From owner-freebsd-questions@FreeBSD.ORG  Fri Jul  2 15:25:24 2010
Return-Path: <owner-freebsd-questions@FreeBSD.ORG>
Delivered-To: freebsd-questions@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 3BEBF1065686
	for <freebsd-questions@freebsd.org>;
	Fri,  2 Jul 2010 15:25:24 +0000 (UTC)
	(envelope-from freebsd-questions-local@be-well.ilk.org)
Received: from mail6.sea5.speakeasy.net (mail6.sea5.speakeasy.net
	[69.17.117.50]) by mx1.freebsd.org (Postfix) with ESMTP id 183C78FC19
	for <freebsd-questions@freebsd.org>;
	Fri,  2 Jul 2010 15:25:23 +0000 (UTC)
Received: (qmail 32012 invoked from network); 2 Jul 2010 15:25:22 -0000
Received: from dsl092-078-145.bos1.dsl.speakeasy.net (HELO be-well.ilk.org)
	([66.92.78.145])
	(envelope-sender <freebsd-questions-local@be-well.ilk.org>)
	by mail6.sea5.speakeasy.net (qmail-ldap-1.03) with SMTP
	for <freebsd-questions@freebsd.org>; 2 Jul 2010 15:25:22 -0000
Received: by be-well.ilk.org (Postfix, from userid 1147)
	id D8CC95084D; Fri,  2 Jul 2010 11:25:20 -0400 (EDT)
From: Lowell Gilbert <freebsd-questions-local@be-well.ilk.org>
To: freebsd-questions@freebsd.org
References: <4C2DF07F.1020509@tundraware.com>
Date: Fri, 02 Jul 2010 11:25:20 -0400
In-Reply-To: <4C2DF07F.1020509@tundraware.com> (Tim Daneliuk's message of
	"Fri, 02 Jul 2010 08:58:23 -0500")
Message-ID: <44630xq527.fsf@be-well.ilk.org>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.2 (berkeley-unix)
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Subject: Re: 'file' Command Giving False Positives
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions>
List-Post: <mailto:freebsd-questions@freebsd.org>
List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Fri, 02 Jul 2010 15:25:24 -0000

Tim Daneliuk <tundra@tundraware.com> writes:

> I have a data file with the content:
>
>    LZasdadqjwjqwjqwjeqwe
>
>
> 'file' (incorrectly) reports this as an MS-DOS executable.

Why is it incorrect?  "LZ" as the first two bytes in a file is (unless
my memory is badly mistaken) exactly what the old command.com looked for
as the flag of an executable.

> Does anyone happen to know the proper changes to 'magic' that would
> fix this?

That would be tricky, given that MS-DOS *would*, in fact, think this
file was a valid executable.  I don't think the syntax of "magic" is
powerful enough to distinguish this from a "real" executable.  You might
be able to do it by adding file(1) support for looking for invalid
opcodes, but that would get hairy very quickly...