1.\" $File: file.man,v 1.118 2015/09/11 17:24:09 christos Exp $ 2.Dd September 11, 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.It Li regex Ta 8192 Ta length limit for regex searches 320.El 321.It Fl r , Fl Fl raw 322Don't translate unprintable characters to \eooo. 323Normally 324.Nm 325translates unprintable characters to their octal representation. 326.It Fl s , Fl Fl special-files 327Normally, 328.Nm 329only attempts to read and determine the type of argument files which 330.Xr stat 2 331reports are ordinary files. 332This prevents problems, because reading special files may have peculiar 333consequences. 334Specifying the 335.Fl s 336option causes 337.Nm 338to also read argument files which are block or character special files. 339This is useful for determining the filesystem types of the data in raw 340disk partitions, which are block special files. 341This option also causes 342.Nm 343to disregard the file size as reported by 344.Xr stat 2 345since on some systems it reports a zero size for raw disk partitions. 346.It Fl v , Fl Fl version 347Print the version of the program and exit. 348.It Fl z , Fl Fl uncompress 349Try to look inside compressed files. 350.It Fl Z , Fl Fl uncompress-noreport 351Try to look inside compressed files, but report information about the contents 352only not the compression. 353.It Fl 0 , Fl Fl print0 354Output a null character 355.Sq \e0 356after the end of the filename. 357Nice to 358.Xr cut 1 359the output. 360This does not affect the separator, which is still printed. 361.It Fl -help 362Print a help message and exit. 363.El 364.Sh FILES 365.Bl -tag -width __MAGIC__.mgc -compact 366.It Pa __MAGIC__.mgc 367Default compiled list of magic. 368.It Pa __MAGIC__ 369Directory containing default magic files. 370.El 371.Sh ENVIRONMENT 372The environment variable 373.Ev MAGIC 374can be used to set the default magic file name. 375If that variable is set, then 376.Nm 377will not attempt to open 378.Pa $HOME/.magic . 379.Nm 380adds 381.Dq Pa .mgc 382to the value of this variable as appropriate. 383However, 384.Pa file 385has to exist in order for 386.Pa file.mime 387to be considered. 388The environment variable 389.Ev POSIXLY_CORRECT 390controls (on systems that support symbolic links), whether 391.Nm 392will attempt to follow symlinks or not. 393If set, then 394.Nm 395follows symlink, otherwise it does not. 396This is also controlled by the 397.Fl L 398and 399.Fl h 400options. 401.Sh SEE ALSO 402.Xr magic __FSECTION__ , 403.Xr hexdump 1 , 404.Xr od 1 , 405.Xr strings 1 , 406.Xr fstyp 8 407.Sh STANDARDS CONFORMANCE 408This program is believed to exceed the System V Interface Definition 409of FILE(CMD), as near as one can determine from the vague language 410contained therein. 411Its behavior is mostly compatible with the System V program of the same name. 412This version knows more magic, however, so it will produce 413different (albeit more accurate) output in many cases. 414.\" URL: http://www.opengroup.org/onlinepubs/009695399/utilities/file.html 415.Pp 416The one significant difference 417between this version and System V 418is that this version treats any white space 419as a delimiter, so that spaces in pattern strings must be escaped. 420For example, 421.Bd -literal -offset indent 422\*[Gt]10 string language impress\ (imPRESS data) 423.Ed 424.Pp 425in an existing magic file would have to be changed to 426.Bd -literal -offset indent 427\*[Gt]10 string language\e impress (imPRESS data) 428.Ed 429.Pp 430In addition, in this version, if a pattern string contains a backslash, 431it must be escaped. 432For example 433.Bd -literal -offset indent 4340 string \ebegindata Andrew Toolkit document 435.Ed 436.Pp 437in an existing magic file would have to be changed to 438.Bd -literal -offset indent 4390 string \e\ebegindata Andrew Toolkit document 440.Ed 441.Pp 442SunOS releases 3.2 and later from Sun Microsystems include a 443.Nm 444command derived from the System V one, but with some extensions. 445This version differs from Sun's only in minor ways. 446It includes the extension of the 447.Sq \*[Am] 448operator, used as, 449for example, 450.Bd -literal -offset indent 451\*[Gt]16 long\*[Am]0x7fffffff \*[Gt]0 not stripped 452.Ed 453.Sh MAGIC DIRECTORY 454The magic file entries have been collected from various sources, 455mainly USENET, and contributed by various authors. 456Christos Zoulas (address below) will collect additional 457or corrected magic file entries. 458A consolidation of magic file entries 459will be distributed periodically. 460.Pp 461The order of entries in the magic file is significant. 462Depending on what system you are using, the order that 463they are put together may be incorrect. 464If your old 465.Nm 466command uses a magic file, 467keep the old magic file around for comparison purposes 468(rename it to 469.Pa __MAGIC__.orig ) . 470.Sh EXAMPLES 471.Bd -literal -offset indent 472$ file file.c file /dev/{wd0a,hda} 473file.c: C program text 474file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), 475 dynamically linked (uses shared libs), stripped 476/dev/wd0a: block special (0/0) 477/dev/hda: block special (3/0) 478 479$ file -s /dev/wd0{b,d} 480/dev/wd0b: data 481/dev/wd0d: x86 boot sector 482 483$ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10} 484/dev/hda: x86 boot sector 485/dev/hda1: Linux/i386 ext2 filesystem 486/dev/hda2: x86 boot sector 487/dev/hda3: x86 boot sector, extended partition table 488/dev/hda4: Linux/i386 ext2 filesystem 489/dev/hda5: Linux/i386 swap file 490/dev/hda6: Linux/i386 swap file 491/dev/hda7: Linux/i386 swap file 492/dev/hda8: Linux/i386 swap file 493/dev/hda9: empty 494/dev/hda10: empty 495 496$ file -i file.c file /dev/{wd0a,hda} 497file.c: text/x-c 498file: application/x-executable 499/dev/hda: application/x-not-regular-file 500/dev/wd0a: application/x-not-regular-file 501 502.Ed 503.Sh HISTORY 504There has been a 505.Nm 506command in every 507.Dv UNIX since at least Research Version 4 508(man page dated November, 1973). 509The System V version introduced one significant major change: 510the external list of magic types. 511This slowed the program down slightly but made it a lot more flexible. 512.Pp 513This program, based on the System V version, 514was written by Ian Darwin 515.Aq ian@darwinsys.com 516without looking at anybody else's source code. 517.Pp 518John Gilmore revised the code extensively, making it better than 519the first version. 520Geoff Collyer found several inadequacies 521and provided some magic file entries. 522Contributions by the 523.Sq \*[Am] 524operator by Rob McMahon, 525.Aq cudcv@warwick.ac.uk , 5261989. 527.Pp 528Guy Harris, 529.Aq guy@netapp.com , 530made many changes from 1993 to the present. 5311989. 532.Pp 533Primary development and maintenance from 1990 to the present by 534Christos Zoulas 535.Aq christos@astron.com . 536.Pp 537Altered by Chris Lowth 538.Aq chris@lowth.com , 5392000: handle the 540.Fl i 541option to output mime type strings, using an alternative 542magic file and internal logic. 543.Pp 544Altered by Eric Fischer 545.Aq enf@pobox.com , 546July, 2000, 547to identify character codes and attempt to identify the languages 548of non-ASCII files. 549.Pp 550Altered by Reuben Thomas 551.Aq rrt@sc3d.org , 5522007-2011, to improve MIME support, merge MIME and non-MIME magic, 553support directories as well as files of magic, apply many bug fixes, 554update and fix a lot of magic, improve the build system, improve the 555documentation, and rewrite the Python bindings in pure Python. 556.Pp 557The list of contributors to the 558.Sq magic 559directory (magic files) 560is too long to include here. 561You know who you are; thank you. 562Many contributors are listed in the source files. 563.Sh LEGAL NOTICE 564Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. 565Covered by the standard Berkeley Software Distribution copyright; see the file 566COPYING in the source distribution. 567.Pp 568The files 569.Pa tar.h 570and 571.Pa is_tar.c 572were written by John Gilmore from his public-domain 573.Xr tar 1 574program, and are not covered by the above license. 575.Sh RETURN CODE 576.Nm 577returns 0 on success, and non-zero on error. 578.Sh BUGS 579.Pp 580Please report bugs and send patches to the bug tracker at 581.Pa http://bugs.gw.com/ 582or the mailing list at 583.Aq file@mx.gw.com 584(visit 585.Pa http://mx.gw.com/mailman/listinfo/file 586first to subscribe). 587.Sh TODO 588.Pp 589Fix output so that tests for MIME and APPLE flags are not needed all 590over the place, and actual output is only done in one place. 591This needs a design. 592Suggestion: push possible outputs on to a list, then pick the 593last-pushed (most specific, one hopes) value at the end, or 594use a default if the list is empty. 595This should not slow down evaluation. 596.Pp 597The handling of 598.Dv MAGIC_CONTINUE 599and printing \e012- between entries is clumsy and complicated; refactor 600and centralize. 601.Pp 602Some of the encoding logic is hard-coded in encoding.c and can be moved 603to the magic files if we had a !:charset annotation 604.Pp 605Continue to squash all magic bugs. 606See Debian BTS for a good source. 607.Pp 608Store arbitrarily long strings, for example for %s patterns, so that 609they can be printed out. 610Fixes Debian bug #271672. 611This can be done by allocating strings in a string pool, storing the 612string pool at the end of the magic file and converting all the string 613pointers to relative offsets from the string pool. 614.Pp 615Add syntax for relative offsets after current level (Debian bug #466037). 616.Pp 617Make file -ki work, i.e. give multiple MIME types. 618.Pp 619Add a zip library so we can peek inside Office2007 documents to 620print more details about their contents. 621.Pp 622Add an option to print URLs for the sources of the file descriptions. 623.Pp 624Combine script searches and add a way to map executable names to MIME 625types (e.g. have a magic value for !:mime which causes the resulting 626string to be looked up in a table). 627This would avoid adding the same magic repeatedly for each new 628hash-bang interpreter. 629.Pp 630When a file descriptor is available, we can skip and adjust the buffer 631instead of the hacky buffer management we do now. 632.Pp 633Fix 634.Dq name 635and 636.Dq use 637to check for consistency at compile time (duplicate 638.Dq name , 639.Dq use 640pointing to undefined 641.Dq name 642). 643Make 644.Dq name 645/ 646.Dq use 647more efficient by keeping a sorted list of names. 648Special-case ^ to flip endianness in the parser so that it does not 649have to be escaped, and document it. 650.Pp 651If the offsets specified internally in the file exceed the buffer size 652( 653.Dv HOWMANY 654variable in file.h), then we don't seek to that offset, but we give up. 655It would be better if buffer managements was done when the file descriptor 656is available so move around the file. 657One must be careful though because this has performance (and thus security 658considerations). 659.Sh AVAILABILITY 660You can obtain the original author's latest version by anonymous FTP 661on 662.Pa ftp.astron.com 663in the directory 664.Pa /pub/file/file-X.YZ.tar.gz . 665