FILE(1)                                                   FILE(1)

NAME
       file - determine file type

SYNOPSIS
       file [ -vbczL ] [ -f namefile ] [ -m magicfiles ] file ...

DESCRIPTION
       This manual page documents version 3.26 of the  file  com-
       mand.   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 ASCII characters and is prob-
       ably  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  modifying  the  file /usr/share/magic or the
       program 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  -
       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 number 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 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 informa-
       tion  in  these  files  is  read  from  the   magic   file
       /usr/share/magic.

       If  an argument appears to be an ASCII file, file attempts
       to guess its language.  The language tests look  for  par-
       ticular  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  pro-
       gram.  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) and determine whether an unknown file should  be
       labelled as `ascii text' or `data'.

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

       -m list Specify  an  alternate  list  of  files containing
               magic numbers.  This can be a single  file,  or  a
               colon-separated list of files.

       -z      Try to look inside compressed files.

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

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

       -f 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.

       -L      option  causes  symlinks  to  be  followed, as the
               like-named option in ls(1).  (on systems that sup-
               port symbolic links).

FILES
       /usr/share/magic - default list of magic numbers

ENVIRONMENT
       The  environment  variable  MAGIC  can  be used to set the
       default magic number files.

SEE ALSO
       magic(4) - description of magic file format.
       strings(1), od(1), hexdump(1) - tools for  examining  non-
       textfiles.

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 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 extension of the  `&'  opera-
       tor, 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  consolida-
       tion  of  magic  file entries will be distributed periodi-
       cally.

       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
       /usr/share/magic.orig).

HISTORY
       There has been a file command in every UNIX since at least
       Research Version 6 (man page dated  January,  1975).   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 bet-
       ter than the first version.  Geoff Collyer  found  several
       inadequacies  and  provided  some magic file entries.  The
       program has undergone continued evolution since.

AUTHOR
       Written  by  Ian  F.  Darwin,  UUCP   address   {utzoo   |
       ihnp4}!darwin!ian,  Internet  address  ian@sq.com,  postal
       address: P.O. Box 603, Station F, Toronto, Ontario, CANADA
       M4Y 2L8.

       Altered  by  Rob  McMahon,  cudcv@warwick.ac.uk,  1989, to
       extend the `&' operator from simple `x&y != 0' to `x&y  op
       z'.

       Altered by Guy Harris, guy@netapp.com, 1993, to:

              put  the ``old-style'' `&' operator back the way it
              was, because 1) Rob McMahon's change broke the pre-
              vious  style  of  usage, 2) the SunOS ``new-style''
              `&' operator, which this version of file  supports,
              also handles `x&y op z', and 3) Rob's change wasn't
              documented in any case;

              put in multiple levels of `>';

              put in ``beshort'', ``leshort'', etc.  keywords  to
              look  at  numbers  in  the  file in a specific byte
              order, rather than in the native byte order of  the
              process running file.

       Changes by Ian Darwin and various authors including Chris-
       tos Zoulas (christos@astron.com), 1990-1997.

LEGAL NOTICE
       Copyright (c) Ian F. Darwin, Toronto, Canada, 1986,  1987,
       1988, 1989, 1990, 1991, 1992, 1993.

       This  software  is not subject to and may not be made sub-
       ject to any license of the American  Telephone  and  Tele-
       graph  Company,  Sun  Microsystems Inc., Digital Equipment
       Inc., Lotus Development Inc., the Regents of  the  Univer-
       sity  of  California, The X Consortium or MIT, or The Free
       Software Foundation.

       This software is not subject to any  export  provision  of
       the  United  States  Department  of  Commerce,  and may be
       exported to any country or planet.

       Permission is granted to anyone to use this  software  for
       any  purpose  on  any computer system, and to alter it and
       redistribute it freely, subject to the following  restric-
       tions:

       1.  The  author is not responsible for the consequences of
       use of this software, no matter how awful,  even  if  they
       arise from flaws in it.

       2. The origin of this software must not be misrepresented,
       either by explicit claim or by omission.  Since few  users
       ever  read  sources, credits must appear in the documenta-
       tion.

       3. Altered versions must be plainly marked  as  such,  and
       must not be misrepresented as being the original software.
       Since few users ever read sources, credits must appear  in
       the documentation.

       4. This notice may not be removed or altered.

       A few support files (getopt, strtok) distributed with this
       package are by Henry Spencer and are subject to  the  same
       terms as above.

       A  few  simple  support files (strtol, strchr) distributed
       with this package are in the public domain;  they  are  so
       marked.

       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 restrictions.

BUGS
       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 environments) for faster
       startup.  Then the program would run as fast as  the  Ver-
       sion  7  program of the same name, with the flexibility of
       the System V version.

       File uses several algorithms that favor speed  over  accu-
       racy,  thus  it  can be misled about the contents of ASCII
       files.

       The support for ASCII  files  (primarily  for  programming
       languages)  is simplistic, inefficient and requires recom-
       pilation to update.

       There should be an ``else'' clause to follow a  series  of
       continuation lines.

       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  key-
       words  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 off-
       set 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. ``Newsgroups:'' 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.

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

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

                   Copyright but distributable                  1