1.\" $NetBSD: file.1,v 1.12 2013/03/23 16:15:57 christos Exp $ 2.\" 3.\" $File: file.man,v 1.102 2013/01/04 15:39:22 christos Exp $ 4.Dd October 25, 2012 5.Dt FILE 1 6.Os 7.Sh NAME 8.Nm file 9.Nd determine file type 10.Sh SYNOPSIS 11.Nm 12.Bk -words 13.Op Fl bchiklLNnprsvz0 14.Op Fl Fl apple 15.Op Fl Fl mime-encoding 16.Op Fl Fl mime-type 17.Op Fl e Ar testname 18.Op Fl F Ar separator 19.Op Fl f Ar namefile 20.Op Fl m Ar magicfiles 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 5.14 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 /usr/share/misc/magic.mgc , 107or the files in the directory 108.Pa /usr/share/misc/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 b , Fl Fl brief 170Do not prepend filenames to output lines (brief mode). 171.It Fl C , Fl Fl compile 172Write a 173.Pa magic.mgc 174output file that contains a pre-parsed version of the magic file or directory. 175.It Fl c , Fl Fl checking-printout 176Cause a checking printout of the parsed form of the magic file. 177This is usually used in conjunction with the 178.Fl m 179flag to debug a new magic file before installing it. 180.It Fl e , Fl Fl exclude Ar testname 181Exclude the test named in 182.Ar testname 183from the list of tests made to determine the file type. 184Valid test names are: 185.Bl -tag -width compress 186.It apptype 187.Dv EMX 188application type (only on EMX). 189.It ascii 190Various types of text files (this test will try to guess the text 191encoding, irrespective of the setting of the 192.Sq encoding 193option). 194.It encoding 195Different text encodings for soft magic tests. 196.It tokens 197Ignored for backwards compatibility. 198.It cdf 199Prints details of Compound Document Files. 200.It compress 201Checks for, and looks inside, compressed files. 202.It elf 203Prints ELF file details. 204.It soft 205Consults magic files. 206.It tar 207Examines tar files. 208.El 209.It Fl F , Fl Fl separator Ar separator 210Use the specified string as the separator between the filename and the 211file result returned. 212Defaults to 213.Sq \&: . 214.It Fl f , Fl Fl files-from Ar namefile 215Read the names of the files to be examined from 216.Ar namefile 217(one per line) 218before the argument list. 219Either 220.Ar namefile 221or at least one filename argument must be present; 222to test the standard input, use 223.Sq - 224as a filename argument. 225Please note that 226.Ar namefile 227is unwrapped and the enclosed filenames are processed when this option is 228encountered and before any further options processing is done. 229This allows one to process multiple lists of files with different command line 230arguments on the same 231.Nm 232invocation. 233Thus if you want to set the delimiter, you need to do it before you specify 234the list of files, like: 235.Dq Fl F Ar @ Fl f Ar namefile , 236instead of: 237.Dq Fl f Ar namefile Fl F Ar @ . 238.It Fl h , Fl Fl no-dereference 239option causes symlinks not to be followed 240(on systems that support symbolic links). 241This is the default if the environment variable 242.Dv POSIXLY_CORRECT 243is not defined. 244.It Fl i , Fl Fl mime 245Causes the file command to output mime type strings rather than the more 246traditional human readable ones. 247Thus it may say 248.Sq text/plain; charset=us-ascii 249rather than 250.Dq ASCII text . 251.It Fl Fl mime-type , Fl Fl mime-encoding 252Like 253.Fl i , 254but print only the specified element(s). 255.It Fl k , Fl Fl keep-going 256Don't stop at the first match, keep going. 257Subsequent matches will be 258have the string 259.Sq "\[rs]012\- " 260prepended. 261(If you want a newline, see the 262.Fl r 263option.) 264The magic pattern with the highest strength (see the 265.Fl l 266option) comes first. 267.It Fl l , Fl Fl list 268Shows a list of patterns and their strength sorted descending by 269.Xr magic 4 270strength 271which is used for the matching (see also the 272.Fl k 273option). 274.It Fl L , Fl Fl dereference 275option causes symlinks to be followed, as the like-named option in 276.Xr ls 1 277(on systems that support symbolic links). 278This is the default if the environment variable 279.Ev POSIXLY_CORRECT 280is defined. 281.It Fl m , Fl Fl magic-file Ar magicfiles 282Specify an alternate list of files and directories containing magic. 283This can be a single item, or a colon-separated list. 284If a compiled magic file is found alongside a file or directory, 285it will be used instead. 286.It Fl N , Fl Fl no-pad 287Don't pad filenames so that they align in the output. 288.It Fl n , Fl Fl no-buffer 289Force stdout to be flushed after checking each file. 290This is only useful if checking a list of files. 291It is intended to be used by programs that want filetype output from a pipe. 292.It Fl p , Fl Fl preserve-date 293On systems that support 294.Xr utime 3 295or 296.Xr utimes 2 , 297attempt to preserve the access time of files analyzed, to pretend that 298.Nm 299never read them. 300.It Fl r , Fl Fl raw 301Don't translate unprintable characters to \eooo. 302Normally 303.Nm 304translates unprintable characters to their octal representation. 305.It Fl s , Fl Fl special-files 306Normally, 307.Nm 308only attempts to read and determine the type of argument files which 309.Xr stat 2 310reports are ordinary files. 311This prevents problems, because reading special files may have peculiar 312consequences. 313Specifying the 314.Fl s 315option causes 316.Nm 317to also read argument files which are block or character special files. 318This is useful for determining the filesystem types of the data in raw 319disk partitions, which are block special files. 320This option also causes 321.Nm 322to disregard the file size as reported by 323.Xr stat 2 324since on some systems it reports a zero size for raw disk partitions. 325.It Fl v , Fl Fl version 326Print the version of the program and exit. 327.It Fl z , Fl Fl uncompress 328Try to look inside compressed files. 329.It Fl 0 , Fl Fl print0 330Output a null character 331.Sq \e0 332after the end of the filename. 333Nice to 334.Xr cut 1 335the output. 336This does not affect the separator which is still printed. 337.It Fl -help 338Print a help message and exit. 339.El 340.Sh FILES 341.Bl -tag -width /usr/share/misc/magic.mgc -compact 342.It Pa /usr/share/misc/magic.mgc 343Default compiled list of magic. 344.It Pa /usr/share/misc/magic 345Directory containing default magic files. 346.El 347.Sh ENVIRONMENT 348The environment variable 349.Ev MAGIC 350can be used to set the default magic file name. 351If that variable is set, then 352.Nm 353will not attempt to open 354.Pa $HOME/.magic . 355.Nm 356adds 357.Dq Pa .mgc 358to the value of this variable as appropriate. 359However, 360.Pa file 361has to exist in order for 362.Pa file.mime 363to be considered. 364The environment variable 365.Ev POSIXLY_CORRECT 366controls (on systems that support symbolic links), whether 367.Nm 368will attempt to follow symlinks or not. 369If set, then 370.Nm 371follows symlink, otherwise it does not. 372This is also controlled by the 373.Fl L 374and 375.Fl h 376options. 377.Sh SEE ALSO 378.Xr magic 5 , 379.Xr hexdump 1 , 380.Xr od 1 , 381.Xr strings 1 , 382.Sh STANDARDS CONFORMANCE 383This program is believed to exceed the System V Interface Definition 384of FILE(CMD), as near as one can determine from the vague language 385contained therein. 386Its behavior is mostly compatible with the System V program of the same name. 387This version knows more magic, however, so it will produce 388different (albeit more accurate) output in many cases. 389.\" URL: http://www.opengroup.org/onlinepubs/009695399/utilities/file.html 390.Pp 391The one significant difference 392between this version and System V 393is that this version treats any white space 394as a delimiter, so that spaces in pattern strings must be escaped. 395For example, 396.Bd -literal -offset indent 397\*[Gt]10 string language impress\ (imPRESS data) 398.Ed 399.Pp 400in an existing magic file would have to be changed to 401.Bd -literal -offset indent 402\*[Gt]10 string language\e impress (imPRESS data) 403.Ed 404.Pp 405In addition, in this version, if a pattern string contains a backslash, 406it must be escaped. 407For example 408.Bd -literal -offset indent 4090 string \ebegindata Andrew Toolkit document 410.Ed 411.Pp 412in an existing magic file would have to be changed to 413.Bd -literal -offset indent 4140 string \e\ebegindata Andrew Toolkit document 415.Ed 416.Pp 417SunOS releases 3.2 and later from Sun Microsystems include a 418.Nm 419command derived from the System V one, but with some extensions. 420This version differs from Sun's only in minor ways. 421It includes the extension of the 422.Sq \*[Am] 423operator, used as, 424for example, 425.Bd -literal -offset indent 426\*[Gt]16 long\*[Am]0x7fffffff \*[Gt]0 not stripped 427.Ed 428.Sh MAGIC DIRECTORY 429The magic file entries have been collected from various sources, 430mainly USENET, and contributed by various authors. 431Christos Zoulas (address below) will collect additional 432or corrected magic file entries. 433A consolidation of magic file entries 434will be distributed periodically. 435.Pp 436The order of entries in the magic file is significant. 437Depending on what system you are using, the order that 438they are put together may be incorrect. 439If your old 440.Nm 441command uses a magic file, 442keep the old magic file around for comparison purposes 443(rename it to 444.Pa /usr/share/misc/magic.orig ) . 445.Sh EXAMPLES 446.Bd -literal -offset indent 447$ file file.c file /dev/{wd0a,hda} 448file.c: C program text 449file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), 450 dynamically linked (uses shared libs), stripped 451/dev/wd0a: block special (0/0) 452/dev/hda: block special (3/0) 453 454$ file -s /dev/wd0{b,d} 455/dev/wd0b: data 456/dev/wd0d: x86 boot sector 457 458$ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10} 459/dev/hda: x86 boot sector 460/dev/hda1: Linux/i386 ext2 filesystem 461/dev/hda2: x86 boot sector 462/dev/hda3: x86 boot sector, extended partition table 463/dev/hda4: Linux/i386 ext2 filesystem 464/dev/hda5: Linux/i386 swap file 465/dev/hda6: Linux/i386 swap file 466/dev/hda7: Linux/i386 swap file 467/dev/hda8: Linux/i386 swap file 468/dev/hda9: empty 469/dev/hda10: empty 470 471$ file -i file.c file /dev/{wd0a,hda} 472file.c: text/x-c 473file: application/x-executable 474/dev/hda: application/x-not-regular-file 475/dev/wd0a: application/x-not-regular-file 476 477.Ed 478.Sh HISTORY 479There has been a 480.Nm 481command in every 482.Dv UNIX since at least Research Version 4 483(man page dated November, 1973). 484The System V version introduced one significant major change: 485the external list of magic types. 486This slowed the program down slightly but made it a lot more flexible. 487.Pp 488This program, based on the System V version, 489was written by Ian Darwin 490.Aq ian@darwinsys.com 491without looking at anybody else's source code. 492.Pp 493John Gilmore revised the code extensively, making it better than 494the first version. 495Geoff Collyer found several inadequacies 496and provided some magic file entries. 497Contributions by the 498.Sq \*[Am] 499operator by Rob McMahon, 500.Aq cudcv@warwick.ac.uk , 5011989. 502.Pp 503Guy Harris, 504.Aq guy@netapp.com , 505made many changes from 1993 to the present. 5061989. 507.Pp 508Primary development and maintenance from 1990 to the present by 509Christos Zoulas 510.Aq christos@astron.com . 511.Pp 512Altered by Chris Lowth 513.Aq chris@lowth.com , 5142000: handle the 515.Fl i 516option to output mime type strings, using an alternative 517magic file and internal logic. 518.Pp 519Altered by Eric Fischer 520.Aq enf@pobox.com , 521July, 2000, 522to identify character codes and attempt to identify the languages 523of non-ASCII files. 524.Pp 525Altered by Reuben Thomas 526.Aq rrt@sc3d.org , 5272007-2011, to improve MIME support, merge MIME and non-MIME magic, 528support directories as well as files of magic, apply many bug fixes, 529update and fix a lot of magic, improve the build system, improve the 530documentation, and rewrite the Python bindings in pure Python. 531.Pp 532The list of contributors to the 533.Sq magic 534directory (magic files) 535is too long to include here. 536You know who you are; thank you. 537Many contributors are listed in the source files. 538.Sh LEGAL NOTICE 539Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. 540Covered by the standard Berkeley Software Distribution copyright; see the file 541COPYING in the source distribution. 542.Pp 543The files 544.Pa tar.h 545and 546.Pa is_tar.c 547were written by John Gilmore from his public-domain 548.Xr tar 1 549program, and are not covered by the above license. 550.Sh RETURN CODE 551.Nm 552returns 0 on success, and non-zero on error. 553.Sh BUGS 554.Pp 555Please report bugs and send patches to the bug tracker at 556.Pa http://bugs.gw.com/ 557or the mailing list at 558.Aq file@mx.gw.com . 559.Sh TODO 560.Pp 561Fix output so that tests for MIME and APPLE flags are not needed all 562over the place, and actual output is only done in one place. 563This needs a design. 564Suggestion: push possible outputs on to a list, then pick the 565last-pushed (most specific, one hopes) value at the end, or 566use a default if the list is empty. 567This should not slow down evaluation. 568.Pp 569Continue to squash all magic bugs. 570See Debian BTS for a good source. 571.Pp 572Store arbitrarily long strings, for example for %s patterns, so that 573they can be printed out. 574Fixes Debian bug #271672. 575Would require more complex store/load code in apprentice. 576.Pp 577Add syntax for relative offsets after current level (Debian bug #466037). 578.Pp 579Make file -ki work, i.e. give multiple MIME types. 580.Pp 581Add a zip library so we can peek inside Office2007 documents to 582figure out what they are. 583.Pp 584Add an option to print URLs for the sources of the file descriptions. 585.Pp 586Combine script searches and add a way to map executable names to MIME 587types (e.g. have a magic value for !:mime which causes the resulting 588string to be looked up in a table). 589This would avoid adding the same magic repeatedly for each new 590hash-bang interpreter. 591.Pp 592Fix 593.Dq name 594and 595.Dq use 596to check for consistency at compile time (duplicate 597.Dq name , 598.Dq use 599pointing to undefined 600.Dq name 601). 602Make 603.Dq name 604/ 605.Dq use 606more efficient by keeping a sorted list of names. 607Special-case ^ to flip endianness in the parser so that it does not 608have to be escaped, and document it. 609.Sh AVAILABILITY 610You can obtain the original author's latest version by anonymous FTP 611on 612.Pa ftp.astron.com 613in the directory 614.Pa /pub/file/file-X.YZ.tar.gz . 615