Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!umd5!uvaarpa!mer6g
From: mer6g@uvaarpa.virginia.edu (Marc E. Rouleau)
Newsgroups: comp.sources.d
Subject: Re: Perl: Hacking The !# Simulation
Message-ID: <75@uvaarpa.virginia.edu>
Date: 2 May 88 15:01:23 GMT
References: <67@uvaarpa.virginia.edu> <394@dsinc.UUCP>
Reply-To: mer6g@uvaarpa.Virginia.EDU (Marc E. Rouleau)
Organization: University of Virginia, Charlottesville
Lines: 36

>>eval "exec /bin/perl `/usr/local/ksh -c \"whence $0\"` $*"
>>	if $running_via_sh;
>>
>>The only folks still left in the cold are those who have only the Bourne
>>shell (sh(1)).
>
>Even those are not left out in the cold, they can use the type internal
>command which finds the executable.

But "type" prints its output in "whence -v" format, so further processing with
something like expr(1) would be necessary.

Also, not all sh's have a builtin "type": our 4.3bsd Microvax and 4.3bsd Vax
11/780 are examples.  (Now I know that 4.3bsd machines are lucky enough to have
the #! hack and therefore need not be considered in an all-inclusive solution
to this problem--I'm just wondering if _all_ sh's on machines which do _not_
have the #! hack do indeed have the "type" builtin ...)

>Now we need a way to have it automatically determine the shell type and use
>the appropriate command if needed.

I think this is all becoming much too complicated.  The original idea is
relatively elegant and simple, and, in the absence of #! for System V, it
seems like the next best thing; _however_, I really think the path-searching
complexity oughta be implemented within perl.

What if we could do something like this:

eval "exec /bin/perl -S $0 $*"
	if $running_via_sh;

The -S switch would cause the script file to be searched for either using an
algorithm implemented within perl (best case) or else by running a program
(ksh, csh, sh) the path to which is configurable and compiled in (acceptable
case).

	-- Marc Rouleau