From owner-freebsd-questions@FreeBSD.ORG  Mon Oct 13 12:08:25 2014
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])
 (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTPS id F384CF8F
 for <freebsd-questions@freebsd.org>; Mon, 13 Oct 2014 12:08:24 +0000 (UTC)
Received: from fly.hiwaay.net (fly.hiwaay.net [216.180.54.1])
 (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits))
 (Client did not present a certificate)
 by mx1.freebsd.org (Postfix) with ESMTPS id BE9CBA59
 for <freebsd-questions@freebsd.org>; Mon, 13 Oct 2014 12:08:24 +0000 (UTC)
Received: from kabini1.local (rbn1-216-180-19-48.adsl.hiwaay.net
 [216.180.19.48]) (authenticated bits=0)
 by fly.hiwaay.net (8.13.8/8.13.8/fly) with ESMTP id s9DC8GVr022348
 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO)
 for <freebsd-questions@freebsd.org>; Mon, 13 Oct 2014 07:08:17 -0500
Message-ID: <543BC227.50004@hiwaay.net>
Date: Mon, 13 Oct 2014 07:14:31 -0500
From: "William A. Mahaffey III" <wam@hiwaay.net>
User-Agent: Mozilla/5.0 (X11; FreeBSD amd64;
 rv:31.0) Gecko/20100101 Thunderbird/31.1.2
MIME-Version: 1.0
To: freebsd-questions@freebsd.org
Subject: Re: sh man page ....
References: <5437FB8B.9080008@hiwaay.net>
 <20141010183814.3ae32a05@gumby.homeunix.com> <5438755B.2000108@hiwaay.net>
 <20141013124649.4082d94f@gumby.homeunix.com>
In-Reply-To: <20141013124649.4082d94f@gumby.homeunix.com>
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.18-1
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, 13 Oct 2014 12:08:25 -0000

On 10/13/14 06:46, RW wrote:
> On Fri, 10 Oct 2014 19:10:03 -0500
> William A. Mahaffey III wrote:
>
>
>> Straight out of the script which is failing. Under linux, if I call
>> the script w/ no '-s #' option, the variable 'slept' is not set, &
>> linux (or more accurately linux bash) evaluates that to the value oif
>> zero (0).
>>
>>
>> [wam@kabini1, ~, 7:07:22pm] 386 % sh
>> $ if [ 0 -lt $(($slept)) ] ; then echo -n "$cmd: sleeping $slept secs
>> ...." ; sleep $(($slept)) ; echo " done." ; fi
>> arithmetic expression: expecting primary: ""
>> [wam@kabini1, ~, 7:07:45pm] 387 %
>
> The problem here is that you have:
>
>    [ 0 -lt $(($slept)) ]
>
> If you change it to the normal usage
>
>    [ 0 -lt $((slept)) ]
>
> it works as expected.
>
> Is there any particular reason for the extra "$"?
>
> I guess the difference is not in the handling of uninitialised
> variables, but specifically in the handling of $(()) which is an error
> in sh, but not is bash.
> _______________________________________________
> freebsd-questions@freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-questions
> To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org"
>

Good question. I am *not* a bash/shell wiz, but I think the extra "$" 
was needed to get bash to behave (Linux, FC14 64-bit, i.e. a bit dated). 
Not 100% on that, but pretty sure ....

-- 

	William A. Mahaffey III

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

	"The M1 Garand is without doubt the finest implement of war
	 ever devised by man."
                            -- Gen. George S. Patton Jr.