1FILE(1)                   BSD General Commands Manual                  FILE(1)
2

NAME

4     file — determine file type
5

SYNOPSIS

7     file [-bcdEhiklLNnprsSvzZ0] [--apple] [--exclude-quiet] [--extension]
8          [--mime-encoding] [--mime-type] [-e testname] [-F separator]
9          [-f namefile] [-m magicfiles] [-P name=value] file ...
10     file -C [-m magicfiles]
11     file [--help]
12

DESCRIPTION

14     This manual page documents version 5.40 of the file command.
15
16     file tests each argument in an attempt to classify it.  There are three
17     sets of tests, performed in this order: filesystem tests, magic tests,
18     and language tests.  The first test that succeeds causes the file type to
19     be printed.
20
21     The type printed will usually contain one of the words text (the file
22     contains only printing characters and a few common control characters and
23     is probably safe to read on an ASCII terminal), executable (the file con‐
24     tains the result of compiling a program in a form understandable to some
25     UNIX kernel or another), or data meaning anything else (data is usually
26     “binary” or non-printable).  Exceptions are well-known file formats (core
27     files, tar archives) that are known to contain binary data.  When modify‐
28     ing magic files or the program itself, make sure to preserve these
29     keywords.  Users depend on knowing that all the readable files in a di‐
30     rectory have the word “text” printed.  Don't do as Berkeley did and
31     change “shell commands text” to “shell script”.
32
33     The filesystem tests are based on examining the return from a stat(2)
34     system call.  The program checks to see if the file is empty, or if it's
35     some sort of special file.  Any known file types appropriate to the sys‐
36     tem you are running on (sockets, symbolic links, or named pipes (FIFOs)
37     on those systems that implement them) are intuited if they are defined in
38     the system header file <sys/stat.h>.
39
40     The magic tests are used to check for files with data in particular fixed
41     formats.  The canonical example of this is a binary executable (compiled
42     program) a.out file, whose format is defined in <elf.h>, <a.out.h> and
43     possibly <exec.h> in the standard include directory.  These files have a
44     “magic number” stored in a particular place near the beginning of the
45     file that tells the UNIX operating system that the file is a binary exe‐
46     cutable, and which of several types thereof.  The concept of a “magic
47     number” has been applied by extension to data files.  Any file with some
48     invariant identifier at a small fixed offset into the file can usually be
49     described in this way.  The information identifying these files is read
50     from the compiled magic file /usr/share/misc/magic.mgc, or the files in
51     the directory /usr/share/misc/magic if the compiled file does not exist.
52     In addition, if $HOME/.magic.mgc or $HOME/.magic exists, it will be used
53     in preference to the system magic files.
54
55     If a file does not match any of the entries in the magic file, it is ex‐
56     amined to see if it seems to be a text file.  ASCII, ISO-8859-x, non-ISO
57     8-bit extended-ASCII character sets (such as those used on Macintosh and
58     IBM PC systems), UTF-8-encoded Unicode, UTF-16-encoded Unicode, and
59     EBCDIC character sets can be distinguished by the different ranges and
60     sequences of bytes that constitute printable text in each set.  If a file
61     passes any of these tests, its character set is reported.  ASCII,
62     ISO-8859-x, UTF-8, and extended-ASCII files are identified as “text” be‐
63     cause they will be mostly readable on nearly any terminal; UTF-16 and
64     EBCDIC are only “character data” because, while they contain text, it is
65     text that will require translation before it can be read.  In addition,
66     file will attempt to determine other characteristics of text-type files.
67     If the lines of a file are terminated by CR, CRLF, or NEL, instead of the
68     Unix-standard LF, this will be reported.  Files that contain embedded es‐
69     cape sequences or overstriking will also be identified.
70
71     Once file has determined the character set used in a text-type file, it
72     will attempt to determine in what language the file is written.  The lan‐
73     guage tests look for particular strings (cf.  <names.h>) that can appear
74     anywhere in the first few blocks of a file.  For example, the keyword .br
75     indicates that the file is most likely a troff(1) input file, just as the
76     keyword struct indicates a C program.  These tests are less reliable than
77     the previous two groups, so they are performed last.  The language test
78     routines also test for some miscellany (such as tar(1) archives, JSON
79     files).
80
81     Any file that cannot be identified as having been written in any of the
82     character sets listed above is simply said to be “data”.
83

OPTIONS

85     --apple
86             Causes the file command to output the file type and creator code
87             as used by older MacOS versions.  The code consists of eight let‐
88             ters, the first describing the file type, the latter the creator.
89             This option works properly only for file formats that have the
90             apple-style output defined.
91
92     -b, --brief
93             Do not prepend filenames to output lines (brief mode).
94
95     -C, --compile
96             Write a magic.mgc output file that contains a pre-parsed version
97             of the magic file or directory.
98
99     -c, --checking-printout
100             Cause a checking printout of the parsed form of the magic file.
101             This is usually used in conjunction with the -m option to debug a
102             new magic file before installing it.
103
104     -d      Prints internal debugging information to stderr.
105
106     -E      On filesystem errors (file not found etc), instead of handling
107             the error as regular output as POSIX mandates and keep going, is‐
108             sue an error message and exit.
109
110     -e, --exclude testname
111             Exclude the test named in testname from the list of tests made to
112             determine the file type.  Valid test names are:
113
114             apptype   EMX application type (only on EMX).
115
116             ascii     Various types of text files (this test will try to
117                       guess the text encoding, irrespective of the setting of
118                       the ‘encoding’ option).
119
120             encoding  Different text encodings for soft magic tests.
121
122             tokens    Ignored for backwards compatibility.
123
124             cdf       Prints details of Compound Document Files.
125
126             compress  Checks for, and looks inside, compressed files.
127
128             csv       Checks Comma Separated Value files.
129
130             elf       Prints ELF file details, provided soft magic tests are
131                       enabled and the elf magic is found.
132
133             json      Examines JSON (RFC-7159) files by parsing them for com‐
134                       pliance.
135
136             soft      Consults magic files.
137
138             tar       Examines tar files by verifying the checksum of the 512
139                       byte tar header.  Excluding this test can provide more
140                       detailed content description by using the soft magic
141                       method.
142
143             text      A synonym for ‘ascii’.
144
145     --exclude-quiet
146             Like --exclude but ignore tests that file does not know about.
147             This is intended for compatibility with older versions of file.
148
149     --extension
150             Print a slash-separated list of valid extensions for the file
151             type found.
152
153     -F, --separator separator
154             Use the specified string as the separator between the filename
155             and the file result returned.  Defaults to ‘:’.
156
157     -f, --files-from namefile
158             Read the names of the files to be examined from namefile (one per
159             line) before the argument list.  Either namefile or at least one
160             filename argument must be present; to test the standard input,
161             use ‘-’ as a filename argument.  Please note that namefile is un‐
162             wrapped and the enclosed filenames are processed when this option
163             is encountered and before any further options processing is done.
164             This allows one to process multiple lists of files with different
165             command line arguments on the same file invocation.  Thus if you
166             want to set the delimiter, you need to do it before you specify
167             the list of files, like: “-F @ -f namefile”, instead of: “-f
168             namefile -F @”.
169
170     -h, --no-dereference
171             This option causes symlinks not to be followed (on systems that
172             support symbolic links).  This is the default if the environment
173             variable POSIXLY_CORRECT is not defined.
174
175     -i, --mime
176             Causes the file command to output mime type strings rather than
177             the more traditional human readable ones.  Thus it may say
178             ‘text/plain; charset=us-ascii’ rather than “ASCII text”.
179
180     --mime-type, --mime-encoding
181             Like -i, but print only the specified element(s).
182
183     -k, --keep-going
184             Don't stop at the first match, keep going.  Subsequent matches
185             will be have the string ‘\012- ’ prepended.  (If you want a new‐
186             line, see the -r option.)  The magic pattern with the highest
187             strength (see the -l option) comes first.
188
189     -l, --list
190             Shows a list of patterns and their strength sorted descending by
191             magic(5) strength which is used for the matching (see also the -k
192             option).
193
194     -L, --dereference
195             This option causes symlinks to be followed, as the like-named op‐
196             tion in ls(1) (on systems that support symbolic links).  This is
197             the default if the environment variable POSIXLY_CORRECT is de‐
198             fined.
199
200     -m, --magic-file magicfiles
201             Specify an alternate list of files and directories containing
202             magic.  This can be a single item, or a colon-separated list.  If
203             a compiled magic file is found alongside a file or directory, it
204             will be used instead.
205
206     -N, --no-pad
207             Don't pad filenames so that they align in the output.
208
209     -n, --no-buffer
210             Force stdout to be flushed after checking each file.  This is
211             only useful if checking a list of files.  It is intended to be
212             used by programs that want filetype output from a pipe.
213
214     -p, --preserve-date
215             On systems that support utime(3) or utimes(2), attempt to pre‐
216             serve the access time of files analyzed, to pretend that file
217             never read them.
218
219     -P, --parameter name=value
220             Set various parameter limits.
221
222                   Name         Default    Explanation
223                   bytes        1048576    max number of bytes to read from
224                                                                          file
225                   elf_notes    256        max ELF notes processed
226                   elf_phnum    2048       max ELF program sections processed
227                   elf_shnum    32768      max ELF sections processed
228                   encoding     65536      max number of bytes to scan for
229                                                                          encoding
230                                                                          evaluation
231                   indir        50         recursion limit for indirect magic
232                   name         50         use count limit for name/use magic
233                   regex        8192       length limit for regex searches
234
235     -r, --raw
236             Don't translate unprintable characters to \ooo.  Normally file
237             translates unprintable characters to their octal representation.
238
239     -s, --special-files
240             Normally, file only attempts to read and determine the type of
241             argument files which stat(2) reports are ordinary files.  This
242             prevents problems, because reading special files may have pecu‐
243             liar consequences.  Specifying the -s option causes file to also
244             read argument files which are block or character special files.
245             This is useful for determining the filesystem types of the data
246             in raw disk partitions, which are block special files.  This op‐
247             tion also causes file to disregard the file size as reported by
248             stat(2) since on some systems it reports a zero size for raw disk
249             partitions.
250
251     -S, --no-sandbox
252             On systems where libseccomp
253             (https://github.com/seccomp/libseccomp) is available, the -S op‐
254             tion disables sandboxing which is enabled by default.  This op‐
255             tion is needed for file to execute external decompressing pro‐
256             grams, i.e. when the -z option is specified and the built-in de‐
257             compressors are not available.  On systems where sandboxing is
258             not available, this option has no effect.
259
260     -v, --version
261             Print the version of the program and exit.
262
263     -z, --uncompress
264             Try to look inside compressed files.
265
266     -Z, --uncompress-noreport
267             Try to look inside compressed files, but report information about
268             the contents only not the compression.
269
270     -0, --print0
271             Output a null character ‘\0’ after the end of the filename.  Nice
272             to cut(1) the output.  This does not affect the separator, which
273             is still printed.
274
275             If this option is repeated more than once, then file prints just
276             the filename followed by a NUL followed by the description (or
277             ERROR: text) followed by a second NUL for each entry.
278
279     --help  Print a help message and exit.
280

ENVIRONMENT

282     The environment variable MAGIC can be used to set the default magic file
283     name.  If that variable is set, then file will not attempt to open
284     $HOME/.magic.  file adds “.mgc” to the value of this variable as appro‐
285     priate.  The environment variable POSIXLY_CORRECT controls (on systems
286     that support symbolic links), whether file will attempt to follow sym‐
287     links or not.  If set, then file follows symlink, otherwise it does not.
288     This is also controlled by the -L and -h options.
289

FILES

291     /usr/share/misc/magic.mgc  Default compiled list of magic.
292     /usr/share/misc/magic      Directory containing default magic files.
293

EXIT STATUS

295     file will exit with 0 if the operation was successful or >0 if an error
296     was encountered.  The following errors cause diagnostic messages, but
297     don't affect the program exit code (as POSIX requires), unless -E is
298     specified:
299           A file cannot be found
300           There is no permission to read a file
301           The file type cannot be determined
302

EXAMPLES

304           $ file file.c file /dev/{wd0a,hda}
305           file.c:   C program text
306           file:     ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV),
307                     dynamically linked (uses shared libs), stripped
308           /dev/wd0a: block special (0/0)
309           /dev/hda: block special (3/0)
310
311           $ file -s /dev/wd0{b,d}
312           /dev/wd0b: data
313           /dev/wd0d: x86 boot sector
314
315           $ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10}
316           /dev/hda:   x86 boot sector
317           /dev/hda1:  Linux/i386 ext2 filesystem
318           /dev/hda2:  x86 boot sector
319           /dev/hda3:  x86 boot sector, extended partition table
320           /dev/hda4:  Linux/i386 ext2 filesystem
321           /dev/hda5:  Linux/i386 swap file
322           /dev/hda6:  Linux/i386 swap file
323           /dev/hda7:  Linux/i386 swap file
324           /dev/hda8:  Linux/i386 swap file
325           /dev/hda9:  empty
326           /dev/hda10: empty
327
328           $ file -i file.c file /dev/{wd0a,hda}
329           file.c:      text/x-c
330           file:        application/x-executable
331           /dev/hda:    application/x-not-regular-file
332           /dev/wd0a:   application/x-not-regular-file
333
334

SEE ALSO

336     hexdump(1), od(1), strings(1), magic(5)
337

STANDARDS CONFORMANCE

339     This program is believed to exceed the System V Interface Definition of
340     FILE(CMD), as near as one can determine from the vague language contained
341     therein.  Its behavior is mostly compatible with the System V program of
342     the same name.  This version knows more magic, however, so it will pro‐
343     duce different (albeit more accurate) output in many cases.
344
345     The one significant difference between this version and System V is that
346     this version treats any white space as a delimiter, so that spaces in
347     pattern strings must be escaped.  For example,
348
349           >10     string  language impress        (imPRESS data)
350
351     in an existing magic file would have to be changed to
352
353           >10     string  language\ impress       (imPRESS data)
354
355     In addition, in this version, if a pattern string contains a backslash,
356     it must be escaped.  For example
357
358           0       string          \begindata      Andrew Toolkit document
359
360     in an existing magic file would have to be changed to
361
362           0       string          \\begindata     Andrew Toolkit document
363
364     SunOS releases 3.2 and later from Sun Microsystems include a file command
365     derived from the System V one, but with some extensions.  This version
366     differs from Sun's only in minor ways.  It includes the extension of the
367     ‘&’ operator, used as, for example,
368
369           >16     long&0x7fffffff >0              not stripped
370

SECURITY

372     On systems where libseccomp (https://github.com/seccomp/libseccomp) is
373     available, file is enforces limiting system calls to only the ones neces‐
374     sary for the operation of the program.  This enforcement does not provide
375     any security benefit when file is asked to decompress input files running
376     external programs with the -z option.  To enable execution of external
377     decompressors, one needs to disable sandboxing using the -S option.
378

MAGIC DIRECTORY

380     The magic file entries have been collected from various sources, mainly
381     USENET, and contributed by various authors.  Christos Zoulas (address be‐
382     low) will collect additional or corrected magic file entries.  A consoli‐
383     dation of magic file entries will be distributed periodically.
384
385     The order of entries in the magic file is significant.  Depending on what
386     system you are using, the order that they are put together may be incor‐
387     rect.  If your old file command uses a magic file, keep the old magic
388     file around for comparison purposes (rename it to
389     /usr/share/misc/magic.orig).
390

HISTORY

392     There has been a file command in every UNIX since at least Research
393     Version 4 (man page dated November, 1973).  The System V version intro‐
394     duced one significant major change: the external list of magic types.
395     This slowed the program down slightly but made it a lot more flexible.
396
397     This program, based on the System V version, was written by Ian Darwin
398     ⟨ian@darwinsys.com⟩ without looking at anybody else's source code.
399
400     John Gilmore revised the code extensively, making it better than the
401     first version.  Geoff Collyer found several inadequacies and provided
402     some magic file entries.  Contributions of the ‘&’ operator by Rob McMa‐
403     hon, ⟨cudcv@warwick.ac.uk⟩, 1989.
404
405     Guy Harris, ⟨guy@netapp.com⟩, made many changes from 1993 to the present.
406
407     Primary development and maintenance from 1990 to the present by Christos
408     Zoulas ⟨christos@astron.com⟩.
409
410     Altered by Chris Lowth ⟨chris@lowth.com⟩, 2000: handle the -i option to
411     output mime type strings, using an alternative magic file and internal
412     logic.
413
414     Altered by Eric Fischer ⟨enf@pobox.com⟩, July, 2000, to identify charac‐
415     ter codes and attempt to identify the languages of non-ASCII files.
416
417     Altered by Reuben Thomas ⟨rrt@sc3d.org⟩, 2007-2011, to improve MIME sup‐
418     port, merge MIME and non-MIME magic, support directories as well as files
419     of magic, apply many bug fixes, update and fix a lot of magic, improve
420     the build system, improve the documentation, and rewrite the Python bind‐
421     ings in pure Python.
422
423     The list of contributors to the ‘magic’ directory (magic files) is too
424     long to include here.  You know who you are; thank you.  Many contribu‐
425     tors are listed in the source files.
426
428     Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999.  Covered by the
429     standard Berkeley Software Distribution copyright; see the file COPYING
430     in the source distribution.
431
432     The files tar.h and is_tar.c were written by John Gilmore from his pub‐
433     lic-domain tar(1) program, and are not covered by the above license.
434

BUGS

436     Please report bugs and send patches to the bug tracker at
437     https://bugs.astron.com/ or the mailing list at ⟨file@astron.com⟩ (visit
438     https://mailman.astron.com/mailman/listinfo/file first to subscribe).
439

TODO

441     Fix output so that tests for MIME and APPLE flags are not needed all over
442     the place, and actual output is only done in one place.  This needs a de‐
443     sign.  Suggestion: push possible outputs on to a list, then pick the
444     last-pushed (most specific, one hopes) value at the end, or use a default
445     if the list is empty.  This should not slow down evaluation.
446
447     The handling of MAGIC_CONTINUE and printing \012- between entries is
448     clumsy and complicated; refactor and centralize.
449
450     Some of the encoding logic is hard-coded in encoding.c and can be moved
451     to the magic files if we had a !:charset annotation.
452
453     Continue to squash all magic bugs.  See Debian BTS for a good source.
454
455     Store arbitrarily long strings, for example for %s patterns, so that they
456     can be printed out.  Fixes Debian bug #271672.  This can be done by allo‐
457     cating strings in a string pool, storing the string pool at the end of
458     the magic file and converting all the string pointers to relative offsets
459     from the string pool.
460
461     Add syntax for relative offsets after current level (Debian bug #466037).
462
463     Make file -ki work, i.e. give multiple MIME types.
464
465     Add a zip library so we can peek inside Office2007 documents to print
466     more details about their contents.
467
468     Add an option to print URLs for the sources of the file descriptions.
469
470     Combine script searches and add a way to map executable names to MIME
471     types (e.g. have a magic value for !:mime which causes the resulting
472     string to be looked up in a table).  This would avoid adding the same
473     magic repeatedly for each new hash-bang interpreter.
474
475     When a file descriptor is available, we can skip and adjust the buffer
476     instead of the hacky buffer management we do now.
477
478     Fix “name” and “use” to check for consistency at compile time (duplicate
479     “name”, “use” pointing to undefined “name” ).  Make “name” / “use” more
480     efficient by keeping a sorted list of names.  Special-case ^ to flip en‐
481     dianness in the parser so that it does not have to be escaped, and docu‐
482     ment it.
483
484     If the offsets specified internally in the file exceed the buffer size (
485     HOWMANY variable in file.h), then we don't seek to that offset, but we
486     give up.  It would be better if buffer managements was done when the file
487     descriptor is available so we can seek around the file.  One must be
488     careful though because this has performance and thus security considera‐
489     tions, because one can slow down things by repeateadly seeking.
490
491     There is support now for keeping separate buffers and having offsets from
492     the end of the file, but the internal buffer management still needs an
493     overhaul.
494

AVAILABILITY

496     You can obtain the original author's latest version by anonymous FTP on
497     ftp.astron.com in the directory /pub/file/file-X.YZ.tar.gz.
498
499BSD                            February 5, 2021                            BSD
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