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This manual page documents version
5.03 of the command. 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 test that succeeds causes the file
type to be printed. The type printed will usually contain one of the words
(the file contains only printing characters and a few common control characters
and is probably safe to read on an terminal), (the file contains the
result of compiling a program in a form understandable to some kernel
or another), or meaning anything else (data is usually 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 Users depend on knowing that all the readable files
in a directory have the word printed. Don’t do as Berkeley did and change
to The filesystem tests are based on examining the return from a 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) file, whose format is defined in and possibly in the standard
include directory. These files have a stored in a particular place near
the beginning of the file that tells the that the file is a binary executable,
and which of several types thereof. The concept of a 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 or the files
in the directory if the compiled file does not exist. In addition, if
or 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 because they will be mostly readable on nearly any terminal; UTF-16
and EBCDIC are only because, while they contain text, it is text that
will require translation before it can be read. In addition, 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 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. ) that can
appear anywhere in the first few blocks of a file. For example, the keyword
indicates that the file is most likely a input file, just as the keyword
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 archives). Any file that cannot be identified
as having been written in any of the character sets listed above is simply
said to be
Do not prepend filenames to output lines (brief mode).
Cause a checking printout of the parsed form of the magic file. This is
usually used in conjunction with the flag to debug a new magic file before
installing it. Write a output file that contains a pre-parsed version of
the magic file or directory. Exclude the test named in from the list of
tests made to determine the file type. Valid test names are: application
type (only on EMX). Various types of text files (this test will try to
guess the text encoding, irrespective of the setting of the option). Different
text encodings for soft magic tests. Looks for known tokens inside text
files. Prints details of Compound Document Files. Checks for, and looks
inside, compressed files. Prints ELF file details. Consults magic files.
Examines tar files. Read the names of the files to be examined from
(one per line) before the argument list. Either or at least one filename
argument must be present; to test the standard input, use as a filename
argument. Use the specified string as the separator between the filename
and the file result returned. Defaults to option causes symlinks not to
be followed (on systems that support symbolic links). This is the default
if the environment variable is not defined. Causes the file command to
output mime type strings rather than the more traditional human readable
ones. Thus it may say rather than 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
file. (See the FILES section, below). Like but print only the specified
element(s). Don’t stop at the first match, keep going. Subsequent matches
will be have the string prepended. (If you want a newline, see the option.)
option causes symlinks to be followed, as the like-named option in (on
systems that support symbolic links). This is the default if the environment
variable is defined. 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. 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. Don’t pad filenames so that
they align in the output. On systems that support or attempt to preserve
the access time of files analyzed, to pretend that never read them. Don’t
translate unprintable characters to \ooo. Normally translates unprintable
characters to their octal representation. Normally, only attempts to read
and determine the type of argument files which reports are ordinary files.
This prevents problems, because reading special files may have peculiar
consequences. Specifying the option causes 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 to disregard the file size as reported
by since on some systems it reports a zero size for raw disk partitions.
Print the version of the program and exit. Try to look inside compressed
files. Output a null character after the end of the filename. Nice to
the output. This does not affect the separator which is still printed. Print
a help message and exit.
Default compiled list of magic. Directory
containing default magic files.
The environment variable can
be used to set the default magic file name. If that variable is set, then
will not attempt to open adds to the value of this variable as appropriate.
The environment variable controls (on systems that support symbolic links),
whether will attempt to follow symlinks or not. If set, then follows symlink,
otherwise it does not. This is also controlled by the and options.
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 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
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.
If your old command uses a magic file, keep the old magic file around
for comparison purposes (rename it to
$ 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
There has been a command in every (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 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 identify 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 magic, support directories
as well as files of magic, apply many bug fixes and improve the build system.
The list of contributors to the directory (magic files) is too long to
include here. You know who you are; thank you. Many contributors are listed
in the source files.
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 and were
written by John Gilmore from his public-domain program, and are not covered
by the above license.
There must be a better way to automate the construction
of the Magic file from all the glop in Magdir. What is it? 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 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 a guess is. We
end up removing guesses (e.g. as first 5 chars of file) because they are
not as good as other guesses (e.g. versus ). 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.
returns 0 on success,
and non-zero on error.
You can obtain the original author’s latest
version by anonymous FTP on in the directory
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