Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cmcl2!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn)
Newsgroups: comp.unix.wizards
Subject: Re: How does Unix kernel find /bin/sh?
Keywords: #!/bin/sh
Message-ID: <10851@smoke.BRL.MIL>
Date: 28 Aug 89 08:26:54 GMT
References: <5@minya.UUCP>
Reply-To: gwyn@brl.arpa (Doug Gwyn)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 21

In article <5@minya.UUCP> jc@minya.UUCP (John Chambers) writes:
>the "#!" notation.  You'd think by now that everyone would realize
>what a Good Idea this is, and it'd have been installed everywhere.

I think it's slated for SVR4.0.  However, not everyone agrees that
it's a Good Thing.  It causes problems when porting scripts across
systems, because the various interpreter utilities may not have
identical pathnames across systems.  Also, some of us have relied
on System V NOT understanding the #! convention, and our scripts
will break when SVR4.0 arrives.

>The problem is simple:  when I exec a script directly, the kernel
>doesn't run /bin/sh, it runs /bin/bsh!

No, it's run under whatever shell you're already running.  The
shell forks a subshell to handle the script, after the direct
exec() system call fails.

>I've yet to see any mention of the "#!" notation in any document anywhere;

It's documented in the 4.3BSD PRM under EXECVE(2).