1.\" $File: file.man,v 1.98 2011/12/08 12:12:46 rrt Exp $ 2.Dd October 17, 2011 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 bchiklLNnprsvz0 12.Op Fl Fl apple 13.Op Fl Fl mime-encoding 14.Op Fl Fl mime-type 15.Op Fl e Ar testname 16.Op Fl F Ar separator 17.Op Fl f Ar namefile 18.Op Fl m Ar magicfiles 19.Ar 20.Ek 21.Nm 22.Fl C 23.Op Fl m Ar magicfiles 24.Nm 25.Op Fl Fl help 26.Sh DESCRIPTION 27This manual page documents version __VERSION__ of the 28.Nm 29command. 30.Pp 31.Nm 32tests each argument in an attempt to classify it. 33There are three sets of tests, performed in this order: 34filesystem tests, magic tests, and language tests. 35The 36.Em first 37test that succeeds causes the file type to be printed. 38.Pp 39The type printed will usually contain one of the words 40.Em text 41(the file contains only 42printing characters and a few common control 43characters and is probably safe to read on an 44.Dv ASCII 45terminal), 46.Em executable 47(the file contains the result of compiling a program 48in a form understandable to some 49.Tn UNIX 50kernel or another), 51or 52.Em data 53meaning anything else (data is usually 54.Dq binary 55or non-printable). 56Exceptions are well-known file formats (core files, tar archives) 57that are known to contain binary data. 58When modifying magic files or the program itself, make sure to 59.Em "preserve these keywords" . 60Users depend on knowing that all the readable files in a directory 61have the word 62.Dq text 63printed. 64Don't do as Berkeley did and change 65.Dq shell commands text 66to 67.Dq shell script . 68.Pp 69The filesystem tests are based on examining the return from a 70.Xr stat 2 71system call. 72The program checks to see if the file is empty, 73or if it's some sort of special file. 74Any known file types appropriate to the system you are running on 75(sockets, symbolic links, or named pipes (FIFOs) on those systems that 76implement them) 77are intuited if they are defined in the system header file 78.In sys/stat.h . 79.Pp 80The magic tests are used to check for files with data in 81particular fixed formats. 82The canonical example of this is a binary executable (compiled program) 83.Dv a.out 84file, whose format is defined in 85.In elf.h , 86.In a.out.h 87and possibly 88.In exec.h 89in the standard include directory. 90These files have a 91.Dq "magic number" 92stored in a particular place 93near the beginning of the file that tells the 94.Tn UNIX 95operating system 96that the file is a binary executable, and which of several types thereof. 97The concept of a 98.Dq "magic" 99has been applied by extension to data files. 100Any file with some invariant identifier at a small fixed 101offset into the file can usually be described in this way. 102The information identifying these files is read from the compiled 103magic file 104.Pa __MAGIC__.mgc , 105or the files in the directory 106.Pa __MAGIC__ 107if the compiled file does not exist. 108In addition, if 109.Pa $HOME/.magic.mgc 110or 111.Pa $HOME/.magic 112exists, it will be used in preference to the system magic files. 113.Pp 114If a file does not match any of the entries in the magic file, 115it is examined to see if it seems to be a text file. 116ASCII, ISO-8859-x, non-ISO 8-bit extended-ASCII character sets 117(such as those used on Macintosh and IBM PC systems), 118UTF-8-encoded Unicode, UTF-16-encoded Unicode, and EBCDIC 119character sets can be distinguished by the different 120ranges and sequences of bytes that constitute printable text 121in each set. 122If a file passes any of these tests, its character set is reported. 123ASCII, ISO-8859-x, UTF-8, and extended-ASCII files are identified 124as 125.Dq text 126because they will be mostly readable on nearly any terminal; 127UTF-16 and EBCDIC are only 128.Dq character data 129because, while 130they contain text, it is text that will require translation 131before it can be read. 132In addition, 133.Nm 134will attempt to determine other characteristics of text-type files. 135If the lines of a file are terminated by CR, CRLF, or NEL, instead 136of the Unix-standard LF, this will be reported. 137Files that contain embedded escape sequences or overstriking 138will also be identified. 139.Pp 140Once 141.Nm 142has determined the character set used in a text-type file, 143it will 144attempt to determine in what language the file is written. 145The language tests look for particular strings (cf. 146.In names.h ) 147that can appear anywhere in the first few blocks of a file. 148For example, the keyword 149.Em .br 150indicates that the file is most likely a 151.Xr troff 1 152input file, just as the keyword 153.Em struct 154indicates a C program. 155These tests are less reliable than the previous 156two groups, so they are performed last. 157The language test routines also test for some miscellany 158(such as 159.Xr tar 1 160archives). 161.Pp 162Any file that cannot be identified as having been written 163in any of the character sets listed above is simply said to be 164.Dq data . 165.Sh OPTIONS 166.Bl -tag -width indent 167.It Fl b , Fl Fl brief 168Do not prepend filenames to output lines (brief mode). 169.It Fl C , Fl Fl compile 170Write a 171.Pa magic.mgc 172output file that contains a pre-parsed version of the magic file or directory. 173.It Fl c , Fl Fl checking-printout 174Cause a checking printout of the parsed form of the magic file. 175This is usually used in conjunction with the 176.Fl m 177flag to debug a new magic file before installing it. 178.It Fl e , Fl Fl exclude Ar testname 179Exclude the test named in 180.Ar testname 181from the list of tests made to determine the file type. 182Valid test names are: 183.Bl -tag -width compress 184.It apptype 185.Dv EMX 186application type (only on EMX). 187.It ascii 188Various types of text files (this test will try to guess the text 189encoding, irrespective of the setting of the 190.Sq encoding 191option). 192.It encoding 193Different text encodings for soft magic tests. 194.It tokens 195Ignored for backwards compatibility. 196.It cdf 197Prints details of Compound Document Files. 198.It compress 199Checks for, and looks inside, compressed files. 200.It elf 201Prints ELF file details. 202.It soft 203Consults magic files. 204.It tar 205Examines tar files. 206.El 207.It Fl F , Fl Fl separator Ar separator 208Use the specified string as the separator between the filename and the 209file result returned. 210Defaults to 211.Sq \&: . 212.It Fl f , Fl Fl files-from Ar namefile 213Read the names of the files to be examined from 214.Ar namefile 215(one per line) 216before the argument list. 217Either 218.Ar namefile 219or at least one filename argument must be present; 220to test the standard input, use 221.Sq - 222as a filename argument. 223Please note that 224.Ar namefile 225is unwrapped and the enclosed filenames are processed when this option is 226encountered and before any further options processing is done. 227This allows one to process multiple lists of files with different command line 228arguments on the same 229.Nm 230invocation. 231Thus if you want to set the delimiter, you need to do it before you specify 232the list of files, like: 233.Dq Fl F Ar @ Fl f Ar namefile , 234instead of: 235.Dq Fl f Ar namefile Fl F Ar @ . 236.It Fl h , Fl Fl no-dereference 237option causes symlinks not to be followed 238(on systems that support symbolic links). 239This is the default if the environment variable 240.Dv POSIXLY_CORRECT 241is not defined. 242.It Fl i , Fl Fl mime 243Causes the file command to output mime type strings rather than the more 244traditional human readable ones. 245Thus it may say 246.Sq text/plain; charset=us-ascii 247rather than 248.Dq ASCII text . 249.It Fl Fl mime-type , Fl Fl mime-encoding 250Like 251.Fl i , 252but print only the specified element(s). 253.It Fl k , Fl Fl keep-going 254Don't stop at the first match, keep going. 255Subsequent matches will be 256have the string 257.Sq "\[rs]012\- " 258prepended. 259(If you want a newline, see the 260.Fl r 261option.) 262.It Fl l , Fl Fl list 263Print information about the strength of each magic pattern. 264.It Fl L , Fl Fl dereference 265option causes symlinks to be followed, as the like-named option in 266.Xr ls 1 267(on systems that support symbolic links). 268This is the default if the environment variable 269.Ev POSIXLY_CORRECT 270is defined. 271.It Fl l 272Shows sorted patterns list in the order which is used for the matching. 273.It Fl m , Fl Fl magic-file Ar magicfiles 274Specify an alternate list of files and directories containing magic. 275This can be a single item, or a colon-separated list. 276If a compiled magic file is found alongside a file or directory, 277it will be used instead. 278.It Fl N , Fl Fl no-pad 279Don't pad filenames so that they align in the output. 280.It Fl n , Fl Fl no-buffer 281Force stdout to be flushed after checking each file. 282This is only useful if checking a list of files. 283It is intended to be used by programs that want filetype output from a pipe. 284.It Fl p , Fl Fl preserve-date 285On systems that support 286.Xr utime 3 287or 288.Xr utimes 2 , 289attempt to preserve the access time of files analyzed, to pretend that 290.Nm 291never read them. 292.It Fl r , Fl Fl raw 293Don't translate unprintable characters to \eooo. 294Normally 295.Nm 296translates unprintable characters to their octal representation. 297.It Fl s , Fl Fl special-files 298Normally, 299.Nm 300only attempts to read and determine the type of argument files which 301.Xr stat 2 302reports are ordinary files. 303This prevents problems, because reading special files may have peculiar 304consequences. 305Specifying the 306.Fl s 307option causes 308.Nm 309to also read argument files which are block or character special files. 310This is useful for determining the filesystem types of the data in raw 311disk partitions, which are block special files. 312This option also causes 313.Nm 314to disregard the file size as reported by 315.Xr stat 2 316since on some systems it reports a zero size for raw disk partitions. 317.It Fl v , Fl Fl version 318Print the version of the program and exit. 319.It Fl z , Fl Fl uncompress 320Try to look inside compressed files. 321.It Fl 0 , Fl Fl print0 322Output a null character 323.Sq \e0 324after the end of the filename. 325Nice to 326.Xr cut 1 327the output. 328This does not affect the separator which is still printed. 329.It Fl -help 330Print a help message and exit. 331.El 332.Sh FILES 333.Bl -tag -width __MAGIC__.mgc -compact 334.It Pa __MAGIC__.mgc 335Default compiled list of magic. 336.It Pa __MAGIC__ 337Directory containing default magic files. 338.El 339.Sh ENVIRONMENT 340The environment variable 341.Ev MAGIC 342can be used to set the default magic file name. 343If that variable is set, then 344.Nm 345will not attempt to open 346.Pa $HOME/.magic . 347.Nm 348adds 349.Dq Pa .mgc 350to the value of this variable as appropriate. 351However, 352.Pa file 353has to exist in order for 354.Pa file.mime 355to be considered. 356The environment variable 357.Ev POSIXLY_CORRECT 358controls (on systems that support symbolic links), whether 359.Nm 360will attempt to follow symlinks or not. 361If set, then 362.Nm 363follows symlink, otherwise it does not. 364This is also controlled by the 365.Fl L 366and 367.Fl h 368options. 369.Sh SEE ALSO 370.Xr magic __FSECTION__ , 371.Xr hexdump 1 , 372.Xr od 1 , 373.Xr strings 1 , 374.Sh STANDARDS CONFORMANCE 375This program is believed to exceed the System V Interface Definition 376of FILE(CMD), as near as one can determine from the vague language 377contained therein. 378Its behavior is mostly compatible with the System V program of the same name. 379This version knows more magic, however, so it will produce 380different (albeit more accurate) output in many cases. 381.\" URL: http://www.opengroup.org/onlinepubs/009695399/utilities/file.html 382.Pp 383The one significant difference 384between this version and System V 385is that this version treats any white space 386as a delimiter, so that spaces in pattern strings must be escaped. 387For example, 388.Bd -literal -offset indent 389\*[Gt]10 string language impress\ (imPRESS data) 390.Ed 391.Pp 392in an existing magic file would have to be changed to 393.Bd -literal -offset indent 394\*[Gt]10 string language\e impress (imPRESS data) 395.Ed 396.Pp 397In addition, in this version, if a pattern string contains a backslash, 398it must be escaped. 399For example 400.Bd -literal -offset indent 4010 string \ebegindata Andrew Toolkit document 402.Ed 403.Pp 404in an existing magic file would have to be changed to 405.Bd -literal -offset indent 4060 string \e\ebegindata Andrew Toolkit document 407.Ed 408.Pp 409SunOS releases 3.2 and later from Sun Microsystems include a 410.Nm 411command derived from the System V one, but with some extensions. 412This version differs from Sun's only in minor ways. 413It includes the extension of the 414.Sq \*[Am] 415operator, used as, 416for example, 417.Bd -literal -offset indent 418\*[Gt]16 long\*[Am]0x7fffffff \*[Gt]0 not stripped 419.Ed 420.Sh MAGIC DIRECTORY 421The magic file entries have been collected from various sources, 422mainly USENET, and contributed by various authors. 423Christos Zoulas (address below) will collect additional 424or corrected magic file entries. 425A consolidation of magic file entries 426will be distributed periodically. 427.Pp 428The order of entries in the magic file is significant. 429Depending on what system you are using, the order that 430they are put together may be incorrect. 431If your old 432.Nm 433command uses a magic file, 434keep the old magic file around for comparison purposes 435(rename it to 436.Pa __MAGIC__.orig ) . 437.Sh EXAMPLES 438.Bd -literal -offset indent 439$ file file.c file /dev/{wd0a,hda} 440file.c: C program text 441file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), 442 dynamically linked (uses shared libs), stripped 443/dev/wd0a: block special (0/0) 444/dev/hda: block special (3/0) 445 446$ file -s /dev/wd0{b,d} 447/dev/wd0b: data 448/dev/wd0d: x86 boot sector 449 450$ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10} 451/dev/hda: x86 boot sector 452/dev/hda1: Linux/i386 ext2 filesystem 453/dev/hda2: x86 boot sector 454/dev/hda3: x86 boot sector, extended partition table 455/dev/hda4: Linux/i386 ext2 filesystem 456/dev/hda5: Linux/i386 swap file 457/dev/hda6: Linux/i386 swap file 458/dev/hda7: Linux/i386 swap file 459/dev/hda8: Linux/i386 swap file 460/dev/hda9: empty 461/dev/hda10: empty 462 463$ file -i file.c file /dev/{wd0a,hda} 464file.c: text/x-c 465file: application/x-executable 466/dev/hda: application/x-not-regular-file 467/dev/wd0a: application/x-not-regular-file 468 469.Ed 470.Sh HISTORY 471There has been a 472.Nm 473command in every 474.Dv UNIX since at least Research Version 4 475(man page dated November, 1973). 476The System V version introduced one significant major change: 477the external list of magic types. 478This slowed the program down slightly but made it a lot more flexible. 479.Pp 480This program, based on the System V version, 481was written by Ian Darwin 482.Aq ian@darwinsys.com 483without looking at anybody else's source code. 484.Pp 485John Gilmore revised the code extensively, making it better than 486the first version. 487Geoff Collyer found several inadequacies 488and provided some magic file entries. 489Contributions by the 490.Sq \*[Am] 491operator by Rob McMahon, 492.Aq cudcv@warwick.ac.uk , 4931989. 494.Pp 495Guy Harris, 496.Aq guy@netapp.com , 497made many changes from 1993 to the present. 4981989. 499.Pp 500Primary development and maintenance from 1990 to the present by 501Christos Zoulas 502.Aq christos@astron.com . 503.Pp 504Altered by Chris Lowth 505.Aq chris@lowth.com , 5062000: handle the 507.Fl i 508option to output mime type strings, using an alternative 509magic file and internal logic. 510.Pp 511Altered by Eric Fischer 512.Aq enf@pobox.com , 513July, 2000, 514to identify character codes and attempt to identify the languages 515of non-ASCII files. 516.Pp 517Altered by Reuben Thomas 518.Aq rrt@sc3d.org , 5192007-2011, to improve MIME support, merge MIME and non-MIME magic, 520support directories as well as files of magic, apply many bug fixes, 521update and fix a lot of magic, improve the build system, improve the 522documentation, and rewrite the Python bindings in pure Python. 523.Pp 524The list of contributors to the 525.Sq magic 526directory (magic files) 527is too long to include here. 528You know who you are; thank you. 529Many contributors are listed in the source files. 530.Sh LEGAL NOTICE 531Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. 532Covered by the standard Berkeley Software Distribution copyright; see the file 533COPYING in the source distribution. 534.Pp 535The files 536.Pa tar.h 537and 538.Pa is_tar.c 539were written by John Gilmore from his public-domain 540.Xr tar 1 541program, and are not covered by the above license. 542.Sh RETURN CODE 543.Nm 544returns 0 on success, and non-zero on error. 545.Sh BUGS 546.Pp 547Please report bugs and send patches to the bug tracker at 548.Pa http://bugs.gw.com/ 549or the mailing list at 550.Aq file@mx.gw.com . 551.Sh TODO 552.Pp 553Fix output so that tests for MIME and APPLE flags are not needed all 554over the place, and actual output is only done in one place. This 555needs a design. Suggestion: push possible outputs on to a list, then 556pick the last-pushed (most specific, one hopes) value at the end, or 557use a default if the list is empty. This should not slow down evaluation. 558.Pp 559Continue to squash all magic bugs. See Debian BTS for a good source. 560.Pp 561Store arbitrarily long strings, for example for %s patterns, so that 562they can be printed out. Fixes Debian bug #271672. Would require more 563complex store/load code in apprentice. 564.Pp 565Add syntax for relative offsets after current level (Debian bug #466037). 566.Pp 567Make file -ki work, i.e. give multiple MIME types. 568.Pp 569Add a zip library so we can peek inside Office2007 documents to 570figure out what they are. 571.Pp 572Add an option to print URLs for the sources of the file descriptions. 573.Sh AVAILABILITY 574You can obtain the original author's latest version by anonymous FTP 575on 576.Pa ftp.astron.com 577in the directory 578.Pa /pub/file/file-X.YZ.tar.gz . 579