From owner-freebsd-questions@FreeBSD.ORG  Fri Aug 15 03:05:56 2014
Return-Path: <owner-freebsd-questions@FreeBSD.ORG>
Delivered-To: freebsd-questions@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115])
 (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTPS id B0CD0DF6
 for <freebsd-questions@freebsd.org>; Fri, 15 Aug 2014 03:05:56 +0000 (UTC)
Received: from sdf.lonestar.org (mx.sdf.org [192.94.73.24])
 (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
 (Client CN "mx.sdf.org", Issuer "SDF.ORG" (not verified))
 by mx1.freebsd.org (Postfix) with ESMTPS id 73719273F
 for <freebsd-questions@freebsd.org>; Fri, 15 Aug 2014 03:05:55 +0000 (UTC)
Received: from sdf.org (IDENT:cary@sdf.lonestar.org [192.94.73.15])
 by sdf.lonestar.org (8.14.8/8.14.5) with ESMTP id s7F35ftv027464
 (using TLSv1/SSLv3 with cipher DHE-RSA-AES256-GCM-SHA384 (256 bits) verified
 NO); Fri, 15 Aug 2014 03:05:42 GMT
Received: (from cary@localhost)
 by sdf.org (8.14.8/8.12.8/Submit) id s7F35fk4000760;
 Fri, 15 Aug 2014 03:05:41 GMT
Date: Fri, 15 Aug 2014 03:05:41 +0000
From: Cary <cary@SDF.ORG>
To: Warren Block <wblock@wonkity.com>, Rick Miller <vmiller@hostileadmin.com>, 
 FreeBSD Questions <freebsd-questions@freebsd.org>
Subject: Re: /bin/sh script not behaving as expected
Message-ID: <20140815030541.GA20578@SDF.ORG>
Mail-Followup-To: Warren Block <wblock@wonkity.com>,
 Rick Miller <vmiller@hostileadmin.com>,
 FreeBSD Questions <freebsd-questions@freebsd.org>
References: <CAHzLAVE1E8hZvZEnDko8-7cfx6JYypezi3oxs4vKKjxDzSzZnw@mail.gmail.com>
 <alpine.BSF.2.11.1408141143010.53473@wonkity.com>
 <20140815015559.GA21249@SDF.ORG>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20140815015559.GA21249@SDF.ORG>
User-Agent: Mutt/1.5.23 (2014-03-12)
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: Fri, 15 Aug 2014 03:05:56 -0000

On Fri, Aug 15, 2014 at 01:55:59AM +0000, Cary wrote:
> > On Thu, 14 Aug 2014, Rick Miller wrote:
> > 
> > >Hi all,
> > >
> > >#! /bin/sh
> > >
> > >disks="da2 da1 da0";
> > >
> > >for d in ${disks}; do
> > >  if [ -z "${disk}" -o "${disk}" '>' "${d}" ]; then
> > >     : ${disk:=${d}};
> > >  fi
> > >done
> > 
> > The algorithm is not clear to me,
> 
> Nor me. 
> Rick,  I don't understand the test.  Would just
> 					
> if [ -z "${disk}" ]; then 
> 
> suffice ?  Single-quoting the > operator looks like an error that would have
> prevented the shell from executing the script.

Ok, it is possible. 
You can see that with or without quotes around the comparison operator
the test is the same.

$ if [ foo != bas ] ; then echo bar;fi
bar
$ if [ foo '!=' bas ] ; then echo bar;fi
bar

> > or, more correctly,
> > 
> >   disk=`sysctl -n kern.disks | tr " " "\n" | sort | head -n1`
> > _______________________________________________



-- 
cary@sdf.org
SDF Public Access UNIX System - http://sdf.org