file(1) — Linux manual page


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

NAME         top

     file — determine file type

SYNOPSIS         top

     file [-bcdEhiklLNnprsSvzZ0] [--apple] [--exclude-quiet] [--extension]
          [--mime-encoding] [--mime-type] [-e testname] [-F separator]
          [-f namefile] [-m magicfiles] [-P name=value] file ...
     file -C [-m magicfiles]
     file [--help]

DESCRIPTION         top

     This manual page documents version 5.39 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 control characters
     and is probably safe to read on an ASCII terminal), executable (the
     file contains the result of compiling a program in a form understand‐
     able 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 modifying magic files or the program itself, 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 <sys/stat.h>.

     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 <elf.h>,
     <a.out.h> and possibly <exec.h> 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 the compiled magic file
     /usr/local/share/misc/magic.mgc, or the files in the directory
     /usr/local/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 Macin‐
     tosh and IBM PC systems), UTF-8-encoded Unicode, UTF-16-encoded Uni‐
     code, 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 iden‐
     tified 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 charac‐
     teristics 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.  <names.h>) 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, JSON files).

     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         top

             Causes the file command to output the file type and creator
             code as used by older MacOS versions.  The code consists of
             eight letters, the first describing the file type, the latter
             the creator.  This option works properly only for file formats
             that have the apple-style output defined.

     -b, --brief
             Do not prepend filenames to output lines (brief mode).

     -C, --compile
             Write a magic.mgc output file that contains a pre-parsed ver‐
             sion 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.

     -d      Prints internal debugging information to stderr.

     -E      On filesystem errors (file not found etc), instead of handling
             the error as regular output as POSIX mandates and keep going,
             issue an error message and exit.

     -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.

             csv       Checks Comma Separated Value files.

             elf       Prints ELF file details, provided soft magic tests
                       are enabled and the elf magic is found.

             json      Examines JSON (RFC-7159) files by parsing them for

             soft      Consults magic files.

             tar       Examines tar files by verifying the checksum of the
                       512 byte tar header.  Excluding this test can provide
                       more detailed content description by using the soft
                       magic method.

             text      A synonym for ‘ascii’.

             Like --exclude but ignore tests that file does not know about.
             This is intended for compatilibity with older versions of file.

             Print a slash-separated list of valid extensions for the file
             type found.

     -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 stan‐
             dard 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 sup‐
             port symbolic links).  This is the default if the environment
             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.)  The magic pattern with the high‐
             est strength (see the -l option) comes first.

     -l, --list
             Shows a list of patterns and their strength sorted descending
             by magic(4) strength which is used for the matching (see also
             the -k option).

     -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.

     -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 direc‐
             tory, 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 pre‐
             serve the access time of files analyzed, to pretend that file
             never read them.

     -P, --parameter name=value
             Set various parameter limits.

                   Name         Default    Explanation
                   bytes        1048576    max number of bytes to read from
                   elf_notes    256        max ELF notes processed
                   elf_phnum    2048       max ELF program sections
                   elf_shnum    32768      max ELF sections processed
                   indir        50         recursion limit for indirect
                   name         50         use count limit for name/use
                   regex        8192       length limit for regex searches

     -r, --raw
             Don't translate unprintable characters to \ooo.  Normally file
             translates unprintable characters to their octal representa‐

     -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 pecu‐
             liar consequences.  Specifying the -s option causes file to
             also read argument files which are block or character special
             files.  This is useful for determining 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.

     -S, --no-sandbox
             On systems where libseccomp
             ( ) is available, the -S
             flag disables sandboxing which is enabled by default.  This
             option is needed for file to execute external decompressing
             programs, i.e. when the -z flag is specified and the built-in
             decompressors are not available.  On systems where sandboxing
             is not available, this option has no effect.

     -v, --version
             Print the version of the program and exit.

     -z, --uncompress
             Try to look inside compressed files.

     -Z, --uncompress-noreport
             Try to look inside compressed files, but report information
             about the contents only not the compression.

     -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.

             If this option is repeated more than once, then file prints
             just the filename followed by a NUL followed by the description
             (or ERROR: text) followed by a second NUL for each entry.

     --help  Print a help message and exit.

ENVIRONMENT         top

     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 appro‐
     priate.  The environment variable POSIXLY_CORRECT controls (on systems
     that support symbolic links), whether file will attempt to follow sym‐
     links or not.  If set, then file follows symlink, otherwise it does
     not.  This is also controlled by the -L and -h options.

FILES         top

     /usr/local/share/misc/magic.mgc  Default compiled list of magic.
     /usr/local/share/misc/magic      Directory containing default magic

EXIT STATUS         top

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

EXAMPLES         top

           $ 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

SEE ALSO         top

     hexdump(1), od(1), strings(1), magic(4)


     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 version 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 com‐
     mand derived from the System V one, but with some extensions.  This
     version differs from Sun's only in minor ways.  It includes the exten‐
     sion of the ‘&’ operator, used as, for example,

           >16     long&0x7fffffff >0              not stripped

SECURITY         top

     On systems where libseccomp ( ) is
     available, file is enforces limiting system calls to only the ones nec‐
     essary for the operation of the program.  This enforcement does not
     provide any security benefit when file is asked to decompress input
     files running external programs with the -z option.  To enable execu‐
     tion of external decompressors, one needs to disable sandboxing using
     the -S flag.


     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.  If your old file command uses a magic file, keep the old
     magic file around for comparison purposes (rename it to

HISTORY         top

     There has been a file command in every UNIX since at least Research
     Version 4 (man page dated November, 1973).  The System V version intro‐
     duced 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
     ⟨⟩ 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 of the ‘&’ operator by Rob
     McMahon, ⟨⟩, 1989.

     Guy Harris, ⟨⟩, made many changes from 1993 to the

     Primary development and maintenance from 1990 to the present by Chris‐
     tos Zoulas ⟨⟩.

     Altered by Chris Lowth ⟨⟩, 2000: handle the -i option to
     output mime type strings, using an alternative magic file and internal

     Altered by Eric Fischer ⟨⟩, July, 2000, to identify char‐
     acter codes and attempt to identify the languages of non-ASCII files.

     Altered by Reuben Thomas ⟨⟩, 2007-2011, to improve MIME
     support, merge MIME and non-MIME magic, support directories 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 contribu‐
     tors are listed in the source files.

LEGAL NOTICE         top

     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 pub‐
     lic-domain tar(1) program, and are not covered by the above license.

BUGS         top

     Please report bugs and send patches to the bug tracker at  or the mailing list at ⟨⟩
     (visit  first to sub‐

TODO         top

     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

     The handling of MAGIC_CONTINUE and printing \012- between entries is
     clumsy and complicated; refactor and centralize.

     Some of the encoding logic is hard-coded in encoding.c and can be moved
     to the magic files if we had a !:charset annotation

     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.  This can be done
     by allocating strings in a string pool, storing the string pool at the
     end of the magic file and converting all the string pointers to rela‐
     tive offsets from the string pool.

     Add syntax for relative offsets after current level (Debian bug

     Make file -ki work, i.e. give multiple MIME types.

     Add a zip library so we can peek inside Office2007 documents to print
     more details about their contents.

     Add an option to print URLs for the sources of the file descriptions.

     Combine script searches and add a way to map executable names to MIME
     types (e.g. have a magic value for !:mime which causes the resulting
     string to be looked up in a table).  This would avoid adding the same
     magic repeatedly for each new hash-bang interpreter.

     When a file descriptor is available, we can skip and adjust the buffer
     instead of the hacky buffer management we do now.

     Fix “name” and “use” to check for consistency at compile time (dupli‐
     cate “name”, “use” pointing to undefined “name” ).  Make “name” / “use”
     more efficient by keeping a sorted list of names.  Special-case ^ to
     flip endianness in the parser so that it does not have to be escaped,
     and document it.

     If the offsets specified internally in the file exceed the buffer size
     ( HOWMANY variable in file.h), then we don't seek to that offset, but
     we give up.  It would be better if buffer managements was done when the
     file descriptor is available so move around the file.  One must be
     careful though because this has performance (and thus security consid‐

AVAILABILITY         top

     You can obtain the original author's latest version by anonymous FTP on in the directory /pub/file/file-X.YZ.tar.gz.

COLOPHON         top

     This page is part of the file (a file type guesser) project.  Informa‐
     tion about the project can be found at
     If you have a bug report for this manual page, see
     ⟨⟩.  This page was obtained from the
     project's upstream Git read-only mirror of the CVS repository
     ⟨⟩ on 2020-09-18.  (At that time, the
     date of the most recent commit that was found in the repository was
     2020-09-18.)  If you discover any rendering problems in this HTML ver‐
     sion of the page, or you believe there is a better or more up-to-date
     source for the page, or you have corrections or improvements to the
     information in this COLOPHON (which is not part of the original manual
     page), send a mail to

BSD                             June 7, 2020                             BSD

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