Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!amdcad!ames!vsi1!wyse!mips!dce
From: dce@mips.COM (David Elliott)
Newsgroups: comp.unix.questions
Subject: Re: test the exit status inside a shell
Keywords: exit status
Message-ID: <4312@dunkshot.mips.COM>
Date: 1 Oct 88 21:28:12 GMT
References: <5651@sgistl.SGI.COM> <3741@boulder.Colorado.EDU> <703@necis.UUCP> <826@philmds.UUCP>
Reply-To: dce@dunkshot.UUCP (David Elliott)
Organization: MIPS Computer Systems, Sunnyvale, CA
Lines: 32

In article <826@philmds.UUCP> leo@philmds.UUCP (Leo de Wit) writes:
>while command1; do commands; done  # while command1 succeeds do the commands
>until command1; do commands; done  # until command1 succeeds do the commands
>if command1; do commands; done     # if command1 succeeds do the commands
	      ^^           ^^^^

"if" in sh uses "then" and "fi", not "do" and "done", but that's not what
I followed up for.

An interesting note about while and until is that the actual syntax is

	while list; do list; done

where a "list" is a list of commands (the semicolons can be newlines).

This means that the loop

	a=no
	while
		echo "Enter a new value for a: \c"
		[ "$a" != "no" ]
	do
		read a
		echo "Entered $a"
	done

is a legal loop.  I've only seen this used once, but it could be useful
as fast machines make it more reasonable to use sh to write interactive
commands.

-- 
David Elliott		dce@mips.com  or  {ames,prls,pyramid,decwrl}!mips!dce