From owner-freebsd-stable  Sun Feb 25 10:50:48 2001
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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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