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

NAME

4     file — determine file type
5

SYNOPSIS

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

DESCRIPTION

14     This manual page documents version 5.38 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
30     directory 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     has been applied by extension to data files.  Any file with some invari‐
48     ant 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
56     examined to see if it seems to be a text file.  ASCII, ISO-8859-x, non-
57     ISO 8-bit extended-ASCII character sets (such as those used on Macintosh
58     and 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”
63     because 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
69     escape 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 flag 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,
108             issue 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     --extension
146             Print a slash-separated list of valid extensions for the file
147             type found.
148
149     -F, --separator separator
150             Use the specified string as the separator between the filename
151             and the file result returned.  Defaults to ‘:’.
152
153     -f, --files-from namefile
154             Read the names of the files to be examined from namefile (one per
155             line) before the argument list.  Either namefile or at least one
156             filename argument must be present; to test the standard input,
157             use ‘-’ as a filename argument.  Please note that namefile is
158             unwrapped and the enclosed filenames are processed when this
159             option is encountered and before any further options processing
160             is done.  This allows one to process multiple lists of files with
161             different command line arguments on the same file invocation.
162             Thus if you want to set the delimiter, you need to do it before
163             you specify the list of files, like: “-F @ -f namefile”, instead
164             of: “-f namefile -F @”.
165
166     -h, --no-dereference
167             option causes symlinks not to be followed (on systems that sup‐
168             port symbolic links).  This is the default if the environment
169             variable POSIXLY_CORRECT is not defined.
170
171     -i, --mime
172             Causes the file command to output mime type strings rather than
173             the more traditional human readable ones.  Thus it may say
174             ‘text/plain; charset=us-ascii’ rather than “ASCII text”.
175
176     --mime-type, --mime-encoding
177             Like -i, but print only the specified element(s).
178
179     -k, --keep-going
180             Don't stop at the first match, keep going.  Subsequent matches
181             will be have the string ‘\012- ’ prepended.  (If you want a new‐
182             line, see the -r option.)  The magic pattern with the highest
183             strength (see the -l option) comes first.
184
185     -l, --list
186             Shows a list of patterns and their strength sorted descending by
187             magic(5) strength which is used for the matching (see also the -k
188             option).
189
190     -L, --dereference
191             option causes symlinks to be followed, as the like-named option
192             in ls(1) (on systems that support symbolic links).  This is the
193             default if the environment variable POSIXLY_CORRECT is defined.
194
195     -m, --magic-file magicfiles
196             Specify an alternate list of files and directories containing
197             magic.  This can be a single item, or a colon-separated list.  If
198             a compiled magic file is found alongside a file or directory, it
199             will be used instead.
200
201     -N, --no-pad
202             Don't pad filenames so that they align in the output.
203
204     -n, --no-buffer
205             Force stdout to be flushed after checking each file.  This is
206             only useful if checking a list of files.  It is intended to be
207             used by programs that want filetype output from a pipe.
208
209     -p, --preserve-date
210             On systems that support utime(3) or utimes(2), attempt to pre‐
211             serve the access time of files analyzed, to pretend that file
212             never read them.
213
214     -P, --parameter name=value
215             Set various parameter limits.
216
217                   Name         Default    Explanation
218                   indir        15         recursion limit for indirect magic
219                   name         30         use count limit for name/use magic
220                   elf_notes    256        max ELF notes processed
221                   elf_phnum    128        max ELF program sections processed
222                   elf_shnum    32768      max ELF sections processed
223                   regex        8192       length limit for regex searches
224                   bytes        1048576    max number of bytes to read from
225                                                                          file
226
227     -r, --raw
228             Don't translate unprintable characters to \ooo.  Normally file
229             translates unprintable characters to their octal representation.
230
231     -s, --special-files
232             Normally, file only attempts to read and determine the type of
233             argument files which stat(2) reports are ordinary files.  This
234             prevents problems, because reading special files may have pecu‐
235             liar consequences.  Specifying the -s option causes file to also
236             read argument files which are block or character special files.
237             This is useful for determining the filesystem types of the data
238             in raw disk partitions, which are block special files.  This
239             option also causes file to disregard the file size as reported by
240             stat(2) since on some systems it reports a zero size for raw disk
241             partitions.
242
243     -S, --no-sandbox
244             On systems where libseccomp
245             (https://github.com/seccomp/libseccomp) is available, the -S flag
246             disables sandboxing which is enabled by default.  This option is
247             needed for file to execute external decompressing programs, i.e.
248             when the -z flag is specified and the built-in decompressors are
249             not available.  On systems where sandboxing is not available,
250             this option has no effect.
251
252     -v, --version
253             Print the version of the program and exit.
254
255     -z, --uncompress
256             Try to look inside compressed files.
257
258     -Z, --uncompress-noreport
259             Try to look inside compressed files, but report information about
260             the contents only not the compression.
261
262     -0, --print0
263             Output a null character ‘\0’ after the end of the filename.  Nice
264             to cut(1) the output.  This does not affect the separator, which
265             is still printed.
266
267             If this option is repeated more than once, then file prints just
268             the filename followed by a NUL followed by the description (or
269             ERROR: text) followed by a second NUL for each entry.
270
271     --help  Print a help message and exit.
272

ENVIRONMENT

274     The environment variable MAGIC can be used to set the default magic file
275     name.  If that variable is set, then file will not attempt to open
276     $HOME/.magic.  file adds “.mgc” to the value of this variable as appro‐
277     priate.  The environment variable POSIXLY_CORRECT controls (on systems
278     that support symbolic links), whether file will attempt to follow sym‐
279     links or not.  If set, then file follows symlink, otherwise it does not.
280     This is also controlled by the -L and -h options.
281

FILES

283     /usr/share/misc/magic.mgc  Default compiled list of magic.
284     /usr/share/misc/magic      Directory containing default magic files.
285

EXIT STATUS

287     file will exit with 0 if the operation was successful or >0 if an error
288     was encountered.  The following errors cause diagnostic messages, but
289     don't affect the program exit code (as POSIX requires), unless -E is
290     specified:
291           ·   A file cannot be found
292           ·   There is no permission to read a file
293           ·   The file type cannot be determined
294

EXAMPLES

296           $ file file.c file /dev/{wd0a,hda}
297           file.c:   C program text
298           file:     ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV),
299                     dynamically linked (uses shared libs), stripped
300           /dev/wd0a: block special (0/0)
301           /dev/hda: block special (3/0)
302
303           $ file -s /dev/wd0{b,d}
304           /dev/wd0b: data
305           /dev/wd0d: x86 boot sector
306
307           $ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10}
308           /dev/hda:   x86 boot sector
309           /dev/hda1:  Linux/i386 ext2 filesystem
310           /dev/hda2:  x86 boot sector
311           /dev/hda3:  x86 boot sector, extended partition table
312           /dev/hda4:  Linux/i386 ext2 filesystem
313           /dev/hda5:  Linux/i386 swap file
314           /dev/hda6:  Linux/i386 swap file
315           /dev/hda7:  Linux/i386 swap file
316           /dev/hda8:  Linux/i386 swap file
317           /dev/hda9:  empty
318           /dev/hda10: empty
319
320           $ file -i file.c file /dev/{wd0a,hda}
321           file.c:      text/x-c
322           file:        application/x-executable
323           /dev/hda:    application/x-not-regular-file
324           /dev/wd0a:   application/x-not-regular-file
325
326

SEE ALSO

328     hexdump(1), od(1), strings(1), magic(5)
329

STANDARDS CONFORMANCE

331     This program is believed to exceed the System V Interface Definition of
332     FILE(CMD), as near as one can determine from the vague language contained
333     therein.  Its behavior is mostly compatible with the System V program of
334     the same name.  This version knows more magic, however, so it will pro‐
335     duce different (albeit more accurate) output in many cases.
336
337     The one significant difference between this version and System V is that
338     this version treats any white space as a delimiter, so that spaces in
339     pattern strings must be escaped.  For example,
340
341           >10     string  language impress        (imPRESS data)
342
343     in an existing magic file would have to be changed to
344
345           >10     string  language\ impress       (imPRESS data)
346
347     In addition, in this version, if a pattern string contains a backslash,
348     it must be escaped.  For example
349
350           0       string          \begindata      Andrew Toolkit document
351
352     in an existing magic file would have to be changed to
353
354           0       string          \\begindata     Andrew Toolkit document
355
356     SunOS releases 3.2 and later from Sun Microsystems include a file command
357     derived from the System V one, but with some extensions.  This version
358     differs from Sun's only in minor ways.  It includes the extension of the
359     ‘&’ operator, used as, for example,
360
361           >16     long&0x7fffffff >0              not stripped
362

SECURITY

364     On systems where libseccomp (https://github.com/seccomp/libseccomp) is
365     available, file is enforces limiting system calls to only the ones neces‐
366     sary for the operation of the program.  This enforcement does not provide
367     any security benefit when file is asked to decompress input files running
368     external programs with the -z option.  To enable execution of external
369     decompressors, one needs to disable sandboxing using the -S flag.
370

MAGIC DIRECTORY

372     The magic file entries have been collected from various sources, mainly
373     USENET, and contributed by various authors.  Christos Zoulas (address
374     below) will collect additional or corrected magic file entries.  A con‐
375     solidation of magic file entries will be distributed periodically.
376
377     The order of entries in the magic file is significant.  Depending on what
378     system you are using, the order that they are put together may be incor‐
379     rect.  If your old file command uses a magic file, keep the old magic
380     file around for comparison purposes (rename it to
381     /usr/share/misc/magic.orig).
382

HISTORY

384     There has been a file command in every UNIX since at least Research
385     Version 4 (man page dated November, 1973).  The System V version intro‐
386     duced one significant major change: the external list of magic types.
387     This slowed the program down slightly but made it a lot more flexible.
388
389     This program, based on the System V version, was written by Ian Darwin
390     ⟨ian@darwinsys.com⟩ without looking at anybody else's source code.
391
392     John Gilmore revised the code extensively, making it better than the
393     first version.  Geoff Collyer found several inadequacies and provided
394     some magic file entries.  Contributions of the ‘&’ operator by Rob McMa‐
395     hon, ⟨cudcv@warwick.ac.uk⟩, 1989.
396
397     Guy Harris, ⟨guy@netapp.com⟩, made many changes from 1993 to the present.
398
399     Primary development and maintenance from 1990 to the present by Christos
400     Zoulas ⟨christos@astron.com⟩.
401
402     Altered by Chris Lowth ⟨chris@lowth.com⟩, 2000: handle the -i option to
403     output mime type strings, using an alternative magic file and internal
404     logic.
405
406     Altered by Eric Fischer ⟨enf@pobox.com⟩, July, 2000, to identify charac‐
407     ter codes and attempt to identify the languages of non-ASCII files.
408
409     Altered by Reuben Thomas ⟨rrt@sc3d.org⟩, 2007-2011, to improve MIME sup‐
410     port, merge MIME and non-MIME magic, support directories as well as files
411     of magic, apply many bug fixes, update and fix a lot of magic, improve
412     the build system, improve the documentation, and rewrite the Python bind‐
413     ings in pure Python.
414
415     The list of contributors to the ‘magic’ directory (magic files) is too
416     long to include here.  You know who you are; thank you.  Many contribu‐
417     tors are listed in the source files.
418
420     Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999.  Covered by the
421     standard Berkeley Software Distribution copyright; see the file COPYING
422     in the source distribution.
423
424     The files tar.h and is_tar.c were written by John Gilmore from his pub‐
425     lic-domain tar(1) program, and are not covered by the above license.
426

BUGS

428     Please report bugs and send patches to the bug tracker at
429     https://bugs.astron.com/ or the mailing list at ⟨file@astron.com⟩ (visit
430     https://mailman.astron.com/mailman/listinfo/file first to subscribe).
431

TODO

433     Fix output so that tests for MIME and APPLE flags are not needed all over
434     the place, and actual output is only done in one place.  This needs a
435     design.  Suggestion: push possible outputs on to a list, then pick the
436     last-pushed (most specific, one hopes) value at the end, or use a default
437     if the list is empty.  This should not slow down evaluation.
438
439     The handling of MAGIC_CONTINUE and printing \012- between entries is
440     clumsy and complicated; refactor and centralize.
441
442     Some of the encoding logic is hard-coded in encoding.c and can be moved
443     to the magic files if we had a !:charset annotation
444
445     Continue to squash all magic bugs.  See Debian BTS for a good source.
446
447     Store arbitrarily long strings, for example for %s patterns, so that they
448     can be printed out.  Fixes Debian bug #271672.  This can be done by allo‐
449     cating strings in a string pool, storing the string pool at the end of
450     the magic file and converting all the string pointers to relative offsets
451     from the string pool.
452
453     Add syntax for relative offsets after current level (Debian bug #466037).
454
455     Make file -ki work, i.e. give multiple MIME types.
456
457     Add a zip library so we can peek inside Office2007 documents to print
458     more details about their contents.
459
460     Add an option to print URLs for the sources of the file descriptions.
461
462     Combine script searches and add a way to map executable names to MIME
463     types (e.g. have a magic value for !:mime which causes the resulting
464     string to be looked up in a table).  This would avoid adding the same
465     magic repeatedly for each new hash-bang interpreter.
466
467     When a file descriptor is available, we can skip and adjust the buffer
468     instead of the hacky buffer management we do now.
469
470     Fix “name” and “use” to check for consistency at compile time (duplicate
471     “name”, “use” pointing to undefined “name” ).  Make “name” / “use” more
472     efficient by keeping a sorted list of names.  Special-case ^ to flip
473     endianness in the parser so that it does not have to be escaped, and doc‐
474     ument it.
475
476     If the offsets specified internally in the file exceed the buffer size (
477     HOWMANY variable in file.h), then we don't seek to that offset, but we
478     give up.  It would be better if buffer managements was done when the file
479     descriptor is available so move around the file.  One must be careful
480     though because this has performance (and thus security considerations).
481

AVAILABILITY

483     You can obtain the original author's latest version by anonymous FTP on
484     ftp.astron.com in the directory /pub/file/file-X.YZ.tar.gz.
485
486BSD                              July 13, 2019                             BSD
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