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FILE(1)                   BSD General Commands Manual                  FILE(1)

NAME
     file -- determine file type

SYNOPSIS
     file [-bcdDhiIkLnNprsvz] [--mime-type] [--mime-encoding] [-f namefile] [-m magicfiles] [-M magicfiles]
          file
     file -C [-m magicfiles]
     file [--help]

DESCRIPTION
     This manual page documents version 5.04 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 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 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 modify-ing modifying
     ing magic files or the program itself, make sure to preserve these keywords.  Users 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'.

     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 tests are used to check for files with data in particular fixed formats.  The canonical exam-ple example
     ple of this is a binary executable (compiled program) a.out file, whose format is defined in <elf.h>,
     <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 a `magic' 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 identifying these files is read
     from the compiled magic file /usr/share/file/magic.mgc, or the files in the directory
     /usr/share/file/magic if the compiled 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 over-striking overstriking
     striking 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, --compile
             Write a magic.mgc output file that contains a pre-parsed version of the magic file or direc-tory. directory.
             tory.

     -c, --checking-printout
             Cause a checking printout of the parsed form of the magic file.  This is usually used in con-junction conjunction
             junction with the -m flag to debug a new magic file before installing it.

     -C, --compile
             Write a magic.mgc output file that contains a pre-parsed version of the magic file or direc-tory. directory.
             tory.

     -d      Apply the default system tests; this is the default behavior unless -M is specified.

     -D      Print debugging messages.

     -e, --exclude testname
             Exclude the test named in testname from the list of tests made to determine the file type.
             Valid test names are:

             apptype   EMX application type (only on EMX).

             text      Various types of text files (this test will try to guess the text encoding, irrespec-tive irrespective
                       tive of the setting of the `encoding' option).

             encoding  Different text encodings for soft magic tests.

             tokens    Looks for known tokens inside text files.

             cdf       Prints details of Compound Document Files.

             compress  Checks for, and looks inside, compressed files.

             elf       Prints ELF file details.

             soft      Consults magic files.

             tar       Examines tar files.

     -F, --separator separator
             Use the specified string as the separator between the filename and the file result returned.
             Defaults to `:'.

     -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 standard
             input, use `-' as a filename argument.

     -h, --no-dereference
             option causes symlinks not to be followed (on systems that support symbolic links).

     -i      If the file is a regular file, do not classify its contents.

     -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 handles files recognized by the command
             itself (such as many of the text file types, directories etc), and makes use of an alternative
             `magic' file.  (See the FILES section, below).

     --mime-type, --mime-encoding
             Like -I, but print only the specified element(s).

     -k, --keep-going
             Don't stop at the first match, keep going. Subsequent matches will be have the string `\012- '
             prepended.  (If you want a newline, see the `-r' option.)

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

     -m, --magic-file list
             Specify an alternate list of files and directories containing magic.  This can be a single
             item, or a colon-separated list.  If a compiled magic file is found alongside a file or direc-tory, directory,
             tory, it will be used instead.

     -M list
             Like -m, except that the default rules are not applied unless -d is specified.

     -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.

     -p, --preserve-date
             On systems that support utime(2) or utimes(2), attempt to preserve the access time of files
             analyzed, to pretend that file never read them.

     -r, --raw
             No operation, included for historical compatibility.

     -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 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.

     -0, --print0
             Output a null character `\0' after the end of the filename. Nice to cut(1) the output. This
             does not affect the separator which is still printed.

     --help  Print a help message and exit.

FILES
     /usr/share/file/magic.mgc  Default compiled list of magic.
     /usr/share/file/magic      Directory containing default magic files.

ENVIRONMENT
     The environment variable MAGIC can be used to set the default magic file name.  file adds `.mgc' to the
     value of this variable as appropriate.

LEGACY DESCRIPTION
     In legacy mode, the -D, -I, and -M options do not exist.

     The -d, -i, and -r options behave differently.  The -d option provides debugging information (same as
     -D in conformance mode).  The -i option displays mime type information (same as -I in conformance
     mode).  The -r option will disable the translation of unprintable characters (by default, this transla-tion translation
     tion is already disabled in conformance mode).

     Furthermore, the -h option becomes the default symlink behavior (don't follow symlinks) unless
     POSIXLY_CORRECT is set.

     For more information about legacy mode, see compat(5).

SEE ALSO
     magic(5), strings(1), od(1), hexdump(1,) otool(1), compat(5)

STANDARDS CONFORMANCE
     This program conforms to Version 3 of the Single UNIX Specification (``SUSv3'').  Its behavior 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 exam-ple example
     ple

           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 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     long&0x7fffffff >0              not stripped

MAGIC DIRECTORY
     The magic file entries have been collected from various sources, mainly USENET, and contributed by var-ious various
     ious authors.  Christos Zoulas (address below) will collect additional or corrected magic file entries.
     A consolidation 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
           /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 introduced one significant major change: the external list of magic 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, using
     an alternative magic file and internal logic.

     Altered by Eric Fischer (enf@pobox.com), July, 2000, to identify character codes and attempt to iden-tify identify
     tify the languages of non-ASCII files.

     Altered by Reuben Thomas (rrt@sc3d.org), 2007 to 2008, to improve MIME support and merge MIME and non-MIME nonMIME
     MIME magic, support directories as well as files of magic, apply many bug fixes and improve the build
     system.

     The list of contributors to the `magic' directory (magic files) is too long to include here.  You know
     who you are; thank you.  Many contributors are listed in the source files.

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(1) 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?

     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.

     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.

     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.  `Fromas 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 manual page, and particularly this section, is too long.

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

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

BSD                             October 9, 2008                            BSD

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