1.\" $File: file.man,v 1.96 2011/07/12 11:23:38 rrt Exp $ 2.Dd April 20, 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 195Looks for known tokens inside text files. 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. 223.It Fl h , Fl Fl no-dereference 224option causes symlinks not to be followed 225(on systems that support symbolic links). 226This is the default if the environment variable 227.Dv POSIXLY_CORRECT 228is not defined. 229.It Fl i , Fl Fl mime 230Causes the file command to output mime type strings rather than the more 231traditional human readable ones. 232Thus it may say 233.Sq text/plain; charset=us-ascii 234rather than 235.Dq ASCII text . 236.It Fl Fl mime-type , Fl Fl mime-encoding 237Like 238.Fl i , 239but print only the specified element(s). 240.It Fl k , Fl Fl keep-going 241Don't stop at the first match, keep going. 242Subsequent matches will be 243have the string 244.Sq "\[rs]012\- " 245prepended. 246(If you want a newline, see the 247.Fl r 248option.) 249.It Fl l , Fl Fl list 250Print information about the strength of each magic pattern. 251.It Fl L , Fl Fl dereference 252option causes symlinks to be followed, as the like-named option in 253.Xr ls 1 254(on systems that support symbolic links). 255This is the default if the environment variable 256.Ev POSIXLY_CORRECT 257is defined. 258.It Fl l 259Shows sorted patterns list in the order which is used for the matching. 260.It Fl m , Fl Fl magic-file Ar magicfiles 261Specify an alternate list of files and directories containing magic. 262This can be a single item, or a colon-separated list. 263If a compiled magic file is found alongside a file or directory, 264it will be used instead. 265.It Fl N , Fl Fl no-pad 266Don't pad filenames so that they align in the output. 267.It Fl n , Fl Fl no-buffer 268Force stdout to be flushed after checking each file. 269This is only useful if checking a list of files. 270It is intended to be used by programs that want filetype output from a pipe. 271.It Fl p , Fl Fl preserve-date 272On systems that support 273.Xr utime 3 274or 275.Xr utimes 2 , 276attempt to preserve the access time of files analyzed, to pretend that 277.Nm 278never read them. 279.It Fl r , Fl Fl raw 280Don't translate unprintable characters to \eooo. 281Normally 282.Nm 283translates unprintable characters to their octal representation. 284.It Fl s , Fl Fl special-files 285Normally, 286.Nm 287only attempts to read and determine the type of argument files which 288.Xr stat 2 289reports are ordinary files. 290This prevents problems, because reading special files may have peculiar 291consequences. 292Specifying the 293.Fl s 294option causes 295.Nm 296to also read argument files which are block or character special files. 297This is useful for determining the filesystem types of the data in raw 298disk partitions, which are block special files. 299This option also causes 300.Nm 301to disregard the file size as reported by 302.Xr stat 2 303since on some systems it reports a zero size for raw disk partitions. 304.It Fl v , Fl Fl version 305Print the version of the program and exit. 306.It Fl z , Fl Fl uncompress 307Try to look inside compressed files. 308.It Fl 0 , Fl Fl print0 309Output a null character 310.Sq \e0 311after the end of the filename. 312Nice to 313.Xr cut 1 314the output. 315This does not affect the separator which is still printed. 316.It Fl -help 317Print a help message and exit. 318.El 319.Sh FILES 320.Bl -tag -width __MAGIC__.mgc -compact 321.It Pa __MAGIC__.mgc 322Default compiled list of magic. 323.It Pa __MAGIC__ 324Directory containing default magic files. 325.El 326.Sh ENVIRONMENT 327The environment variable 328.Ev MAGIC 329can be used to set the default magic file name. 330If that variable is set, then 331.Nm 332will not attempt to open 333.Pa $HOME/.magic . 334.Nm 335adds 336.Dq Pa .mgc 337to the value of this variable as appropriate. 338However, 339.Pa file 340has to exist in order for 341.Pa file.mime 342to be considered. 343The environment variable 344.Ev POSIXLY_CORRECT 345controls (on systems that support symbolic links), whether 346.Nm 347will attempt to follow symlinks or not. 348If set, then 349.Nm 350follows symlink, otherwise it does not. 351This is also controlled by the 352.Fl L 353and 354.Fl h 355options. 356.Sh SEE ALSO 357.Xr magic __FSECTION__ , 358.Xr hexdump 1 , 359.Xr od 1 , 360.Xr strings 1 , 361.Sh STANDARDS CONFORMANCE 362This program is believed to exceed the System V Interface Definition 363of FILE(CMD), as near as one can determine from the vague language 364contained therein. 365Its behavior is mostly compatible with the System V program of the same name. 366This version knows more magic, however, so it will produce 367different (albeit more accurate) output in many cases. 368.\" URL: http://www.opengroup.org/onlinepubs/009695399/utilities/file.html 369.Pp 370The one significant difference 371between this version and System V 372is that this version treats any white space 373as a delimiter, so that spaces in pattern strings must be escaped. 374For example, 375.Bd -literal -offset indent 376\*[Gt]10 string language impress\ (imPRESS data) 377.Ed 378.Pp 379in an existing magic file would have to be changed to 380.Bd -literal -offset indent 381\*[Gt]10 string language\e impress (imPRESS data) 382.Ed 383.Pp 384In addition, in this version, if a pattern string contains a backslash, 385it must be escaped. 386For example 387.Bd -literal -offset indent 3880 string \ebegindata Andrew Toolkit document 389.Ed 390.Pp 391in an existing magic file would have to be changed to 392.Bd -literal -offset indent 3930 string \e\ebegindata Andrew Toolkit document 394.Ed 395.Pp 396SunOS releases 3.2 and later from Sun Microsystems include a 397.Nm 398command derived from the System V one, but with some extensions. 399This version differs from Sun's only in minor ways. 400It includes the extension of the 401.Sq \*[Am] 402operator, used as, 403for example, 404.Bd -literal -offset indent 405\*[Gt]16 long\*[Am]0x7fffffff \*[Gt]0 not stripped 406.Ed 407.Sh MAGIC DIRECTORY 408The magic file entries have been collected from various sources, 409mainly USENET, and contributed by various authors. 410Christos Zoulas (address below) will collect additional 411or corrected magic file entries. 412A consolidation of magic file entries 413will be distributed periodically. 414.Pp 415The order of entries in the magic file is significant. 416Depending on what system you are using, the order that 417they are put together may be incorrect. 418If your old 419.Nm 420command uses a magic file, 421keep the old magic file around for comparison purposes 422(rename it to 423.Pa __MAGIC__.orig ) . 424.Sh EXAMPLES 425.Bd -literal -offset indent 426$ file file.c file /dev/{wd0a,hda} 427file.c: C program text 428file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), 429 dynamically linked (uses shared libs), stripped 430/dev/wd0a: block special (0/0) 431/dev/hda: block special (3/0) 432 433$ file -s /dev/wd0{b,d} 434/dev/wd0b: data 435/dev/wd0d: x86 boot sector 436 437$ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10} 438/dev/hda: x86 boot sector 439/dev/hda1: Linux/i386 ext2 filesystem 440/dev/hda2: x86 boot sector 441/dev/hda3: x86 boot sector, extended partition table 442/dev/hda4: Linux/i386 ext2 filesystem 443/dev/hda5: Linux/i386 swap file 444/dev/hda6: Linux/i386 swap file 445/dev/hda7: Linux/i386 swap file 446/dev/hda8: Linux/i386 swap file 447/dev/hda9: empty 448/dev/hda10: empty 449 450$ file -i file.c file /dev/{wd0a,hda} 451file.c: text/x-c 452file: application/x-executable 453/dev/hda: application/x-not-regular-file 454/dev/wd0a: application/x-not-regular-file 455 456.Ed 457.Sh HISTORY 458There has been a 459.Nm 460command in every 461.Dv UNIX since at least Research Version 4 462(man page dated November, 1973). 463The System V version introduced one significant major change: 464the external list of magic types. 465This slowed the program down slightly but made it a lot more flexible. 466.Pp 467This program, based on the System V version, 468was written by Ian Darwin 469.Aq ian@darwinsys.com 470without looking at anybody else's source code. 471.Pp 472John Gilmore revised the code extensively, making it better than 473the first version. 474Geoff Collyer found several inadequacies 475and provided some magic file entries. 476Contributions by the 477.Sq \*[Am] 478operator by Rob McMahon, 479.Aq cudcv@warwick.ac.uk , 4801989. 481.Pp 482Guy Harris, 483.Aq guy@netapp.com , 484made many changes from 1993 to the present. 4851989. 486.Pp 487Primary development and maintenance from 1990 to the present by 488Christos Zoulas 489.Aq christos@astron.com . 490.Pp 491Altered by Chris Lowth 492.Aq chris@lowth.com , 4932000: handle the 494.Fl i 495option to output mime type strings, using an alternative 496magic file and internal logic. 497.Pp 498Altered by Eric Fischer 499.Aq enf@pobox.com , 500July, 2000, 501to identify character codes and attempt to identify the languages 502of non-ASCII files. 503.Pp 504Altered by Reuben Thomas 505.Aq rrt@sc3d.org , 5062007-2011, to improve MIME support, merge MIME and non-MIME magic, 507support directories as well as files of magic, apply many bug fixes, 508update and fix a lot of magic, improve the build system, improve the 509documentation, and rewrite the Python bindings in pure Python. 510.Pp 511The list of contributors to the 512.Sq magic 513directory (magic files) 514is too long to include here. 515You know who you are; thank you. 516Many contributors are listed in the source files. 517.Sh LEGAL NOTICE 518Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. 519Covered by the standard Berkeley Software Distribution copyright; see the file 520COPYING in the source distribution. 521.Pp 522The files 523.Pa tar.h 524and 525.Pa is_tar.c 526were written by John Gilmore from his public-domain 527.Xr tar 1 528program, and are not covered by the above license. 529.Sh RETURN CODE 530.Nm 531returns 0 on success, and non-zero on error. 532.Sh BUGS 533.Pp 534Please report bugs and send patches to the bug tracker at 535.Pa http://bugs.gw.com/ 536or the mailing list at 537.Aq file@mx.gw.com . 538.Sh TODO 539.Pp 540Fix output so that tests for MIME and APPLE flags are not needed all 541over the place, and actual output is only done in one place. This 542needs a design. Suggestion: push possible outputs on to a list, then 543pick the last-pushed (most specific, one hopes) value at the end, or 544use a default if the list is empty. This should not slow down evaluation. 545.Pp 546Continue to squash all magic bugs. See Debian BTS for a good source. 547.Pp 548Store arbitrarily long strings, for example for %s patterns, so that 549they can be printed out. Fixes Debian bug #271672. Would require more 550complex store/load code in apprentice. 551.Pp 552Add syntax for relative offsets after current level (Debian bug #466037). 553.Pp 554Make file -ki work, i.e. give multiple MIME types. 555.Pp 556Add a zip library so we can peek inside Office2007 documents to 557figure out what they are. 558.Pp 559Add an option to print URLs for the sources of the file descriptions. 560.Sh AVAILABILITY 561You can obtain the original author's latest version by anonymous FTP 562on 563.Pa ftp.astron.com 564in the directory 565.Pa /pub/file/file-X.YZ.tar.gz . 566