file/README

** README for file(1) Command **
@(#) $File: README,v 1.40 2008/04/23 03:45:20 christos Exp $

E-mail: christos@astron.com
Mailing List: file@mx.gw.com

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

This is Release 4.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 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).
PORTING - read this only if the program won't compile.
Makefile - read this next, adapt it as needed (particularly
	the location of the old existing file command and
	the man page layouts), type "make" to compile, 
	"make try" to try it out against your old version.
	Expect some diffs, particularly since your original
	file(1) may not grok the embedded-space ("\ ") in
	the current magic file, or may even not use the
	magic file.
apprentice.c - parses /etc/magic to learn magic
ascmagic.c - third & last set of tests, based on hardwired assumptions.
core - not included in distribution due to mailer limitations.
debug.c - includes -c printout routine
file.1 - man page for the command
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.
file.c - main program
file.h - header file
fsmagic.c - first set of tests the program runs, based on filesystem info
is_tar.c, tar.h - knows about tarchives (courtesy John Gilmore).
magdir - directory of /etc/magic pieces
	magdir/Makefile - ADJUST THIS FOR YOUR CONFIGURATION
names.h - header file for ascmagic.c
softmagic.c - 2nd set of tests, based on /etc/magic
readelf.[ch] - Stand-alone elf parsing code.
compress.c - on-the-fly decompression.
print.c - print results, errors, warnings.

------------------------------------------------------------------------------

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

- 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:

	ftp://ftp.astron.com/pub/file/

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();
        read_error();
      }
      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
http://gnuwin32.sourceforge.net/

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