1.\" $File: file.man,v 1.117 2015/06/03 19:51:27 christos Exp $ 2.Dd June 3, 2015 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.El 320.It Fl r , Fl Fl raw 321Don't translate unprintable characters to \eooo. 322Normally 323.Nm 324translates unprintable characters to their octal representation. 325.It Fl s , Fl Fl special-files 326Normally, 327.Nm 328only attempts to read and determine the type of argument files which 329.Xr stat 2 330reports are ordinary files. 331This prevents problems, because reading special files may have peculiar 332consequences. 333Specifying the 334.Fl s 335option causes 336.Nm 337to also read argument files which are block or character special files. 338This is useful for determining the filesystem types of the data in raw 339disk partitions, which are block special files. 340This option also causes 341.Nm 342to disregard the file size as reported by 343.Xr stat 2 344since on some systems it reports a zero size for raw disk partitions. 345.It Fl v , Fl Fl version 346Print the version of the program and exit. 347.It Fl z , Fl Fl uncompress 348Try to look inside compressed files. 349.It Fl Z , Fl Fl uncompress-noreport 350Try to look inside compressed files, but report information about the contents 351only not the compression. 352.It Fl 0 , Fl Fl print0 353Output a null character 354.Sq \e0 355after the end of the filename. 356Nice to 357.Xr cut 1 358the output. 359This does not affect the separator, which is still printed. 360.It Fl -help 361Print a help message and exit. 362.El 363.Sh FILES 364.Bl -tag -width __MAGIC__.mgc -compact 365.It Pa __MAGIC__.mgc 366Default compiled list of magic. 367.It Pa __MAGIC__ 368Directory containing default magic files. 369.El 370.Sh ENVIRONMENT 371The environment variable 372.Ev MAGIC 373can be used to set the default magic file name. 374If that variable is set, then 375.Nm 376will not attempt to open 377.Pa $HOME/.magic . 378.Nm 379adds 380.Dq Pa .mgc 381to the value of this variable as appropriate. 382However, 383.Pa file 384has to exist in order for 385.Pa file.mime 386to be considered. 387The environment variable 388.Ev POSIXLY_CORRECT 389controls (on systems that support symbolic links), whether 390.Nm 391will attempt to follow symlinks or not. 392If set, then 393.Nm 394follows symlink, otherwise it does not. 395This is also controlled by the 396.Fl L 397and 398.Fl h 399options. 400.Sh SEE ALSO 401.Xr magic __FSECTION__ , 402.Xr hexdump 1 , 403.Xr od 1 , 404.Xr strings 1 , 405.Xr fstyp 8 406.Sh STANDARDS CONFORMANCE 407This program is believed to exceed the System V Interface Definition 408of FILE(CMD), as near as one can determine from the vague language 409contained therein. 410Its behavior is mostly compatible with the System V program of the same name. 411This version knows more magic, however, so it will produce 412different (albeit more accurate) output in many cases. 413.\" URL: http://www.opengroup.org/onlinepubs/009695399/utilities/file.html 414.Pp 415The one significant difference 416between this version and System V 417is that this version treats any white space 418as a delimiter, so that spaces in pattern strings must be escaped. 419For example, 420.Bd -literal -offset indent 421\*[Gt]10 string language impress\ (imPRESS data) 422.Ed 423.Pp 424in an existing magic file would have to be changed to 425.Bd -literal -offset indent 426\*[Gt]10 string language\e impress (imPRESS data) 427.Ed 428.Pp 429In addition, in this version, if a pattern string contains a backslash, 430it must be escaped. 431For example 432.Bd -literal -offset indent 4330 string \ebegindata Andrew Toolkit document 434.Ed 435.Pp 436in an existing magic file would have to be changed to 437.Bd -literal -offset indent 4380 string \e\ebegindata Andrew Toolkit document 439.Ed 440.Pp 441SunOS releases 3.2 and later from Sun Microsystems include a 442.Nm 443command derived from the System V one, but with some extensions. 444This version differs from Sun's only in minor ways. 445It includes the extension of the 446.Sq \*[Am] 447operator, used as, 448for example, 449.Bd -literal -offset indent 450\*[Gt]16 long\*[Am]0x7fffffff \*[Gt]0 not stripped 451.Ed 452.Sh MAGIC DIRECTORY 453The magic file entries have been collected from various sources, 454mainly USENET, and contributed by various authors. 455Christos Zoulas (address below) will collect additional 456or corrected magic file entries. 457A consolidation of magic file entries 458will be distributed periodically. 459.Pp 460The order of entries in the magic file is significant. 461Depending on what system you are using, the order that 462they are put together may be incorrect. 463If your old 464.Nm 465command uses a magic file, 466keep the old magic file around for comparison purposes 467(rename it to 468.Pa __MAGIC__.orig ) . 469.Sh EXAMPLES 470.Bd -literal -offset indent 471$ file file.c file /dev/{wd0a,hda} 472file.c: C program text 473file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), 474 dynamically linked (uses shared libs), stripped 475/dev/wd0a: block special (0/0) 476/dev/hda: block special (3/0) 477 478$ file -s /dev/wd0{b,d} 479/dev/wd0b: data 480/dev/wd0d: x86 boot sector 481 482$ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10} 483/dev/hda: x86 boot sector 484/dev/hda1: Linux/i386 ext2 filesystem 485/dev/hda2: x86 boot sector 486/dev/hda3: x86 boot sector, extended partition table 487/dev/hda4: Linux/i386 ext2 filesystem 488/dev/hda5: Linux/i386 swap file 489/dev/hda6: Linux/i386 swap file 490/dev/hda7: Linux/i386 swap file 491/dev/hda8: Linux/i386 swap file 492/dev/hda9: empty 493/dev/hda10: empty 494 495$ file -i file.c file /dev/{wd0a,hda} 496file.c: text/x-c 497file: application/x-executable 498/dev/hda: application/x-not-regular-file 499/dev/wd0a: application/x-not-regular-file 500 501.Ed 502.Sh HISTORY 503There has been a 504.Nm 505command in every 506.Dv UNIX since at least Research Version 4 507(man page dated November, 1973). 508The System V version introduced one significant major change: 509the external list of magic types. 510This slowed the program down slightly but made it a lot more flexible. 511.Pp 512This program, based on the System V version, 513was written by Ian Darwin 514.Aq ian@darwinsys.com 515without looking at anybody else's source code. 516.Pp 517John Gilmore revised the code extensively, making it better than 518the first version. 519Geoff Collyer found several inadequacies 520and provided some magic file entries. 521Contributions by the 522.Sq \*[Am] 523operator by Rob McMahon, 524.Aq cudcv@warwick.ac.uk , 5251989. 526.Pp 527Guy Harris, 528.Aq guy@netapp.com , 529made many changes from 1993 to the present. 5301989. 531.Pp 532Primary development and maintenance from 1990 to the present by 533Christos Zoulas 534.Aq christos@astron.com . 535.Pp 536Altered by Chris Lowth 537.Aq chris@lowth.com , 5382000: handle the 539.Fl i 540option to output mime type strings, using an alternative 541magic file and internal logic. 542.Pp 543Altered by Eric Fischer 544.Aq enf@pobox.com , 545July, 2000, 546to identify character codes and attempt to identify the languages 547of non-ASCII files. 548.Pp 549Altered by Reuben Thomas 550.Aq rrt@sc3d.org , 5512007-2011, to improve MIME support, merge MIME and non-MIME magic, 552support directories as well as files of magic, apply many bug fixes, 553update and fix a lot of magic, improve the build system, improve the 554documentation, and rewrite the Python bindings in pure Python. 555.Pp 556The list of contributors to the 557.Sq magic 558directory (magic files) 559is too long to include here. 560You know who you are; thank you. 561Many contributors are listed in the source files. 562.Sh LEGAL NOTICE 563Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. 564Covered by the standard Berkeley Software Distribution copyright; see the file 565COPYING in the source distribution. 566.Pp 567The files 568.Pa tar.h 569and 570.Pa is_tar.c 571were written by John Gilmore from his public-domain 572.Xr tar 1 573program, and are not covered by the above license. 574.Sh RETURN CODE 575.Nm 576returns 0 on success, and non-zero on error. 577.Sh BUGS 578.Pp 579Please report bugs and send patches to the bug tracker at 580.Pa http://bugs.gw.com/ 581or the mailing list at 582.Aq file@mx.gw.com 583(visit 584.Pa http://mx.gw.com/mailman/listinfo/file 585first to subscribe). 586.Sh TODO 587.Pp 588Fix output so that tests for MIME and APPLE flags are not needed all 589over the place, and actual output is only done in one place. 590This needs a design. 591Suggestion: push possible outputs on to a list, then pick the 592last-pushed (most specific, one hopes) value at the end, or 593use a default if the list is empty. 594This should not slow down evaluation. 595.Pp 596The handling of 597.Dv MAGIC_CONTINUE 598and printing \e012- between entries is clumsy and complicated; refactor 599and centralize. 600.Pp 601Some of the encoding logic is hard-coded in encoding.c and can be moved 602to the magic files if we had a !:charset annotation 603.Pp 604Continue to squash all magic bugs. 605See Debian BTS for a good source. 606.Pp 607Store arbitrarily long strings, for example for %s patterns, so that 608they can be printed out. 609Fixes Debian bug #271672. 610This can be done by allocating strings in a string pool, storing the 611string pool at the end of the magic file and converting all the string 612pointers to relative offsets from the string pool. 613.Pp 614Add syntax for relative offsets after current level (Debian bug #466037). 615.Pp 616Make file -ki work, i.e. give multiple MIME types. 617.Pp 618Add a zip library so we can peek inside Office2007 documents to 619print more details about their contents. 620.Pp 621Add an option to print URLs for the sources of the file descriptions. 622.Pp 623Combine script searches and add a way to map executable names to MIME 624types (e.g. have a magic value for !:mime which causes the resulting 625string to be looked up in a table). 626This would avoid adding the same magic repeatedly for each new 627hash-bang interpreter. 628.Pp 629When a file descriptor is available, we can skip and adjust the buffer 630instead of the hacky buffer management we do now. 631.Pp 632Fix 633.Dq name 634and 635.Dq use 636to check for consistency at compile time (duplicate 637.Dq name , 638.Dq use 639pointing to undefined 640.Dq name 641). 642Make 643.Dq name 644/ 645.Dq use 646more efficient by keeping a sorted list of names. 647Special-case ^ to flip endianness in the parser so that it does not 648have to be escaped, and document it. 649.Pp 650If the offsets specified internally in the file exceed the buffer size 651( 652.Dv HOWMANY 653variable in file.h), then we don't seek to that offset, but we give up. 654It would be better if buffer managements was done when the file descriptor 655is available so move around the file. 656One must be careful though because this has performance (and thus security 657considerations). 658.Sh AVAILABILITY 659You can obtain the original author's latest version by anonymous FTP 660on 661.Pa ftp.astron.com 662in the directory 663.Pa /pub/file/file-X.YZ.tar.gz . 664