Man Pages

file(1) - phpMan file(1) - phpMan

Command: man perldoc info search(apropos)  


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

NAME
     file - determine file type

SYNOPSIS
     file [-bchikLNnprsvz0] [--apple] [--mime-encoding] [--mime-type] [-e testname] [-F separator] [-f namefile]
          [-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 modifying 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

     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 #include <a.out.h>
     and possibly #include <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/misc/magic.mgc, or the files in the
     directory /usr/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 /etc/magic exists, it will be
     used together with other 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 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 lan-
     guage the file is written.  The language tests look for particular strings (cf.  #include <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 directory.

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

     -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, --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). 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. 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 support sym-
             bolic links).  This is the default if the environment variable POSIXLY_CORRECT is defined.

     -m, --magic-file magicfiles
             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-pad
             Don't pad filenames so that they align in the output.

     -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
             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 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/misc/magic.mgc  Default compiled list of magic.
     /usr/share/misc/magic      Directory containing 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 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/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 <ianATdarwinsys.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@war-
     wick.ac.uk, 1989.

     Guy Harris, guyATnetapp.com, made many changes from 1993 to the present.

     Primary development and maintenance from 1990 to the present by Christos Zoulas (christosATastron.com).

     Altered by Chris Lowth, chrisATlowth.com, 2000: Handle the -i option to output mime type strings, using an alter-
     native magic file and internal logic.

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

     Altered by Reuben Thomas (rrtATsc3d.org), 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 distribution.

     The files tar.h and is_tar.c were written by John Gilmore from his public-domain tar(1) program, and are not cov-
     ered 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 recompi-
     lation 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.

     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

BSD                             October 9, 2008                            BSD