FILE(1) 						      General Commands Manual							   FILE(1)

NAME

       file - determine file type

SYNOPSIS

       file [ -bciknsvzL ] [ -f namefile ] [ -m magicfiles ] file
       file -C [ -m magicfile ]

DESCRIPTION

       This manual page documents version 3.39 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/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 and change ``shell commands text'' to ``shell script''.  Note that the file /usr/share/magic is built mechanically
       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 particular 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/magic.mgc , or /usr/share/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 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
       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''.

OPTIONS

       -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 conjunction with -m to debug a	new  magic
	       file before installing it.

       -C      Write a magic.mgc output file that contains a pre-parsed version of file.

       -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.

       -i      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 handles
	       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      Don't stop at the first match, keep going.

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

       -n      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.

       -v      Print the version of the program and exit.

       -z      Try to look inside compressed files.

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

       -s      Normally, file only attempts to read and determine the type of argument files which stat(2) reports are ordinary files.	This  pre-
	       vents  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 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.

FILES

       /usr/share/magic.mgc - defaults compiled list of magic numbers

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

       /usr/share/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 files.

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
       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	   egindata	  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 `' operator, used as, for example,
       16   long0x7fffffff 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 consolidation of magic file entries will be distributed period-
       ically.

       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).

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 Christos 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 character 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.

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 public-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 environments)
       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. ``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.  The new support for multiple character codes makes it even slower.

       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 						   FILE(1)