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Path: utzoo!watmath!clyde!burl!ulysses!mhuxl!ihnp4!ihuxt!martillo
From: martillo@ihuxt.UUCP (Yehoyaqim Martillo)
Newsgroups: net.unix-wizards
Subject: Re: Why parse lines with colons
Message-ID: <641@ihuxt.UUCP>
Date: Thu, 12-Jul-84 13:07:51 EDT
Article-I.D.: ihuxt.641
Posted: Thu Jul 12 13:07:51 1984
Date-Received: Fri, 13-Jul-84 04:33:27 EDT
References: <526@spuxll.UUCP>
Organization: AT&T Bell Labs, Naperville, IL
Lines: 37



>One of the reasons /bin/sh (bsh to those who like csh)
>parses lines with ":" in the beginning is because of
>constructs like the following:

>: ${FOO:-default}

>This effectively sets $FOO to a default value if not previously
>set.  

According to my shell manual the value of this expression is $FOO is FOO
is set and not not null otherwise, the value is default.  The value of FOO
does not change.  I believe he means 

: ${FOO:=default}
	
>The longhand way would be:

>if [ "${FOO}" = "" ]
>then
>	FOO=default
>fi

He could just as well have used:

FOO=${FOO:-default}
	
which avoids the ":" and takes hardly any (and probably no) more time to
execute.

-- 

Who wouldn't break for whales?

Yehoyaqim Shemtob Martillo