: General date syntax. (line 40) 19981* last DAY: Day of week items. (line 15) 19982* last DAY <1>: Options for date. (line 11) 19983* last in date strings: General date syntax. (line 22) 19984* last modified dates, displaying in du: du invocation. (line 197) 19985* last part of files, outputting: tail invocation. (line 6) 19986* lcase: Combination. (line 71) 19987* LCASE: Combination. (line 71) 19988* lcase, converting to: dd invocation. (line 138) 19989* lchown: chown invocation. (line 106) 19990* lchown <1>: chown invocation. (line 118) 19991* lchown <2>: chgrp invocation. (line 34) 19992* lchown <3>: chgrp invocation. (line 46) 19993* LC_ALL: sort invocation. (line 23) 19994* LC_ALL <1>: ls invocation. (line 17) 19995* LC_COLLATE: sort invocation. (line 23) 19996* LC_COLLATE <1>: uniq invocation. (line 21) 19997* LC_COLLATE <2>: comm invocation. (line 12) 19998* LC_COLLATE <3>: Sorting files for join. 19999 (line 16) 20000* LC_COLLATE <4>: Relations for expr. (line 22) 20001* LC_CTYPE: sort invocation. (line 79) 20002* LC_CTYPE <1>: sort invocation. (line 87) 20003* LC_CTYPE <2>: sort invocation. (line 94) 20004* LC_CTYPE <3>: sort invocation. (line 143) 20005* LC_CTYPE <4>: printf invocation. (line 74) 20006* LC_MESSAGES: pr invocation. (line 13) 20007* LC_NUMERIC: Block size. (line 57) 20008* LC_NUMERIC <1>: Floating point. (line 29) 20009* LC_NUMERIC <2>: sort invocation. (line 105) 20010* LC_NUMERIC <3>: sort invocation. (line 126) 20011* LC_NUMERIC <4>: sort invocation. (line 160) 20012* LC_NUMERIC <5>: printf invocation. (line 61) 20013* LC_TIME: pr invocation. (line 85) 20014* LC_TIME <1>: sort invocation. (line 150) 20015* LC_TIME <2>: Formatting file timestamps. 20016 (line 28) 20017* LC_TIME <3>: Formatting file timestamps. 20018 (line 73) 20019* LC_TIME <4>: Formatting file timestamps. 20020 (line 97) 20021* LC_TIME <5>: du invocation. (line 219) 20022* LC_TIME <6>: date invocation. (line 11) 20023* leading directories, creating missing: install invocation. (line 67) 20024* leading directory components, stripping: basename invocation. 20025 (line 6) 20026* leap seconds: touch invocation. (line 99) 20027* leap seconds <1>: Time conversion specifiers. 20028 (line 32) 20029* leap seconds <2>: Time conversion specifiers. 20030 (line 36) 20031* leap seconds <3>: Options for date. (line 119) 20032* leap seconds <4>: Examples of date. (line 104) 20033* leap seconds <5>: General date syntax. (line 65) 20034* leap seconds <6>: Time of day items. (line 14) 20035* leap seconds <7>: Seconds since the Epoch. 20036 (line 26) 20037* left margin: pr invocation. (line 180) 20038* length: String expressions. (line 50) 20039* limiting output of du: du invocation. (line 74) 20040* line: Special. (line 46) 20041* line buffered: stdbuf invocation. (line 6) 20042* line count: wc invocation. (line 6) 20043* line numbering: nl invocation. (line 6) 20044* line separator character: split invocation. (line 148) 20045* line settings of terminal: stty invocation. (line 6) 20046* line-breaking: fmt invocation. (line 19) 20047* line-by-line comparison: comm invocation. (line 6) 20048* LINES: Special. (line 39) 20049* link: link invocation. (line 6) 20050* links, creating: link invocation. (line 6) 20051* links, creating <1>: ln invocation. (line 6) 20052* Linux file system types: df invocation. (line 211) 20053* literal conversion specifiers: Literal conversion specifiers. 20054 (line 6) 20055* litout: Combination. (line 59) 20056* ln: ln invocation. (line 6) 20057* ln format for nl: nl invocation. (line 93) 20058* lnext: Characters. (line 66) 20059* local file system types: df invocation. (line 211) 20060* local settings: Local. (line 6) 20061* logging out and continuing to run: nohup invocation. (line 6) 20062* logical and operator: Connectives for test. 20063 (line 29) 20064* logical and operator <1>: Relations for expr. (line 17) 20065* logical connectives: Connectives for test. 20066 (line 6) 20067* logical connectives <1>: Relations for expr. (line 6) 20068* logical or operator: Connectives for test. 20069 (line 33) 20070* logical or operator <1>: Relations for expr. (line 11) 20071* logical pages, numbering on: nl invocation. (line 12) 20072* login name, printing: logname invocation. (line 6) 20073* login sessions, printing users with: users invocation. (line 6) 20074* login time: who invocation. (line 11) 20075* logname: logname invocation. (line 6) 20076* long ls format: What information is listed. 20077 (line 131) 20078* lower: Character sets. (line 100) 20079* lowercase, translating to output: Output. (line 12) 20080* ls: ls invocation. (line 6) 20081* LS_BLOCK_SIZE: Block size. (line 12) 20082* LS_COLORS: General output formatting. 20083 (line 31) 20084* LS_COLORS <1>: dircolors invocation. 20085 (line 23) 20086* lutimes: touch invocation. (line 70) 20087* machine type: uname invocation. (line 42) 20088* machine-readable stty output: stty invocation. (line 41) 20089* MacKenzie, D.: Introduction. (line 29) 20090* MacKenzie, David: Authors of parse_datetime. 20091 (line 6) 20092* Makefiles, installing programs in: install invocation. (line 29) 20093* manipulating files: Basic operations. (line 6) 20094* manipulation of file names: File name manipulation. 20095 (line 6) 20096* mark parity: Control. (line 16) 20097* match: String expressions. (line 36) 20098* matching patterns: String expressions. (line 11) 20099* MD5: md5sum invocation. (line 6) 20100* md5sum: md5sum invocation. (line 6) 20101* mebibyte, definition of: Block size. (line 89) 20102* mebibytes for file sizes: du invocation. (line 127) 20103* megabyte, definition of: Block size. (line 86) 20104* merging files: paste invocation. (line 6) 20105* merging files in parallel: pr invocation. (line 6) 20106* merging sorted files: sort invocation. (line 53) 20107* message status: who invocation. (line 94) 20108* message-digest, 128-bit: md5sum invocation. (line 6) 20109* message-digest, 160-bit: sha1sum invocation. (line 6) 20110* message-digest, 224-bit: sha2 utilities. (line 6) 20111* message-digest, 256-bit: sha2 utilities. (line 6) 20112* message-digest, 384-bit: sha2 utilities. (line 6) 20113* message-digest, 512-bit: b2sum invocation. (line 6) 20114* message-digest, 512-bit <1>: sha2 utilities. (line 6) 20115* Meyering, J.: Introduction. (line 29) 20116* Meyering, Jim: Authors of parse_datetime. 20117 (line 6) 20118* midnight in date strings: Time of day items. (line 21) 20119* min: Special. (line 7) 20120* minute in date strings: Relative items in date strings. 20121 (line 15) 20122* minutes, time zone correction by: Time of day items. (line 29) 20123* mkdir: mkdir invocation. (line 6) 20124* mkfifo: mkfifo invocation. (line 6) 20125* mknod: mknod invocation. (line 6) 20126* mktemp: mktemp invocation. (line 6) 20127* modem control: Control. (line 38) 20128* modes and umask: Umask and Protection. 20129 (line 6) 20130* modes of created directories, setting: mkdir invocation. (line 19) 20131* modes of created FIFOs, setting: mkfifo invocation. (line 21) 20132* modification timestamp, sorting files by: Sorting the output. 20133 (line 36) 20134* modified command invocation: Modified command invocation. 20135 (line 6) 20136* modified environment, running a program in a: env invocation. 20137 (line 6) 20138* modify time, changing: touch invocation. (line 85) 20139* month in date strings: Relative items in date strings. 20140 (line 15) 20141* month names in date strings: Calendar date items. (line 38) 20142* months, sorting by: sort invocation. (line 150) 20143* months, written-out: General date syntax. (line 32) 20144* MS-DOS file system: df invocation. (line 219) 20145* MS-Windows file system: df invocation. (line 219) 20146* mtime: File timestamps. (line 6) 20147* mtime, changing: touch invocation. (line 85) 20148* mtime-greater-atime file check: File characteristic tests. 20149 (line 27) 20150* multicall: Multi-call invocation. 20151 (line 6) 20152* multicolumn output, generating: pr invocation. (line 6) 20153* multiple changes to permissions: Multiple Changes. (line 6) 20154* multiplication: Numeric expressions. (line 16) 20155* multipliers after numbers: dd invocation. (line 337) 20156* multithreaded sort: sort invocation. (line 361) 20157* mv: mv invocation. (line 6) 20158* name follow option: tail invocation. (line 56) 20159* name of kernel: uname invocation. (line 66) 20160* named pipe check: File type tests. (line 28) 20161* named pipes, creating: mkfifo invocation. (line 6) 20162* network node name: uname invocation. (line 47) 20163* never interactive option: rm invocation. (line 56) 20164* newer files, copying only: cp invocation. (line 359) 20165* newer files, moving only: mv invocation. (line 84) 20166* newer-than file check: File characteristic tests. 20167 (line 15) 20168* newline echoing after kill: Local. (line 26) 20169* newline, echoing: Local. (line 29) 20170* newline, translating to crlf: Output. (line 19) 20171* newline, translating to return: Input. (line 28) 20172* next DAY: Day of week items. (line 15) 20173* next DAY <1>: Options for date. (line 11) 20174* next in date strings: General date syntax. (line 22) 20175* NFS file system type: df invocation. (line 206) 20176* NFS mounts from BSD to HP-UX: What information is listed. 20177 (line 244) 20178* NFS mounts from BSD to HP-UX <1>: du invocation. (line 266) 20179* nice: nice invocation. (line 6) 20180* niceness: nice invocation. (line 6) 20181* nl: nl invocation. (line 6) 20182* nl <1>: Combination. (line 18) 20183* nlN: Output. (line 39) 20184* no dereference: chcon invocation. (line 26) 20185* no-op: true invocation. (line 6) 20186* noatime: dd invocation. (line 278) 20187* nocache: dd invocation. (line 246) 20188* nocreat: dd invocation. (line 176) 20189* noctty: dd invocation. (line 284) 20190* node name: uname invocation. (line 47) 20191* noerror: dd invocation. (line 185) 20192* noflsh: Local. (line 32) 20193* nofollow: dd invocation. (line 289) 20194* nohup: nohup invocation. (line 6) 20195* nohup.out: nohup invocation. (line 6) 20196* nohup.out <1>: nohup invocation. (line 20) 20197* nolinks: dd invocation. (line 292) 20198* non-directories, copying as special files: cp invocation. (line 96) 20199* non-directories, copying as special files <1>: cp invocation. 20200 (line 252) 20201* non-directory suffix, stripping: dirname invocation. (line 6) 20202* nonblock: dd invocation. (line 275) 20203* nonblocking I/O: dd invocation. (line 275) 20204* nonblocking stty setting: Special. (line 30) 20205* none backup method: Backup options. (line 31) 20206* none color option: General output formatting. 20207 (line 24) 20208* none dd status=: dd invocation. (line 71) 20209* none hyperlink option: General output formatting. 20210 (line 63) 20211* none, sorting option for ls: Sorting the output. (line 60) 20212* nonempty file check: File characteristic tests. 20213 (line 12) 20214* nonprinting characters, ignoring: sort invocation. (line 143) 20215* nonzero-length string check: String tests. (line 19) 20216* noon in date strings: Time of day items. (line 21) 20217* not-equal string check: String tests. (line 28) 20218* notrunc: dd invocation. (line 182) 20219* now in date strings: Relative items in date strings. 20220 (line 33) 20221* noxfer dd status=: dd invocation. (line 75) 20222* NO_NEW_PRIVS: runcon invocation. (line 22) 20223* nproc: nproc invocation. (line 6) 20224* NTFS file system: df invocation. (line 219) 20225* ntfs file system file: df invocation. (line 219) 20226* number of inputs to merge, nmerge: sort invocation. (line 262) 20227* numbered backup method: Backup options. (line 35) 20228* numbering lines: nl invocation. (line 6) 20229* numbers, written-out: General date syntax. (line 22) 20230* numeric expressions: Numeric expressions. (line 6) 20231* numeric field padding: Padding and other flags. 20232 (line 6) 20233* numeric modes: Numeric Modes. (line 6) 20234* numeric operations: Numeric operations. (line 6) 20235* numeric sequences: seq invocation. (line 6) 20236* numeric sort: sort invocation. (line 160) 20237* numeric tests: Numeric tests. (line 6) 20238* numeric uid and gid: What information is listed. 20239 (line 225) 20240* numeric user and group IDs: What information is listed. 20241 (line 225) 20242* numfmt: numfmt invocation. (line 6) 20243* obs: dd invocation. (line 30) 20244* ocrnl: Output. (line 16) 20245* octal dump of files: od invocation. (line 6) 20246* octal numbers for file modes: Numeric Modes. (line 6) 20247* od: od invocation. (line 6) 20248* odd parity: Control. (line 13) 20249* oddp: Combination. (line 14) 20250* of: dd invocation. (line 21) 20251* ofdel: Output. (line 34) 20252* ofill: Output. (line 30) 20253* oflag: dd invocation. (line 200) 20254* olcuc: Output. (line 12) 20255* older-than file check: File characteristic tests. 20256 (line 19) 20257* once interactive option: rm invocation. (line 57) 20258* one file system, restricting du to: du invocation. (line 263) 20259* one file system, restricting rm to: rm invocation. (line 65) 20260* one-line output format: df invocation. (line 148) 20261* onlcr: Output. (line 19) 20262* onlret: Output. (line 27) 20263* onocr: Output. (line 23) 20264* operating on characters: Operating on characters. 20265 (line 6) 20266* operating on sorted files: Operating on sorted files. 20267 (line 6) 20268* operating system name: uname invocation. (line 58) 20269* opost: Output. (line 9) 20270* option delimiter: Common options. (line 43) 20271* options for date: Options for date. (line 6) 20272* or operator: Connectives for test. 20273 (line 33) 20274* or operator <1>: Relations for expr. (line 11) 20275* ordinal numbers: General date syntax. (line 22) 20276* ospeed: Special. (line 19) 20277* other permissions: Setting Permissions. (line 27) 20278* output block size: dd invocation. (line 30) 20279* output file name prefix: split invocation. (line 15) 20280* output file name prefix <1>: csplit invocation. (line 63) 20281* output file name suffix: csplit invocation. (line 67) 20282* output format: stat invocation. (line 49) 20283* output format <1>: stat invocation. (line 58) 20284* output format, portable: df invocation. (line 148) 20285* output NUL-byte-terminated lines: md5sum invocation. (line 128) 20286* output NUL-byte-terminated lines <1>: readlink invocation. (line 65) 20287* output NUL-byte-terminated lines <2>: du invocation. (line 26) 20288* output NUL-byte-terminated lines <3>: basename invocation. (line 42) 20289* output NUL-byte-terminated lines <4>: dirname invocation. (line 31) 20290* output NUL-byte-terminated lines <5>: realpath invocation. (line 71) 20291* output NUL-byte-terminated lines <6>: printenv invocation. (line 19) 20292* output NUL-byte-terminated lines <7>: env invocation. (line 90) 20293* output of entire files: Output of entire files. 20294 (line 6) 20295* output of parts of files: Output of parts of files. 20296 (line 6) 20297* output settings: Output. (line 6) 20298* output tabs: pr invocation. (line 117) 20299* overwriting of input, allowed: sort invocation. (line 288) 20300* overwriting of input, allowed <1>: shuf invocation. (line 36) 20301* owned by effective group ID check: Access permission tests. 20302 (line 31) 20303* owned by effective user ID check: Access permission tests. 20304 (line 28) 20305* owner of file, permissions for: Setting Permissions. (line 23) 20306* owner, default: Mode Structure. (line 27) 20307* ownership of installed files, setting: install invocation. (line 91) 20308* p for FIFO file: mknod invocation. (line 28) 20309* pad character: Output. (line 34) 20310* pad instead of timing for delaying: Output. (line 30) 20311* padding of numeric fields: Padding and other flags. 20312 (line 6) 20313* paragraphs, reformatting: fmt invocation. (line 6) 20314* parenb: Control. (line 9) 20315* parent directories and cp: cp invocation. (line 239) 20316* parent directories, creating: mkdir invocation. (line 34) 20317* parent directories, creating missing: install invocation. (line 67) 20318* parent directories, removing: rmdir invocation. (line 22) 20319* parentheses for grouping: expr invocation. (line 31) 20320* parity: Combination. (line 10) 20321* parity errors, marking: Input. (line 18) 20322* parity, ignoring: Input. (line 15) 20323* parmrk: Input. (line 18) 20324* parodd: Control. (line 13) 20325* parse_datetime: Date input formats. (line 6) 20326* parsing date strings: Options for date. (line 11) 20327* parts of files, output of: Output of parts of files. 20328 (line 6) 20329* pass8: Combination. (line 55) 20330* paste: paste invocation. (line 6) 20331* Paterson, R.: Introduction. (line 29) 20332* PATH: env invocation. (line 28) 20333* pathchk: pathchk invocation. (line 6) 20334* pattern matching: String expressions. (line 11) 20335* pebibyte, definition of: Block size. (line 104) 20336* permission tests: Access permission tests. 20337 (line 6) 20338* permissions of installed files, setting: install invocation. 20339 (line 79) 20340* permissions, changing access: chmod invocation. (line 6) 20341* permissions, copying existing: Copying Permissions. (line 6) 20342* permissions, for changing file timestamps: touch invocation. 20343 (line 21) 20344* permissions, output by ls: What information is listed. 20345 (line 182) 20346* petabyte, definition of: Block size. (line 101) 20347* phone directory order: sort invocation. (line 87) 20348* pieces, splitting a file into: split invocation. (line 6) 20349* Pinard, F.: Introduction. (line 29) 20350* Pinard, F. <1>: Authors of parse_datetime. 20351 (line 19) 20352* pipe fitting: tee invocation. (line 6) 20353* Plass, Michael F.: fmt invocation. (line 19) 20354* platform, hardware: uname invocation. (line 35) 20355* pm in date strings: Time of day items. (line 21) 20356* portable file names, checking for: pathchk invocation. (line 6) 20357* portable output format: df invocation. (line 148) 20358* POSIX: Introduction. (line 11) 20359* POSIX output format: df invocation. (line 148) 20360* POSIXLY_CORRECT: Common options. (line 11) 20361* POSIXLY_CORRECT <1>: Standards conformance. 20362 (line 6) 20363* POSIXLY_CORRECT <2>: pr invocation. (line 85) 20364* POSIXLY_CORRECT <3>: sort invocation. (line 299) 20365* POSIXLY_CORRECT <4>: sort invocation. (line 416) 20366* POSIXLY_CORRECT <5>: dd invocation. (line 406) 20367* POSIXLY_CORRECT <6>: echo invocation. (line 65) 20368* POSIXLY_CORRECT <7>: printf invocation. (line 53) 20369* POSIXLY_CORRECT <8>: id invocation. (line 15) 20370* POSIXLY_CORRECT, and block size: Block size. (line 12) 20371* pr: pr invocation. (line 6) 20372* prime factors: factor invocation. (line 6) 20373* print: Character sets. (line 102) 20374* print machine hardware name: arch invocation. (line 6) 20375* print name of current directory: pwd invocation. (line 6) 20376* print system information: uname invocation. (line 6) 20377* print terminal file name: tty invocation. (line 6) 20378* Print the number of processors: nproc invocation. (line 6) 20379* printenv: printenv invocation. (line 6) 20380* printf: printf invocation. (line 6) 20381* printing all or some environment variables: printenv invocation. 20382 (line 6) 20383* printing color database: dircolors invocation. 20384 (line 45) 20385* printing current user information: who invocation. (line 6) 20386* printing current usernames: users invocation. (line 6) 20387* printing groups a user is in: groups invocation. (line 6) 20388* printing real and effective user and group IDs: id invocation. 20389 (line 6) 20390* printing text: echo invocation. (line 6) 20391* printing text, commands for: Printing text. (line 6) 20392* printing the current time: date invocation. (line 6) 20393* printing the effective user ID: whoami invocation. (line 6) 20394* printing the host identifier: hostid invocation. (line 6) 20395* printing the hostname: hostname invocation. (line 6) 20396* printing the system uptime and load: uptime invocation. (line 6) 20397* printing user’s login name: logname invocation. (line 6) 20398* printing, preparing files for: pr invocation. (line 6) 20399* process zero-terminated items: head invocation. (line 55) 20400* process zero-terminated items <1>: tail invocation. (line 188) 20401* process zero-terminated items <2>: sort invocation. (line 384) 20402* process zero-terminated items <3>: shuf invocation. (line 55) 20403* process zero-terminated items <4>: uniq invocation. (line 139) 20404* process zero-terminated items <5>: comm invocation. (line 88) 20405* process zero-terminated items <6>: cut invocation. (line 94) 20406* process zero-terminated items <7>: paste invocation. (line 72) 20407* process zero-terminated items <8>: General options in join. 20408 (line 93) 20409* process zero-terminated items <9>: numfmt invocation. (line 115) 20410* processes, commands for controlling: Process control. (line 6) 20411* progress dd status=: dd invocation. (line 79) 20412* prompting, and ln: ln invocation. (line 98) 20413* prompting, and mv: mv invocation. (line 37) 20414* prompting, and rm: rm invocation. (line 11) 20415* prompts, forcing: mv invocation. (line 70) 20416* prompts, omitting: mv invocation. (line 64) 20417* prompts, omitting <1>: mv invocation. (line 77) 20418* prterase: Local. (line 46) 20419* ptx: ptx invocation. (line 6) 20420* punct: Character sets. (line 104) 20421* pure numbers in date strings: Pure numbers in date strings. 20422 (line 6) 20423* pwd: pwd invocation. (line 6) 20424* quit: Characters. (line 21) 20425* quoting style: Formatting the file names. 20426 (line 34) 20427* radix for file offsets: od invocation. (line 36) 20428* random seed: Random sources. (line 31) 20429* random sort: sort invocation. (line 189) 20430* random source for shredding: shred invocation. (line 133) 20431* random source for shuffling: shuf invocation. (line 42) 20432* random source for sorting: sort invocation. (line 304) 20433* random sources: Random sources. (line 6) 20434* ranges: Character sets. (line 44) 20435* raw: Combination. (line 43) 20436* read errors, ignoring: dd invocation. (line 185) 20437* read from stdin and write to stdout and files: tee invocation. 20438 (line 6) 20439* read permission: Mode Structure. (line 12) 20440* read permission, symbolic: Setting Permissions. (line 52) 20441* read system call, and holes: cp invocation. (line 299) 20442* readable file check: Access permission tests. 20443 (line 15) 20444* readlink: readlink invocation. (line 6) 20445* real user and group IDs, printing: id invocation. (line 6) 20446* realpath: realpath invocation. (line 6) 20447* realpath <1>: realpath invocation. (line 6) 20448* realpath <2>: realpath invocation. (line 6) 20449* realpath <3>: readlink invocation. (line 6) 20450* record separator character: split invocation. (line 148) 20451* recursive directory listing: Which files are listed. 20452 (line 90) 20453* recursively changing access permissions: chmod invocation. (line 73) 20454* recursively changing file ownership: chown invocation. (line 150) 20455* recursively changing group ownership: chgrp invocation. (line 77) 20456* recursively copying directories: cp invocation. (line 96) 20457* recursively copying directories <1>: cp invocation. (line 252) 20458* redirection: Redirection. (line 6) 20459* reference file: chcon invocation. (line 30) 20460* reformatting paragraph text: fmt invocation. (line 6) 20461* regular expression matching: String expressions. (line 11) 20462* regular file check: File type tests. (line 19) 20463* relations, numeric or string: Relations for expr. (line 6) 20464* relative items in date strings: Relative items in date strings. 20465 (line 6) 20466* release of kernel: uname invocation. (line 62) 20467* relpath: realpath invocation. (line 49) 20468* remainder: Numeric expressions. (line 16) 20469* remote hostname: who invocation. (line 11) 20470* removing characters: Squeezing and deleting. 20471 (line 6) 20472* removing empty directories: rmdir invocation. (line 6) 20473* removing files after shredding: shred invocation. (line 144) 20474* removing files or directories: rm invocation. (line 6) 20475* removing files or directories (via the unlink syscall): unlink invocation. 20476 (line 6) 20477* removing permissions: Setting Permissions. (line 38) 20478* repeat output values: shuf invocation. (line 47) 20479* repeated characters: Character sets. (line 66) 20480* repeated lines, outputting: uniq invocation. (line 63) 20481* repeated output of a string: yes invocation. (line 6) 20482* restricted deletion flag: Mode Structure. (line 52) 20483* restricted security context: runcon invocation. (line 22) 20484* return, ignoring: Input. (line 31) 20485* return, translating to newline: Input. (line 34) 20486* return, translating to newline <1>: Output. (line 16) 20487* reverse sorting: sort invocation. (line 183) 20488* reverse sorting <1>: Sorting the output. (line 27) 20489* reversing files: tac invocation. (line 6) 20490* rm: rm invocation. (line 6) 20491* rmdir: rmdir invocation. (line 6) 20492* rn format for nl: nl invocation. (line 95) 20493* root as default owner: install invocation. (line 91) 20494* root directory, allow recursive destruction: rm invocation. (line 88) 20495* root directory, allow recursive modification: chown invocation. 20496 (line 131) 20497* root directory, allow recursive modification <1>: chgrp invocation. 20498 (line 59) 20499* root directory, allow recursive modification <2>: chmod invocation. 20500 (line 58) 20501* root directory, disallow recursive destruction: rm invocation. 20502 (line 81) 20503* root directory, disallow recursive modification: chown invocation. 20504 (line 126) 20505* root directory, disallow recursive modification <1>: chgrp invocation. 20506 (line 54) 20507* root directory, disallow recursive modification <2>: chmod invocation. 20508 (line 53) 20509* root directory, running a program in a specified: chroot invocation. 20510 (line 6) 20511* rows: Special. (line 22) 20512* rprnt: Characters. (line 60) 20513* RTS/CTS flow control: Control. (line 41) 20514* run commands with bounded time: timeout invocation. (line 6) 20515* run with security context: runcon invocation. (line 6) 20516* runcon: runcon invocation. (line 6) 20517* running a program in a modified environment: env invocation. 20518 (line 6) 20519* running a program in a specified root directory: chroot invocation. 20520 (line 6) 20521* rz format for nl: nl invocation. (line 97) 20522* Salz, Rich: Authors of parse_datetime. 20523 (line 6) 20524* same file check: File characteristic tests. 20525 (line 23) 20526* sane: Combination. (line 26) 20527* scheduling, affecting: nice invocation. (line 6) 20528* screen columns: fold invocation. (line 14) 20529* scripts arguments: env invocation. (line 188) 20530* seconds since the epoch: Time conversion specifiers. 20531 (line 32) 20532* section delimiters of pages: nl invocation. (line 63) 20533* security context: What information is listed. 20534 (line 259) 20535* security context <1>: cp invocation. (line 384) 20536* security context <2>: install invocation. (line 96) 20537* security context <3>: install invocation. (line 139) 20538* security context <4>: mv invocation. (line 117) 20539* security context <5>: mkdir invocation. (line 56) 20540* security context <6>: mkfifo invocation. (line 28) 20541* security context <7>: mknod invocation. (line 53) 20542* security context <8>: id invocation. (line 51) 20543* seek: dd invocation. (line 51) 20544* seek_bytes: dd invocation. (line 325) 20545* self-backups: cp invocation. (line 51) 20546* SELinux: What information is listed. 20547 (line 259) 20548* SELinux <1>: install invocation. (line 96) 20549* SELinux <2>: id invocation. (line 51) 20550* SELinux context: SELinux context. (line 6) 20551* SELinux, context: SELinux context. (line 6) 20552* SELinux, restoring security context: mv invocation. (line 117) 20553* SELinux, setting/restoring security context: cp invocation. (line 384) 20554* SELinux, setting/restoring security context <1>: install invocation. 20555 (line 139) 20556* SELinux, setting/restoring security context <2>: mkdir invocation. 20557 (line 56) 20558* SELinux, setting/restoring security context <3>: mkfifo invocation. 20559 (line 28) 20560* SELinux, setting/restoring security context <4>: mknod invocation. 20561 (line 53) 20562* send a signal to processes: kill invocation. (line 6) 20563* sentences and line-breaking: fmt invocation. (line 19) 20564* separator for numbers in seq: seq invocation. (line 44) 20565* seq: seq invocation. (line 6) 20566* sequence of numbers: seq invocation. (line 6) 20567* set-group-ID: Mode Structure. (line 45) 20568* set-group-ID check: Access permission tests. 20569 (line 9) 20570* set-user-ID: Mode Structure. (line 39) 20571* set-user-ID check: Access permission tests. 20572 (line 18) 20573* setgid: Mode Structure. (line 45) 20574* setting permissions: Setting Permissions. (line 41) 20575* setting the hostname: hostname invocation. (line 6) 20576* setting the time: Setting the time. (line 6) 20577* setuid: Mode Structure. (line 39) 20578* setup for color: dircolors invocation. 20579 (line 6) 20580* sh syntax for color setup: dircolors invocation. 20581 (line 34) 20582* SHA-1: sha1sum invocation. (line 6) 20583* SHA-2: sha2 utilities. (line 6) 20584* sha1sum: sha1sum invocation. (line 6) 20585* sha224sum: sha2 utilities. (line 6) 20586* sha256sum: sha2 utilities. (line 6) 20587* sha384sum: sha2 utilities. (line 6) 20588* sha512sum: sha2 utilities. (line 6) 20589* shebang arguments: env invocation. (line 188) 20590* SHELL environment variable, and color: General output formatting. 20591 (line 31) 20592* SHELL environment variable, and color <1>: dircolors invocation. 20593 (line 23) 20594* shell utilities: Top. (line 18) 20595* shred: shred invocation. (line 6) 20596* shuf: shuf invocation. (line 6) 20597* shuffling files: shuf invocation. (line 6) 20598* SI output: Block size. (line 42) 20599* SI output <1>: What information is listed. 20600 (line 251) 20601* SI output <2>: df invocation. (line 167) 20602* SI output <3>: du invocation. (line 145) 20603* signals, specifying: Signal specifications. 20604 (line 6) 20605* simple backup method: Backup options. (line 44) 20606* SIMPLE_BACKUP_SUFFIX: Backup options. (line 49) 20607* single quotes, and env -S: env invocation. (line 264) 20608* single-column output of files: General output formatting. 20609 (line 10) 20610* size: Special. (line 39) 20611* size for main memory sorting: sort invocation. (line 316) 20612* size of file to shred: shred invocation. (line 138) 20613* size of files, reporting: What information is listed. 20614 (line 236) 20615* size of files, sorting files by: Sorting the output. (line 32) 20616* skip: dd invocation. (line 46) 20617* skip_bytes: dd invocation. (line 319) 20618* sleep: sleep invocation. (line 6) 20619* socket check: File type tests. (line 31) 20620* software flow control: Input. (line 45) 20621* sort: sort invocation. (line 6) 20622* sort field: sort invocation. (line 231) 20623* sort stability: sort invocation. (line 12) 20624* sort stability <1>: sort invocation. (line 309) 20625* sort’s last-resort comparison: sort invocation. (line 12) 20626* sort’s last-resort comparison <1>: sort invocation. (line 309) 20627* sorted files, operations on: Operating on sorted files. 20628 (line 6) 20629* sorting files: sort invocation. (line 6) 20630* sorting ls output: Sorting the output. (line 6) 20631* space: Character sets. (line 106) 20632* space parity: Control. (line 16) 20633* sparse: dd invocation. (line 146) 20634* sparse files, copying: cp invocation. (line 299) 20635* sparse files, creating: truncate invocation. (line 13) 20636* special characters: Characters. (line 6) 20637* special file types: Special file types. (line 6) 20638* special file types <1>: Special file types. (line 9) 20639* special files: mknod invocation. (line 11) 20640* special settings: Special. (line 6) 20641* specifying sets of characters: Character sets. (line 6) 20642* speed: Special. (line 49) 20643* split: split invocation. (line 6) 20644* splitting a file into pieces: split invocation. (line 6) 20645* splitting a file into pieces by context: csplit invocation. (line 6) 20646* squeezing blank lines: cat invocation. (line 36) 20647* squeezing empty lines: cat invocation. (line 36) 20648* squeezing repeat characters: Squeezing and deleting. 20649 (line 6) 20650* Stallman, R.: Introduction. (line 29) 20651* standard input: Common options. (line 47) 20652* standard output: Common options. (line 47) 20653* standard streams, buffering: stdbuf invocation. (line 6) 20654* start: Characters. (line 48) 20655* stat: stat invocation. (line 6) 20656* status: dd invocation. (line 66) 20657* status <1>: Characters. (line 45) 20658* status time, printing or sorting by: Sorting the output. (line 13) 20659* status time, show the most recent: du invocation. (line 204) 20660* stdbuf: stdbuf invocation. (line 6) 20661* stick parity: Control. (line 16) 20662* sticky: Mode Structure. (line 52) 20663* sticky bit check: Access permission tests. 20664 (line 12) 20665* stop: Characters. (line 51) 20666* stop bits: Control. (line 32) 20667* strftime and date: date invocation. (line 20) 20668* string constants, outputting: od invocation. (line 81) 20669* string expressions: String expressions. (line 6) 20670* string tests: String tests. (line 6) 20671* strip directory and suffix from file names: basename invocation. 20672 (line 6) 20673* stripping non-directory suffix: dirname invocation. (line 6) 20674* stripping symbol table information: install invocation. (line 113) 20675* stripping trailing slashes: cp invocation. (line 332) 20676* stripping trailing slashes <1>: mv invocation. (line 98) 20677* stty: stty invocation. (line 6) 20678* substr: String expressions. (line 40) 20679* subtracting permissions: Setting Permissions. (line 38) 20680* subtraction: Numeric expressions. (line 12) 20681* successful exit: true invocation. (line 6) 20682* suffix, stripping from file names: basename invocation. (line 6) 20683* sum: sum invocation. (line 6) 20684* summarizing files: Summarizing files. (line 6) 20685* superblock, writing: sync invocation. (line 11) 20686* supplementary groups, printing: groups invocation. (line 6) 20687* susp: Characters. (line 54) 20688* swab (byte-swapping): dd invocation. (line 159) 20689* swap space, saving text image in: Mode Structure. (line 52) 20690* swtch: Characters. (line 42) 20691* symbol table information, stripping: install invocation. (line 113) 20692* symbol table information, stripping, program: install invocation. 20693 (line 116) 20694* symbolic (soft) links, creating: ln invocation. (line 6) 20695* symbolic link check: File type tests. (line 23) 20696* symbolic link to directory, controlling traversal of: Traversing symlinks. 20697 (line 6) 20698* symbolic link to directory, never traverse: Traversing symlinks. 20699 (line 26) 20700* symbolic link to directory, never traverse <1>: chown invocation. 20701 (line 171) 20702* symbolic link to directory, never traverse <2>: chgrp invocation. 20703 (line 99) 20704* symbolic link to directory, never traverse <3>: chcon invocation. 20705 (line 56) 20706* symbolic link to directory, traverse each that is encountered: Traversing symlinks. 20707 (line 22) 20708* symbolic link to directory, traverse each that is encountered <1>: chown invocation. 20709 (line 158) 20710* symbolic link to directory, traverse each that is encountered <2>: chgrp invocation. 20711 (line 86) 20712* symbolic link to directory, traverse each that is encountered <3>: chcon invocation. 20713 (line 52) 20714* symbolic link to directory, traverse if on the command line: Traversing symlinks. 20715 (line 18) 20716* symbolic link to directory, traverse if on the command line <1>: chown invocation. 20717 (line 153) 20718* symbolic link to directory, traverse if on the command line <2>: chgrp invocation. 20719 (line 81) 20720* symbolic link to directory, traverse if on the command line <3>: chcon invocation. 20721 (line 47) 20722* symbolic link, defined: ln invocation. (line 42) 20723* symbolic links and ln: ln invocation. (line 182) 20724* symbolic links and pwd: pwd invocation. (line 26) 20725* symbolic links, changing group: chgrp invocation. (line 46) 20726* symbolic links, changing owner: chown invocation. (line 83) 20727* symbolic links, changing owner <1>: chown invocation. (line 106) 20728* symbolic links, changing owner <2>: chown invocation. (line 118) 20729* symbolic links, changing owner <3>: chgrp invocation. (line 34) 20730* symbolic links, changing time: touch invocation. (line 70) 20731* symbolic links, copying: cp invocation. (line 109) 20732* symbolic links, copying <1>: cp invocation. (line 162) 20733* symbolic links, copying with: cp invocation. (line 337) 20734* symbolic links, dereferencing: Which files are listed. 20735 (line 36) 20736* symbolic links, dereferencing <1>: Which files are listed. 20737 (line 41) 20738* symbolic links, dereferencing <2>: Which files are listed. 20739 (line 83) 20740* symbolic links, dereferencing in du: du invocation. (line 117) 20741* symbolic links, dereferencing in du <1>: du invocation. (line 133) 20742* symbolic links, dereferencing in stat: stat invocation. (line 22) 20743* symbolic links, following: dd invocation. (line 289) 20744* symbolic links, permissions of: chmod invocation. (line 10) 20745* symbolic modes: Symbolic Modes. (line 6) 20746* symlinks, resolution: realpath invocation. (line 6) 20747* sync: sync invocation. (line 6) 20748* sync <1>: dd invocation. (line 243) 20749* sync (padding with ASCII NULs): dd invocation. (line 164) 20750* Synchronize cached writes to persistent storage: sync invocation. 20751 (line 6) 20752* synchronize disk and memory: sync invocation. (line 6) 20753* synchronized data and metadata I/O: dd invocation. (line 243) 20754* synchronized data and metadata writes, before finishing: dd invocation. 20755 (line 192) 20756* synchronized data reads: dd invocation. (line 235) 20757* synchronized data writes, before finishing: dd invocation. (line 188) 20758* system context: System context. (line 6) 20759* system information, printing: arch invocation. (line 6) 20760* system information, printing <1>: nproc invocation. (line 6) 20761* system information, printing <2>: uname invocation. (line 6) 20762* system name, printing: hostname invocation. (line 6) 20763* System V sum: sum invocation. (line 31) 20764* tab stops, setting: expand invocation. (line 22) 20765* tabN: Output. (line 51) 20766* tabs: Combination. (line 66) 20767* tabs to spaces, converting: expand invocation. (line 6) 20768* tac: tac invocation. (line 6) 20769* tagged paragraphs: fmt invocation. (line 40) 20770* tail: tail invocation. (line 6) 20771* tandem: Input. (line 45) 20772* target directory: Target directory. (line 6) 20773* target directory <1>: Target directory. (line 15) 20774* target directory <2>: Target directory. (line 31) 20775* target directory <3>: cp invocation. (line 350) 20776* target directory <4>: cp invocation. (line 354) 20777* target directory <5>: install invocation. (line 125) 20778* target directory <6>: install invocation. (line 130) 20779* target directory <7>: mv invocation. (line 108) 20780* target directory <8>: mv invocation. (line 112) 20781* target directory <9>: ln invocation. (line 171) 20782* target directory <10>: ln invocation. (line 175) 20783* tebibyte, definition of: Block size. (line 99) 20784* tee: tee invocation. (line 6) 20785* telephone directory order: sort invocation. (line 87) 20786* temporary directory: sort invocation. (line 353) 20787* temporary files and directories: mktemp invocation. (line 6) 20788* terabyte, definition of: Block size. (line 96) 20789* terminal check: File type tests. (line 34) 20790* terminal file name, printing: tty invocation. (line 6) 20791* terminal lines, currently used: who invocation. (line 11) 20792* terminal settings: stty invocation. (line 6) 20793* terminal, using color iff: General output formatting. 20794 (line 25) 20795* terminal, using hyperlink iff: General output formatting. 20796 (line 64) 20797* terse output: stat invocation. (line 69) 20798* test: test invocation. (line 6) 20799* text: dd invocation. (line 299) 20800* text I/O: dd invocation. (line 299) 20801* text image, saving in swap space: Mode Structure. (line 52) 20802* text input files: md5sum invocation. (line 109) 20803* text utilities: Top. (line 18) 20804* text, displaying: echo invocation. (line 6) 20805* text, reformatting: fmt invocation. (line 6) 20806* this in date strings: Relative items in date strings. 20807 (line 33) 20808* time: touch invocation. (line 56) 20809* time <1>: Special. (line 11) 20810* time conversion specifiers: Time conversion specifiers. 20811 (line 6) 20812* time formats: pr invocation. (line 78) 20813* time formats <1>: date invocation. (line 20) 20814* time limit: timeout invocation. (line 6) 20815* time of day item: Time of day items. (line 6) 20816* time setting: Setting the time. (line 6) 20817* time style: Formatting file timestamps. 20818 (line 24) 20819* time style <1>: du invocation. (line 214) 20820* time units: timeout invocation. (line 56) 20821* time units <1>: sleep invocation. (line 11) 20822* time zone correction: Time of day items. (line 29) 20823* time zone item: General date syntax. (line 40) 20824* time zone item <1>: Time zone items. (line 6) 20825* time, printing or setting: date invocation. (line 6) 20826* timeout: timeout invocation. (line 6) 20827* timestamps of installed files, preserving: install invocation. 20828 (line 103) 20829* timestamps, changing file: touch invocation. (line 6) 20830* TIME_STYLE: Formatting file timestamps. 20831 (line 103) 20832* TIME_STYLE <1>: du invocation. (line 242) 20833* TMPDIR: sort invocation. (line 64) 20834* TMPDIR <1>: sort invocation. (line 353) 20835* today in date strings: Relative items in date strings. 20836 (line 33) 20837* tomorrow: Options for date. (line 11) 20838* tomorrow in date strings: Relative items in date strings. 20839 (line 29) 20840* topological sort: tsort invocation. (line 6) 20841* tostop: Local. (line 41) 20842* total counts: wc invocation. (line 12) 20843* touch: touch invocation. (line 6) 20844* tr: tr invocation. (line 6) 20845* trailing slashes: Trailing slashes. (line 6) 20846* translating characters: Translating. (line 6) 20847* true: true invocation. (line 6) 20848* truncate: truncate invocation. (line 6) 20849* truncating output file, avoiding: dd invocation. (line 182) 20850* truncating, file sizes: truncate invocation. (line 6) 20851* tsort: tsort invocation. (line 6) 20852* tty: tty invocation. (line 6) 20853* two-way parity: Control. (line 9) 20854* type size: od invocation. (line 122) 20855* TZ: pr invocation. (line 91) 20856* TZ <1>: Formatting file timestamps. 20857 (line 17) 20858* TZ <2>: touch invocation. (line 35) 20859* TZ <3>: stat invocation. (line 212) 20860* TZ <4>: who invocation. (line 26) 20861* TZ <5>: date invocation. (line 16) 20862* TZ <6>: Options for date. (line 119) 20863* TZ <7>: Specifying time zone rules. 20864 (line 6) 20865* u, and disabling special characters: Characters. (line 12) 20866* ucase, converting to: dd invocation. (line 141) 20867* umask and modes: Umask and Protection. 20868 (line 6) 20869* uname: uname invocation. (line 6) 20870* unblock: dd invocation. (line 132) 20871* unexpand: unexpand invocation. (line 6) 20872* Unicode: printf invocation. (line 74) 20873* uniq: uniq invocation. (line 6) 20874* unique lines, outputting: uniq invocation. (line 127) 20875* uniquify files: uniq invocation. (line 6) 20876* uniquifying output: sort invocation. (line 369) 20877* Universal Time: Options for date. (line 119) 20878* unlink: unlink invocation. (line 6) 20879* unprintable characters, ignoring: sort invocation. (line 143) 20880* unsorted directory listing: Sorting the output. (line 20) 20881* upper: Character sets. (line 108) 20882* uppercase, translating to lowercase: Input. (line 50) 20883* uptime: uptime invocation. (line 6) 20884* use time, changing: touch invocation. (line 48) 20885* use time, printing or sorting files by: Sorting the output. (line 13) 20886* use time, printing or sorting files by <1>: Sorting the output. 20887 (line 44) 20888* use time, show the most recent: du invocation. (line 204) 20889* user IDs, disambiguating: Disambiguating names and IDs. 20890 (line 6) 20891* user information, commands for: User information. (line 6) 20892* user name, printing: logname invocation. (line 6) 20893* user names, disambiguating: Disambiguating names and IDs. 20894 (line 6) 20895* usernames, printing current: users invocation. (line 6) 20896* users: users invocation. (line 6) 20897* UTC: Options for date. (line 119) 20898* utmp: logname invocation. (line 6) 20899* utmp <1>: users invocation. (line 14) 20900* utmp <2>: who invocation. (line 15) 20901* valid file names, checking for: pathchk invocation. (line 6) 20902* variable-length records, converting to fixed-length: dd invocation. 20903 (line 41) 20904* vdir: vdir invocation. (line 6) 20905* verbose ls format: What information is listed. 20906 (line 131) 20907* verifying MD5 checksums: md5sum invocation. (line 76) 20908* verifying MD5 checksums <1>: md5sum invocation. (line 82) 20909* verifying MD5 checksums <2>: md5sum invocation. (line 90) 20910* verifying MD5 checksums <3>: md5sum invocation. (line 118) 20911* verifying MD5 checksums <4>: md5sum invocation. (line 123) 20912* version number sort: sort invocation. (line 177) 20913* version number, finding: Common options. (line 40) 20914* version of kernel: uname invocation. (line 77) 20915* version, sorting option for ls: Sorting the output. (line 67) 20916* version-control Emacs variable: Backup options. (line 24) 20917* VERSION_CONTROL: Backup options. (line 13) 20918* VERSION_CONTROL <1>: cp invocation. (line 79) 20919* VERSION_CONTROL <2>: install invocation. (line 41) 20920* VERSION_CONTROL <3>: mv invocation. (line 59) 20921* VERSION_CONTROL <4>: ln invocation. (line 82) 20922* vertical sorted files in columns: General output formatting. 20923 (line 16) 20924* vtN: Output. (line 59) 20925* wc: wc invocation. (line 6) 20926* week in date strings: Relative items in date strings. 20927 (line 15) 20928* werase: Characters. (line 63) 20929* who: who invocation. (line 6) 20930* who am i: who invocation. (line 21) 20931* whoami: whoami invocation. (line 6) 20932* word count: wc invocation. (line 6) 20933* working context: Working context. (line 6) 20934* working directory, printing: pwd invocation. (line 6) 20935* wrap data: base64 invocation. (line 22) 20936* wrapping long input lines: fold invocation. (line 6) 20937* writable file check: Access permission tests. 20938 (line 21) 20939* write permission: Mode Structure. (line 14) 20940* write permission, symbolic: Setting Permissions. (line 54) 20941* write, allowed: who invocation. (line 94) 20942* wtmp: users invocation. (line 14) 20943* wtmp <1>: who invocation. (line 15) 20944* xcase: Local. (line 36) 20945* xdigit: Character sets. (line 110) 20946* xfs file system type: df invocation. (line 211) 20947* XON/XOFF flow control: Input. (line 40) 20948* year in date strings: Relative items in date strings. 20949 (line 15) 20950* yes: yes invocation. (line 6) 20951* yesterday: Options for date. (line 11) 20952* yesterday in date strings: Relative items in date strings. 20953 (line 29) 20954* yottabyte, definition of: Block size. (line 116) 20955* Youmans, B.: Introduction. (line 29) 20956* zero-length string check: String tests. (line 15) 20957* zettabyte, definition of: Block size. (line 111) 20958 20959 20960 20961Tag Table: 20962Node: Top8619 20963Node: Introduction23195 20964Node: Common options25080 20965Node: Exit status28517 20966Node: Backup options29337 20967Node: Block size31383 20968Node: Floating point36720 20969Node: Signal specifications38579 20970Node: Disambiguating names and IDs40749 20971Ref: Disambiguating names and IDs-Footnote-142366 20972Node: Random sources42436 20973Node: Target directory44445 20974Node: Trailing slashes48095 20975Node: Traversing symlinks49134 20976Node: Treating / specially50266 20977Node: Special built-in utilities51900 20978Node: Standards conformance53099 20979Node: Multi-call invocation54845 20980Node: Output of entire files55407 20981Node: cat invocation56144 20982Node: tac invocation58086 20983Node: nl invocation59519 20984Node: od invocation63586 20985Node: base32 invocation71408 20986Node: base64 invocation71935 20987Node: basenc invocation73434 20988Node: Formatting file contents77101 20989Node: fmt invocation77552 20990Node: pr invocation80546 20991Node: fold invocation92822 20992Node: Output of parts of files94337 20993Node: head invocation94834 20994Node: tail invocation97762 20995Node: split invocation108802 20996Node: csplit invocation117034 20997Node: Summarizing files122472 20998Node: wc invocation123183 20999Node: sum invocation126510 21000Node: cksum invocation127976 21001Node: b2sum invocation129155 21002Node: md5sum invocation129856 21003Node: sha1sum invocation136665 21004Node: sha2 utilities137730 21005Node: Operating on sorted files138261 21006Node: sort invocation138848 21007Ref: sort invocation-Footnote-1164709 21008Node: shuf invocation165319 21009Node: uniq invocation168520 21010Node: comm invocation174581 21011Node: ptx invocation178609 21012Node: General options in ptx181443 21013Node: Charset selection in ptx182043 21014Node: Input processing in ptx182956 21015Node: Output formatting in ptx188501 21016Node: Compatibility in ptx195337 21017Node: tsort invocation198720 21018Node: tsort background201924 21019Node: Operating on fields203632 21020Node: cut invocation203994 21021Node: paste invocation208774 21022Node: join invocation210937 21023Node: General options in join212401 21024Node: Sorting files for join217593 21025Node: Working with fields219303 21026Ref: Working with fields-Footnote-1220886 21027Node: Paired and unpaired lines220983 21028Node: Header lines223921 21029Node: Set operations224832 21030Node: Operating on characters226352 21031Node: tr invocation226775 21032Node: Character sets228531 21033Node: Translating233279 21034Node: Squeezing and deleting235450 21035Node: expand invocation238720 21036Node: unexpand invocation240888 21037Node: Directory listing243409 21038Node: ls invocation243907 21039Ref: ls invocation-Footnote-1246011 21040Node: Which files are listed246255 21041Node: What information is listed250265 21042Node: Sorting the output260146 21043Node: General output formatting263055 21044Node: Formatting file timestamps269118 21045Node: Formatting the file names274724 21046Node: dir invocation278083 21047Node: vdir invocation278510 21048Node: dircolors invocation278935 21049Node: Basic operations280741 21050Node: cp invocation281361 21051Node: dd invocation299714 21052Node: install invocation317254 21053Node: mv invocation323602 21054Node: rm invocation328884 21055Node: shred invocation333770 21056Node: Special file types344128 21057Node: link invocation345657 21058Node: ln invocation346914 21059Node: mkdir invocation355949 21060Node: mkfifo invocation358723 21061Node: mknod invocation360198 21062Node: readlink invocation362740 21063Node: rmdir invocation365299 21064Node: unlink invocation366616 21065Node: Changing file attributes367610 21066Node: chown invocation368430 21067Node: chgrp invocation375824 21068Node: chmod invocation380066 21069Node: touch invocation383584 21070Node: Disk usage389299 21071Node: df invocation389980 21072Node: du invocation399817 21073Node: stat invocation411007 21074Node: sync invocation420219 21075Node: truncate invocation422390 21076Node: Printing text424424 21077Node: echo invocation424798 21078Node: printf invocation427566 21079Node: yes invocation433608 21080Node: Conditions434260 21081Node: false invocation434855 21082Node: true invocation435944 21083Node: test invocation437277 21084Node: File type tests439414 21085Node: Access permission tests440333 21086Node: File characteristic tests441253 21087Node: String tests442144 21088Node: Numeric tests442914 21089Node: Connectives for test443749 21090Node: expr invocation445003 21091Node: String expressions447515 21092Node: Numeric expressions450220 21093Node: Relations for expr450928 21094Node: Examples of expr452157 21095Node: Redirection452906 21096Node: tee invocation453371 21097Node: File name manipulation459955 21098Node: basename invocation460530 21099Node: dirname invocation462749 21100Node: pathchk invocation464566 21101Node: mktemp invocation466377 21102Node: realpath invocation472195 21103Node: Realpath usage examples475258 21104Node: Working context477073 21105Node: pwd invocation477717 21106Node: stty invocation479136 21107Node: Control482121 21108Node: Input483197 21109Node: Output484951 21110Node: Local486369 21111Node: Combination488456 21112Node: Characters490868 21113Node: Special492695 21114Node: printenv invocation494944 21115Node: tty invocation495955 21116Node: User information496689 21117Node: id invocation497324 21118Node: logname invocation500037 21119Node: whoami invocation500694 21120Node: groups invocation501201 21121Node: users invocation502436 21122Node: who invocation503616 21123Node: System context506951 21124Node: date invocation507616 21125Node: Time conversion specifiers509390 21126Node: Date conversion specifiers512129 21127Node: Literal conversion specifiers515594 21128Node: Padding and other flags515966 21129Node: Setting the time519029 21130Node: Options for date520180 21131Node: Examples of date525089 21132Ref: %s-examples526591 21133Node: arch invocation529812 21134Node: nproc invocation530371 21135Node: uname invocation531591 21136Node: hostname invocation534304 21137Node: hostid invocation535134 21138Node: uptime invocation536007 21139Node: SELinux context537487 21140Node: chcon invocation537862 21141Node: runcon invocation540267 21142Node: Modified command invocation542042 21143Node: chroot invocation542734 21144Ref: chroot invocation-Footnote-1546628 21145Node: env invocation547145 21146Node: nice invocation563675 21147Node: nohup invocation567808 21148Node: stdbuf invocation570310 21149Node: timeout invocation573244 21150Node: Process control576188 21151Node: kill invocation576411 21152Node: Delaying579605 21153Node: sleep invocation579802 21154Node: Numeric operations581158 21155Node: factor invocation581543 21156Node: numfmt invocation583347 21157Node: seq invocation595100 21158Node: File permissions599375 21159Node: Mode Structure600068 21160Node: Symbolic Modes603747 21161Node: Setting Permissions604865 21162Node: Copying Permissions607531 21163Node: Changing Special Mode Bits608401 21164Node: Conditional Executability610283 21165Node: Multiple Changes610835 21166Node: Umask and Protection612508 21167Node: Numeric Modes613653 21168Node: Operator Numeric Modes615999 21169Node: Directory Setuid and Setgid617059 21170Node: File timestamps619914 21171Node: Date input formats623237 21172Node: General date syntax625671 21173Node: Calendar date items628802 21174Node: Time of day items630879 21175Node: Time zone items633183 21176Node: Combined date and time of day items634587 21177Node: Day of week items635458 21178Node: Relative items in date strings636542 21179Node: Pure numbers in date strings639452 21180Node: Seconds since the Epoch640441 21181Node: Specifying time zone rules642104 21182Node: Authors of parse_datetime644576 21183Ref: Authors of get_date644767 21184Node: Version sort ordering645766 21185Node: Version sort overview646079 21186Node: Using version sort in GNU coreutils647204 21187Node: Origin of version sort and differences from natural sort648646 21188Node: Correct/Incorrect ordering and Expected/Unexpected results649636 21189Node: Implementation Details650547 21190Node: Version-sort ordering rules651407 21191Node: Version sort is not the same as numeric sort654137 21192Node: Punctuation Characters656202 21193Node: Punctuation Characters vs letters657986 21194Node: Tilde ~ character658958 21195Node: Version sort ignores locale660398 21196Node: Differences from the official Debian Algorithm661642 21197Node: Minus/Hyphen and Colon characters662229 21198Node: Additional hard-coded priorities in GNU coreutils' version sort663851 21199Node: Special handling of file extensions665185 21200Node: Advanced Topics669842 21201Node: Comparing two strings using Debian's algorithm670188 21202Node: Reporting bugs or incorrect results672090 21203Node: Other version/natural sort implementations673370 21204Node: Related Source code675517 21205Node: Opening the software toolbox676270 21206Node: Toolbox introduction677068 21207Node: I/O redirection679812 21208Node: The who command682697 21209Node: The cut command683622 21210Node: The sort command684724 21211Node: The uniq command685442 21212Node: Putting the tools together686157 21213Ref: Putting the tools together-Footnote-1698294 21214Node: GNU Free Documentation License698368 21215Node: Concept index723747 21216 21217End Tag Table 21218 21219 21220Local Variables: 21221coding: utf-8 21222End: 21223