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FILE(1)							  FILE(1)

NAME
       file - determine file type

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

DESCRIPTION
       This manual page documents version 3.25 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/contrib/share/magic or
       the program itself,  preserve  these  keywords  .   People
       depend  on knowing that all the readable files in a direc-
       tory 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/con-
       trib/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

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FILE(1)							  FILE(1)

       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/contrib/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

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FILE(1)							  FILE(1)

       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/con-
       trib/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.

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FILE(1)							  FILE(1)

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,

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FILE(1)							  FILE(1)

       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

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FILE(1)							  FILE(1)

       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			6

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