1 .TH FILE __CSECTION__ "Copyright but distributable"
2 .\" $Id: file.man,v 1.58 2006/05/03 19:20:25 christos Exp $
32 This manual page documents version __VERSION__ of the
37 tests each argument in an attempt to classify it.
38 There are three sets of tests, performed in this order:
39 filesystem tests, magic number tests, and language tests.
42 test that succeeds causes the file type to be printed.
44 The type printed will usually contain one of the words
46 (the file contains only
47 printing characters and a few common control
48 characters and is probably safe to read on an
52 (the file contains the result of compiling a program
53 in a form understandable to some \s-1UNIX\s0 kernel or another),
56 meaning anything else (data is usually `binary' or non-printable).
57 Exceptions are well-known file formats (core files, tar archives)
58 that are known to contain binary data.
59 When modifying the file
61 or the program itself,
62 .B "preserve these keywords" .
63 People depend on knowing that all the readable files in a directory
64 have the word ``text'' printed.
65 Don't do as Berkeley did and change ``shell commands text''
69 is built mechanically from a large number of small files in
72 in the source distribution of this program.
74 The filesystem tests are based on examining the return from a
77 The program checks to see if the file is empty,
78 or if it's some sort of special file.
79 Any known file types appropriate to the system you are running on
80 (sockets, symbolic links, or named pipes (FIFOs) on those systems that
82 are intuited if they are defined in
83 the system header file
86 The magic number tests are used to check for files with data in
87 particular fixed formats.
88 The canonical example of this is a binary executable (compiled program)
90 file, whose format is defined in
94 in the standard include directory.
95 These files have a `magic number' stored in a particular place
96 near the beginning of the file that tells the \s-1UNIX\s0 operating system
97 that the file is a binary executable, and which of several types thereof.
98 The concept of `magic number' has been applied by extension to data files.
99 Any file with some invariant identifier at a small fixed
100 offset into the file can usually be described in this way.
101 The information identifying these files is read from the compiled
106 if the compile file does not exist. In addition
109 .I $HOME/.magic.mgc ,
114 If a file does not match any of the entries in the magic file,
115 it is examined to see if it seems to be a text file.
116 ASCII, ISO-8859-x, non-ISO 8-bit extended-ASCII character sets
117 (such as those used on Macintosh and IBM PC systems),
118 UTF-8-encoded Unicode, UTF-16-encoded Unicode, and EBCDIC
119 character sets can be distinguished by the different
120 ranges and sequences of bytes that constitute printable text
122 If a file passes any of these tests, its character set is reported.
123 ASCII, ISO-8859-x, UTF-8, and extended-ASCII files are identified
124 as ``text'' because they will be mostly readable on nearly any terminal;
125 UTF-16 and EBCDIC are only ``character data'' because, while
126 they contain text, it is text that will require translation
127 before it can be read.
130 will attempt to determine other characteristics of text-type files.
131 If the lines of a file are terminated by CR, CRLF, or NEL, instead
132 of the Unix-standard LF, this will be reported.
133 Files that contain embedded escape sequences or overstriking
134 will also be identified.
138 has determined the character set used in a text-type file,
140 attempt to determine in what language the file is written.
141 The language tests look for particular strings (cf
143 that can appear anywhere in the first few blocks of a file.
144 For example, the keyword
146 indicates that the file is most likely a
148 input file, just as the keyword
150 indicates a C program.
151 These tests are less reliable than the previous
152 two groups, so they are performed last.
153 The language test routines also test for some miscellany
158 Any file that cannot be identified as having been written
159 in any of the character sets listed above is simply said to be ``data''.
163 Do not prepend filenames to output lines (brief mode).
165 .B "\-c, \-\-checking\-printout"
166 Cause a checking printout of the parsed form of the magic file.
167 This is usually used in conjunction with
169 to debug a new magic file before installing it.
171 .B "\-C, \-\-compile"
172 Write a magic.mgc output file that contains a pre-parsed version of
175 .BI "\-f, \-\-files\-from" " namefile"
176 Read the names of the files to be examined from
179 before the argument list.
182 or at least one filename argument must be present;
183 to test the standard input, use ``\-'' as a filename argument.
185 .BI "\-F, \-\-separator" " separator"
186 Use the specified string as the separator between the filename and the
187 file result returned. Defaults to ``:''.
189 .B "\-h, \-\-no-dereference"
190 option causes symlinks not to be followed
191 (on systems that support symbolic links). This is the default if the
197 Causes the file command to output mime type strings rather than the more
198 traditional human readable ones. Thus it may say
199 ``text/plain; charset=us-ascii''
202 In order for this option to work, file changes the way
203 it handles files recognized by the command itself (such as many of the
204 text file types, directories etc), and makes use of an alternative
206 (See ``FILES'' section, below).
208 .B "\-k, \-\-keep\-going"
209 Don't stop at the first match, keep going.
211 .B "\-L, \-\-dereference"
212 option causes symlinks to be followed, as the like-named option in
214 (on systems that support symbolic links).
215 This is the default if the environment variable
219 .BI "\-m, \-\-magic\-file" " list"
220 Specify an alternate list of files containing magic numbers.
221 This can be a single file, or a colon-separated list of files.
222 If a compiled magic file is found alongside, it will be used instead.
223 With the \-i or \-\-mime option, the program adds ".mime" to each file name.
225 .B "\-n, \-\-no\-buffer"
226 Force stdout to be flushed after checking each file.
227 This is only useful if checking a list of files.
228 It is intended to be used by programs that want filetype output from a pipe.
230 .B "\-N, \-\-no\-pad"
231 Don't pad filenames so that they align in the output.
233 .B "\-p, \-\-preserve\-date"
234 On systems that support
238 attempt to preserve the access time of files analyzed, to pretend that
243 Don't translate unprintable characters to \eooo.
246 translates unprintable characters to their octal representation.
248 .B "\-s, \-\-special\-files"
251 only attempts to read and determine the type of argument files which
253 reports are ordinary files.
254 This prevents problems, because reading special files may have peculiar
260 to also read argument files which are block or character special files.
261 This is useful for determining the filesystem types of the data in raw
262 disk partitions, which are block special files.
263 This option also causes
265 to disregard the file size as reported by
267 since on some systems it reports a zero size for raw disk partitions.
269 .B "\-v, \-\-version"
270 Print the version of the program and exit.
272 .B "\-z, \-\-uncompress"
273 Try to look inside compressed files.
276 Print a help message and exit.
280 Default compiled list of magic numbers
283 Default list of magic numbers
285 .I __MAGIC__.mime.mgc
286 Default compiled list of magic numbers, used to output mime types when
287 the -i option is specified.
290 Default list of magic numbers, used to output mime types when the -i option
294 The environment variable
296 can be used to set the default magic number file name.
297 If that variable is set, then
299 will not attempt to open
302 adds ".mime" and/or ".mgc" to the value of this variable as appropriate.
303 The environment variable
305 controls (on systems that support symbolic links), if
307 will attempt to follow symlinks or not. If set, then
309 follows symlink, otherwise it does not. This is also controlled
316 .BR magic (__FSECTION__)
317 \- description of magic file format.
319 .BR strings (1), " od" (1), " hexdump(1)"
320 \- tools for examining non-textfiles.
321 .SH STANDARDS CONFORMANCE
322 This program is believed to exceed the System V Interface Definition
323 of FILE(CMD), as near as one can determine from the vague language
325 Its behavior is mostly compatible with the System V program of the same name.
326 This version knows more magic, however, so it will produce
327 different (albeit more accurate) output in many cases.
328 .\" URL: http://www.opengroup.org/onlinepubs/009695399/utilities/file.html
330 The one significant difference
331 between this version and System V
332 is that this version treats any white space
333 as a delimiter, so that spaces in pattern strings must be escaped.
336 >10 string language impress\ (imPRESS data)
338 in an existing magic file would have to be changed to
340 >10 string language\e impress (imPRESS data)
342 In addition, in this version, if a pattern string contains a backslash,
346 0 string \ebegindata Andrew Toolkit document
348 in an existing magic file would have to be changed to
350 0 string \e\ebegindata Andrew Toolkit document
353 SunOS releases 3.2 and later from Sun Microsystems include a
355 command derived from the System V one, but with some extensions.
356 My version differs from Sun's only in minor ways.
357 It includes the extension of the `&' operator, used as,
360 >16 long&0x7fffffff >0 not stripped
362 The magic file entries have been collected from various sources,
363 mainly USENET, and contributed by various authors.
364 Christos Zoulas (address below) will collect additional
365 or corrected magic file entries.
366 A consolidation of magic file entries
367 will be distributed periodically.
369 The order of entries in the magic file is significant.
370 Depending on what system you are using, the order that
371 they are put together may be incorrect.
374 command uses a magic file,
375 keep the old magic file around for comparison purposes
377 .IR __MAGIC__.orig ).
380 $ file file.c file /dev/{wd0a,hda}
381 file.c: C program text
382 file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV),
383 dynamically linked (uses shared libs), stripped
384 /dev/wd0a: block special (0/0)
385 /dev/hda: block special (3/0)
386 $ file -s /dev/wd0{b,d}
388 /dev/wd0d: x86 boot sector
389 $ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10}
390 /dev/hda: x86 boot sector
391 /dev/hda1: Linux/i386 ext2 filesystem
392 /dev/hda2: x86 boot sector
393 /dev/hda3: x86 boot sector, extended partition table
394 /dev/hda4: Linux/i386 ext2 filesystem
395 /dev/hda5: Linux/i386 swap file
396 /dev/hda6: Linux/i386 swap file
397 /dev/hda7: Linux/i386 swap file
398 /dev/hda8: Linux/i386 swap file
402 $ file -i file.c file /dev/{wd0a,hda}
404 file: application/x-executable, dynamically linked (uses shared libs),
406 /dev/hda: application/x-not-regular-file
407 /dev/wd0a: application/x-not-regular-file
413 command in every \s-1UNIX\s0 since at least Research Version 4
414 (man page dated November, 1973).
415 The System V version introduced one significant major change:
416 the external list of magic number types.
417 This slowed the program down slightly but made it a lot more flexible.
419 This program, based on the System V version,
420 was written by Ian Darwin <ian@darwinsys.com>
421 without looking at anybody else's source code.
423 John Gilmore revised the code extensively, making it better than
425 Geoff Collyer found several inadequacies
426 and provided some magic file entries.
427 Contributions by the `&' operator by Rob McMahon, cudcv@warwick.ac.uk, 1989.
429 Guy Harris, guy@netapp.com, made many changes from 1993 to the present.
431 Primary development and maintenance from 1990 to the present by
432 Christos Zoulas (christos@astron.com).
434 Altered by Chris Lowth, chris@lowth.com, 2000:
435 Handle the ``-i'' option to output mime type strings and using an alternative
436 magic file and internal logic.
438 Altered by Eric Fischer (enf@pobox.com), July, 2000,
439 to identify character codes and attempt to identify the languages
442 The list of contributors to the "Magdir" directory (source for the
444 file) is too long to include here.
445 You know who you are; thank you.
447 Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999.
448 Covered by the standard Berkeley Software Distribution copyright; see the file
449 LEGAL.NOTICE in the source distribution.
455 were written by John Gilmore from his public-domain
457 program, and are not covered by the above license.
459 There must be a better way to automate the construction of the Magic
460 file from all the glop in Magdir.
462 Better yet, the magic file should be compiled into binary (say,
464 or, better yet, fixed-length
466 strings for use in heterogenous network environments) for faster startup.
467 Then the program would run as fast as the Version 7 program of the same name,
468 with the flexibility of the System V version.
471 uses several algorithms that favor speed over accuracy,
472 thus it can be misled about the contents of
478 files (primarily for programming languages)
479 is simplistic, inefficient and requires recompilation to update.
481 There should be an ``else'' clause to follow a series of continuation lines.
483 The magic file and keywords should have regular expression support.
486 as a field delimiter is ugly and makes
487 it hard to edit the files, but is entrenched.
489 It might be advisable to allow upper-case letters in keywords
492 commands vs man page macros.
493 Regular expression support would make this easy.
495 The program doesn't grok \s-2FORTRAN\s0.
496 It should be able to figure \s-2FORTRAN\s0 by seeing some keywords which
497 appear indented at the start of line.
498 Regular expression support would make this easy.
500 The list of keywords in
502 probably belongs in the Magic file.
503 This could be done by using some keyword like `*' for the offset value.
505 Another optimization would be to sort
506 the magic file so that we can just run down all the
507 tests for the first byte, first word, first long, etc, once we
509 Complain about conflicts in the magic file entries.
510 Make a rule that the magic entries sort based on file offset rather
511 than position within the magic file?
513 The program should provide a way to give an estimate
514 of ``how good'' a guess is.
515 We end up removing guesses (e.g. ``From '' as first 5 chars of file) because
516 they are not as good as other guesses (e.g. ``Newsgroups:'' versus
518 Still, if the others don't pan out, it should be possible to use the
521 This program is slower than some vendors' file commands.
522 The new support for multiple character codes makes it even slower.
524 This manual page, and particularly this section, is too long.
526 You can obtain the original author's latest version by anonymous FTP
530 .I /pub/file/file-X.YZ.tar.gz