1.\" $NetBSD: file.1,v 1.7 2011/05/13 21:15:34 christos Exp $ 2.\" 3.\" $File: file.man,v 1.94 2011/04/20 19:08:44 christos 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 5.07 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 . 238In order for this option to work, 239.Nm 240changes the way 241it handles files recognized by the command itself (such as many of the 242text file types, directories etc), and makes use of an alternative 243.Dq magic 244file. 245(See the 246.Sx FILES 247section, below). 248.It Fl Fl mime-type , Fl Fl mime-encoding 249Like 250.Fl i , 251but print only the specified element(s). 252.It Fl k , Fl Fl keep-going 253Don't stop at the first match, keep going. 254Subsequent matches will be 255have the string 256.Sq "\[rs]012\- " 257prepended. 258(If you want a newline, see the 259.Fl r 260option.) 261.It Fl l , Fl Fl list 262Print information about the strength of each magic pattern. 263.It Fl L , Fl Fl dereference 264option causes symlinks to be followed, as the like-named option in 265.Xr ls 1 266(on systems that support symbolic links). 267This is the default if the environment variable 268.Ev POSIXLY_CORRECT 269is defined. 270.It Fl l 271Shows sorted patterns list in the order which is used for the matching. 272.It Fl m , Fl Fl magic-file Ar magicfiles 273Specify an alternate list of files and directories containing magic. 274This can be a single item, or a colon-separated list. 275If a compiled magic file is found alongside a file or directory, 276it will be used instead. 277.It Fl N , Fl Fl no-pad 278Don't pad filenames so that they align in the output. 279.It Fl n , Fl Fl no-buffer 280Force stdout to be flushed after checking each file. 281This is only useful if checking a list of files. 282It is intended to be used by programs that want filetype output from a pipe. 283.It Fl p , Fl Fl preserve-date 284On systems that support 285.Xr utime 3 286or 287.Xr utimes 2 , 288attempt to preserve the access time of files analyzed, to pretend that 289.Nm 290never read them. 291.It Fl r , Fl Fl raw 292Don't translate unprintable characters to \eooo. 293Normally 294.Nm 295translates unprintable characters to their octal representation. 296.It Fl s , Fl Fl special-files 297Normally, 298.Nm 299only attempts to read and determine the type of argument files which 300.Xr stat 2 301reports are ordinary files. 302This prevents problems, because reading special files may have peculiar 303consequences. 304Specifying the 305.Fl s 306option causes 307.Nm 308to also read argument files which are block or character special files. 309This is useful for determining the filesystem types of the data in raw 310disk partitions, which are block special files. 311This option also causes 312.Nm 313to disregard the file size as reported by 314.Xr stat 2 315since on some systems it reports a zero size for raw disk partitions. 316.It Fl v , Fl Fl version 317Print the version of the program and exit. 318.It Fl z , Fl Fl uncompress 319Try to look inside compressed files. 320.It Fl 0 , Fl Fl print0 321Output a null character 322.Sq \e0 323after the end of the filename. 324Nice to 325.Xr cut 1 326the output. 327This does not affect the separator which is still printed. 328.It Fl -help 329Print a help message and exit. 330.El 331.Sh FILES 332.Bl -tag -width /usr/share/misc/magic.mgc -compact 333.It Pa /usr/share/misc/magic.mgc 334Default compiled list of magic. 335.It Pa /usr/share/misc/magic 336Directory containing default magic files. 337.El 338.Sh ENVIRONMENT 339The environment variable 340.Ev MAGIC 341can be used to set the default magic file name. 342If that variable is set, then 343.Nm 344will not attempt to open 345.Pa $HOME/.magic . 346.Nm 347adds 348.Dq Pa .mgc 349to the value of this variable as appropriate. 350However, 351.Pa file 352has to exist in order for 353.Pa file.mime 354to be considered. 355The environment variable 356.Ev POSIXLY_CORRECT 357controls (on systems that support symbolic links), whether 358.Nm 359will attempt to follow symlinks or not. 360If set, then 361.Nm 362follows symlink, otherwise it does not. 363This is also controlled by the 364.Fl L 365and 366.Fl h 367options. 368.Sh SEE ALSO 369.Xr hexdump 1 , 370.Xr od 1 , 371.Xr strings 1 , 372.Xr od 1 , 373.Xr hexdump 1 , 374.Xr magic 5 375.Sh STANDARDS CONFORMANCE 376This program is believed to exceed the System V Interface Definition 377of FILE(CMD), as near as one can determine from the vague language 378contained therein. 379Its behavior is mostly compatible with the System V program of the same name. 380This version knows more magic, however, so it will produce 381different (albeit more accurate) output in many cases. 382.\" URL: http://www.opengroup.org/onlinepubs/009695399/utilities/file.html 383.Pp 384The one significant difference 385between this version and System V 386is that this version treats any white space 387as a delimiter, so that spaces in pattern strings must be escaped. 388For example, 389.Bd -literal -offset indent 390\*[Gt]10 string language impress\ (imPRESS data) 391.Ed 392.Pp 393in an existing magic file would have to be changed to 394.Bd -literal -offset indent 395\*[Gt]10 string language\e impress (imPRESS data) 396.Ed 397.Pp 398In addition, in this version, if a pattern string contains a backslash, 399it must be escaped. 400For example 401.Bd -literal -offset indent 4020 string \ebegindata Andrew Toolkit document 403.Ed 404.Pp 405in an existing magic file would have to be changed to 406.Bd -literal -offset indent 4070 string \e\ebegindata Andrew Toolkit document 408.Ed 409.Pp 410SunOS releases 3.2 and later from Sun Microsystems include a 411.Nm 412command derived from the System V one, but with some extensions. 413This version differs from Sun's only in minor ways. 414It includes the extension of the 415.Sq \*[Am] 416operator, used as, 417for example, 418.Bd -literal -offset indent 419\*[Gt]16 long\*[Am]0x7fffffff \*[Gt]0 not stripped 420.Ed 421.Sh MAGIC DIRECTORY 422The magic file entries have been collected from various sources, 423mainly USENET, and contributed by various authors. 424Christos Zoulas (address below) will collect additional 425or corrected magic file entries. 426A consolidation of magic file entries 427will be distributed periodically. 428.Pp 429The order of entries in the magic file is significant. 430Depending on what system you are using, the order that 431they are put together may be incorrect. 432If your old 433.Nm 434command uses a magic file, 435keep the old magic file around for comparison purposes 436(rename it to 437.Pa /usr/share/misc/magic.orig ) . 438.Sh EXAMPLES 439.Bd -literal -offset indent 440$ file file.c file /dev/{wd0a,hda} 441file.c: C program text 442file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), 443 dynamically linked (uses shared libs), stripped 444/dev/wd0a: block special (0/0) 445/dev/hda: block special (3/0) 446 447$ file -s /dev/wd0{b,d} 448/dev/wd0b: data 449/dev/wd0d: x86 boot sector 450 451$ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10} 452/dev/hda: x86 boot sector 453/dev/hda1: Linux/i386 ext2 filesystem 454/dev/hda2: x86 boot sector 455/dev/hda3: x86 boot sector, extended partition table 456/dev/hda4: Linux/i386 ext2 filesystem 457/dev/hda5: Linux/i386 swap file 458/dev/hda6: Linux/i386 swap file 459/dev/hda7: Linux/i386 swap file 460/dev/hda8: Linux/i386 swap file 461/dev/hda9: empty 462/dev/hda10: empty 463 464$ file -i file.c file /dev/{wd0a,hda} 465file.c: text/x-c 466file: application/x-executable 467/dev/hda: application/x-not-regular-file 468/dev/wd0a: application/x-not-regular-file 469 470.Ed 471.Sh HISTORY 472There has been a 473.Nm 474command in every 475.Dv UNIX since at least Research Version 4 476(man page dated November, 1973). 477The System V version introduced one significant major change: 478the external list of magic types. 479This slowed the program down slightly but made it a lot more flexible. 480.Pp 481This program, based on the System V version, 482was written by Ian Darwin 483.Aq ian@darwinsys.com 484without looking at anybody else's source code. 485.Pp 486John Gilmore revised the code extensively, making it better than 487the first version. 488Geoff Collyer found several inadequacies 489and provided some magic file entries. 490Contributions by the 491.Sq \*[Am] 492operator by Rob McMahon, 493.Aq cudcv@warwick.ac.uk , 4941989. 495.Pp 496Guy Harris, 497.Aq guy@netapp.com , 498made many changes from 1993 to the present. 4991989. 500.Pp 501Primary development and maintenance from 1990 to the present by 502Christos Zoulas 503.Aq christos@astron.com . 504.Pp 505Altered by Chris Lowth 506.Aq chris@lowth.com , 5072000: handle the 508.Fl i 509option to output mime type strings, using an alternative 510magic file and internal logic. 511.Pp 512Altered by Eric Fischer 513.Aq enf@pobox.com , 514July, 2000, 515to identify character codes and attempt to identify the languages 516of non-ASCII files. 517.Pp 518Altered by Reuben Thomas 519.Aq rrt@sc3d.org , 5202007-2011, to improve MIME support, merge MIME and non-MIME magic, 521support directories as well as files of magic, apply many bug fixes, 522update and fix a lot of magic, improve the build system, improve the 523documentation, and rewrite the Python bindings in pure Python. 524.Pp 525The list of contributors to the 526.Sq magic 527directory (magic files) 528is too long to include here. 529You know who you are; thank you. 530Many contributors are listed in the source files. 531.Sh LEGAL NOTICE 532Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. 533Covered by the standard Berkeley Software Distribution copyright; see the file 534COPYING in the source distribution. 535.Pp 536The files 537.Pa tar.h 538and 539.Pa is_tar.c 540were written by John Gilmore from his public-domain 541.Xr tar 1 542program, and are not covered by the above license. 543.Sh RETURN CODE 544.Nm 545returns 0 on success, and non-zero on error. 546.Sh BUGS 547.Pp 548Please report bugs and send patches to the bug tracker at 549.Pa http://bugs.gw.com/ 550or the mailing list at 551.Aq file@mx.gw.com . 552.Sh TODO 553.Pp 554Fix output so that tests for MIME and APPLE flags are not needed all 555over the place, and actual output is only done in one place. This 556needs a design. Suggestion: push possible outputs on to a list, then 557pick the last-pushed (most specific, one hopes) value at the end, or 558use a default if the list is empty. This should not slow down evaluation. 559.Pp 560Continue to squash all magic bugs. See Debian BTS for a good source. 561.Pp 562Store arbitrarily long strings, for example for %s patterns, so that 563they can be printed out. Fixes Debian bug #271672. Would require more 564complex store/load code in apprentice. 565.Pp 566Add syntax for relative offsets after current level (Debian bug #466037). 567.Pp 568Make file -ki work, i.e. give multiple MIME types. 569.Pp 570Add a zip library so we can peek inside Office2007 documents to 571figure out what they are. 572.Pp 573Don't complain when ~/.magic is not compiled. 574.Pp 575Add an option to print URLs for the sources of the file descriptions. 576.Sh AVAILABILITY 577You can obtain the original author's latest version by anonymous FTP 578on 579.Pa ftp.astron.com 580in the directory 581.Pa /pub/file/file-X.YZ.tar.gz . 582