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Re: sh weirdness?

From: der Mouse <mouse%Rodents-Montreal.ORG@localhost>
Subject: sh weirdness?
Date: Fri, 17 Sep 2010 15:52:36 -0400 (EDT)

> I've been trying to use some external software across various of my
> NetBSD machines, and have run into a problem that I've tracked down to
> a difference in sh behaviour.  Fortunately, a small test case exists.
> Running this
> sh -n -c 'case foo in (bar | baz) echo one; esac'
> on 4.0.1 returns nothing, but on 1.4T, it gives
> Syntax error: word unexpected (expecting ")")
> Can anyone explain what this syntax (with the leading open paren and no
> closing ;;) does?  The 4.0.1 sh manpage is no help; it lists only the
> no-( with-;; syntax, even though the sh it supposedly describes accepts
> this mutant version.  Based on the context in which I found it, it
> looks as though the case above is probably semantically equivalent to
> "case foo in bar|baz) echo one;; esac", but I hesitate to just replace
> it without actually understanding what the code I'm replacing does.

It is equivalent indeed. As far as I know, this syntax is mandated by
POSIX Shell Command Language (e.g. as described in [1]). The leading
parenthesis as well as the ';;' for the last case are both optional.



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