Path: utzoo!utgpu!watserv1!watmath!att!att!emory!samsung!cs.utexas.edu!sun-barr!apple!altos!megadon!clp
From: gwc@root.co.uk (Geoff Clare)
Newsgroups: comp.unix
Subject: Re: Shell scripts starting with "#"
Message-ID: <2236@megadon.UUCP>
Date: 24 Oct 90 02:53:24 GMT
References: <3695@zorba.Tynan.COM> <2136@megadon.UUCP> <2225@megadon.UUCP> <2227@megadon.UUCP>
Sender: clp@megadon.UUCP
Organization: UniSoft Ltd., London, England
Lines: 28
Approved: clp@megadon.UUCP

In <2227@megadon.UUCP> peter@ficc.ferranti.com (Peter da Silva) writes:
>So if you do:
>	#!/bin/sh
>	: || exec /bin/sh $0 $argv:q
>	(alias) >/dev/null 2>&1 && exec /bin/sh $0 "$@"
>
>It'll work for the bourne shell, the korn shell, and the c shell, whether
>or not you have #! working. Geeze.

But only if your script treats a single null argument the same as no
arguments, and doesn't have any special characters in it's name.
If you want to be that little bit more robust, replace Peter's

	$0 "$@"
with
	"$0" ${1+"$@"}

It's probably also worth pointing out that mechanisms of this type
rely on the process which executes the script being well behaved.
If executed from a program which does an

	execl("/somewhere/your_script", "ha ha, gotcha!", (char *)0);

or from a shell whose local search path is different to the value of
PATH it exports, then all bets are off.
-- 
Geoff Clare <gwc@root.co.uk>  (Dumb American mailers: ...!uunet!root.co.uk!gwc)
UniSoft Limited, Hayne Street, London EC1A 9HH, England.   Tel: +44-71-315-6600