Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!usenet.ins.cwru.edu!cwns1!chet
From: chet@cwns1.CWRU.EDU (Chet Ramey)
Newsgroups: comp.unix.shell
Subject: Re: Bourne shell differences w.r.t functions?
Keywords: Bourne shell, /bin/sh, functions, ksh, bash, argument list, POSIX
Message-ID: <1990Sep17.155018.4700@usenet.ins.cwru.edu>
Date: 17 Sep 90 15:50:18 GMT
References: <1990Sep13.163836.19937@cs.umn.edu> <1990Sep13.221943.15220@usenet.ins.cwru.edu> <3693@segue.segue.com>
Sender: news@usenet.ins.cwru.edu
Reply-To: chet@po.CWRU.Edu
Organization: Case Western Reserve Univ. Cleveland, Ohio, (USA)
Lines: 60

In article <3693@segue.segue.com> bruce@segue.segue.com (Bruce Adler) writes:

I wrote:
$ >Systems with /bin/sh based on the AT&T s5r3 /bin/sh.  This version of
$ >the shell preserves the dollar variables around a series of function
$ >calls.  The s5r3.2 /bin/sh also allows recursive functions.

$ I don't think this is precisely correct.  Perhaps you meant that only 
$ the *positional* parameters are preserved around a function call.  The
$ *local* variables aren't preserved.

Yes, I meant the positional parameters.  AT&T Bourne shells do not have local
variables.  All variables are global.

$ What does the following script do on your system:
$ 
$ 	#!/bin/sh
$ 	set -- yes
$ 	lvar="yes"
$ 	foobar() { lvar=$1; }
$ 	foobar no
$ 	echo positional variable $1, local varibale $lvar

The /bin/sh running on my system is bash.  Running your script unmodified
says positional yes, local no.  Changing the script so that `lvar' is a
real local variable (making the script read `local lvar=$1'), says
positional yes, local yes.

$ My s5r3.2 based Bourne shell says positional yes, local no.  If your 
$ shell doesn't preserve local variables then it's difficult to implement
$ real recursive functions (i.e. a function that invokes itself).

True, but the s5r3.2 sh does not prohibit them:

zen$ sh53 				<----- s5r3.2 sh
zen$ f()
> {
> if [ $1 -eq 0 ] ; then
>         return
> else
>       echo $1
>       f `expr $1 - 1`
> fi
> }
zen$ f 5
5
4
3
2
1

It just limits their usefulness.

Chet
-- 
Chet Ramey				``Levi Stubbs' tears run down
Network Services Group			  his face...''
Case Western Reserve University	
chet@ins.CWRU.Edu