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** README for file(1) Command **
@(#) $File: README,v 1.42 2009/02/14 15:16:24 christos Exp $

Mailing List:

Phone: Do not even think of telephoning me about this program. Send cash first!

This is Release 5.x of Ian Darwin's (copyright but distributable)
file(1) command. This version is the standard "file" command for Linux,
*BSD, and other systems. (See "patchlevel.h" for the exact release number).

The major changes for 5.x are CDF file parsing, indirect magic, and
overhaul in mime and ascii encoding handling.

The major feature of 4.x is the refactoring of the code into a library,
and the re-write of the file command in terms of that library. The library
itself, libmagic can be used by 3rd party programs that wish to identify
file types without having to fork() and exec() file. The prime contributor
for 4.0 was M\xe5ns Rullg\xe5rd.

UNIX is a trademark of UNIX System Laboratories.

The prime contributor to Release 3.8 was Guy Harris, who put in megachanges
including byte-order independence.

The prime contributor to Release 3.0 was Christos Zoulas, who put
in hundreds of lines of source code changes, including his own
ANSIfication of the code (I liked my own ANSIfication better, but
his (__P()) is the "Berkeley standard" way of doing it, and I wanted UCB
to include the code...), his HP-like "indirection" (a feature of
the HP file command, I think), and his mods that finally got the
uncompress (-z) mode finished and working.

This release has compiled in numerous environments; see PORTING
for a list and problems.

This fine freeware file(1) follows the USG (System V) model of the file
command, rather than the Research (V7) version or the V7-derived 4.[23]
Berkeley one. That is, the file /etc/magic contains much of the ritual
information that is the source of this program's power. My version
knows a little more magic (including tar archives) than System V; the
/etc/magic parsing seems to be compatible with the (poorly documented)
System V /etc/magic format (with one exception; see the man page).

In addition, the /etc/magic file is built from a subdirectory
for easier(?) maintenance.  I will act as a clearinghouse for
magic numbers assigned to all sorts of data files that
are in reasonable circulation. Send your magic numbers,
in magic(5) format please, to the maintainer, Christos Zoulas.

COPYING - read this first.
README - read this second (you are currently reading this file).
INSTALL - read on how to install

src/apprentice.c - parses /etc/magic to learn magic
src/apptype.c - used for OS/2 specific application type magic
src/asprintf.c - replacement for OS's that don't have it.
src/ascmagic.c - third & last set of tests, based on hardwired assumptions.
src/cdf.c - parser for Microsoft Compound Document Files
src/cdf_time.c - time converter for CDF.
src/compress.c - handles decompressing files to look inside.
src/encoding.c - handles unicode encodings
src/file.c - the main program
src/file.h - header file
src/fsmagic.c - first set of tests the program runs, based on filesystem info
src/funcs.c - utilility functions
src/getopt_long.c - used for OS/2 specific application type magic
src/is_tar.c, tar.h - knows about tarchives (courtesy John Gilmore).
src/names.h - header file for ascmagic.c
src/magic.c - the libmagic api
src/print.c - print results, errors, warnings.
src/readcdf.c - CDF wrapper.
src/readelf.[ch] - Stand-alone elf parsing code.
src/softmagic.c - 2nd set of tests, based on /etc/magic
src/strlcat.c - used for OS/2 specific application type magic
src/strlcpy.c - used for OS/2 specific application type magic
src/vasprintf.c - used for OS/2 specific application type magic
doc/file.1 - man page for the command
doc/magic.4 - man page for the magic file, courtesy Guy Harris.
	Install as magic.4 on USG and magic.5 on V7 or Berkeley; cf Makefile.
Magdir - directory of /etc/magic pieces


If you submit a new magic entry please make sure you read the following

- Initial match is preferably at least 32 bits long, and is a _unique_ match
- If this is not feasible, use additional check
- Match of <= 16 bits are not accepted
- Delay printing string as much as possible, don't print output too early
- Avoid printf arbitrary byte as string, which can be a source of
  crash and buffer overflow

- Provide complete information with entry:
  * One line short summary
  * Optional long description
  * File extension, if applicable
  * Full name and contact method (for discussion when entry has problem)
  * Further reference, such as documentation of format


You can download the latest version of file from:

If your gzip sometimes fails to decompress things complaining about a short
file, apply this patch [which is going to be in the next version of gzip]:
*** -   Tue Oct 29 02:06:35 1996
--- util.c      Sun Jul 21 21:51:38 1996
*** 106,111 ****
--- 108,114 ----
      if (insize == 0) {
        if (eof_ok) return EOF;
+       flush_window();
      bytes_in += (ulg)insize;

Parts of this software were developed at SoftQuad Inc., developers
of SGML/HTML/XML publishing software, in Toronto, Canada.
SoftQuad was swallowed up by Corel in 2002
and does not exist any longer.

From: Kees Zeelenberg

An MS-Windows (Win32) port of File-4.17 is available from

File is an implementation of the Unix File(1) command.
It knows the 'magic number' of several thousands of file types.