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From: davidsen@sixhub.UUCP (Wm E. Davidsen Jr)
Newsgroups: comp.unix.shell
Subject: Re: Bourne-shell incompatibilities
Keywords: Bourne shell arguments
Message-ID: <2836@sixhub.UUCP>
Date: 9 Jan 91 01:52:41 GMT
References: <18476@shlump.nac.dec.com> <3074@wyse.wyse.com> <442@minya.UUCP>
Reply-To: davidsen@sixhub.UUCP (bill davidsen)
Organization: *IX Public Access UNIX, Schenectady NY
Lines: 20

In article <442@minya.UUCP> jc@minya.UUCP (John Chambers) writes:

| Often only one of these is accepted by any particular /bin/sh, and the
| other is a syntax error.  Sometimes both are accepted (with different
| meanings).  

  I don't dispute what you say, but I have never seen a sh which didn't
buy {$a-b} notation. Of course the meaning is different when both are
available, the whole : set of expansions was added about SysIII (my
SysIII system is down or I'd check).

${a-b}		if $a is undefined use b instead
${a:-b}		if $a is undefined *or null* use b instead

and so on for all the other operators.
-- 
bill davidsen - davidsen@sixhub.uucp (uunet!crdgw1!sixhub!davidsen)
    sysop *IX BBS and Public Access UNIX
    moderator of comp.binaries.ibm.pc and 80386 mailing list
"Stupidity, like virtue, is its own reward" -me