1FILE(1) BSD General Commands Manual FILE(1)
2
4 file — determine file type
5
7 file [-bchiklLNnprsvz0] [--apple] [--mime-encoding] [--mime-type]
8 [-e testname] [-F separator] [-f namefile] [-m magicfiles] file ...
9 file -C [-m magicfiles]
10 file [--help]
11
13 This manual page documents version 5.11 of the file command.
14 file tests each argument in an attempt to classify it. There are three
16 sets of tests, performed in this order: filesystem tests, magic tests,
17 and language tests. The first test that succeeds causes the file type to
18 be printed.
19 The type printed will usually contain one of the words text (the file
21 contains only printing characters and a few common control characters and
22 is probably safe to read on an ASCII terminal), executable (the file con‐
23 tains the result of compiling a program in a form understandable to some
24 UNIX kernel or another), or data meaning anything else (data is usually
25 “binary” or non-printable). Exceptions are well-known file formats (core
26 files, tar archives) that are known to contain binary data. When modify‐
27 ing magic files or the program itself, make sure to preserve these
28 keywords. Users depend on knowing that all the readable files in a
29 directory have the word “text” printed. Don't do as Berkeley did and
30 change “shell commands text” to “shell script”.
31 The filesystem tests are based on examining the return from a stat(2)
33 system call. The program checks to see if the file is empty, or if it's
34 some sort of special file. Any known file types appropriate to the sys‐
35 tem you are running on (sockets, symbolic links, or named pipes (FIFOs)
36 on those systems that implement them) are intuited if they are defined in
37 the system header file <sys/stat.h>.
38 The magic tests are used to check for files with data in particular fixed
40 formats. The canonical example of this is a binary executable (compiled
41 program) a.out file, whose format is defined in <elf.h>, <a.out.h> and
42 possibly <exec.h> in the standard include directory. These files have a
43 “magic number” stored in a particular place near the beginning of the
44 file that tells the UNIX operating system that the file is a binary exe‐
45 cutable, and which of several types thereof. The concept of a “magic”
46 has been applied by extension to data files. Any file with some invari‐
47 ant identifier at a small fixed offset into the file can usually be
48 described in this way. The information identifying these files is read
49 from the compiled magic file /usr/share/misc/magic.mgc, or the files in
50 the directory /usr/share/misc/magic if the compiled file does not exist.
51 In addition, if $HOME/.magic.mgc or $HOME/.magic exists, it will be used
52 in preference to the system magic files.
53 If a file does not match any of the entries in the magic file, it is
55 examined to see if it seems to be a text file. ASCII, ISO-8859-x, non-
56 ISO 8-bit extended-ASCII character sets (such as those used on Macintosh
57 and IBM PC systems), UTF-8-encoded Unicode, UTF-16-encoded Unicode, and
58 EBCDIC character sets can be distinguished by the different ranges and
59 sequences of bytes that constitute printable text in each set. If a file
60 passes any of these tests, its character set is reported. ASCII,
61 ISO-8859-x, UTF-8, and extended-ASCII files are identified as “text”
62 because they will be mostly readable on nearly any terminal; UTF-16 and
63 EBCDIC are only “character data” because, while they contain text, it is
64 text that will require translation before it can be read. In addition,
65 file will attempt to determine other characteristics of text-type files.
66 If the lines of a file are terminated by CR, CRLF, or NEL, instead of the
67 Unix-standard LF, this will be reported. Files that contain embedded
68 escape sequences or overstriking will also be identified.
69 Once file has determined the character set used in a text-type file, it
71 will attempt to determine in what language the file is written. The lan‐
72 guage tests look for particular strings (cf. <names.h>) that can appear
73 anywhere in the first few blocks of a file. For example, the keyword .br
74 indicates that the file is most likely a troff(1) input file, just as the
75 keyword struct indicates a C program. These tests are less reliable than
76 the previous two groups, so they are performed last. The language test
77 routines also test for some miscellany (such as tar(1) archives).
78 Any file that cannot be identified as having been written in any of the
80 character sets listed above is simply said to be “data”.
81
83 -b, --brief
84 Do not prepend filenames to output lines (brief mode).
85 -C, --compile
87 Write a magic.mgc output file that contains a pre-parsed version
88 of the magic file or directory.
89 -c, --checking-printout
91 Cause a checking printout of the parsed form of the magic file.
92 This is usually used in conjunction with the -m flag to debug a
93 new magic file before installing it.
94 -e, --exclude testname
96 Exclude the test named in testname from the list of tests made to
97 determine the file type. Valid test names are:
98 apptype EMX application type (only on EMX).
100 ascii Various types of text files (this test will try to
102 guess the text encoding, irrespective of the setting of
103 the ‘encoding’ option).
104 encoding Different text encodings for soft magic tests.
106 tokens Ignored for backwards compatibility.
108 cdf Prints details of Compound Document Files.
110 compress Checks for, and looks inside, compressed files.
112 elf Prints ELF file details.
114 soft Consults magic files.
116 tar Examines tar files.
118 -F, --separator separator
120 Use the specified string as the separator between the filename
121 and the file result returned. Defaults to ‘:’.
122 -f, --files-from namefile
124 Read the names of the files to be examined from namefile (one per
125 line) before the argument list. Either namefile or at least one
126 filename argument must be present; to test the standard input,
127 use ‘-’ as a filename argument. Please note that namefile is
128 unwrapped and the enclosed filenames are processed when this
129 option is encountered and before any further options processing
130 is done. This allows one to process multiple lists of files with
131 different command line arguments on the same file invocation.
132 Thus if you want to set the delimiter, you need to do it before
133 you specify the list of files, like: “-F @ -f namefile”, instead
134 of: “-f namefile -F @”.
135 -h, --no-dereference
137 option causes symlinks not to be followed (on systems that sup‐
138 port symbolic links). This is the default if the environment
139 variable POSIXLY_CORRECT is not defined.
140 -i, --mime
142 Causes the file command to output mime type strings rather than
143 the more traditional human readable ones. Thus it may say
144 ‘text/plain; charset=us-ascii’ rather than “ASCII text”.
145 --mime-type, --mime-encoding
147 Like -i, but print only the specified element(s).
148 -k, --keep-going
150 Don't stop at the first match, keep going. Subsequent matches
151 will be have the string ‘\012- ’ prepended. (If you want a new‐
152 line, see the -r option.)
153 -l, --list
155 Print information about the strength of each magic pattern.
156 -L, --dereference
158 option causes symlinks to be followed, as the like-named option
159 in ls(1) (on systems that support symbolic links). This is the
160 default if the environment variable POSIXLY_CORRECT is defined.
161 -l Shows sorted patterns list in the order which is used for the
163 matching.
164 -m, --magic-file magicfiles
166 Specify an alternate list of files and directories containing
167 magic. This can be a single item, or a colon-separated list. If
168 a compiled magic file is found alongside a file or directory, it
169 will be used instead.
170 -N, --no-pad
172 Don't pad filenames so that they align in the output.
173 -n, --no-buffer
175 Force stdout to be flushed after checking each file. This is
176 only useful if checking a list of files. It is intended to be
177 used by programs that want filetype output from a pipe.
178 -p, --preserve-date
180 On systems that support utime(3) or utimes(2), attempt to pre‐
181 serve the access time of files analyzed, to pretend that file
182 never read them.
183 -r, --raw
185 Don't translate unprintable characters to \ooo. Normally file
186 translates unprintable characters to their octal representation.
187 -s, --special-files
189 Normally, file only attempts to read and determine the type of
190 argument files which stat(2) reports are ordinary files. This
191 prevents problems, because reading special files may have pecu‐
192 liar consequences. Specifying the -s option causes file to also
193 read argument files which are block or character special files.
194 This is useful for determining the filesystem types of the data
195 in raw disk partitions, which are block special files. This
196 option also causes file to disregard the file size as reported by
197 stat(2) since on some systems it reports a zero size for raw disk
198 partitions.
199 -v, --version
201 Print the version of the program and exit.
202 -z, --uncompress
204 Try to look inside compressed files.
205 -0, --print0
207 Output a null character ‘\0’ after the end of the filename. Nice
208 to cut(1) the output. This does not affect the separator which
209 is still printed.
210 --help Print a help message and exit.
212
214 /usr/share/misc/magic.mgc Default compiled list of magic.
215 /usr/share/misc/magic Directory containing default magic files.
216
218 The environment variable MAGIC can be used to set the default magic file
219 name. If that variable is set, then file will not attempt to open
220 $HOME/.magic. file adds “.mgc” to the value of this variable as appro‐
221 priate. However, file has to exist in order for file.mime to be consid‐
222 ered. The environment variable POSIXLY_CORRECT controls (on systems that
223 support symbolic links), whether file will attempt to follow symlinks or
224 not. If set, then file follows symlink, otherwise it does not. This is
225 also controlled by the -L and -h options.
226
228 magic(5), hexdump(1), od(1), strings(1),
229
231 This program is believed to exceed the System V Interface Definition of
232 FILE(CMD), as near as one can determine from the vague language contained
233 therein. Its behavior is mostly compatible with the System V program of
234 the same name. This version knows more magic, however, so it will pro‐
235 duce different (albeit more accurate) output in many cases.
236 The one significant difference between this version and System V is that
238 this version treats any white space as a delimiter, so that spaces in
239 pattern strings must be escaped. For example,
240 >10 string language impress (imPRESS data)
242 in an existing magic file would have to be changed to
244 >10 string language\ impress (imPRESS data)
246 In addition, in this version, if a pattern string contains a backslash,
248 it must be escaped. For example
249 0 string \begindata Andrew Toolkit document
251 in an existing magic file would have to be changed to
253 0 string \\begindata Andrew Toolkit document
255 SunOS releases 3.2 and later from Sun Microsystems include a file command
257 derived from the System V one, but with some extensions. This version
258 differs from Sun's only in minor ways. It includes the extension of the
259 ‘&’ operator, used as, for example,
260 >16 long&0x7fffffff >0 not stripped
262
264 The magic file entries have been collected from various sources, mainly
265 USENET, and contributed by various authors. Christos Zoulas (address
266 below) will collect additional or corrected magic file entries. A con‐
267 solidation of magic file entries will be distributed periodically.
268 The order of entries in the magic file is significant. Depending on what
270 system you are using, the order that they are put together may be incor‐
271 rect. If your old file command uses a magic file, keep the old magic
272 file around for comparison purposes (rename it to
273 /usr/share/misc/magic.orig).
274
276 $ file file.c file /dev/{wd0a,hda}
277 file.c: C program text
278 file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV),
279 dynamically linked (uses shared libs), stripped
280 /dev/wd0a: block special (0/0)
281 /dev/hda: block special (3/0)
282 $ file -s /dev/wd0{b,d}
284 /dev/wd0b: data
285 /dev/wd0d: x86 boot sector
286 $ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10}
288 /dev/hda: x86 boot sector
289 /dev/hda1: Linux/i386 ext2 filesystem
290 /dev/hda2: x86 boot sector
291 /dev/hda3: x86 boot sector, extended partition table
292 /dev/hda4: Linux/i386 ext2 filesystem
293 /dev/hda5: Linux/i386 swap file
294 /dev/hda6: Linux/i386 swap file
295 /dev/hda7: Linux/i386 swap file
296 /dev/hda8: Linux/i386 swap file
297 /dev/hda9: empty
298 /dev/hda10: empty
299 $ file -i file.c file /dev/{wd0a,hda}
301 file.c: text/x-c
302 file: application/x-executable
303 /dev/hda: application/x-not-regular-file
304 /dev/wd0a: application/x-not-regular-file
305
308 There has been a file command in every UNIX since at least Research
309 Version 4 (man page dated November, 1973). The System V version intro‐
310 duced one significant major change: the external list of magic types.
311 This slowed the program down slightly but made it a lot more flexible.
312 This program, based on the System V version, was written by Ian Darwin
314 ⟨ian@darwinsys.com⟩ without looking at anybody else's source code.
315 John Gilmore revised the code extensively, making it better than the
317 first version. Geoff Collyer found several inadequacies and provided
318 some magic file entries. Contributions by the ‘&’ operator by Rob McMa‐
319 hon, ⟨cudcv@warwick.ac.uk⟩, 1989.
320 Guy Harris, ⟨guy@netapp.com⟩, made many changes from 1993 to the present.
322 1989.
323 Primary development and maintenance from 1990 to the present by Christos
325 Zoulas ⟨christos@astron.com⟩.
326 Altered by Chris Lowth ⟨chris@lowth.com⟩, 2000: handle the -i option to
328 output mime type strings, using an alternative magic file and internal
329 logic.
330 Altered by Eric Fischer ⟨enf@pobox.com⟩, July, 2000, to identify charac‐
332 ter codes and attempt to identify the languages of non-ASCII files.
333 Altered by Reuben Thomas ⟨rrt@sc3d.org⟩, 2007-2011, to improve MIME sup‐
335 port, merge MIME and non-MIME magic, support directories as well as files
336 of magic, apply many bug fixes, update and fix a lot of magic, improve
337 the build system, improve the documentation, and rewrite the Python bind‐
338 ings in pure Python.
339 The list of contributors to the ‘magic’ directory (magic files) is too
341 long to include here. You know who you are; thank you. Many contribu‐
342 tors are listed in the source files.
343
345 Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. Covered by the
346 standard Berkeley Software Distribution copyright; see the file COPYING
347 in the source distribution.
348 The files tar.h and is_tar.c were written by John Gilmore from his pub‐
350 lic-domain tar(1) program, and are not covered by the above license.
351
353 file returns 0 on success, and non-zero on error.
354 If the file named by the file operand does not exist, cannot be read, or
356 the type of the file named by the file operand cannot be determined, this
357 is not be considered an error that affects the exit status.
358
360 Please report bugs and send patches to the bug tracker at
361 http://bugs.gw.com/ or the mailing list at ⟨file@mx.gw.com⟩.
362
364 Fix output so that tests for MIME and APPLE flags are not needed all over
365 the place, and actual output is only done in one place. This needs a
366 design. Suggestion: push possible outputs on to a list, then pick the
367 last-pushed (most specific, one hopes) value at the end, or use a default
368 if the list is empty. This should not slow down evaluation.
369 Continue to squash all magic bugs. See Debian BTS for a good source.
371 Store arbitrarily long strings, for example for %s patterns, so that they
373 can be printed out. Fixes Debian bug #271672. Would require more complex
374 store/load code in apprentice.
375 Add syntax for relative offsets after current level (Debian bug #466037).
377 Make file -ki work, i.e. give multiple MIME types.
379 Add a zip library so we can peek inside Office2007 documents to figure
381 out what they are.
382 Add an option to print URLs for the sources of the file descriptions.
384
386 You can obtain the original author's latest version by anonymous FTP on
387 ftp.astron.com in the directory /pub/file/file-X.YZ.tar.gz.
388BSD October 17, 2011 BSD