1.\" $File: file.man,v 1.120 2016/03/31 17:51:12 christos 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.El 217.It Fl Fl extension 218Print a slash-separated list of valid extensions for the file type found. 219.It Fl F , Fl Fl separator Ar separator 220Use the specified string as the separator between the filename and the 221file result returned. 222Defaults to 223.Sq \&: . 224.It Fl f , Fl Fl files-from Ar namefile 225Read the names of the files to be examined from 226.Ar namefile 227(one per line) 228before the argument list. 229Either 230.Ar namefile 231or at least one filename argument must be present; 232to test the standard input, use 233.Sq - 234as a filename argument. 235Please note that 236.Ar namefile 237is unwrapped and the enclosed filenames are processed when this option is 238encountered and before any further options processing is done. 239This allows one to process multiple lists of files with different command line 240arguments on the same 241.Nm 242invocation. 243Thus if you want to set the delimiter, you need to do it before you specify 244the list of files, like: 245.Dq Fl F Ar @ Fl f Ar namefile , 246instead of: 247.Dq Fl f Ar namefile Fl F Ar @ . 248.It Fl h , Fl Fl no-dereference 249option causes symlinks not to be followed 250(on systems that support symbolic links). 251This is the default if the environment variable 252.Dv POSIXLY_CORRECT 253is not defined. 254.It Fl i , Fl Fl mime 255Causes the file command to output mime type strings rather than the more 256traditional human readable ones. 257Thus it may say 258.Sq text/plain; charset=us-ascii 259rather than 260.Dq ASCII text . 261.It Fl Fl mime-type , Fl Fl mime-encoding 262Like 263.Fl i , 264but print only the specified element(s). 265.It Fl k , Fl Fl keep-going 266Don't stop at the first match, keep going. 267Subsequent matches will be 268have the string 269.Sq "\[rs]012\- " 270prepended. 271(If you want a newline, see the 272.Fl r 273option.) 274The magic pattern with the highest strength (see the 275.Fl l 276option) comes first. 277.It Fl l , Fl Fl list 278Shows a list of patterns and their strength sorted descending by 279.Xr magic 4 280strength 281which is used for the matching (see also the 282.Fl k 283option). 284.It Fl L , Fl Fl dereference 285option causes symlinks to be followed, as the like-named option in 286.Xr ls 1 287(on systems that support symbolic links). 288This is the default if the environment variable 289.Ev POSIXLY_CORRECT 290is defined. 291.It Fl m , Fl Fl magic-file Ar magicfiles 292Specify an alternate list of files and directories containing magic. 293This can be a single item, or a colon-separated list. 294If a compiled magic file is found alongside a file or directory, 295it will be used instead. 296.It Fl N , Fl Fl no-pad 297Don't pad filenames so that they align in the output. 298.It Fl n , Fl Fl no-buffer 299Force stdout to be flushed after checking each file. 300This is only useful if checking a list of files. 301It is intended to be used by programs that want filetype output from a pipe. 302.It Fl p , Fl Fl preserve-date 303On systems that support 304.Xr utime 3 305or 306.Xr utimes 2 , 307attempt to preserve the access time of files analyzed, to pretend that 308.Nm 309never read them. 310.It Fl P , Fl Fl parameter Ar name=value 311Set various parameter limits. 312.Bl -column "elf_phnum" "Default" "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX" -offset indent 313.It Sy "Name" Ta Sy "Default" Ta Sy "Explanation" 314.It Li indir Ta 15 Ta recursion limit for indirect magic 315.It Li name Ta 30 Ta use count limit for name/use magic 316.It Li elf_notes Ta 256 Ta max ELF notes processed 317.It Li elf_phnum Ta 128 Ta max ELF program sections processed 318.It Li elf_shnum Ta 32768 Ta max ELF sections processed 319.It Li regex Ta 8192 Ta length limit for regex searches 320.It Li bytes Ta 1048576 Ta max number of bytes to read from file 321.El 322.It Fl r , Fl Fl raw 323Don't translate unprintable characters to \eooo. 324Normally 325.Nm 326translates unprintable characters to their octal representation. 327.It Fl s , Fl Fl special-files 328Normally, 329.Nm 330only attempts to read and determine the type of argument files which 331.Xr stat 2 332reports are ordinary files. 333This prevents problems, because reading special files may have peculiar 334consequences. 335Specifying the 336.Fl s 337option causes 338.Nm 339to also read argument files which are block or character special files. 340This is useful for determining the filesystem types of the data in raw 341disk partitions, which are block special files. 342This option also causes 343.Nm 344to disregard the file size as reported by 345.Xr stat 2 346since on some systems it reports a zero size for raw disk partitions. 347.It Fl v , Fl Fl version 348Print the version of the program and exit. 349.It Fl z , Fl Fl uncompress 350Try to look inside compressed files. 351.It Fl Z , Fl Fl uncompress-noreport 352Try to look inside compressed files, but report information about the contents 353only not the compression. 354.It Fl 0 , Fl Fl print0 355Output a null character 356.Sq \e0 357after the end of the filename. 358Nice to 359.Xr cut 1 360the output. 361This does not affect the separator, which is still printed. 362.Pp 363If this option is repeated more than once, then 364.Nm 365prints just the filename followed by a NUL followed by the description 366(or ERROR: text) followed by a second NUL for each entry. 367.It Fl -help 368Print a help message and exit. 369.El 370.Sh FILES 371.Bl -tag -width __MAGIC__.mgc -compact 372.It Pa __MAGIC__.mgc 373Default compiled list of magic. 374.It Pa __MAGIC__ 375Directory containing default magic files. 376.El 377.Sh ENVIRONMENT 378The environment variable 379.Ev MAGIC 380can be used to set the default magic file name. 381If that variable is set, then 382.Nm 383will not attempt to open 384.Pa $HOME/.magic . 385.Nm 386adds 387.Dq Pa .mgc 388to the value of this variable as appropriate. 389However, 390.Pa file 391has to exist in order for 392.Pa file.mime 393to be considered. 394The environment variable 395.Ev POSIXLY_CORRECT 396controls (on systems that support symbolic links), whether 397.Nm 398will attempt to follow symlinks or not. 399If set, then 400.Nm 401follows symlink, otherwise it does not. 402This is also controlled by the 403.Fl L 404and 405.Fl h 406options. 407.Sh SEE ALSO 408.Xr magic __FSECTION__ , 409.Xr hexdump 1 , 410.Xr od 1 , 411.Xr strings 1 , 412.Xr fstyp 8 413.Sh STANDARDS CONFORMANCE 414This program is believed to exceed the System V Interface Definition 415of FILE(CMD), as near as one can determine from the vague language 416contained therein. 417Its behavior is mostly compatible with the System V program of the same name. 418This version knows more magic, however, so it will produce 419different (albeit more accurate) output in many cases. 420.\" URL: http://www.opengroup.org/onlinepubs/009695399/utilities/file.html 421.Pp 422The one significant difference 423between this version and System V 424is that this version treats any white space 425as a delimiter, so that spaces in pattern strings must be escaped. 426For example, 427.Bd -literal -offset indent 428\*[Gt]10 string language impress\ (imPRESS data) 429.Ed 430.Pp 431in an existing magic file would have to be changed to 432.Bd -literal -offset indent 433\*[Gt]10 string language\e impress (imPRESS data) 434.Ed 435.Pp 436In addition, in this version, if a pattern string contains a backslash, 437it must be escaped. 438For example 439.Bd -literal -offset indent 4400 string \ebegindata Andrew Toolkit document 441.Ed 442.Pp 443in an existing magic file would have to be changed to 444.Bd -literal -offset indent 4450 string \e\ebegindata Andrew Toolkit document 446.Ed 447.Pp 448SunOS releases 3.2 and later from Sun Microsystems include a 449.Nm 450command derived from the System V one, but with some extensions. 451This version differs from Sun's only in minor ways. 452It includes the extension of the 453.Sq \*[Am] 454operator, used as, 455for example, 456.Bd -literal -offset indent 457\*[Gt]16 long\*[Am]0x7fffffff \*[Gt]0 not stripped 458.Ed 459.Sh MAGIC DIRECTORY 460The magic file entries have been collected from various sources, 461mainly USENET, and contributed by various authors. 462Christos Zoulas (address below) will collect additional 463or corrected magic file entries. 464A consolidation of magic file entries 465will be distributed periodically. 466.Pp 467The order of entries in the magic file is significant. 468Depending on what system you are using, the order that 469they are put together may be incorrect. 470If your old 471.Nm 472command uses a magic file, 473keep the old magic file around for comparison purposes 474(rename it to 475.Pa __MAGIC__.orig ) . 476.Sh EXAMPLES 477.Bd -literal -offset indent 478$ file file.c file /dev/{wd0a,hda} 479file.c: C program text 480file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), 481 dynamically linked (uses shared libs), stripped 482/dev/wd0a: block special (0/0) 483/dev/hda: block special (3/0) 484 485$ file -s /dev/wd0{b,d} 486/dev/wd0b: data 487/dev/wd0d: x86 boot sector 488 489$ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10} 490/dev/hda: x86 boot sector 491/dev/hda1: Linux/i386 ext2 filesystem 492/dev/hda2: x86 boot sector 493/dev/hda3: x86 boot sector, extended partition table 494/dev/hda4: Linux/i386 ext2 filesystem 495/dev/hda5: Linux/i386 swap file 496/dev/hda6: Linux/i386 swap file 497/dev/hda7: Linux/i386 swap file 498/dev/hda8: Linux/i386 swap file 499/dev/hda9: empty 500/dev/hda10: empty 501 502$ file -i file.c file /dev/{wd0a,hda} 503file.c: text/x-c 504file: application/x-executable 505/dev/hda: application/x-not-regular-file 506/dev/wd0a: application/x-not-regular-file 507 508.Ed 509.Sh HISTORY 510There has been a 511.Nm 512command in every 513.Dv UNIX since at least Research Version 4 514(man page dated November, 1973). 515The System V version introduced one significant major change: 516the external list of magic types. 517This slowed the program down slightly but made it a lot more flexible. 518.Pp 519This program, based on the System V version, 520was written by Ian Darwin 521.Aq ian@darwinsys.com 522without looking at anybody else's source code. 523.Pp 524John Gilmore revised the code extensively, making it better than 525the first version. 526Geoff Collyer found several inadequacies 527and provided some magic file entries. 528Contributions by the 529.Sq \*[Am] 530operator by Rob McMahon, 531.Aq cudcv@warwick.ac.uk , 5321989. 533.Pp 534Guy Harris, 535.Aq guy@netapp.com , 536made many changes from 1993 to the present. 5371989. 538.Pp 539Primary development and maintenance from 1990 to the present by 540Christos Zoulas 541.Aq christos@astron.com . 542.Pp 543Altered by Chris Lowth 544.Aq chris@lowth.com , 5452000: handle the 546.Fl i 547option to output mime type strings, using an alternative 548magic file and internal logic. 549.Pp 550Altered by Eric Fischer 551.Aq enf@pobox.com , 552July, 2000, 553to identify character codes and attempt to identify the languages 554of non-ASCII files. 555.Pp 556Altered by Reuben Thomas 557.Aq rrt@sc3d.org , 5582007-2011, to improve MIME support, merge MIME and non-MIME magic, 559support directories as well as files of magic, apply many bug fixes, 560update and fix a lot of magic, improve the build system, improve the 561documentation, and rewrite the Python bindings in pure Python. 562.Pp 563The list of contributors to the 564.Sq magic 565directory (magic files) 566is too long to include here. 567You know who you are; thank you. 568Many contributors are listed in the source files. 569.Sh LEGAL NOTICE 570Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. 571Covered by the standard Berkeley Software Distribution copyright; see the file 572COPYING in the source distribution. 573.Pp 574The files 575.Pa tar.h 576and 577.Pa is_tar.c 578were written by John Gilmore from his public-domain 579.Xr tar 1 580program, and are not covered by the above license. 581.Sh RETURN CODE 582.Nm 583returns 0 on success, and non-zero on error. 584.Sh BUGS 585.Pp 586Please report bugs and send patches to the bug tracker at 587.Pa http://bugs.gw.com/ 588or the mailing list at 589.Aq file@mx.gw.com 590(visit 591.Pa http://mx.gw.com/mailman/listinfo/file 592first to subscribe). 593.Sh TODO 594.Pp 595Fix output so that tests for MIME and APPLE flags are not needed all 596over the place, and actual output is only done in one place. 597This needs a design. 598Suggestion: push possible outputs on to a list, then pick the 599last-pushed (most specific, one hopes) value at the end, or 600use a default if the list is empty. 601This should not slow down evaluation. 602.Pp 603The handling of 604.Dv MAGIC_CONTINUE 605and printing \e012- between entries is clumsy and complicated; refactor 606and centralize. 607.Pp 608Some of the encoding logic is hard-coded in encoding.c and can be moved 609to the magic files if we had a !:charset annotation 610.Pp 611Continue to squash all magic bugs. 612See Debian BTS for a good source. 613.Pp 614Store arbitrarily long strings, for example for %s patterns, so that 615they can be printed out. 616Fixes Debian bug #271672. 617This can be done by allocating strings in a string pool, storing the 618string pool at the end of the magic file and converting all the string 619pointers to relative offsets from the string pool. 620.Pp 621Add syntax for relative offsets after current level (Debian bug #466037). 622.Pp 623Make file -ki work, i.e. give multiple MIME types. 624.Pp 625Add a zip library so we can peek inside Office2007 documents to 626print more details about their contents. 627.Pp 628Add an option to print URLs for the sources of the file descriptions. 629.Pp 630Combine script searches and add a way to map executable names to MIME 631types (e.g. have a magic value for !:mime which causes the resulting 632string to be looked up in a table). 633This would avoid adding the same magic repeatedly for each new 634hash-bang interpreter. 635.Pp 636When a file descriptor is available, we can skip and adjust the buffer 637instead of the hacky buffer management we do now. 638.Pp 639Fix 640.Dq name 641and 642.Dq use 643to check for consistency at compile time (duplicate 644.Dq name , 645.Dq use 646pointing to undefined 647.Dq name 648). 649Make 650.Dq name 651/ 652.Dq use 653more efficient by keeping a sorted list of names. 654Special-case ^ to flip endianness in the parser so that it does not 655have to be escaped, and document it. 656.Pp 657If the offsets specified internally in the file exceed the buffer size 658( 659.Dv HOWMANY 660variable in file.h), then we don't seek to that offset, but we give up. 661It would be better if buffer managements was done when the file descriptor 662is available so move around the file. 663One must be careful though because this has performance (and thus security 664considerations). 665.Sh AVAILABILITY 666You can obtain the original author's latest version by anonymous FTP 667on 668.Pa ftp.astron.com 669in the directory 670.Pa /pub/file/file-X.YZ.tar.gz . 671