FILE(1)                                                                FILE(1)


       file - determine file type


       file  [  -bchikLnNprsvz  ] [ -f namefile ] [ -F separator ] [ -m magic-
       files ] file ...
       file -C [ -m magicfile ]


       This manual page documents version 4.16 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 number
       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 the file /usr/share/file/magic or the pro-
       gram  itself,  preserve these keywords .  People 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’’.  Note that the file /usr/share/file/magic is  built  mechani-
       cally  from a large number of small files in the subdirectory Magdir in
       the source distribution of this program.

       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 number tests are used to check for files with data in partic-
       ular fixed formats.  The canonical example of this  is  a  binary  exe-
       cutable  (compiled  program)  a.out  file,  whose  format is defined in
       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 ‘magic number’ 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 identi-
       fying   these   files   is   read   from   the   compiled   magic  file
       /usr/share/file/magic.mgc , or  /usr/share/file/magic  if  the  compile
       file  does  not exist. In addition file will look in $HOME/.magic.mgc ,
       or $HOME/.magic for magic entries.

       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)

       Any file that cannot be identified as having been written in any of the
       character sets listed above is simply said to be ‘‘data’’.


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

       -c, --checking-printout
               Cause a checking printout of the parsed form of the magic file.
               This  is  usually  used  in  conjunction with -m to debug a new
               magic file before installing it.

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

       -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.

       -F, --separator separator
               Use the specified string as the separator between the  filename
               and the file result returned. Defaults to ‘‘:’’.

       -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’’.
               In order for this option to work, file changes the way it  han-
               dles  files  recognised  by the command itself (such as many of
               the text file types, directories etc),  and  makes  use  of  an
               alternative ‘‘magic’’ file.  (See ‘‘FILES’’ section, below).

       -k, --keep-going
               Don’t stop at the first match, keep going.

       -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 list
               Specify an alternate list of files  containing  magic  numbers.
               This  can be a single file, or a colon-separated list of files.
               If a compiled magic file is found alongside, it  will  be  used
               instead.   With  the  -i  or  --mime  option,  the program adds
               ".mime" to each file name.

       -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.

       -N, --no-pad
               Don’t pad filenames so that they align in the output.

       -p, --preserve-date
               On systems that support utime(2) or utimes(2), attempt to  pre-
               serve  the  access  time  of  files  analyzed,  to pretend that
               file(2) never read them.

       -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.

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

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

       --help  Print a help message and exit.


              Default compiled list of magic numbers

              Default list of magic numbers

              Default  compiled  list  of  magic  numbers, used to output mime
              types when the -i option is specified.

              Default list of magic numbers, used to output  mime  types  when
              the -i option is specified.


       The  environment  variable  MAGIC  can be used to set the default magic
       number file name.  If that variable is set, then file will not  attempt
       to open $HOME/.magic .  file adds ".mime" and/or ".mgc" to the value of
       this variable as appropriate.  The environment variable POSIXLY_CORRECT
       controls (on systems that support symbolic links), if 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.


       magic(5) - description of magic file format.
       strings(1), od(1), hexdump(1) - tools for examining non-textfiles.


       This program is believed to exceed the System V Interface Definition of
       FILE(CMD), as near as one can determine from the  vague  language  con-
       tained  therein.   Its behaviour 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(1)
       command derived from the System V one, but with  some  extensions.   My
       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


       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 con-
       solidation 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


       $ 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, dynamically linked (uses shared libs),
       not stripped
       /dev/hda:    application/x-not-regular-file
       /dev/wd0a:   application/x-not-regular-file


       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 number
       types.  This slowed the program down slightly but made it  a  lot  more

       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 by  the  ‘&’  operator  by  Rob
       McMahon,, 1989.

       Guy Harris,, made many changes from 1993 to the present.

       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 and using an  alternative  magic  file  and
       internal logic.

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

       The list of contributors to the  "Magdir"  directory  (source  for  the
       /usr/share/file/magic  file) is too long to include here.  You know who
       you are; thank you.


       Copyright (c) Ian F. Darwin, Toronto, Canada,  1986-1999.   Covered  by
       the  standard  Berkeley  Software  Distribution copyright; see the file
       LEGAL.NOTICE in the source distribution.

       The files tar.h and is_tar.c were written by John Gilmore from his pub-
       lic-domain tar program, and are not covered by the above license.


       There  must  be  a better way to automate the construction of the Magic
       file from all the glop in magdir.  What is it?  Better yet,  the  magic
       file  should  be  compiled  into  binary  (say, ndbm(3) or, better yet,
       fixed-length ASCII strings for use  in  heterogenous  network  environ-
       ments)  for  faster startup.  Then the program would run as fast as the
       Version 7 program of the same name, with the flexibility of the  System
       V version.

       File  uses  several  algorithms that favor speed over accuracy, thus it
       can be misled about the contents of text files.

       The support for text files (primarily  for  programming  languages)  is
       simplistic, inefficient and requires recompilation to update.

       There  should  be an ‘‘else’’ clause to follow a series of continuation

       The magic file and keywords should  have  regular  expression  support.
       Their  use  of ASCII TAB as a field delimiter is ugly and makes it hard
       to edit the files, but is entrenched.

       It might be advisable to allow upper-case letters in keywords for e.g.,
       troff(1) commands vs man page macros.  Regular expression support would
       make this easy.

       The program doesn’t grok FORTRAN.  It should be able to figure  FORTRAN
       by  seeing  some  keywords  which appear indented at the start of line.
       Regular expression support would make this easy.

       The list of keywords in ascmagic probably belongs in  the  Magic  file.
       This could be done by using some keyword like ‘*’ for the offset value.

       Another optimisation would be to sort the magic file  so  that  we  can
       just run down all the tests for the first byte, first word, first long,
       etc, once we have fetched it.  Complain about conflicts  in  the  magic
       file  entries.   Make  a rule that the magic entries sort based on file
       offset rather than position within the magic file?

       The program should provide a way to give an estimate of ‘‘how good’’  a
       guess  is.  We end up removing guesses (e.g. ‘‘From ’’ as first 5 chars
       of file) because they are not as good as other  guesses  (e.g.  ‘‘News-
       groups:’’  versus  ‘‘Return-Path:’’).   Still,  if the others don’t pan
       out, it should be possible to use the first guess.

       This program is slower than some vendors’ file commands.  The new  sup-
       port for multiple character codes makes it even slower.

       This manual page, and particularly this section, is too long.


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

                          Copyright but distributable                  FILE(1)

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