FILE linux command manual

FILE(1)                                                                FILE(1)

       file - determine file type

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

       This manual page documents version 4.07 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 con-
       tain binary data.  When modifying the  file  /usr/share/file/magic  or
       the  program itself, preserve these keywords .  People depend on know-
       ing 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 mechanically from a large number of small files in the subdirec-
       tory 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 .

       The  magic  number tests are used to check for files with data in par-
       ticular 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  iden-
       tifying   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.

       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 differ-
       ent 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 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).

       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 '':''.

       -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).

       -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
               peculiar consequences.  Specifying the -s option  causes  file
               to  also read argument files which are block or character spe-
               cial files.  This is useful  for  determining  the  filesystem
               types of the data in raw disk partitions, which are block spe-
               cial 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.

              Local additions to magic wisdom.

       The environment variable MAGIC can be used to set  the  default  magic
       number  file  name.   file  adds ".mime" and/or ".mgc" to the value of
       this variable as appropriate.

       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
       contained 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

       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 back-
       slash, 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 consolidation of magic file entries  will  be  distributed

       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
       introduced  one  significant  major change: the external list of magic
       number 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 by 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 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
       /etc/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
       public-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  sup-
       port 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

       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)