1.\" $File: file.man,v 1.121 2016/06/07 22:09:20 rrt Exp $ 2.Dd March 13, 2016 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 bcEhiklLNnprsvzZ0 12.Op Fl Fl apple 13.Op Fl Fl extension 14.Op Fl Fl mime-encoding 15.Op Fl Fl mime-type 16.Op Fl e Ar testname 17.Op Fl F Ar separator 18.Op Fl f Ar namefile 19.Op Fl m Ar magicfiles 20.Op Fl P Ar name=value 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 __VERSION__ 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 __MAGIC__.mgc , 107or the files in the directory 108.Pa __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 Fl apple 170Causes the file command to output the file type and creator code as 171used by older MacOS versions. The code consists of eight letters, 172the first describing the file type, the latter the creator. 173.It Fl b , Fl Fl brief 174Do not prepend filenames to output lines (brief mode). 175.It Fl C , Fl Fl compile 176Write a 177.Pa magic.mgc 178output file that contains a pre-parsed version of the magic file or directory. 179.It Fl c , Fl Fl checking-printout 180Cause a checking printout of the parsed form of the magic file. 181This is usually used in conjunction with the 182.Fl m 183flag to debug a new magic file before installing it. 184.It Fl E 185On filesystem errors (file not found etc), instead of handling the error 186as regular output as POSIX mandates and keep going, issue an error message 187and exit. 188.It Fl e , Fl Fl exclude Ar testname 189Exclude the test named in 190.Ar testname 191from the list of tests made to determine the file type. 192Valid test names are: 193.Bl -tag -width compress 194.It apptype 195.Dv EMX 196application type (only on EMX). 197.It ascii 198Various types of text files (this test will try to guess the text 199encoding, irrespective of the setting of the 200.Sq encoding 201option). 202.It encoding 203Different text encodings for soft magic tests. 204.It tokens 205Ignored for backwards compatibility. 206.It cdf 207Prints details of Compound Document Files. 208.It compress 209Checks for, and looks inside, compressed files. 210.It elf 211Prints ELF file details. 212.It soft 213Consults magic files. 214.It tar 215Examines tar files. 216.It text 217A synonym for 218.Sq ascii . 219.El 220.It Fl Fl extension 221Print a slash-separated list of valid extensions for the file type found. 222.It Fl F , Fl Fl separator Ar separator 223Use the specified string as the separator between the filename and the 224file result returned. 225Defaults to 226.Sq \&: . 227.It Fl f , Fl Fl files-from Ar namefile 228Read the names of the files to be examined from 229.Ar namefile 230(one per line) 231before the argument list. 232Either 233.Ar namefile 234or at least one filename argument must be present; 235to test the standard input, use 236.Sq - 237as a filename argument. 238Please note that 239.Ar namefile 240is unwrapped and the enclosed filenames are processed when this option is 241encountered and before any further options processing is done. 242This allows one to process multiple lists of files with different command line 243arguments on the same 244.Nm 245invocation. 246Thus if you want to set the delimiter, you need to do it before you specify 247the list of files, like: 248.Dq Fl F Ar @ Fl f Ar namefile , 249instead of: 250.Dq Fl f Ar namefile Fl F Ar @ . 251.It Fl h , Fl Fl no-dereference 252option causes symlinks not to be followed 253(on systems that support symbolic links). 254This is the default if the environment variable 255.Dv POSIXLY_CORRECT 256is not defined. 257.It Fl i , Fl Fl mime 258Causes the file command to output mime type strings rather than the more 259traditional human readable ones. 260Thus it may say 261.Sq text/plain; charset=us-ascii 262rather than 263.Dq ASCII text . 264.It Fl Fl mime-type , Fl Fl mime-encoding 265Like 266.Fl i , 267but print only the specified element(s). 268.It Fl k , Fl Fl keep-going 269Don't stop at the first match, keep going. 270Subsequent matches will be 271have the string 272.Sq "\[rs]012\- " 273prepended. 274(If you want a newline, see the 275.Fl r 276option.) 277The magic pattern with the highest strength (see the 278.Fl l 279option) comes first. 280.It Fl l , Fl Fl list 281Shows a list of patterns and their strength sorted descending by 282.Xr magic 4 283strength 284which is used for the matching (see also the 285.Fl k 286option). 287.It Fl L , Fl Fl dereference 288option causes symlinks to be followed, as the like-named option in 289.Xr ls 1 290(on systems that support symbolic links). 291This is the default if the environment variable 292.Ev POSIXLY_CORRECT 293is defined. 294.It Fl m , Fl Fl magic-file Ar magicfiles 295Specify an alternate list of files and directories containing magic. 296This can be a single item, or a colon-separated list. 297If a compiled magic file is found alongside a file or directory, 298it will be used instead. 299.It Fl N , Fl Fl no-pad 300Don't pad filenames so that they align in the output. 301.It Fl n , Fl Fl no-buffer 302Force stdout to be flushed after checking each file. 303This is only useful if checking a list of files. 304It is intended to be used by programs that want filetype output from a pipe. 305.It Fl p , Fl Fl preserve-date 306On systems that support 307.Xr utime 3 308or 309.Xr utimes 2 , 310attempt to preserve the access time of files analyzed, to pretend that 311.Nm 312never read them. 313.It Fl P , Fl Fl parameter Ar name=value 314Set various parameter limits. 315.Bl -column "elf_phnum" "Default" "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX" -offset indent 316.It Sy "Name" Ta Sy "Default" Ta Sy "Explanation" 317.It Li indir Ta 15 Ta recursion limit for indirect magic 318.It Li name Ta 30 Ta use count limit for name/use magic 319.It Li elf_notes Ta 256 Ta max ELF notes processed 320.It Li elf_phnum Ta 128 Ta max ELF program sections processed 321.It Li elf_shnum Ta 32768 Ta max ELF sections processed 322.It Li regex Ta 8192 Ta length limit for regex searches 323.It Li bytes Ta 1048576 Ta max number of bytes to read from file 324.El 325.It Fl r , Fl Fl raw 326Don't translate unprintable characters to \eooo. 327Normally 328.Nm 329translates unprintable characters to their octal representation. 330.It Fl s , Fl Fl special-files 331Normally, 332.Nm 333only attempts to read and determine the type of argument files which 334.Xr stat 2 335reports are ordinary files. 336This prevents problems, because reading special files may have peculiar 337consequences. 338Specifying the 339.Fl s 340option causes 341.Nm 342to also read argument files which are block or character special files. 343This is useful for determining the filesystem types of the data in raw 344disk partitions, which are block special files. 345This option also causes 346.Nm 347to disregard the file size as reported by 348.Xr stat 2 349since on some systems it reports a zero size for raw disk partitions. 350.It Fl v , Fl Fl version 351Print the version of the program and exit. 352.It Fl z , Fl Fl uncompress 353Try to look inside compressed files. 354.It Fl Z , Fl Fl uncompress-noreport 355Try to look inside compressed files, but report information about the contents 356only not the compression. 357.It Fl 0 , Fl Fl print0 358Output a null character 359.Sq \e0 360after the end of the filename. 361Nice to 362.Xr cut 1 363the output. 364This does not affect the separator, which is still printed. 365.Pp 366If this option is repeated more than once, then 367.Nm 368prints just the filename followed by a NUL followed by the description 369(or ERROR: text) followed by a second NUL for each entry. 370.It Fl -help 371Print a help message and exit. 372.El 373.Sh FILES 374.Bl -tag -width __MAGIC__.mgc -compact 375.It Pa __MAGIC__.mgc 376Default compiled list of magic. 377.It Pa __MAGIC__ 378Directory containing default magic files. 379.El 380.Sh ENVIRONMENT 381The environment variable 382.Ev MAGIC 383can be used to set the default magic file name. 384If that variable is set, then 385.Nm 386will not attempt to open 387.Pa $HOME/.magic . 388.Nm 389adds 390.Dq Pa .mgc 391to the value of this variable as appropriate. 392However, 393.Pa file 394has to exist in order for 395.Pa file.mime 396to be considered. 397The environment variable 398.Ev POSIXLY_CORRECT 399controls (on systems that support symbolic links), whether 400.Nm 401will attempt to follow symlinks or not. 402If set, then 403.Nm 404follows symlink, otherwise it does not. 405This is also controlled by the 406.Fl L 407and 408.Fl h 409options. 410.Sh SEE ALSO 411.Xr magic __FSECTION__ , 412.Xr hexdump 1 , 413.Xr od 1 , 414.Xr strings 1 , 415.Xr fstyp 8 416.Sh STANDARDS CONFORMANCE 417This program is believed to exceed the System V Interface Definition 418of FILE(CMD), as near as one can determine from the vague language 419contained therein. 420Its behavior is mostly compatible with the System V program of the same name. 421This version knows more magic, however, so it will produce 422different (albeit more accurate) output in many cases. 423.\" URL: http://www.opengroup.org/onlinepubs/009695399/utilities/file.html 424.Pp 425The one significant difference 426between this version and System V 427is that this version treats any white space 428as a delimiter, so that spaces in pattern strings must be escaped. 429For example, 430.Bd -literal -offset indent 431\*[Gt]10 string language impress\ (imPRESS data) 432.Ed 433.Pp 434in an existing magic file would have to be changed to 435.Bd -literal -offset indent 436\*[Gt]10 string language\e impress (imPRESS data) 437.Ed 438.Pp 439In addition, in this version, if a pattern string contains a backslash, 440it must be escaped. 441For example 442.Bd -literal -offset indent 4430 string \ebegindata Andrew Toolkit document 444.Ed 445.Pp 446in an existing magic file would have to be changed to 447.Bd -literal -offset indent 4480 string \e\ebegindata Andrew Toolkit document 449.Ed 450.Pp 451SunOS releases 3.2 and later from Sun Microsystems include a 452.Nm 453command derived from the System V one, but with some extensions. 454This version differs from Sun's only in minor ways. 455It includes the extension of the 456.Sq \*[Am] 457operator, used as, 458for example, 459.Bd -literal -offset indent 460\*[Gt]16 long\*[Am]0x7fffffff \*[Gt]0 not stripped 461.Ed 462.Sh MAGIC DIRECTORY 463The magic file entries have been collected from various sources, 464mainly USENET, and contributed by various authors. 465Christos Zoulas (address below) will collect additional 466or corrected magic file entries. 467A consolidation of magic file entries 468will be distributed periodically. 469.Pp 470The order of entries in the magic file is significant. 471Depending on what system you are using, the order that 472they are put together may be incorrect. 473If your old 474.Nm 475command uses a magic file, 476keep the old magic file around for comparison purposes 477(rename it to 478.Pa __MAGIC__.orig ) . 479.Sh EXAMPLES 480.Bd -literal -offset indent 481$ file file.c file /dev/{wd0a,hda} 482file.c: C program text 483file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), 484 dynamically linked (uses shared libs), stripped 485/dev/wd0a: block special (0/0) 486/dev/hda: block special (3/0) 487 488$ file -s /dev/wd0{b,d} 489/dev/wd0b: data 490/dev/wd0d: x86 boot sector 491 492$ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10} 493/dev/hda: x86 boot sector 494/dev/hda1: Linux/i386 ext2 filesystem 495/dev/hda2: x86 boot sector 496/dev/hda3: x86 boot sector, extended partition table 497/dev/hda4: Linux/i386 ext2 filesystem 498/dev/hda5: Linux/i386 swap file 499/dev/hda6: Linux/i386 swap file 500/dev/hda7: Linux/i386 swap file 501/dev/hda8: Linux/i386 swap file 502/dev/hda9: empty 503/dev/hda10: empty 504 505$ file -i file.c file /dev/{wd0a,hda} 506file.c: text/x-c 507file: application/x-executable 508/dev/hda: application/x-not-regular-file 509/dev/wd0a: application/x-not-regular-file 510 511.Ed 512.Sh HISTORY 513There has been a 514.Nm 515command in every 516.Dv UNIX since at least Research Version 4 517(man page dated November, 1973). 518The System V version introduced one significant major change: 519the external list of magic types. 520This slowed the program down slightly but made it a lot more flexible. 521.Pp 522This program, based on the System V version, 523was written by Ian Darwin 524.Aq ian@darwinsys.com 525without looking at anybody else's source code. 526.Pp 527John Gilmore revised the code extensively, making it better than 528the first version. 529Geoff Collyer found several inadequacies 530and provided some magic file entries. 531Contributions by the 532.Sq \*[Am] 533operator by Rob McMahon, 534.Aq cudcv@warwick.ac.uk , 5351989. 536.Pp 537Guy Harris, 538.Aq guy@netapp.com , 539made many changes from 1993 to the present. 5401989. 541.Pp 542Primary development and maintenance from 1990 to the present by 543Christos Zoulas 544.Aq christos@astron.com . 545.Pp 546Altered by Chris Lowth 547.Aq chris@lowth.com , 5482000: handle the 549.Fl i 550option to output mime type strings, using an alternative 551magic file and internal logic. 552.Pp 553Altered by Eric Fischer 554.Aq enf@pobox.com , 555July, 2000, 556to identify character codes and attempt to identify the languages 557of non-ASCII files. 558.Pp 559Altered by Reuben Thomas 560.Aq rrt@sc3d.org , 5612007-2011, to improve MIME support, merge MIME and non-MIME magic, 562support directories as well as files of magic, apply many bug fixes, 563update and fix a lot of magic, improve the build system, improve the 564documentation, and rewrite the Python bindings in pure Python. 565.Pp 566The list of contributors to the 567.Sq magic 568directory (magic files) 569is too long to include here. 570You know who you are; thank you. 571Many contributors are listed in the source files. 572.Sh LEGAL NOTICE 573Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. 574Covered by the standard Berkeley Software Distribution copyright; see the file 575COPYING in the source distribution. 576.Pp 577The files 578.Pa tar.h 579and 580.Pa is_tar.c 581were written by John Gilmore from his public-domain 582.Xr tar 1 583program, and are not covered by the above license. 584.Sh RETURN CODE 585.Nm 586returns 0 on success, and non-zero on error. 587.Sh BUGS 588.Pp 589Please report bugs and send patches to the bug tracker at 590.Pa http://bugs.gw.com/ 591or the mailing list at 592.Aq file@mx.gw.com 593(visit 594.Pa http://mx.gw.com/mailman/listinfo/file 595first to subscribe). 596.Sh TODO 597.Pp 598Fix output so that tests for MIME and APPLE flags are not needed all 599over the place, and actual output is only done in one place. 600This needs a design. 601Suggestion: push possible outputs on to a list, then pick the 602last-pushed (most specific, one hopes) value at the end, or 603use a default if the list is empty. 604This should not slow down evaluation. 605.Pp 606The handling of 607.Dv MAGIC_CONTINUE 608and printing \e012- between entries is clumsy and complicated; refactor 609and centralize. 610.Pp 611Some of the encoding logic is hard-coded in encoding.c and can be moved 612to the magic files if we had a !:charset annotation 613.Pp 614Continue to squash all magic bugs. 615See Debian BTS for a good source. 616.Pp 617Store arbitrarily long strings, for example for %s patterns, so that 618they can be printed out. 619Fixes Debian bug #271672. 620This can be done by allocating strings in a string pool, storing the 621string pool at the end of the magic file and converting all the string 622pointers to relative offsets from the string pool. 623.Pp 624Add syntax for relative offsets after current level (Debian bug #466037). 625.Pp 626Make file -ki work, i.e. give multiple MIME types. 627.Pp 628Add a zip library so we can peek inside Office2007 documents to 629print more details about their contents. 630.Pp 631Add an option to print URLs for the sources of the file descriptions. 632.Pp 633Combine script searches and add a way to map executable names to MIME 634types (e.g. have a magic value for !:mime which causes the resulting 635string to be looked up in a table). 636This would avoid adding the same magic repeatedly for each new 637hash-bang interpreter. 638.Pp 639When a file descriptor is available, we can skip and adjust the buffer 640instead of the hacky buffer management we do now. 641.Pp 642Fix 643.Dq name 644and 645.Dq use 646to check for consistency at compile time (duplicate 647.Dq name , 648.Dq use 649pointing to undefined 650.Dq name 651). 652Make 653.Dq name 654/ 655.Dq use 656more efficient by keeping a sorted list of names. 657Special-case ^ to flip endianness in the parser so that it does not 658have to be escaped, and document it. 659.Pp 660If the offsets specified internally in the file exceed the buffer size 661( 662.Dv HOWMANY 663variable in file.h), then we don't seek to that offset, but we give up. 664It would be better if buffer managements was done when the file descriptor 665is available so move around the file. 666One must be careful though because this has performance (and thus security 667considerations). 668.Sh AVAILABILITY 669You can obtain the original author's latest version by anonymous FTP 670on 671.Pa ftp.astron.com 672in the directory 673.Pa /pub/file/file-X.YZ.tar.gz . 674