source: main/trunk/binaries/windows/bin/GNUfile/man/cat1/file.1.txt@ 31442

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

NAME
     file -- determine file type

SYNOPSIS
     file [-bchikLnNprsvz] [--mime-type] [--mime-encoding]
          [-f namefile] [-F separator] [-m magicfiles] file
     file -C [-m magicfile]
     file [--help]

DESCRIPTION
     This manual page documents version 5.03 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 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).  Excep-
     tions are well-known file formats (core files, tar ar-
     chives) that are known to contain binary data.  When modi-
     fying 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 example 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 c:/progra~1/file/share/misc/magic.mgc, or the files
     in the directory c:/progra~1/file/share/misc/magic if the
     compiled file does not exist. In addition, if
     $HOME/.magic.mgc or $HOME/.magic exists, it will be used
     in preference to the system magic files.

     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 transla-
     tion 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 particu-
     lar 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) ar-
     chives).

     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 conjunc-
             tion 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 directory.

     -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, irrespective 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, --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.

     -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 sys-
             tems that support 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 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. Subse-
             quent 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 symbolic links).  This is the default if the
             environment variable POSIXLY_CORRECT is defined.

     -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 directory, it will be
             used instead.

     -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 out-
             put.

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

     -r, --raw
             Don't translate unprintable characters to \ooo.
             Normally file translates unprintable characters to
             their octal representation.

     -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 parti-
             tions.

     -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
     c:/progra~1/file/share/misc/magic.mgc  Default compiled
                                            list of magic.
     c:/progra~1/file/share/misc/magic      Directory contain-
                                            ing default magic
                                            files.

ENVIRONMENT
     The environment variable MAGIC can be used to set the
     default magic file name.  If that variable is set, then
     file will not attempt to open $HOME/.magic.  file adds
     `.mgc' to the value of this variable as appropriate.  The
     environment variable POSIXLY_CORRECT controls (on systems
     that support symbolic links), whether 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), strings(1), od(1), hexdump(1,) file(1posix)

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 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 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 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
     c:/progra~1/file/share/misc/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 <[email protected]> without looking at any-
     body 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.  Con-
     tributions by the `&' operator by Rob McMahon, cudcv@war-
     wick.ac.uk, 1989.

     Guy Harris, [email protected], made many changes from 1993 to
     the present.

     Primary development and maintenance from 1990 to the
     present by Christos Zoulas ([email protected]).

     Altered by Chris Lowth, [email protected], 2000: Handle the
     -i option to output mime type strings, using an alterna-
     tive magic file and internal logic.

     Altered by Eric Fischer ([email protected]), July, 2000, to
     identify character codes and attempt to identify the lan-
     guages of non-ASCII files.

     Altered by Reuben Thomas ([email protected]), 2007 to 2008, to
     improve MIME support and merge MIME and non-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 distri-
     bution.

     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 accu-
     racy, thus it can be misled about the contents of text
     files.

     The support for text files (primarily for programming lan-
     guages) is simplistic, inefficient and requires recompila-
     tion 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