FILE(1) BSD General Commands Manual FILE(1)
NAME
file — determine file type
SYNOPSIS
file [-bchiklLNnprsvz0] [--apple] [--mime-encoding] [--mime-type] [-e testname] [-F separator] [-f namefile] [-m magicfiles]
file ...
file -C [-m magicfiles]
file [--help]
DESCRIPTION
This manual page documents version 5.11 of the file command.
file tests each argument in an attempt to classify it. There are three sets of tests, performed in this order: filesystem
tests, magic tests, and language tests. The first test that succeeds causes the file type to be printed.
The type printed will usually contain one of the words text (the file contains only printing characters and a few common con‐
trol characters and is probably safe to read on an ASCII terminal), executable (the file contains the result of compiling a
program in a form understandable to some UNIX kernel or another), or data meaning anything else (data is usually “binary” or
non-printable). Exceptions are well-known file formats (core files, tar archives) that are known to contain binary data.
When adding local definitions to /etc/magic, make sure to preserve these keywords. Users depend on knowing that all the
readable files in a directory have the word “text” printed. Don't do as Berkeley did and change “shell commands text” to
“shell script”.
The filesystem tests are based on examining the return from a stat(2) system call. The program checks to see if the file is
empty, or if it's some sort of special file. Any known file types appropriate to the system you are running on (sockets,
symbolic links, or named pipes (FIFOs) on those systems that implement them) are intuited if they are defined in the system
header file .
The magic tests are used to check for files with data in particular fixed formats. The canonical example of this is a binary
executable (compiled program) a.out file, whose format is defined in , and possibly in the standard
include directory. These files have a “magic number” stored in a particular place near the beginning of the file that tells
the UNIX operating system that the file is a binary executable, and which of several types thereof. The concept of a “magic”
has been applied by extension to data files. Any file with some invariant identifier at a small fixed offset into the file
can usually be described in this way. The information identifying these files is read from /etc/magic and the compiled magic
file /usr/share/misc/magic.mgc, or the files in the directory /usr/share/misc/magic if the compiled file does not exist. In
addition, if $HOME/.magic.mgc or $HOME/.magic exists, it will be used in preference to the system magic files.
If a file does not match any of the entries in the magic file, it is examined to see if it seems to be a text file. ASCII,
ISO-8859-x, non-ISO 8-bit extended-ASCII character sets (such as those used on Macintosh and IBM PC systems), UTF-8-encoded
Unicode, UTF-16-encoded Unicode, and EBCDIC character sets can be distinguished by the different ranges and sequences of
bytes that constitute printable text in each set. If a file passes any of these tests, its character set is reported.
ASCII, ISO-8859-x, UTF-8, and extended-ASCII files are identified as “text” because they will be mostly readable on nearly
any terminal; UTF-16 and EBCDIC are only “character data” because, while they contain text, it is text that will require
translation before it can be read. In addition, file will attempt to determine other characteristics of text-type files. If
the lines of a file are terminated by CR, CRLF, or NEL, instead of the Unix-standard LF, this will be reported. Files that
contain embedded escape sequences or overstriking will also be identified.
Once file has determined the character set used in a text-type file, it will attempt to determine in what language the file
is written. The language tests look for particular strings (cf. ) that can appear anywhere in the first few blocks
of a file. For example, the keyword .br indicates that the file is most likely a troff(1) input file, just as the keyword
struct indicates a C program. These tests are less reliable than the previous two groups, so they are performed last. The
language test routines also test for some miscellany (such as tar(1) archives).
Any file that cannot be identified as having been written in any of the character sets listed above is simply said to be
“data”.
OPTIONS
-b, --brief
Do not prepend filenames to output lines (brief mode).
-C, --compile
Write a magic.mgc output file that contains a pre-parsed version of the magic file or directory.
-c, --checking-printout
Cause a checking printout of the parsed form of the magic file. This is usually used in conjunction with the -m flag
to debug a new magic file before installing it.
-e, --exclude testname
Exclude the test named in testname from the list of tests made to determine the file type. Valid test names are:
apptype EMX application type (only on EMX).
ascii Various types of text files (this test will try to guess the text encoding, irrespective of the setting of
the ‘encoding’ option).
encoding Different text encodings for soft magic tests.
tokens Ignored for backwards compatibility.
cdf Prints details of Compound Document Files.
compress Checks for, and looks inside, compressed files.
elf Prints ELF file details.
soft Consults magic files.
tar Examines tar files.
-F, --separator separator
Use the specified string as the separator between the filename and the file result returned. Defaults to ‘:’.
-f, --files-from namefile
Read the names of the files to be examined from namefile (one per line) before the argument list. Either namefile or
at least one filename argument must be present; to test the standard input, use ‘-’ as a filename argument. Please
note that namefile is unwrapped and the enclosed filenames are processed when this option is encountered and before
any further options processing is done. This allows one to process multiple lists of files with different command
line arguments on the same file invocation. Thus if you want to set the delimiter, you need to do it before you
specify the list of files, like: “-F @ -f namefile”, instead of: “-f namefile -F @”.
-h, --no-dereference
option causes symlinks not to be followed (on systems that support symbolic links). This is the default if the envi‐
ronment variable POSIXLY_CORRECT is not defined.
-i, --mime
Causes the file command to output mime type strings rather than the more traditional human readable ones. Thus it
may say ‘text/plain; charset=us-ascii’ rather than “ASCII text”.
--mime-type, --mime-encoding
Like -i, but print only the specified element(s).
-k, --keep-going
Don't stop at the first match, keep going. Subsequent matches will be have the string ‘\012- ’ prepended. (If you
want a newline, see the -r option.)
-l, --list
Print information about the strength of each magic pattern.
-L, --dereference
option causes symlinks to be followed, as the like-named option in ls(1) (on systems that support symbolic links).
This is the default if the environment variable POSIXLY_CORRECT is defined.
-l Shows sorted patterns list in the order which is used for the matching.
-m, --magic-file magicfiles
Specify an alternate list of files and directories containing magic. This can be a single item, or a colon-separated
list. If a compiled magic file is found alongside a file or directory, it will be used instead.
-N, --no-pad
Don't pad filenames so that they align in the output.
-n, --no-buffer
Force stdout to be flushed after checking each file. This is only useful if checking a list of files. It is
intended to be used by programs that want filetype output from a pipe.
-p, --preserve-date
On systems that support utime(3) or utimes(2), attempt to preserve the access time of files analyzed, to pretend that
file never read them.
-r, --raw
Don't translate unprintable characters to \ooo. Normally file translates unprintable characters to their octal rep‐
resentation.
-s, --special-files
Normally, file only attempts to read and determine the type of argument files which stat(2) reports are ordinary
files. This prevents problems, because reading special files may have peculiar consequences. Specifying the -s
option causes file to also read argument files which are block or character special files. This is useful for deter‐
mining the filesystem types of the data in raw disk partitions, which are block special files. This option also
causes file to disregard the file size as reported by stat(2) since on some systems it reports a zero size for raw
disk partitions.
-v, --version
Print the version of the program and exit.
-z, --uncompress
Try to look inside compressed files.
-0, --print0
Output a null character ‘\0’ after the end of the filename. Nice to cut(1) the output. This does not affect the
separator which is still printed.
--help Print a help message and exit.
FILES
/usr/share/misc/magic.mgc Default compiled list of magic.
/usr/share/misc/magic Directory containing default magic files.
ENVIRONMENT
The environment variable MAGIC can be used to set the default magic file name. If that variable is set, then file will not
attempt to open $HOME/.magic. file adds “.mgc” to the value of this variable as appropriate. However, file has to exist in
order for file.mime to be considered. The environment variable POSIXLY_CORRECT controls (on systems that support symbolic
links), whether file will attempt to follow symlinks or not. If set, then file follows symlink, otherwise it does not. This
is also controlled by the -L and -h options.
SEE ALSO
magic(5), hexdump(1), od(1), strings(1),
STANDARDS CONFORMANCE
This program is believed to exceed the System V Interface Definition of FILE(CMD), as near as one can determine from the
vague language contained therein. Its behavior is mostly compatible with the System V program of the same name. This ver‐
sion knows more magic, however, so it will produce different (albeit more accurate) output in many cases.
The one significant difference between this version and System V is that this version treats any white space as a delimiter,
so that spaces in pattern strings must be escaped. For example,
>10 string language impress (imPRESS data)
in an existing magic file would have to be changed to
>10 string language\ impress (imPRESS data)
In addition, in this version, if a pattern string contains a backslash, it must be escaped. For example
0 string \begindata Andrew Toolkit document
in an existing magic file would have to be changed to
0 string \\begindata Andrew Toolkit document
SunOS releases 3.2 and later from Sun Microsystems include a file command derived from the System V one, but with some exten‐
sions. This version differs from Sun's only in minor ways. It includes the extension of the ‘&’ operator, used as, for
example,
>16 long&0x7fffffff >0 not stripped
MAGIC DIRECTORY
The magic file entries have been collected from various sources, mainly USENET, and contributed by various authors. Christos
Zoulas (address below) will collect additional or corrected magic file entries. A consolidation of magic file entries will
be distributed periodically.
The order of entries in the magic file is significant. Depending on what system you are using, the order that they are put
together may be incorrect.
EXAMPLES
$ file file.c file /dev/{wd0a,hda}
file.c: C program text
file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV),
dynamically linked (uses shared libs), stripped
/dev/wd0a: block special (0/0)
/dev/hda: block special (3/0)
$ file -s /dev/wd0{b,d}
/dev/wd0b: data
/dev/wd0d: x86 boot sector
$ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10}
/dev/hda: x86 boot sector
/dev/hda1: Linux/i386 ext2 filesystem
/dev/hda2: x86 boot sector
/dev/hda3: x86 boot sector, extended partition table
/dev/hda4: Linux/i386 ext2 filesystem
/dev/hda5: Linux/i386 swap file
/dev/hda6: Linux/i386 swap file
/dev/hda7: Linux/i386 swap file
/dev/hda8: Linux/i386 swap file
/dev/hda9: empty
/dev/hda10: empty
$ file -i file.c file /dev/{wd0a,hda}
file.c: text/x-c
file: application/x-executable
/dev/hda: application/x-not-regular-file
/dev/wd0a: application/x-not-regular-file
HISTORY
There has been a file command in every UNIX since at least Research Version 4 (man page dated November, 1973). The System V
version introduced one significant major change: the external list of magic types. This slowed the program down slightly but
made it a lot more flexible.
This program, based on the System V version, was written by Ian Darwin ⟨ian@darwinsys.com⟩ without looking at anybody else's
source code.
John Gilmore revised the code extensively, making it better than the first version. Geoff Collyer found several inadequacies
and provided some magic file entries. Contributions by the ‘&’ operator by Rob McMahon, ⟨cudcv@warwick.ac.uk⟩, 1989.
Guy Harris, ⟨guy@netapp.com⟩, made many changes from 1993 to the present. 1989.
Primary development and maintenance from 1990 to the present by Christos Zoulas ⟨christos@astron.com⟩.
Altered by Chris Lowth ⟨chris@lowth.com⟩, 2000: handle the -i option to output mime type strings, using an alternative magic
file and internal logic.
Altered by Eric Fischer ⟨enf@pobox.com⟩, July, 2000, to identify character codes and attempt to identify the languages of
non-ASCII files.
Altered by Reuben Thomas ⟨rrt@sc3d.org⟩, 2007-2011, to improve MIME support, merge MIME and non-MIME magic, support directo‐
ries as well as files of magic, apply many bug fixes, update and fix a lot of magic, improve the build system, improve the
documentation, and rewrite the Python bindings in pure Python.
The list of contributors to the ‘magic’ directory (magic files) is too long to include here. You know who you are; thank
you. Many contributors are listed in the source files.
LEGAL NOTICE
Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. Covered by the standard Berkeley Software Distribution copyright;
see the file COPYING in the source distribution.
The files tar.h and is_tar.c were written by John Gilmore from his public-domain tar(1) program, and are not covered by the
above license.
RETURN CODE
file returns 0 on success, and non-zero on error.
BUGS
Please report bugs and send patches to the bug tracker at http://bugs.gw.com/ or the mailing list at ⟨file@mx.gw.com⟩.
TODO
Fix output so that tests for MIME and APPLE flags are not needed all over the place, and actual output is only done in one
place. This needs a design. Suggestion: push possible outputs on to a list, then pick the last-pushed (most specific, one
hopes) value at the end, or use a default if the list is empty. This should not slow down evaluation.
Continue to squash all magic bugs. See Debian BTS for a good source.
Store arbitrarily long strings, for example for %s patterns, so that they can be printed out. Fixes Debian bug #271672. Would
require more complex store/load code in apprentice.
Add syntax for relative offsets after current level (Debian bug #466037).
Make file -ki work, i.e. give multiple MIME types.
Add a zip library so we can peek inside Office2007 documents to figure out what they are.
Add an option to print URLs for the sources of the file descriptions.
AVAILABILITY
You can obtain the original author's latest version by anonymous FTP on ftp.astron.com in the directory
/pub/file/file-X.YZ.tar.gz.
BSD October 17, 2011 BSD
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