From owner-freebsd-questions@FreeBSD.ORG  Mon Jun 10 18:59:11 2013
Return-Path: <owner-freebsd-questions@FreeBSD.ORG>
Delivered-To: freebsd-questions@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 by hub.freebsd.org (Postfix) with ESMTP id 2D022F33
 for <freebsd-questions@freebsd.org>; Mon, 10 Jun 2013 18:59:11 +0000 (UTC)
 (envelope-from lconrad@go2france.com)
Received: from omx1.hctc.net (omx1.hctc.net [69.4.62.74])
 by mx1.freebsd.org (Postfix) with ESMTP id 149B31AE3
 for <freebsd-questions@freebsd.org>; Mon, 10 Jun 2013 18:59:10 +0000 (UTC)
Received: from hctc.net (unknown [69.4.62.44])
 by omx1.hctc.net (Postfix) with ESMTP id 622C711462
 for <freebsd-questions@freebsd.org>; Mon, 10 Jun 2013 13:53:31 -0500 (CDT)
X-Default-Received-SPF: pass (skip=loggedin (res=PASS)) x-ip-name=69.4.54.186; 
From: lconrad@go2france.com
To: <freebsd-questions@freebsd.org>
Subject: Bourne shell "if" syntax
Date: Mon, 10 Jun 2013 13:53:26 -0500
Message-ID: <51b620a6.42f.2b6a6400.5605dcf0@go2france.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii; format=flowed
X-Originating-IP: 69.4.54.186
X-Mailer: SurgeWeb - Ajax Webmail Client
X-Authenticated-User: lconrad@go2france.com 
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/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: Mon, 10 Jun 2013 18:59:11 -0000



script fragment:

PTR=`dig @some.dns +short +norec -x a.b.c.d`

echo "$PTR"

if  [  "$PTR"  ==  ""  ]  ;  then

echo "$PTR" >> /path/to/PTR_absent.txt

fi

===========

output for an IP:


a-b-c-d.domain.net.
[: a-b-c-d.domain.net.: unexpected operator

thanks
Len