1.\" $File: file.man,v 1.124 2016/10/19 20:52:45 christos Exp $ 2.Dd October 19, 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 bcdEhiklLNnprsvzZ0 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 d 185Prints internal debugging information to stderr. 186.It Fl E 187On filesystem errors (file not found etc), instead of handling the error 188as regular output as POSIX mandates and keep going, issue an error message 189and exit. 190.It Fl e , Fl Fl exclude Ar testname 191Exclude the test named in 192.Ar testname 193from the list of tests made to determine the file type. 194Valid test names are: 195.Bl -tag -width compress 196.It apptype 197.Dv EMX 198application type (only on EMX). 199.It ascii 200Various types of text files (this test will try to guess the text 201encoding, irrespective of the setting of the 202.Sq encoding 203option). 204.It encoding 205Different text encodings for soft magic tests. 206.It tokens 207Ignored for backwards compatibility. 208.It cdf 209Prints details of Compound Document Files. 210.It compress 211Checks for, and looks inside, compressed files. 212.It elf 213Prints ELF file details, provided soft magic tests are enabled and the 214elf magic is found. 215.It soft 216Consults magic files. 217.It tar 218Examines tar files. 219.It text 220A synonym for 221.Sq ascii . 222.El 223.It Fl Fl extension 224Print a slash-separated list of valid extensions for the file type found. 225.It Fl F , Fl Fl separator Ar separator 226Use the specified string as the separator between the filename and the 227file result returned. 228Defaults to 229.Sq \&: . 230.It Fl f , Fl Fl files-from Ar namefile 231Read the names of the files to be examined from 232.Ar namefile 233(one per line) 234before the argument list. 235Either 236.Ar namefile 237or at least one filename argument must be present; 238to test the standard input, use 239.Sq - 240as a filename argument. 241Please note that 242.Ar namefile 243is unwrapped and the enclosed filenames are processed when this option is 244encountered and before any further options processing is done. 245This allows one to process multiple lists of files with different command line 246arguments on the same 247.Nm 248invocation. 249Thus if you want to set the delimiter, you need to do it before you specify 250the list of files, like: 251.Dq Fl F Ar @ Fl f Ar namefile , 252instead of: 253.Dq Fl f Ar namefile Fl F Ar @ . 254.It Fl h , Fl Fl no-dereference 255option causes symlinks not to be followed 256(on systems that support symbolic links). 257This is the default if the environment variable 258.Dv POSIXLY_CORRECT 259is not defined. 260.It Fl i , Fl Fl mime 261Causes the file command to output mime type strings rather than the more 262traditional human readable ones. 263Thus it may say 264.Sq text/plain; charset=us-ascii 265rather than 266.Dq ASCII text . 267.It Fl Fl mime-type , Fl Fl mime-encoding 268Like 269.Fl i , 270but print only the specified element(s). 271.It Fl k , Fl Fl keep-going 272Don't stop at the first match, keep going. 273Subsequent matches will be 274have the string 275.Sq "\[rs]012\- " 276prepended. 277(If you want a newline, see the 278.Fl r 279option.) 280The magic pattern with the highest strength (see the 281.Fl l 282option) comes first. 283.It Fl l , Fl Fl list 284Shows a list of patterns and their strength sorted descending by 285.Xr magic 4 286strength 287which is used for the matching (see also the 288.Fl k 289option). 290.It Fl L , Fl Fl dereference 291option causes symlinks to be followed, as the like-named option in 292.Xr ls 1 293(on systems that support symbolic links). 294This is the default if the environment variable 295.Ev POSIXLY_CORRECT 296is defined. 297.It Fl m , Fl Fl magic-file Ar magicfiles 298Specify an alternate list of files and directories containing magic. 299This can be a single item, or a colon-separated list. 300If a compiled magic file is found alongside a file or directory, 301it will be used instead. 302.It Fl N , Fl Fl no-pad 303Don't pad filenames so that they align in the output. 304.It Fl n , Fl Fl no-buffer 305Force stdout to be flushed after checking each file. 306This is only useful if checking a list of files. 307It is intended to be used by programs that want filetype output from a pipe. 308.It Fl p , Fl Fl preserve-date 309On systems that support 310.Xr utime 3 311or 312.Xr utimes 2 , 313attempt to preserve the access time of files analyzed, to pretend that 314.Nm 315never read them. 316.It Fl P , Fl Fl parameter Ar name=value 317Set various parameter limits. 318.Bl -column "elf_phnum" "Default" "XXXXXXXXXXXXXXXXXXXXXXXXXXX" -offset indent 319.It Sy "Name" Ta Sy "Default" Ta Sy "Explanation" 320.It Li indir Ta 15 Ta recursion limit for indirect magic 321.It Li name Ta 30 Ta use count limit for name/use magic 322.It Li elf_notes Ta 256 Ta max ELF notes processed 323.It Li elf_phnum Ta 128 Ta max ELF program sections processed 324.It Li elf_shnum Ta 32768 Ta max ELF sections processed 325.It Li regex Ta 8192 Ta length limit for regex searches 326.It Li bytes Ta 1048576 Ta max number of bytes to read from file 327.El 328.It Fl r , Fl Fl raw 329Don't translate unprintable characters to \eooo. 330Normally 331.Nm 332translates unprintable characters to their octal representation. 333.It Fl s , Fl Fl special-files 334Normally, 335.Nm 336only attempts to read and determine the type of argument files which 337.Xr stat 2 338reports are ordinary files. 339This prevents problems, because reading special files may have peculiar 340consequences. 341Specifying the 342.Fl s 343option causes 344.Nm 345to also read argument files which are block or character special files. 346This is useful for determining the filesystem types of the data in raw 347disk partitions, which are block special files. 348This option also causes 349.Nm 350to disregard the file size as reported by 351.Xr stat 2 352since on some systems it reports a zero size for raw disk partitions. 353.It Fl v , Fl Fl version 354Print the version of the program and exit. 355.It Fl z , Fl Fl uncompress 356Try to look inside compressed files. 357.It Fl Z , Fl Fl uncompress-noreport 358Try to look inside compressed files, but report information about the contents 359only not the compression. 360.It Fl 0 , Fl Fl print0 361Output a null character 362.Sq \e0 363after the end of the filename. 364Nice to 365.Xr cut 1 366the output. 367This does not affect the separator, which is still printed. 368.Pp 369If this option is repeated more than once, then 370.Nm 371prints just the filename followed by a NUL followed by the description 372(or ERROR: text) followed by a second NUL for each entry. 373.It Fl -help 374Print a help message and exit. 375.El 376.Sh FILES 377.Bl -tag -width __MAGIC__.mgc -compact 378.It Pa __MAGIC__.mgc 379Default compiled list of magic. 380.It Pa __MAGIC__ 381Directory containing default magic files. 382.El 383.Sh ENVIRONMENT 384The environment variable 385.Ev MAGIC 386can be used to set the default magic file name. 387If that variable is set, then 388.Nm 389will not attempt to open 390.Pa $HOME/.magic . 391.Nm 392adds 393.Dq Pa .mgc 394to the value of this variable as appropriate. 395However, 396.Pa file 397has to exist in order for 398.Pa file.mime 399to be considered. 400The environment variable 401.Ev POSIXLY_CORRECT 402controls (on systems that support symbolic links), whether 403.Nm 404will attempt to follow symlinks or not. 405If set, then 406.Nm 407follows symlink, otherwise it does not. 408This is also controlled by the 409.Fl L 410and 411.Fl h 412options. 413.Sh SEE ALSO 414.Xr magic __FSECTION__ , 415.Xr hexdump 1 , 416.Xr od 1 , 417.Xr strings 1 , 418.Xr fstyp 8 419.Sh STANDARDS CONFORMANCE 420This program is believed to exceed the System V Interface Definition 421of FILE(CMD), as near as one can determine from the vague language 422contained therein. 423Its behavior is mostly compatible with the System V program of the same name. 424This version knows more magic, however, so it will produce 425different (albeit more accurate) output in many cases. 426.\" URL: http://www.opengroup.org/onlinepubs/009695399/utilities/file.html 427.Pp 428The one significant difference 429between this version and System V 430is that this version treats any white space 431as a delimiter, so that spaces in pattern strings must be escaped. 432For example, 433.Bd -literal -offset indent 434\*[Gt]10 string language impress\ (imPRESS data) 435.Ed 436.Pp 437in an existing magic file would have to be changed to 438.Bd -literal -offset indent 439\*[Gt]10 string language\e impress (imPRESS data) 440.Ed 441.Pp 442In addition, in this version, if a pattern string contains a backslash, 443it must be escaped. 444For example 445.Bd -literal -offset indent 4460 string \ebegindata Andrew Toolkit document 447.Ed 448.Pp 449in an existing magic file would have to be changed to 450.Bd -literal -offset indent 4510 string \e\ebegindata Andrew Toolkit document 452.Ed 453.Pp 454SunOS releases 3.2 and later from Sun Microsystems include a 455.Nm 456command derived from the System V one, but with some extensions. 457This version differs from Sun's only in minor ways. 458It includes the extension of the 459.Sq \*[Am] 460operator, used as, 461for example, 462.Bd -literal -offset indent 463\*[Gt]16 long\*[Am]0x7fffffff \*[Gt]0 not stripped 464.Ed 465.Sh MAGIC DIRECTORY 466The magic file entries have been collected from various sources, 467mainly USENET, and contributed by various authors. 468Christos Zoulas (address below) will collect additional 469or corrected magic file entries. 470A consolidation of magic file entries 471will be distributed periodically. 472.Pp 473The order of entries in the magic file is significant. 474Depending on what system you are using, the order that 475they are put together may be incorrect. 476If your old 477.Nm 478command uses a magic file, 479keep the old magic file around for comparison purposes 480(rename it to 481.Pa __MAGIC__.orig ) . 482.Sh EXAMPLES 483.Bd -literal -offset indent 484$ file file.c file /dev/{wd0a,hda} 485file.c: C program text 486file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), 487 dynamically linked (uses shared libs), stripped 488/dev/wd0a: block special (0/0) 489/dev/hda: block special (3/0) 490 491$ file -s /dev/wd0{b,d} 492/dev/wd0b: data 493/dev/wd0d: x86 boot sector 494 495$ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10} 496/dev/hda: x86 boot sector 497/dev/hda1: Linux/i386 ext2 filesystem 498/dev/hda2: x86 boot sector 499/dev/hda3: x86 boot sector, extended partition table 500/dev/hda4: Linux/i386 ext2 filesystem 501/dev/hda5: Linux/i386 swap file 502/dev/hda6: Linux/i386 swap file 503/dev/hda7: Linux/i386 swap file 504/dev/hda8: Linux/i386 swap file 505/dev/hda9: empty 506/dev/hda10: empty 507 508$ file -i file.c file /dev/{wd0a,hda} 509file.c: text/x-c 510file: application/x-executable 511/dev/hda: application/x-not-regular-file 512/dev/wd0a: application/x-not-regular-file 513 514.Ed 515.Sh HISTORY 516There has been a 517.Nm 518command in every 519.Dv UNIX since at least Research Version 4 520(man page dated November, 1973). 521The System V version introduced one significant major change: 522the external list of magic types. 523This slowed the program down slightly but made it a lot more flexible. 524.Pp 525This program, based on the System V version, 526was written by Ian Darwin 527.Aq ian@darwinsys.com 528without looking at anybody else's source code. 529.Pp 530John Gilmore revised the code extensively, making it better than 531the first version. 532Geoff Collyer found several inadequacies 533and provided some magic file entries. 534Contributions by the 535.Sq \*[Am] 536operator by Rob McMahon, 537.Aq cudcv@warwick.ac.uk , 5381989. 539.Pp 540Guy Harris, 541.Aq guy@netapp.com , 542made many changes from 1993 to the present. 5431989. 544.Pp 545Primary development and maintenance from 1990 to the present by 546Christos Zoulas 547.Aq christos@astron.com . 548.Pp 549Altered by Chris Lowth 550.Aq chris@lowth.com , 5512000: handle the 552.Fl i 553option to output mime type strings, using an alternative 554magic file and internal logic. 555.Pp 556Altered by Eric Fischer 557.Aq enf@pobox.com , 558July, 2000, 559to identify character codes and attempt to identify the languages 560of non-ASCII files. 561.Pp 562Altered by Reuben Thomas 563.Aq rrt@sc3d.org , 5642007-2011, to improve MIME support, merge MIME and non-MIME magic, 565support directories as well as files of magic, apply many bug fixes, 566update and fix a lot of magic, improve the build system, improve the 567documentation, and rewrite the Python bindings in pure Python. 568.Pp 569The list of contributors to the 570.Sq magic 571directory (magic files) 572is too long to include here. 573You know who you are; thank you. 574Many contributors are listed in the source files. 575.Sh LEGAL NOTICE 576Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. 577Covered by the standard Berkeley Software Distribution copyright; see the file 578COPYING in the source distribution. 579.Pp 580The files 581.Pa tar.h 582and 583.Pa is_tar.c 584were written by John Gilmore from his public-domain 585.Xr tar 1 586program, and are not covered by the above license. 587.Sh RETURN CODE 588.Nm 589returns 0 on success, and non-zero on error. 590.Sh BUGS 591.Pp 592Please report bugs and send patches to the bug tracker at 593.Pa http://bugs.gw.com/ 594or the mailing list at 595.Aq file@mx.gw.com 596(visit 597.Pa http://mx.gw.com/mailman/listinfo/file 598first to subscribe). 599.Sh TODO 600.Pp 601Fix output so that tests for MIME and APPLE flags are not needed all 602over the place, and actual output is only done in one place. 603This needs a design. 604Suggestion: push possible outputs on to a list, then pick the 605last-pushed (most specific, one hopes) value at the end, or 606use a default if the list is empty. 607This should not slow down evaluation. 608.Pp 609The handling of 610.Dv MAGIC_CONTINUE 611and printing \e012- between entries is clumsy and complicated; refactor 612and centralize. 613.Pp 614Some of the encoding logic is hard-coded in encoding.c and can be moved 615to the magic files if we had a !:charset annotation 616.Pp 617Continue to squash all magic bugs. 618See Debian BTS for a good source. 619.Pp 620Store arbitrarily long strings, for example for %s patterns, so that 621they can be printed out. 622Fixes Debian bug #271672. 623This can be done by allocating strings in a string pool, storing the 624string pool at the end of the magic file and converting all the string 625pointers to relative offsets from the string pool. 626.Pp 627Add syntax for relative offsets after current level (Debian bug #466037). 628.Pp 629Make file -ki work, i.e. give multiple MIME types. 630.Pp 631Add a zip library so we can peek inside Office2007 documents to 632print more details about their contents. 633.Pp 634Add an option to print URLs for the sources of the file descriptions. 635.Pp 636Combine script searches and add a way to map executable names to MIME 637types (e.g. have a magic value for !:mime which causes the resulting 638string to be looked up in a table). 639This would avoid adding the same magic repeatedly for each new 640hash-bang interpreter. 641.Pp 642When a file descriptor is available, we can skip and adjust the buffer 643instead of the hacky buffer management we do now. 644.Pp 645Fix 646.Dq name 647and 648.Dq use 649to check for consistency at compile time (duplicate 650.Dq name , 651.Dq use 652pointing to undefined 653.Dq name 654). 655Make 656.Dq name 657/ 658.Dq use 659more efficient by keeping a sorted list of names. 660Special-case ^ to flip endianness in the parser so that it does not 661have to be escaped, and document it. 662.Pp 663If the offsets specified internally in the file exceed the buffer size 664( 665.Dv HOWMANY 666variable in file.h), then we don't seek to that offset, but we give up. 667It would be better if buffer managements was done when the file descriptor 668is available so move around the file. 669One must be careful though because this has performance (and thus security 670considerations). 671.Sh AVAILABILITY 672You can obtain the original author's latest version by anonymous FTP 673on 674.Pa ftp.astron.com 675in the directory 676.Pa /pub/file/file-X.YZ.tar.gz . 677