Date: Sun, 25 Feb 2001 13:49:57 -0500
From: "Brandon S. Allbery KF8NH" <allbery@ece.cmu.edu>
To: Andreas Klemm <andreas@FreeBSD.org>
Cc: stable@FreeBSD.org, apsfilter-devel@apsfilter.org, =?ISO-8859-1?Q?Michael_Lo=DFin?= <phallobst@web.de>
Subject: Re: Brokenness: : ${TMPDIR:-/tmp} results in empty TMPDIR variable
Message-ID: <112240000.983126997@pyanfar.ece.cmu.edu>
In-Reply-To: <20010225194442.A15290@titan.klemm.gtn.com>
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On Sunday, February 25, 2001 19:44:42 +0100, Andreas Klemm
<andreas@FreeBSD.org> wrote:
+-----
| On Sun, Feb 25, 2001 at 01:24:03PM -0500, Brandon S. Allbery KF8NH wrote:
| > On Sunday, February 25, 2001 13:43:11 +0100, Andreas Klemm
| > <andreas@FreeBSD.ORG> wrote:
| > +-----
| > | Another -STABLE problem:
| > |
| > | : ${TMPDIR:-/tmp}
| > |
| > | The variable stays empty.
| > +--->8
| >
| > It should; the correct idiom is
| >
| > : ${TMPDIR:=/tmp}
|
| I don't understand that, why :- doesn't work....
|
| Well the bash manpage for example states:
|
| ${parameter:-word}
| Use Default Values. If parameter is unset or null,
| the expansion of word is substituted. Otherwise,
| the value of parameter is substituted.
|
| ${parameter:=word}
| Assign Default Values. If parameter is unset or
| null, the expansion of word is assigned to parame-
| ter. The value of parameter is then substituted.
| Positional parameters and special parameters may
| not be assigned to in this way.
+--->8
:- affects only the current expansion; := affects the actual value of the
variable.
| It seems to work this way on other people machines.
+--->8
Are you sure? -/:- and =/:= have behaved this way for as long as I've been
working with Bourne-like shells (call it 1982).
--
brandon s. allbery [os/2][linux][solaris][japh] allbery@kf8nh.apk.net
system administrator [WAY too many hats] allbery@ece.cmu.edu
electrical and computer engineering KF8NH
carnegie mellon university ["better check the oblivious first" -ke6sls]
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