1FILE(1) BSD General Commands Manual FILE(1)
2
4 file — determine file type
5
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
14 This manual page documents version 5.37 of the file command.
15 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 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 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 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 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 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 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
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 -b, --brief
93 Do not prepend filenames to output lines (brief mode).
94 -C, --compile
96 Write a magic.mgc output file that contains a pre-parsed version
97 of the magic file or directory.
98 -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 -d Prints internal debugging information to stderr.
105 -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 -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 apptype EMX application type (only on EMX).
115 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 encoding Different text encodings for soft magic tests.
121 tokens Ignored for backwards compatibility.
123 cdf Prints details of Compound Document Files.
125 compress Checks for, and looks inside, compressed files.
127 elf Prints ELF file details, provided soft magic tests are
129 enabled and the elf magic is found.
130 json Examines JSON (RFC-7159) files by parsing them for com‐
132 pliance.
133 soft Consults magic files.
135 tar Examines tar files by verifying the checksum of the 512
137 byte tar header. Excluding this test can provide more
138 detailed content description by using the soft magic
139 method.
140 text A synonym for ‘ascii’.
142 --extension
144 Print a slash-separated list of valid extensions for the file
145 type found.
146 -F, --separator separator
148 Use the specified string as the separator between the filename
149 and the file result returned. Defaults to ‘:’.
150 -f, --files-from namefile
152 Read the names of the files to be examined from namefile (one per
153 line) before the argument list. Either namefile or at least one
154 filename argument must be present; to test the standard input,
155 use ‘-’ as a filename argument. Please note that namefile is
156 unwrapped and the enclosed filenames are processed when this
157 option is encountered and before any further options processing
158 is done. This allows one to process multiple lists of files with
159 different command line arguments on the same file invocation.
160 Thus if you want to set the delimiter, you need to do it before
161 you specify the list of files, like: “-F @ -f namefile”, instead
162 of: “-f namefile -F @”.
163 -h, --no-dereference
165 option causes symlinks not to be followed (on systems that sup‐
166 port symbolic links). This is the default if the environment
167 variable POSIXLY_CORRECT is not defined.
168 -i, --mime
170 Causes the file command to output mime type strings rather than
171 the more traditional human readable ones. Thus it may say
172 ‘text/plain; charset=us-ascii’ rather than “ASCII text”.
173 --mime-type, --mime-encoding
175 Like -i, but print only the specified element(s).
176 -k, --keep-going
178 Don't stop at the first match, keep going. Subsequent matches
179 will be have the string ‘\012- ’ prepended. (If you want a new‐
180 line, see the -r option.) The magic pattern with the highest
181 strength (see the -l option) comes first.
182 -l, --list
184 Shows a list of patterns and their strength sorted descending by
185 magic(4) strength which is used for the matching (see also the -k
186 option).
187 -L, --dereference
189 option causes symlinks to be followed, as the like-named option
190 in ls(1) (on systems that support symbolic links). This is the
191 default if the environment variable POSIXLY_CORRECT is defined.
192 -m, --magic-file magicfiles
194 Specify an alternate list of files and directories containing
195 magic. This can be a single item, or a colon-separated list. If
196 a compiled magic file is found alongside a file or directory, it
197 will be used instead.
198 -N, --no-pad
200 Don't pad filenames so that they align in the output.
201 -n, --no-buffer
203 Force stdout to be flushed after checking each file. This is
204 only useful if checking a list of files. It is intended to be
205 used by programs that want filetype output from a pipe.
206 -p, --preserve-date
208 On systems that support utime(3) or utimes(2), attempt to pre‐
209 serve the access time of files analyzed, to pretend that file
210 never read them.
211 -P, --parameter name=value
213 Set various parameter limits.
214 Name Default Explanation
216 indir 15 recursion limit for indirect magic
217 name 30 use count limit for name/use magic
218 elf_notes 256 max ELF notes processed
219 elf_phnum 128 max ELF program sections processed
220 elf_shnum 32768 max ELF sections processed
221 regex 8192 length limit for regex searches
222 bytes 1048576 max number of bytes to read from
223 file
224 -r, --raw
226 Don't translate unprintable characters to \ooo. Normally file
227 translates unprintable characters to their octal representation.
228 -s, --special-files
230 Normally, file only attempts to read and determine the type of
231 argument files which stat(2) reports are ordinary files. This
232 prevents problems, because reading special files may have pecu‐
233 liar consequences. Specifying the -s option causes file to also
234 read argument files which are block or character special files.
235 This is useful for determining the filesystem types of the data
236 in raw disk partitions, which are block special files. This
237 option also causes file to disregard the file size as reported by
238 stat(2) since on some systems it reports a zero size for raw disk
239 partitions.
240 -S, --no-sandbox
242 On systems where libseccomp
243 (https://github.com/seccomp/libseccomp) is available, the -S flag
244 disables sandboxing which is enabled by default. This option is
245 needed for file to execute external descompressing programs, i.e.
246 when the -z flag is specified and the built-in decompressors are
247 not available.
248 -v, --version
250 Print the version of the program and exit.
251 -z, --uncompress
253 Try to look inside compressed files.
254 -Z, --uncompress-noreport
256 Try to look inside compressed files, but report information about
257 the contents only not the compression.
258 -0, --print0
260 Output a null character ‘\0’ after the end of the filename. Nice
261 to cut(1) the output. This does not affect the separator, which
262 is still printed.
263 If this option is repeated more than once, then file prints just
265 the filename followed by a NUL followed by the description (or
266 ERROR: text) followed by a second NUL for each entry.
267 --help Print a help message and exit.
269
271 The environment variable MAGIC can be used to set the default magic file
272 name. If that variable is set, then file will not attempt to open
273 $HOME/.magic. file adds “.mgc” to the value of this variable as appro‐
274 priate. The environment variable POSIXLY_CORRECT controls (on systems
275 that support symbolic links), whether file will attempt to follow sym‐
276 links or not. If set, then file follows symlink, otherwise it does not.
277 This is also controlled by the -L and -h options.
278
280 /usr/share/misc/magic.mgc Default compiled list of magic.
281 /usr/share/misc/magic Directory containing default magic files.
282
284 file will exit with 0 if the operation was successful or >0 if an error
285 was encountered. The following errors cause diagnostic messages, but
286 don't affect the program exit code (as POSIX requires), unless -E is
287 specified:
288 · A file cannot be found
289 · There is no permission to read a file
290 · The file type cannot be determined
291
293 $ file file.c file /dev/{wd0a,hda}
294 file.c: C program text
295 file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV),
296 dynamically linked (uses shared libs), stripped
297 /dev/wd0a: block special (0/0)
298 /dev/hda: block special (3/0)
299 $ file -s /dev/wd0{b,d}
301 /dev/wd0b: data
302 /dev/wd0d: x86 boot sector
303 $ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10}
305 /dev/hda: x86 boot sector
306 /dev/hda1: Linux/i386 ext2 filesystem
307 /dev/hda2: x86 boot sector
308 /dev/hda3: x86 boot sector, extended partition table
309 /dev/hda4: Linux/i386 ext2 filesystem
310 /dev/hda5: Linux/i386 swap file
311 /dev/hda6: Linux/i386 swap file
312 /dev/hda7: Linux/i386 swap file
313 /dev/hda8: Linux/i386 swap file
314 /dev/hda9: empty
315 /dev/hda10: empty
316 $ file -i file.c file /dev/{wd0a,hda}
318 file.c: text/x-c
319 file: application/x-executable
320 /dev/hda: application/x-not-regular-file
321 /dev/wd0a: application/x-not-regular-file
322
325 hexdump(1), od(1), strings(1), magic(5)
326
328 This program is believed to exceed the System V Interface Definition of
329 FILE(CMD), as near as one can determine from the vague language contained
330 therein. Its behavior is mostly compatible with the System V program of
331 the same name. This version knows more magic, however, so it will pro‐
332 duce different (albeit more accurate) output in many cases.
333 The one significant difference between this version and System V is that
335 this version treats any white space as a delimiter, so that spaces in
336 pattern strings must be escaped. For example,
337 >10 string language impress (imPRESS data)
339 in an existing magic file would have to be changed to
341 >10 string language\ impress (imPRESS data)
343 In addition, in this version, if a pattern string contains a backslash,
345 it must be escaped. For example
346 0 string \begindata Andrew Toolkit document
348 in an existing magic file would have to be changed to
350 0 string \\begindata Andrew Toolkit document
352 SunOS releases 3.2 and later from Sun Microsystems include a file command
354 derived from the System V one, but with some extensions. This version
355 differs from Sun's only in minor ways. It includes the extension of the
356 ‘&’ operator, used as, for example,
357 >16 long&0x7fffffff >0 not stripped
359
361 On systems where libseccomp (https://github.com/seccomp/libseccomp) is
362 available, file is enforces limiting system calls to only the ones neces‐
363 sary for the operation of the program. This enforcement does not provide
364 any security benefit when file is asked to decompress input files running
365 external programs with the -z option. To enable execution of external
366 decompressors, one needs to disable sandboxing using the -S flag.
367
369 The magic file entries have been collected from various sources, mainly
370 USENET, and contributed by various authors. Christos Zoulas (address
371 below) will collect additional or corrected magic file entries. A con‐
372 solidation of magic file entries will be distributed periodically.
373 The order of entries in the magic file is significant. Depending on what
375 system you are using, the order that they are put together may be incor‐
376 rect. If your old file command uses a magic file, keep the old magic
377 file around for comparison purposes (rename it to
378 /usr/share/misc/magic.orig).
379
381 There has been a file command in every UNIX since at least Research
382 Version 4 (man page dated November, 1973). The System V version intro‐
383 duced one significant major change: the external list of magic types.
384 This slowed the program down slightly but made it a lot more flexible.
385 This program, based on the System V version, was written by Ian Darwin
387 ⟨ian@darwinsys.com⟩ without looking at anybody else's source code.
388 John Gilmore revised the code extensively, making it better than the
390 first version. Geoff Collyer found several inadequacies and provided
391 some magic file entries. Contributions of the ‘&’ operator by Rob McMa‐
392 hon, ⟨cudcv@warwick.ac.uk⟩, 1989.
393 Guy Harris, ⟨guy@netapp.com⟩, made many changes from 1993 to the present.
395 Primary development and maintenance from 1990 to the present by Christos
397 Zoulas ⟨christos@astron.com⟩.
398 Altered by Chris Lowth ⟨chris@lowth.com⟩, 2000: handle the -i option to
400 output mime type strings, using an alternative magic file and internal
401 logic.
402 Altered by Eric Fischer ⟨enf@pobox.com⟩, July, 2000, to identify charac‐
404 ter codes and attempt to identify the languages of non-ASCII files.
405 Altered by Reuben Thomas ⟨rrt@sc3d.org⟩, 2007-2011, to improve MIME sup‐
407 port, merge MIME and non-MIME magic, support directories as well as files
408 of magic, apply many bug fixes, update and fix a lot of magic, improve
409 the build system, improve the documentation, and rewrite the Python bind‐
410 ings in pure Python.
411 The list of contributors to the ‘magic’ directory (magic files) is too
413 long to include here. You know who you are; thank you. Many contribu‐
414 tors are listed in the source files.
415
417 Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. Covered by the
418 standard Berkeley Software Distribution copyright; see the file COPYING
419 in the source distribution.
420 The files tar.h and is_tar.c were written by John Gilmore from his pub‐
422 lic-domain tar(1) program, and are not covered by the above license.
423
425 Please report bugs and send patches to the bug tracker at
426 https://bugs.astron.com/ or the mailing list at ⟨file@astron.com⟩ (visit
427 https://mailman.astron.com/mailman/listinfo/file first to subscribe).
428
430 Fix output so that tests for MIME and APPLE flags are not needed all over
431 the place, and actual output is only done in one place. This needs a
432 design. Suggestion: push possible outputs on to a list, then pick the
433 last-pushed (most specific, one hopes) value at the end, or use a default
434 if the list is empty. This should not slow down evaluation.
435 The handling of MAGIC_CONTINUE and printing \012- between entries is
437 clumsy and complicated; refactor and centralize.
438 Some of the encoding logic is hard-coded in encoding.c and can be moved
440 to the magic files if we had a !:charset annotation
441 Continue to squash all magic bugs. See Debian BTS for a good source.
443 Store arbitrarily long strings, for example for %s patterns, so that they
445 can be printed out. Fixes Debian bug #271672. This can be done by allo‐
446 cating strings in a string pool, storing the string pool at the end of
447 the magic file and converting all the string pointers to relative offsets
448 from the string pool.
449 Add syntax for relative offsets after current level (Debian bug #466037).
451 Make file -ki work, i.e. give multiple MIME types.
453 Add a zip library so we can peek inside Office2007 documents to print
455 more details about their contents.
456 Add an option to print URLs for the sources of the file descriptions.
458 Combine script searches and add a way to map executable names to MIME
460 types (e.g. have a magic value for !:mime which causes the resulting
461 string to be looked up in a table). This would avoid adding the same
462 magic repeatedly for each new hash-bang interpreter.
463 When a file descriptor is available, we can skip and adjust the buffer
465 instead of the hacky buffer management we do now.
466 Fix “name” and “use” to check for consistency at compile time (duplicate
468 “name”, “use” pointing to undefined “name” ). Make “name” / “use” more
469 efficient by keeping a sorted list of names. Special-case ^ to flip
470 endianness in the parser so that it does not have to be escaped, and doc‐
471 ument it.
472 If the offsets specified internally in the file exceed the buffer size (
474 HOWMANY variable in file.h), then we don't seek to that offset, but we
475 give up. It would be better if buffer managements was done when the file
476 descriptor is available so move around the file. One must be careful
477 though because this has performance (and thus security considerations).
478
480 You can obtain the original author's latest version by anonymous FTP on
481 ftp.astron.com in the directory /pub/file/file-X.YZ.tar.gz.
482BSD February 18, 2019 BSD