1.\" $NetBSD: file.1,v 1.8 2011/09/16 21:06:25 christos Exp $ 2.\" 3.\" $File: file.man,v 1.96 2011/07/12 11:23:38 rrt Exp $ 4.Dd April 20, 2011 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 5.09 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 197Looks for known tokens inside text files. 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. 225.It Fl h , Fl Fl no-dereference 226option causes symlinks not to be followed 227(on systems that support symbolic links). 228This is the default if the environment variable 229.Dv POSIXLY_CORRECT 230is not defined. 231.It Fl i , Fl Fl mime 232Causes the file command to output mime type strings rather than the more 233traditional human readable ones. 234Thus it may say 235.Sq text/plain; charset=us-ascii 236rather than 237.Dq ASCII text . 238.It Fl Fl mime-type , Fl Fl mime-encoding 239Like 240.Fl i , 241but print only the specified element(s). 242.It Fl k , Fl Fl keep-going 243Don't stop at the first match, keep going. 244Subsequent matches will be 245have the string 246.Sq "\[rs]012\- " 247prepended. 248(If you want a newline, see the 249.Fl r 250option.) 251.It Fl l , Fl Fl list 252Print information about the strength of each magic pattern. 253.It Fl L , Fl Fl dereference 254option causes symlinks to be followed, as the like-named option in 255.Xr ls 1 256(on systems that support symbolic links). 257This is the default if the environment variable 258.Ev POSIXLY_CORRECT 259is defined. 260.It Fl l 261Shows sorted patterns list in the order which is used for the matching. 262.It Fl m , Fl Fl magic-file Ar magicfiles 263Specify an alternate list of files and directories containing magic. 264This can be a single item, or a colon-separated list. 265If a compiled magic file is found alongside a file or directory, 266it will be used instead. 267.It Fl N , Fl Fl no-pad 268Don't pad filenames so that they align in the output. 269.It Fl n , Fl Fl no-buffer 270Force stdout to be flushed after checking each file. 271This is only useful if checking a list of files. 272It is intended to be used by programs that want filetype output from a pipe. 273.It Fl p , Fl Fl preserve-date 274On systems that support 275.Xr utime 3 276or 277.Xr utimes 2 , 278attempt to preserve the access time of files analyzed, to pretend that 279.Nm 280never read them. 281.It Fl r , Fl Fl raw 282Don't translate unprintable characters to \eooo. 283Normally 284.Nm 285translates unprintable characters to their octal representation. 286.It Fl s , Fl Fl special-files 287Normally, 288.Nm 289only attempts to read and determine the type of argument files which 290.Xr stat 2 291reports are ordinary files. 292This prevents problems, because reading special files may have peculiar 293consequences. 294Specifying the 295.Fl s 296option causes 297.Nm 298to also read argument files which are block or character special files. 299This is useful for determining the filesystem types of the data in raw 300disk partitions, which are block special files. 301This option also causes 302.Nm 303to disregard the file size as reported by 304.Xr stat 2 305since on some systems it reports a zero size for raw disk partitions. 306.It Fl v , Fl Fl version 307Print the version of the program and exit. 308.It Fl z , Fl Fl uncompress 309Try to look inside compressed files. 310.It Fl 0 , Fl Fl print0 311Output a null character 312.Sq \e0 313after the end of the filename. 314Nice to 315.Xr cut 1 316the output. 317This does not affect the separator which is still printed. 318.It Fl -help 319Print a help message and exit. 320.El 321.Sh FILES 322.Bl -tag -width /usr/share/misc/magic.mgc -compact 323.It Pa /usr/share/misc/magic.mgc 324Default compiled list of magic. 325.It Pa /usr/share/misc/magic 326Directory containing default magic files. 327.El 328.Sh ENVIRONMENT 329The environment variable 330.Ev MAGIC 331can be used to set the default magic file name. 332If that variable is set, then 333.Nm 334will not attempt to open 335.Pa $HOME/.magic . 336.Nm 337adds 338.Dq Pa .mgc 339to the value of this variable as appropriate. 340However, 341.Pa file 342has to exist in order for 343.Pa file.mime 344to be considered. 345The environment variable 346.Ev POSIXLY_CORRECT 347controls (on systems that support symbolic links), whether 348.Nm 349will attempt to follow symlinks or not. 350If set, then 351.Nm 352follows symlink, otherwise it does not. 353This is also controlled by the 354.Fl L 355and 356.Fl h 357options. 358.Sh SEE ALSO 359.Xr magic 5 , 360.Xr hexdump 1 , 361.Xr od 1 , 362.Xr strings 1 , 363.Sh STANDARDS CONFORMANCE 364This program is believed to exceed the System V Interface Definition 365of FILE(CMD), as near as one can determine from the vague language 366contained therein. 367Its behavior is mostly compatible with the System V program of the same name. 368This version knows more magic, however, so it will produce 369different (albeit more accurate) output in many cases. 370.\" URL: http://www.opengroup.org/onlinepubs/009695399/utilities/file.html 371.Pp 372The one significant difference 373between this version and System V 374is that this version treats any white space 375as a delimiter, so that spaces in pattern strings must be escaped. 376For example, 377.Bd -literal -offset indent 378\*[Gt]10 string language impress\ (imPRESS data) 379.Ed 380.Pp 381in an existing magic file would have to be changed to 382.Bd -literal -offset indent 383\*[Gt]10 string language\e impress (imPRESS data) 384.Ed 385.Pp 386In addition, in this version, if a pattern string contains a backslash, 387it must be escaped. 388For example 389.Bd -literal -offset indent 3900 string \ebegindata Andrew Toolkit document 391.Ed 392.Pp 393in an existing magic file would have to be changed to 394.Bd -literal -offset indent 3950 string \e\ebegindata Andrew Toolkit document 396.Ed 397.Pp 398SunOS releases 3.2 and later from Sun Microsystems include a 399.Nm 400command derived from the System V one, but with some extensions. 401This version differs from Sun's only in minor ways. 402It includes the extension of the 403.Sq \*[Am] 404operator, used as, 405for example, 406.Bd -literal -offset indent 407\*[Gt]16 long\*[Am]0x7fffffff \*[Gt]0 not stripped 408.Ed 409.Sh MAGIC DIRECTORY 410The magic file entries have been collected from various sources, 411mainly USENET, and contributed by various authors. 412Christos Zoulas (address below) will collect additional 413or corrected magic file entries. 414A consolidation of magic file entries 415will be distributed periodically. 416.Pp 417The order of entries in the magic file is significant. 418Depending on what system you are using, the order that 419they are put together may be incorrect. 420If your old 421.Nm 422command uses a magic file, 423keep the old magic file around for comparison purposes 424(rename it to 425.Pa /usr/share/misc/magic.orig ) . 426.Sh EXAMPLES 427.Bd -literal -offset indent 428$ file file.c file /dev/{wd0a,hda} 429file.c: C program text 430file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), 431 dynamically linked (uses shared libs), stripped 432/dev/wd0a: block special (0/0) 433/dev/hda: block special (3/0) 434 435$ file -s /dev/wd0{b,d} 436/dev/wd0b: data 437/dev/wd0d: x86 boot sector 438 439$ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10} 440/dev/hda: x86 boot sector 441/dev/hda1: Linux/i386 ext2 filesystem 442/dev/hda2: x86 boot sector 443/dev/hda3: x86 boot sector, extended partition table 444/dev/hda4: Linux/i386 ext2 filesystem 445/dev/hda5: Linux/i386 swap file 446/dev/hda6: Linux/i386 swap file 447/dev/hda7: Linux/i386 swap file 448/dev/hda8: Linux/i386 swap file 449/dev/hda9: empty 450/dev/hda10: empty 451 452$ file -i file.c file /dev/{wd0a,hda} 453file.c: text/x-c 454file: application/x-executable 455/dev/hda: application/x-not-regular-file 456/dev/wd0a: application/x-not-regular-file 457 458.Ed 459.Sh HISTORY 460There has been a 461.Nm 462command in every 463.Dv UNIX since at least Research Version 4 464(man page dated November, 1973). 465The System V version introduced one significant major change: 466the external list of magic types. 467This slowed the program down slightly but made it a lot more flexible. 468.Pp 469This program, based on the System V version, 470was written by Ian Darwin 471.Aq ian@darwinsys.com 472without looking at anybody else's source code. 473.Pp 474John Gilmore revised the code extensively, making it better than 475the first version. 476Geoff Collyer found several inadequacies 477and provided some magic file entries. 478Contributions by the 479.Sq \*[Am] 480operator by Rob McMahon, 481.Aq cudcv@warwick.ac.uk , 4821989. 483.Pp 484Guy Harris, 485.Aq guy@netapp.com , 486made many changes from 1993 to the present. 4871989. 488.Pp 489Primary development and maintenance from 1990 to the present by 490Christos Zoulas 491.Aq christos@astron.com . 492.Pp 493Altered by Chris Lowth 494.Aq chris@lowth.com , 4952000: handle the 496.Fl i 497option to output mime type strings, using an alternative 498magic file and internal logic. 499.Pp 500Altered by Eric Fischer 501.Aq enf@pobox.com , 502July, 2000, 503to identify character codes and attempt to identify the languages 504of non-ASCII files. 505.Pp 506Altered by Reuben Thomas 507.Aq rrt@sc3d.org , 5082007-2011, to improve MIME support, merge MIME and non-MIME magic, 509support directories as well as files of magic, apply many bug fixes, 510update and fix a lot of magic, improve the build system, improve the 511documentation, and rewrite the Python bindings in pure Python. 512.Pp 513The list of contributors to the 514.Sq magic 515directory (magic files) 516is too long to include here. 517You know who you are; thank you. 518Many contributors are listed in the source files. 519.Sh LEGAL NOTICE 520Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. 521Covered by the standard Berkeley Software Distribution copyright; see the file 522COPYING in the source distribution. 523.Pp 524The files 525.Pa tar.h 526and 527.Pa is_tar.c 528were written by John Gilmore from his public-domain 529.Xr tar 1 530program, and are not covered by the above license. 531.Sh RETURN CODE 532.Nm 533returns 0 on success, and non-zero on error. 534.Sh BUGS 535.Pp 536Please report bugs and send patches to the bug tracker at 537.Pa http://bugs.gw.com/ 538or the mailing list at 539.Aq file@mx.gw.com . 540.Sh TODO 541.Pp 542Fix output so that tests for MIME and APPLE flags are not needed all 543over the place, and actual output is only done in one place. This 544needs a design. Suggestion: push possible outputs on to a list, then 545pick the last-pushed (most specific, one hopes) value at the end, or 546use a default if the list is empty. This should not slow down evaluation. 547.Pp 548Continue to squash all magic bugs. See Debian BTS for a good source. 549.Pp 550Store arbitrarily long strings, for example for %s patterns, so that 551they can be printed out. Fixes Debian bug #271672. Would require more 552complex store/load code in apprentice. 553.Pp 554Add syntax for relative offsets after current level (Debian bug #466037). 555.Pp 556Make file -ki work, i.e. give multiple MIME types. 557.Pp 558Add a zip library so we can peek inside Office2007 documents to 559figure out what they are. 560.Pp 561Add an option to print URLs for the sources of the file descriptions. 562.Sh AVAILABILITY 563You can obtain the original author's latest version by anonymous FTP 564on 565.Pa ftp.astron.com 566in the directory 567.Pa /pub/file/file-X.YZ.tar.gz . 568