Path: utzoo!attcan!uunet!mcsun!hp4nl!star.cs.vu.nl!maart
From: maart@cs.vu.nl (Maarten Litmaath)
Newsgroups: comp.unix.questions
Subject: Re: Bourne shell oddity
Message-ID: <7257@star.cs.vu.nl>
Date: 8 Aug 90 15:34:27 GMT
References: <9008071535.AA01487@stc06.CTD.ORNL.GOV>
Sender: news@cs.vu.nl
Reply-To: maart@cs.vu.nl (Maarten Litmaath)
Organization: VU Dept. of Computer Science, Amsterdam, The Netherlands
Lines: 42

In article <9008071535.AA01487@stc06.CTD.ORNL.GOV>,
	de5@STC06.CTD.ORNL.GOV (SILL D E) writes:
)...
)#!/bin/sh
)foo=bar
)while true
)do
)    if [ $foo = bar ]
)    then
)        foo=baz
)        echo foo=${foo}
)        break
)    fi
)done </dev/null
)echo foo=${foo}

Most current implementations: foo=bar.
POSIX requires: foo=baz.

)...
)Another Question:  Is there a simple workaround, preferably something
)more elegant than passing values in files?

	foo=bar

	# dup(2) file descriptor 0 to fd 9,
	# then connect fd 0 (== stdin) to /dev/null
	exec 9<&0 < /dev/null

	while true
	do
		...
	done

	# dup() fd 9 back to fd 0,
	# i.e. reconnect fd 0 to the original stdin, then close fd 9
	exec 0<&9 9<&-

	echo foo=$foo
--
   "UNIX was never designed to keep people from doing stupid things, because
    that policy would also keep them from doing clever things."  (Doug Gwyn)