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 5.34 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).
79 Any file that cannot be identified as having been written in any of the
81 character sets listed above is simply said to be “data”.
82
84 --apple
85 Causes the file command to output the file type and creator code
86 as used by older MacOS versions. The code consists of eight let‐
87 ters, the first describing the file type, the latter the creator.
88 -b, --brief
90 Do not prepend filenames to output lines (brief mode).
91 -C, --compile
93 Write a magic.mgc output file that contains a pre-parsed version
94 of the magic file or directory.
95 -c, --checking-printout
97 Cause a checking printout of the parsed form of the magic file.
98 This is usually used in conjunction with the -m flag to debug a
99 new magic file before installing it.
100 -d Prints internal debugging information to stderr.
102 -E On filesystem errors (file not found etc), instead of handling
104 the error as regular output as POSIX mandates and keep going,
105 issue an error message and exit.
106 -e, --exclude testname
108 Exclude the test named in testname from the list of tests made to
109 determine the file type. Valid test names are:
110 apptype EMX application type (only on EMX).
112 ascii Various types of text files (this test will try to
114 guess the text encoding, irrespective of the setting of
115 the ‘encoding’ option).
116 encoding Different text encodings for soft magic tests.
118 tokens Ignored for backwards compatibility.
120 cdf Prints details of Compound Document Files.
122 compress Checks for, and looks inside, compressed files.
124 elf Prints ELF file details, provided soft magic tests are
126 enabled and the elf magic is found.
127 soft Consults magic files.
129 tar Examines tar files by verifying the checksum of the 512
131 byte tar header. Excluding this test can provide more
132 detailed content description by using the soft magic
133 method.
134 text A synonym for ‘ascii’.
136 --extension
138 Print a slash-separated list of valid extensions for the file
139 type found.
140 -F, --separator separator
142 Use the specified string as the separator between the filename
143 and the file result returned. Defaults to ‘:’.
144 -f, --files-from namefile
146 Read the names of the files to be examined from namefile (one per
147 line) before the argument list. Either namefile or at least one
148 filename argument must be present; to test the standard input,
149 use ‘-’ as a filename argument. Please note that namefile is
150 unwrapped and the enclosed filenames are processed when this
151 option is encountered and before any further options processing
152 is done. This allows one to process multiple lists of files with
153 different command line arguments on the same file invocation.
154 Thus if you want to set the delimiter, you need to do it before
155 you specify the list of files, like: “-F @ -f namefile”, instead
156 of: “-f namefile -F @”.
157 -h, --no-dereference
159 option causes symlinks not to be followed (on systems that sup‐
160 port symbolic links). This is the default if the environment
161 variable POSIXLY_CORRECT is not defined.
162 -i, --mime
164 Causes the file command to output mime type strings rather than
165 the more traditional human readable ones. Thus it may say
166 ‘text/plain; charset=us-ascii’ rather than “ASCII text”.
167 --mime-type, --mime-encoding
169 Like -i, but print only the specified element(s).
170 -k, --keep-going
172 Don't stop at the first match, keep going. Subsequent matches
173 will be have the string ‘\012- ’ prepended. (If you want a new‐
174 line, see the -r option.) The magic pattern with the highest
175 strength (see the -l option) comes first.
176 -l, --list
178 Shows a list of patterns and their strength sorted descending by
179 magic(4) strength which is used for the matching (see also the -k
180 option).
181 -L, --dereference
183 option causes symlinks to be followed, as the like-named option
184 in ls(1) (on systems that support symbolic links). This is the
185 default if the environment variable POSIXLY_CORRECT is defined.
186 -m, --magic-file magicfiles
188 Specify an alternate list of files and directories containing
189 magic. This can be a single item, or a colon-separated list. If
190 a compiled magic file is found alongside a file or directory, it
191 will be used instead.
192 -N, --no-pad
194 Don't pad filenames so that they align in the output.
195 -n, --no-buffer
197 Force stdout to be flushed after checking each file. This is
198 only useful if checking a list of files. It is intended to be
199 used by programs that want filetype output from a pipe.
200 -p, --preserve-date
202 On systems that support utime(3) or utimes(2), attempt to pre‐
203 serve the access time of files analyzed, to pretend that file
204 never read them.
205 -P, --parameter name=value
207 Set various parameter limits.
208 Name Default Explanation
210 indir 15 recursion limit for indirect magic
211 name 30 use count limit for name/use magic
212 elf_notes 256 max ELF notes processed
213 elf_phnum 128 max ELF program sections processed
214 elf_shnum 32768 max ELF sections processed
215 regex 8192 length limit for regex searches
216 bytes 1048576 max number of bytes to read from
217 file
218 -r, --raw
220 Don't translate unprintable characters to \ooo. Normally file
221 translates unprintable characters to their octal representation.
222 -s, --special-files
224 Normally, file only attempts to read and determine the type of
225 argument files which stat(2) reports are ordinary files. This
226 prevents problems, because reading special files may have pecu‐
227 liar consequences. Specifying the -s option causes file to also
228 read argument files which are block or character special files.
229 This is useful for determining the filesystem types of the data
230 in raw disk partitions, which are block special files. This
231 option also causes file to disregard the file size as reported by
232 stat(2) since on some systems it reports a zero size for raw disk
233 partitions.
234 -S, --no-sandbox
236 On systems where libseccomp
237 (https://github.com/seccomp/libseccomp) is available, the -S flag
238 disables sandboxing which is enabled by default. This option is
239 needed for file to execute external descompressing programs, i.e.
240 when the -z flag is specified and the built-in decompressors are
241 not available.
242 -v, --version
244 Print the version of the program and exit.
245 -z, --uncompress
247 Try to look inside compressed files.
248 -Z, --uncompress-noreport
250 Try to look inside compressed files, but report information about
251 the contents only not the compression.
252 -0, --print0
254 Output a null character ‘\0’ after the end of the filename. Nice
255 to cut(1) the output. This does not affect the separator, which
256 is still printed.
257 If this option is repeated more than once, then file prints just
259 the filename followed by a NUL followed by the description (or
260 ERROR: text) followed by a second NUL for each entry.
261 --help Print a help message and exit.
263
265 The environment variable MAGIC can be used to set the default magic file
266 name. If that variable is set, then file will not attempt to open
267 $HOME/.magic. file adds “.mgc” to the value of this variable as appro‐
268 priate. The environment variable POSIXLY_CORRECT controls (on systems
269 that support symbolic links), whether file will attempt to follow sym‐
270 links or not. If set, then file follows symlink, otherwise it does not.
271 This is also controlled by the -L and -h options.
272
274 /usr/share/misc/magic.mgc Default compiled list of magic.
275 /usr/share/misc/magic Directory containing default magic files.
276
278 file will exit with 0 if the operation was successful or >0 if an error
279 was encountered. The following errors cause diagnostic messages, but
280 don't affect the program exit code (as POSIX requires), unless -E is
281 specified:
282 · A file cannot be found
283 · There is no permission to read a file
284 · The file type cannot be determined
285
287 $ file file.c file /dev/{wd0a,hda}
288 file.c: C program text
289 file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV),
290 dynamically linked (uses shared libs), stripped
291 /dev/wd0a: block special (0/0)
292 /dev/hda: block special (3/0)
293 $ file -s /dev/wd0{b,d}
295 /dev/wd0b: data
296 /dev/wd0d: x86 boot sector
297 $ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10}
299 /dev/hda: x86 boot sector
300 /dev/hda1: Linux/i386 ext2 filesystem
301 /dev/hda2: x86 boot sector
302 /dev/hda3: x86 boot sector, extended partition table
303 /dev/hda4: Linux/i386 ext2 filesystem
304 /dev/hda5: Linux/i386 swap file
305 /dev/hda6: Linux/i386 swap file
306 /dev/hda7: Linux/i386 swap file
307 /dev/hda8: Linux/i386 swap file
308 /dev/hda9: empty
309 /dev/hda10: empty
310 $ file -i file.c file /dev/{wd0a,hda}
312 file.c: text/x-c
313 file: application/x-executable
314 /dev/hda: application/x-not-regular-file
315 /dev/wd0a: application/x-not-regular-file
316
319 hexdump(1), od(1), strings(1), magic(5)
320
322 This program is believed to exceed the System V Interface Definition of
323 FILE(CMD), as near as one can determine from the vague language contained
324 therein. Its behavior is mostly compatible with the System V program of
325 the same name. This version knows more magic, however, so it will pro‐
326 duce different (albeit more accurate) output in many cases.
327 The one significant difference between this version and System V is that
329 this version treats any white space as a delimiter, so that spaces in
330 pattern strings must be escaped. For example,
331 >10 string language impress (imPRESS data)
333 in an existing magic file would have to be changed to
335 >10 string language\ impress (imPRESS data)
337 In addition, in this version, if a pattern string contains a backslash,
339 it must be escaped. For example
340 0 string \begindata Andrew Toolkit document
342 in an existing magic file would have to be changed to
344 0 string \\begindata Andrew Toolkit document
346 SunOS releases 3.2 and later from Sun Microsystems include a file command
348 derived from the System V one, but with some extensions. This version
349 differs from Sun's only in minor ways. It includes the extension of the
350 ‘&’ operator, used as, for example,
351 >16 long&0x7fffffff >0 not stripped
353
355 On systems where libseccomp (https://github.com/seccomp/libseccomp) is
356 available, file is enforces limiting system calls to only the ones neces‐
357 sary for the operation of the program. This enforcement does not provide
358 any security benefit when file is asked to decompress input files running
359 external programs with the -z option. To enable execution of external
360 decompressors, one needs to disable sandboxing using the -S flag.
361
363 The magic file entries have been collected from various sources, mainly
364 USENET, and contributed by various authors. Christos Zoulas (address
365 below) will collect additional or corrected magic file entries. A con‐
366 solidation of magic file entries will be distributed periodically.
367 The order of entries in the magic file is significant. Depending on what
369 system you are using, the order that they are put together may be incor‐
370 rect. If your old file command uses a magic file, keep the old magic
371 file around for comparison purposes (rename it to
372 /usr/share/misc/magic.orig).
373
375 There has been a file command in every UNIX since at least Research
376 Version 4 (man page dated November, 1973). The System V version intro‐
377 duced one significant major change: the external list of magic types.
378 This slowed the program down slightly but made it a lot more flexible.
379 This program, based on the System V version, was written by Ian Darwin
381 ⟨ian@darwinsys.com⟩ without looking at anybody else's source code.
382 John Gilmore revised the code extensively, making it better than the
384 first version. Geoff Collyer found several inadequacies and provided
385 some magic file entries. Contributions of the ‘&’ operator by Rob McMa‐
386 hon, ⟨cudcv@warwick.ac.uk⟩, 1989.
387 Guy Harris, ⟨guy@netapp.com⟩, made many changes from 1993 to the present.
389 Primary development and maintenance from 1990 to the present by Christos
391 Zoulas ⟨christos@astron.com⟩.
392 Altered by Chris Lowth ⟨chris@lowth.com⟩, 2000: handle the -i option to
394 output mime type strings, using an alternative magic file and internal
395 logic.
396 Altered by Eric Fischer ⟨enf@pobox.com⟩, July, 2000, to identify charac‐
398 ter codes and attempt to identify the languages of non-ASCII files.
399 Altered by Reuben Thomas ⟨rrt@sc3d.org⟩, 2007-2011, to improve MIME sup‐
401 port, merge MIME and non-MIME magic, support directories as well as files
402 of magic, apply many bug fixes, update and fix a lot of magic, improve
403 the build system, improve the documentation, and rewrite the Python bind‐
404 ings in pure Python.
405 The list of contributors to the ‘magic’ directory (magic files) is too
407 long to include here. You know who you are; thank you. Many contribu‐
408 tors are listed in the source files.
409
411 Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. Covered by the
412 standard Berkeley Software Distribution copyright; see the file COPYING
413 in the source distribution.
414 The files tar.h and is_tar.c were written by John Gilmore from his pub‐
416 lic-domain tar(1) program, and are not covered by the above license.
417
419 Please report bugs and send patches to the bug tracker at
420 http://bugs.astron.com/ or the mailing list at ⟨file@astron.com⟩ (visit
421 http://mailman.astron.com/mailman/listinfo/file first to subscribe).
422
424 Fix output so that tests for MIME and APPLE flags are not needed all over
425 the place, and actual output is only done in one place. This needs a
426 design. Suggestion: push possible outputs on to a list, then pick the
427 last-pushed (most specific, one hopes) value at the end, or use a default
428 if the list is empty. This should not slow down evaluation.
429 The handling of MAGIC_CONTINUE and printing \012- between entries is
431 clumsy and complicated; refactor and centralize.
432 Some of the encoding logic is hard-coded in encoding.c and can be moved
434 to the magic files if we had a !:charset annotation
435 Continue to squash all magic bugs. See Debian BTS for a good source.
437 Store arbitrarily long strings, for example for %s patterns, so that they
439 can be printed out. Fixes Debian bug #271672. This can be done by allo‐
440 cating strings in a string pool, storing the string pool at the end of
441 the magic file and converting all the string pointers to relative offsets
442 from the string pool.
443 Add syntax for relative offsets after current level (Debian bug #466037).
445 Make file -ki work, i.e. give multiple MIME types.
447 Add a zip library so we can peek inside Office2007 documents to print
449 more details about their contents.
450 Add an option to print URLs for the sources of the file descriptions.
452 Combine script searches and add a way to map executable names to MIME
454 types (e.g. have a magic value for !:mime which causes the resulting
455 string to be looked up in a table). This would avoid adding the same
456 magic repeatedly for each new hash-bang interpreter.
457 When a file descriptor is available, we can skip and adjust the buffer
459 instead of the hacky buffer management we do now.
460 Fix “name” and “use” to check for consistency at compile time (duplicate
462 “name”, “use” pointing to undefined “name” ). Make “name” / “use” more
463 efficient by keeping a sorted list of names. Special-case ^ to flip
464 endianness in the parser so that it does not have to be escaped, and doc‐
465 ument it.
466 If the offsets specified internally in the file exceed the buffer size (
468 HOWMANY variable in file.h), then we don't seek to that offset, but we
469 give up. It would be better if buffer managements was done when the file
470 descriptor is available so move around the file. One must be careful
471 though because this has performance (and thus security considerations).
472
474 You can obtain the original author's latest version by anonymous FTP on
475 ftp.astron.com in the directory /pub/file/file-X.YZ.tar.gz.
476BSD July 25, 2018 BSD