1.\" $File: file.man,v 1.125 2017/01/03 11:24:46 christos Exp $ 2.Dd October 19, 2016 3.Dt FILE __CSECTION__ 4.Os 5.Sh NAME 6.Nm file 7.Nd determine file type 8.Sh SYNOPSIS 9.Nm 10.Bk -words 11.Op Fl bcdEhiklLNnprsvzZ0 12.Op Fl Fl apple 13.Op Fl Fl extension 14.Op Fl Fl mime-encoding 15.Op Fl Fl mime-type 16.Op Fl e Ar testname 17.Op Fl F Ar separator 18.Op Fl f Ar namefile 19.Op Fl m Ar magicfiles 20.Op Fl P Ar name=value 21.Ar 22.Ek 23.Nm 24.Fl C 25.Op Fl m Ar magicfiles 26.Nm 27.Op Fl Fl help 28.Sh DESCRIPTION 29This manual page documents version __VERSION__ of the 30.Nm 31command. 32.Pp 33.Nm 34tests each argument in an attempt to classify it. 35There are three sets of tests, performed in this order: 36filesystem tests, magic tests, and language tests. 37The 38.Em first 39test that succeeds causes the file type to be printed. 40.Pp 41The type printed will usually contain one of the words 42.Em text 43(the file contains only 44printing characters and a few common control 45characters and is probably safe to read on an 46.Dv ASCII 47terminal), 48.Em executable 49(the file contains the result of compiling a program 50in a form understandable to some 51.Tn UNIX 52kernel or another), 53or 54.Em data 55meaning anything else (data is usually 56.Dq binary 57or non-printable). 58Exceptions are well-known file formats (core files, tar archives) 59that are known to contain binary data. 60When modifying magic files or the program itself, make sure to 61.Em "preserve these keywords" . 62Users depend on knowing that all the readable files in a directory 63have the word 64.Dq text 65printed. 66Don't do as Berkeley did and change 67.Dq shell commands text 68to 69.Dq shell script . 70.Pp 71The filesystem tests are based on examining the return from a 72.Xr stat 2 73system call. 74The program checks to see if the file is empty, 75or if it's some sort of special file. 76Any known file types appropriate to the system you are running on 77(sockets, symbolic links, or named pipes (FIFOs) on those systems that 78implement them) 79are intuited if they are defined in the system header file 80.In sys/stat.h . 81.Pp 82The magic tests are used to check for files with data in 83particular fixed formats. 84The canonical example of this is a binary executable (compiled program) 85.Dv a.out 86file, whose format is defined in 87.In elf.h , 88.In a.out.h 89and possibly 90.In exec.h 91in the standard include directory. 92These files have a 93.Dq "magic number" 94stored in a particular place 95near the beginning of the file that tells the 96.Tn UNIX 97operating system 98that the file is a binary executable, and which of several types thereof. 99The concept of a 100.Dq "magic" 101has been applied by extension to data files. 102Any file with some invariant identifier at a small fixed 103offset into the file can usually be described in this way. 104The information identifying these files is read from the compiled 105magic file 106.Pa __MAGIC__.mgc , 107or the files in the directory 108.Pa __MAGIC__ 109if the compiled file does not exist. 110In addition, if 111.Pa $HOME/.magic.mgc 112or 113.Pa $HOME/.magic 114exists, it will be used in preference to the system magic files. 115.Pp 116If a file does not match any of the entries in the magic file, 117it is examined to see if it seems to be a text file. 118ASCII, ISO-8859-x, non-ISO 8-bit extended-ASCII character sets 119(such as those used on Macintosh and IBM PC systems), 120UTF-8-encoded Unicode, UTF-16-encoded Unicode, and EBCDIC 121character sets can be distinguished by the different 122ranges and sequences of bytes that constitute printable text 123in each set. 124If a file passes any of these tests, its character set is reported. 125ASCII, ISO-8859-x, UTF-8, and extended-ASCII files are identified 126as 127.Dq text 128because they will be mostly readable on nearly any terminal; 129UTF-16 and EBCDIC are only 130.Dq character data 131because, while 132they contain text, it is text that will require translation 133before it can be read. 134In addition, 135.Nm 136will attempt to determine other characteristics of text-type files. 137If the lines of a file are terminated by CR, CRLF, or NEL, instead 138of the Unix-standard LF, this will be reported. 139Files that contain embedded escape sequences or overstriking 140will also be identified. 141.Pp 142Once 143.Nm 144has determined the character set used in a text-type file, 145it will 146attempt to determine in what language the file is written. 147The language tests look for particular strings (cf. 148.In names.h ) 149that can appear anywhere in the first few blocks of a file. 150For example, the keyword 151.Em .br 152indicates that the file is most likely a 153.Xr troff 1 154input file, just as the keyword 155.Em struct 156indicates a C program. 157These tests are less reliable than the previous 158two groups, so they are performed last. 159The language test routines also test for some miscellany 160(such as 161.Xr tar 1 162archives). 163.Pp 164Any file that cannot be identified as having been written 165in any of the character sets listed above is simply said to be 166.Dq data . 167.Sh OPTIONS 168.Bl -tag -width indent 169.It Fl Fl apple 170Causes the file command to output the file type and creator code as 171used by older MacOS versions. The code consists of eight letters, 172the first describing the file type, the latter the creator. 173.It Fl b , Fl Fl brief 174Do not prepend filenames to output lines (brief mode). 175.It Fl C , Fl Fl compile 176Write a 177.Pa magic.mgc 178output file that contains a pre-parsed version of the magic file or directory. 179.It Fl c , Fl Fl checking-printout 180Cause a checking printout of the parsed form of the magic file. 181This is usually used in conjunction with the 182.Fl m 183flag to debug a new magic file before installing it. 184.It Fl d 185Prints internal debugging information to stderr. 186.It Fl E 187On filesystem errors (file not found etc), instead of handling the error 188as regular output as POSIX mandates and keep going, issue an error message 189and exit. 190.It Fl e , Fl Fl exclude Ar testname 191Exclude the test named in 192.Ar testname 193from the list of tests made to determine the file type. 194Valid test names are: 195.Bl -tag -width compress 196.It apptype 197.Dv EMX 198application type (only on EMX). 199.It ascii 200Various types of text files (this test will try to guess the text 201encoding, irrespective of the setting of the 202.Sq encoding 203option). 204.It encoding 205Different text encodings for soft magic tests. 206.It tokens 207Ignored for backwards compatibility. 208.It cdf 209Prints details of Compound Document Files. 210.It compress 211Checks for, and looks inside, compressed files. 212.It elf 213Prints ELF file details, provided soft magic tests are enabled and the 214elf magic is found. 215.It soft 216Consults magic files. 217.It tar 218Examines tar files. 219.It text 220A synonym for 221.Sq ascii . 222.El 223.It Fl Fl extension 224Print a slash-separated list of valid extensions for the file type found. 225.It Fl F , Fl Fl separator Ar separator 226Use the specified string as the separator between the filename and the 227file result returned. 228Defaults to 229.Sq \&: . 230.It Fl f , Fl Fl files-from Ar namefile 231Read the names of the files to be examined from 232.Ar namefile 233(one per line) 234before the argument list. 235Either 236.Ar namefile 237or at least one filename argument must be present; 238to test the standard input, use 239.Sq - 240as a filename argument. 241Please note that 242.Ar namefile 243is unwrapped and the enclosed filenames are processed when this option is 244encountered and before any further options processing is done. 245This allows one to process multiple lists of files with different command line 246arguments on the same 247.Nm 248invocation. 249Thus if you want to set the delimiter, you need to do it before you specify 250the list of files, like: 251.Dq Fl F Ar @ Fl f Ar namefile , 252instead of: 253.Dq Fl f Ar namefile Fl F Ar @ . 254.It Fl h , Fl Fl no-dereference 255option causes symlinks not to be followed 256(on systems that support symbolic links). 257This is the default if the environment variable 258.Dv POSIXLY_CORRECT 259is not defined. 260.It Fl i , Fl Fl mime 261Causes the file command to output mime type strings rather than the more 262traditional human readable ones. 263Thus it may say 264.Sq text/plain; charset=us-ascii 265rather than 266.Dq ASCII text . 267.It Fl Fl mime-type , Fl Fl mime-encoding 268Like 269.Fl i , 270but print only the specified element(s). 271.It Fl k , Fl Fl keep-going 272Don't stop at the first match, keep going. 273Subsequent matches will be 274have the string 275.Sq "\[rs]012\- " 276prepended. 277(If you want a newline, see the 278.Fl r 279option.) 280The magic pattern with the highest strength (see the 281.Fl l 282option) comes first. 283.It Fl l , Fl Fl list 284Shows a list of patterns and their strength sorted descending by 285.Xr magic 4 286strength 287which is used for the matching (see also the 288.Fl k 289option). 290.It Fl L , Fl Fl dereference 291option causes symlinks to be followed, as the like-named option in 292.Xr ls 1 293(on systems that support symbolic links). 294This is the default if the environment variable 295.Ev POSIXLY_CORRECT 296is defined. 297.It Fl m , Fl Fl magic-file Ar magicfiles 298Specify an alternate list of files and directories containing magic. 299This can be a single item, or a colon-separated list. 300If a compiled magic file is found alongside a file or directory, 301it will be used instead. 302.It Fl N , Fl Fl no-pad 303Don't pad filenames so that they align in the output. 304.It Fl n , Fl Fl no-buffer 305Force stdout to be flushed after checking each file. 306This is only useful if checking a list of files. 307It is intended to be used by programs that want filetype output from a pipe. 308.It Fl p , Fl Fl preserve-date 309On systems that support 310.Xr utime 3 311or 312.Xr utimes 2 , 313attempt to preserve the access time of files analyzed, to pretend that 314.Nm 315never read them. 316.It Fl P , Fl Fl parameter Ar name=value 317Set various parameter limits. 318.Bl -column "elf_phnum" "Default" "XXXXXXXXXXXXXXXXXXXXXXXXXXX" -offset indent 319.It Sy "Name" Ta Sy "Default" Ta Sy "Explanation" 320.It Li indir Ta 15 Ta recursion limit for indirect magic 321.It Li name Ta 30 Ta use count limit for name/use magic 322.It Li elf_notes Ta 256 Ta max ELF notes processed 323.It Li elf_phnum Ta 128 Ta max ELF program sections processed 324.It Li elf_shnum Ta 32768 Ta max ELF sections processed 325.It Li regex Ta 8192 Ta length limit for regex searches 326.It Li bytes Ta 1048576 Ta max number of bytes to read from file 327.El 328.It Fl r , Fl Fl raw 329Don't translate unprintable characters to \eooo. 330Normally 331.Nm 332translates unprintable characters to their octal representation. 333.It Fl s , Fl Fl special-files 334Normally, 335.Nm 336only attempts to read and determine the type of argument files which 337.Xr stat 2 338reports are ordinary files. 339This prevents problems, because reading special files may have peculiar 340consequences. 341Specifying the 342.Fl s 343option causes 344.Nm 345to also read argument files which are block or character special files. 346This is useful for determining the filesystem types of the data in raw 347disk partitions, which are block special files. 348This option also causes 349.Nm 350to disregard the file size as reported by 351.Xr stat 2 352since on some systems it reports a zero size for raw disk partitions. 353.It Fl v , Fl Fl version 354Print the version of the program and exit. 355.It Fl z , Fl Fl uncompress 356Try to look inside compressed files. 357.It Fl Z , Fl Fl uncompress-noreport 358Try to look inside compressed files, but report information about the contents 359only not the compression. 360.It Fl 0 , Fl Fl print0 361Output a null character 362.Sq \e0 363after the end of the filename. 364Nice to 365.Xr cut 1 366the output. 367This does not affect the separator, which is still printed. 368.Pp 369If this option is repeated more than once, then 370.Nm 371prints just the filename followed by a NUL followed by the description 372(or ERROR: text) followed by a second NUL for each entry. 373.It Fl -help 374Print a help message and exit. 375.El 376.Sh FILES 377.Bl -tag -width __MAGIC__.mgc -compact 378.It Pa __MAGIC__.mgc 379Default compiled list of magic. 380.It Pa __MAGIC__ 381Directory containing default magic files. 382.El 383.Sh ENVIRONMENT 384The environment variable 385.Ev MAGIC 386can be used to set the default magic file name. 387If that variable is set, then 388.Nm 389will not attempt to open 390.Pa $HOME/.magic . 391.Nm 392adds 393.Dq Pa .mgc 394to the value of this variable as appropriate. 395However, 396.Pa file 397has to exist in order for 398.Pa file.mime 399to be considered. 400The environment variable 401.Ev POSIXLY_CORRECT 402controls (on systems that support symbolic links), whether 403.Nm 404will attempt to follow symlinks or not. 405If set, then 406.Nm 407follows symlink, otherwise it does not. 408This is also controlled by the 409.Fl L 410and 411.Fl h 412options. 413.Sh SEE ALSO 414.Xr hexdump 1 , 415.Xr od 1 , 416.Xr strings 1 , 417.Xr magic __FSECTION__ 418.Sh STANDARDS CONFORMANCE 419This program is believed to exceed the System V Interface Definition 420of FILE(CMD), as near as one can determine from the vague language 421contained therein. 422Its behavior is mostly compatible with the System V program of the same name. 423This version knows more magic, however, so it will produce 424different (albeit more accurate) output in many cases. 425.\" URL: http://www.opengroup.org/onlinepubs/009695399/utilities/file.html 426.Pp 427The one significant difference 428between this version and System V 429is that this version treats any white space 430as a delimiter, so that spaces in pattern strings must be escaped. 431For example, 432.Bd -literal -offset indent 433\*[Gt]10 string language impress\ (imPRESS data) 434.Ed 435.Pp 436in an existing magic file would have to be changed to 437.Bd -literal -offset indent 438\*[Gt]10 string language\e impress (imPRESS data) 439.Ed 440.Pp 441In addition, in this version, if a pattern string contains a backslash, 442it must be escaped. 443For example 444.Bd -literal -offset indent 4450 string \ebegindata Andrew Toolkit document 446.Ed 447.Pp 448in an existing magic file would have to be changed to 449.Bd -literal -offset indent 4500 string \e\ebegindata Andrew Toolkit document 451.Ed 452.Pp 453SunOS releases 3.2 and later from Sun Microsystems include a 454.Nm 455command derived from the System V one, but with some extensions. 456This version differs from Sun's only in minor ways. 457It includes the extension of the 458.Sq \*[Am] 459operator, used as, 460for example, 461.Bd -literal -offset indent 462\*[Gt]16 long\*[Am]0x7fffffff \*[Gt]0 not stripped 463.Ed 464.Sh MAGIC DIRECTORY 465The magic file entries have been collected from various sources, 466mainly USENET, and contributed by various authors. 467Christos Zoulas (address below) will collect additional 468or corrected magic file entries. 469A consolidation of magic file entries 470will be distributed periodically. 471.Pp 472The order of entries in the magic file is significant. 473Depending on what system you are using, the order that 474they are put together may be incorrect. 475If your old 476.Nm 477command uses a magic file, 478keep the old magic file around for comparison purposes 479(rename it to 480.Pa __MAGIC__.orig ) . 481.Sh EXAMPLES 482.Bd -literal -offset indent 483$ file file.c file /dev/{wd0a,hda} 484file.c: C program text 485file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), 486 dynamically linked (uses shared libs), stripped 487/dev/wd0a: block special (0/0) 488/dev/hda: block special (3/0) 489 490$ file -s /dev/wd0{b,d} 491/dev/wd0b: data 492/dev/wd0d: x86 boot sector 493 494$ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10} 495/dev/hda: x86 boot sector 496/dev/hda1: Linux/i386 ext2 filesystem 497/dev/hda2: x86 boot sector 498/dev/hda3: x86 boot sector, extended partition table 499/dev/hda4: Linux/i386 ext2 filesystem 500/dev/hda5: Linux/i386 swap file 501/dev/hda6: Linux/i386 swap file 502/dev/hda7: Linux/i386 swap file 503/dev/hda8: Linux/i386 swap file 504/dev/hda9: empty 505/dev/hda10: empty 506 507$ file -i file.c file /dev/{wd0a,hda} 508file.c: text/x-c 509file: application/x-executable 510/dev/hda: application/x-not-regular-file 511/dev/wd0a: application/x-not-regular-file 512 513.Ed 514.Sh HISTORY 515There has been a 516.Nm 517command in every 518.Dv UNIX since at least Research Version 4 519(man page dated November, 1973). 520The System V version introduced one significant major change: 521the external list of magic types. 522This slowed the program down slightly but made it a lot more flexible. 523.Pp 524This program, based on the System V version, 525was written by Ian Darwin 526.Aq ian@darwinsys.com 527without looking at anybody else's source code. 528.Pp 529John Gilmore revised the code extensively, making it better than 530the first version. 531Geoff Collyer found several inadequacies 532and provided some magic file entries. 533Contributions of the 534.Sq \*[Am] 535operator by Rob McMahon, 536.Aq cudcv@warwick.ac.uk , 5371989. 538.Pp 539Guy Harris, 540.Aq guy@netapp.com , 541made many changes from 1993 to the present. 542.Pp 543Primary development and maintenance from 1990 to the present by 544Christos Zoulas 545.Aq christos@astron.com . 546.Pp 547Altered by Chris Lowth 548.Aq chris@lowth.com , 5492000: handle the 550.Fl i 551option to output mime type strings, using an alternative 552magic file and internal logic. 553.Pp 554Altered by Eric Fischer 555.Aq enf@pobox.com , 556July, 2000, 557to identify character codes and attempt to identify the languages 558of non-ASCII files. 559.Pp 560Altered by Reuben Thomas 561.Aq rrt@sc3d.org , 5622007-2011, to improve MIME support, merge MIME and non-MIME magic, 563support directories as well as files of magic, apply many bug fixes, 564update and fix a lot of magic, improve the build system, improve the 565documentation, and rewrite the Python bindings in pure Python. 566.Pp 567The list of contributors to the 568.Sq magic 569directory (magic files) 570is too long to include here. 571You know who you are; thank you. 572Many contributors are listed in the source files. 573.Sh LEGAL NOTICE 574Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. 575Covered by the standard Berkeley Software Distribution copyright; see the file 576COPYING in the source distribution. 577.Pp 578The files 579.Pa tar.h 580and 581.Pa is_tar.c 582were written by John Gilmore from his public-domain 583.Xr tar 1 584program, and are not covered by the above license. 585.Sh RETURN CODE 586.Nm 587returns 0 on success, and non-zero on error. 588.Sh BUGS 589Please report bugs and send patches to the bug tracker at 590.Pa http://bugs.gw.com/ 591or the mailing list at 592.Aq file@mx.gw.com 593(visit 594.Pa http://mx.gw.com/mailman/listinfo/file 595first to subscribe). 596.Sh TODO 597Fix output so that tests for MIME and APPLE flags are not needed all 598over the place, and actual output is only done in one place. 599This needs a design. 600Suggestion: push possible outputs on to a list, then pick the 601last-pushed (most specific, one hopes) value at the end, or 602use a default if the list is empty. 603This should not slow down evaluation. 604.Pp 605The handling of 606.Dv MAGIC_CONTINUE 607and printing \e012- between entries is clumsy and complicated; refactor 608and centralize. 609.Pp 610Some of the encoding logic is hard-coded in encoding.c and can be moved 611to the magic files if we had a !:charset annotation 612.Pp 613Continue to squash all magic bugs. 614See Debian BTS for a good source. 615.Pp 616Store arbitrarily long strings, for example for %s patterns, so that 617they can be printed out. 618Fixes Debian bug #271672. 619This can be done by allocating strings in a string pool, storing the 620string pool at the end of the magic file and converting all the string 621pointers to relative offsets from the string pool. 622.Pp 623Add syntax for relative offsets after current level (Debian bug #466037). 624.Pp 625Make file -ki work, i.e. give multiple MIME types. 626.Pp 627Add a zip library so we can peek inside Office2007 documents to 628print more details about their contents. 629.Pp 630Add an option to print URLs for the sources of the file descriptions. 631.Pp 632Combine script searches and add a way to map executable names to MIME 633types (e.g. have a magic value for !:mime which causes the resulting 634string to be looked up in a table). 635This would avoid adding the same magic repeatedly for each new 636hash-bang interpreter. 637.Pp 638When a file descriptor is available, we can skip and adjust the buffer 639instead of the hacky buffer management we do now. 640.Pp 641Fix 642.Dq name 643and 644.Dq use 645to check for consistency at compile time (duplicate 646.Dq name , 647.Dq use 648pointing to undefined 649.Dq name 650). 651Make 652.Dq name 653/ 654.Dq use 655more efficient by keeping a sorted list of names. 656Special-case ^ to flip endianness in the parser so that it does not 657have to be escaped, and document it. 658.Pp 659If the offsets specified internally in the file exceed the buffer size 660( 661.Dv HOWMANY 662variable in file.h), then we don't seek to that offset, but we give up. 663It would be better if buffer managements was done when the file descriptor 664is available so move around the file. 665One must be careful though because this has performance (and thus security 666considerations). 667.Sh AVAILABILITY 668You can obtain the original author's latest version by anonymous FTP 669on 670.Pa ftp.astron.com 671in the directory 672.Pa /pub/file/file-X.YZ.tar.gz . 673