Provided by: file_4.16-0ubuntu3_i386 bug

NAME

       file - determine file type

SYNOPSIS

       file  [  -bchikLnNprsvz  ]  [  -f  namefile  ]  [  -F  separator ] [ -m
       magicfiles ] file ...
       file -C [ -m magicfile ]

DESCRIPTION

       This manual page documents version 4.16 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
       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 adding local definitions  to  /etc/magic,
       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 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
       executable  (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
       identifying  these files is read from /etc/magic and 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
       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, --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
               version 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
               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 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 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. Subsequent matches
               will be prepended by ‘‘\012- ’’. (If you want  a  newline,  see
               ‘‘-r’’ option.)

       -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
               preserve  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
               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.

       --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
       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         \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
       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 various 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.

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
       introduced  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
       /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
       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.

RETURN CODE

       file almost always returns 0. It returns a different if it cannot  open
       a file.

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

       This Debian version adds a number of  new  magix  entries.  It  can  be
       obtained from every site carrying a Debian distribution (ftp.debian.org
       and mirrors).