NAME
file — determine file type
SYNOPSIS
file
[-m
mfile]
[-c]
[-f
ffile]
[-h]
[-i]
file ...
UNIX 2003 (onwards) Synopsis
file
[-m
mfile]
[-M
Mfile]
[-c]
[-d]
[-f
ffile]
[-h]
[-i]
file ...
DESCRIPTION
file
performs a series of tests on each
file
in an attempt to classify it.
If
file
appears to be an
ASCII
file,
file
examines the first 512 bytes and tries to guess its language.
If
file
is an executable
a.out
file,
file
prints the version stamp,
provided it is greater than 0 (see the description of the
-V
option in
ld(1)).
file
uses the file
/etc/magic
to identify files that have some sort of
magic number,
that is, any file containing a numeric or string constant
that indicates its type.
Commentary at the beginning of
/etc/magic
explains the format.
Options
file
recognizes the following command-line options:
- -m mfile
Use alternate magic file
mfile.
- -M Mfile
(UNIX 2003 onwards Only)
Use alternate magic file
Mfile.
Do not apply default context-sensitive tests.
- -c
Check the magic file for format errors.
This validation is not normally carried out for reasons of efficiency.
No file classification is done when this option is specified.
- -d
(UNIX 2003 onwards Only)
Apply position-sensitive tests from the default magic file,
/etc/magic,
and default context-sensitive tests to the file.
- -f ffile
Obtain the list of files to be examined from file
ffile.
file
classifies each file whose name appears in
ffile.
- -h
Do not follow symbolic links.
From UNIX 2003 (onwards) environment,
if
-h
is not specified and the
file
is a symbolic link referring to a non-existent file,
it is identified as a symbolic link, as if
-h
has been specified.
- -i
Do not attempt to classify a regular file further.
If the
-M
option is specified with the
-d
option,
-m
option, or both, the concatenation of the position-sensitive tests
specified by these options is applied in the order specified by the
appearance of these options.
EXTERNAL INFLUENCES
For information about the UNIX standard environment, see
standards(5).
Environment Variables
LC_MESSAGES
determines the language in which messages are displayed.
If
LC_MESSAGES
is not specified in the environment or is set to
the empty string, the value of
LANG
is used as a default for each
unspecified or empty variable.
If
LANG
is not specified or is set to the empty string, a default of "C" (see
lang(5))
is used instead of
LANG.
If any internationalization variable contains an invalid setting,
file
behaves as if all internationalization variables are set to "C".
See
environ(5).
International Code Set Support
Single- and multi-byte character code sets are supported.
However, all non-ASCII text files are identified as "data".
WARNINGS
The
file
command for a release interprets the core files
for that particular release correctly.
Using the
file
command on a core file generated on a different release
will report incorrect results.
STANDARDS CONFORMANCE
file: SVID2, SVID3, XPG2, XPG4
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