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FILE(1)								       FILE(1)



NAME
       file - determine file type

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

DESCRIPTION
       This manual page documents version 4.17 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)
       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''.

OPTIONS
       -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-
	       tion.

       -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.

FILES
       /usr/share/file/magic.mgc
	      Default compiled list of magic numbers

       /usr/share/file/magic
	      Default list of magic numbers

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

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


ENVIRONMENT
       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.

SEE ALSO
       magic(5) - 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  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

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 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
       /usr/share/file/magic.orig).

EXAMPLES
       $ 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


HISTORY
       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
       flexible.

       This  program, based on the System V version, was written by Ian Darwin
       <ian@darwinsys.com> 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, cudcv@warwick.ac.uk, 1989.

       Guy Harris, guy@netapp.com, made many changes from 1993 to the present.

       Primary development and maintenance from 1990 to the present by	Chris-
       tos Zoulas (christos@astron.com).

       Altered by Chris Lowth, chris@lowth.com, 2000: Handle the ''-i'' option
       to output mime type strings and using an	 alternative  magic  file  and
       internal logic.

       Altered	by Eric Fischer (enf@pobox.com), 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.

LEGAL NOTICE
       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.

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  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
       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 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.


RETURN CODE
       Returns 0 on success, and non-zero on error.

       If  the	file named by the file operand does not exist, cannot be read,
       or the type of the file named by the file operand cannot be determined,
       this is not be considered an error that affects the exit status.


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



			  Copyright but distributable		       FILE(1)
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