FILE ( 1 ) USER COMMANDSFILE ( 1 )


NAME

file - determine file type

SYNOPSIS

file [ options ] [ file ... ]

DESCRIPTION

file tests and attempts to classify each file argument. Non-regular files are classified by their stat(2) types. Empty and non-readable regular files are classified as such. Otherwise a data block is read from file and this is used to match against the magic file(s) (see MAGIC FILE below). Files with less than 1024 bytes of data are labelled small to note that the sample may be too small for an accurate classification. Failing a content match, the file name extension may be used to classify. As a last resort statistical sampling is done for a small range of languages and applications. Failed matches usually result in the less informative ascii text or binary data.

OPTIONS

-a, --all

List all magic table matches.
-b, --brief|no-filename

Suppress the output line file name prefix.
-c, --mime

List the mime(1) classification for each file . Although the default descriptions are fairly consistent, use --mime for precise classification matching.
-d, --default-magic

Equivalent to --magic=-.
-f, --files|file-list=file

file contains list of file names, one per line, that are classified.
-i, --ignore-magic

Equivalent to --magic=/dev/null.
-l, --list

The loaded magic files are listed and then file exits.
-M, --magic=file

file is loaded as a magic file. More than one --magic option may be specified; the precedence is from left to right. The first --magic option causes the default system magic file to be ignored; the file - may then be specified to explicitly load the default system magic file. To ignore all magic files specify the file /dev/null and no others.
-m, --append-magic=file

file is loaded as a magic file. Equivalent to the --magic option, except that the default system magic file is still loaded last. If --magic is also specified then the default system magic is only loaded if explicity specified.
-p, --pattern|match=pattern

Only files with descriptions matching the sh(1) match pattern are listed. file exits with status 0 if any files match, 0 otherwise.
-q, --quiet|silent

Do not list matching --pattern files.
-L, --logical|dereference

Follow symbolic links.
-P|h, --physical

Don't follow symbolic links.
-w, --warn

Enable magic file parse warning messages.

MAGIC FILE

A magic file specifies file content and name match expressions, descriptions, and mime(1) classifications. Each line in the file consists of five tab separated fields:
[op]offset

offset determines tha data location for the content test. (@expression ) specifies an indirect offset, i.e., the offset is the numeric contents of the data location at expression. The default indirect numeric size is 4 bytes; a B suffix denotes 1 byte, H denotes 2 bytes, and Q denotes 8 bytes. offset may also be one of { atime blocks ctime fstype gid mode mtime name nlink size uid } to access stat(2) information for the current file. The optional op specifies relationships with surrounding magic lines:
+
previous fields in block match, current optional
&
previous and current fields in block match
|
previous fields in block do not match, subsequent skipped
{
start nesting block
}
end nesting block
c{
function declaration and call (1 char names)
}
function return
c()
function call
type
The content data type:
byte
1 byte integer
short

2 byte integer
long
4 byte integer
quad
8 byte integer
date
4 byte time_t
version

4 byte unsigned integer of the form YYYYMMDD for YYYY-MM-DD, 0xYYZZ for YY.ZZ, or 0xWWXXYYZZ for WW.XX.YY.ZZ
edit
substitute operator for string data: %old%new%[glu], where % is any delimiter
match

case insensitive sh(1) match pattern operator for string data
[mask]operator

mask is an optional &number that is masked (bit and) with the content data before comparison. operator is one of { < <= > >= != == }. Numeric values may be decimal, octal or hex.
description

The description text. Care was taken to maintain consistency between all descriptions, i.e., character case, grammatical parts placement, and punctuation, making description pattern matches feasible. description may contain one printf(3) format specification for the current data value at offset.
mime
The mime(1) type/subtype. This provides a standard and consistent matching key space.

FILES

lib/file/magic

Default magic file on $PATH.

SEE ALSO

find(1), ls(1), mime(1), tw(1)

IMPLEMENTATION

version

file (AT&T Research) 2011-08-01
author

Glenn Fowler <glenn.s.fowler@gmail.com>
copyright

Copyright © 1989-2012 AT&T Intellectual Property
license

http://www.eclipse.org/org/documents/epl-v10.html