Re: shebang pointing to script?

[John Kirk <dystan@pac.net>]

Hi Hao and all,

On Fri, Apr 14, 2000 at 04:17:27PM -0400, Simply Hao wrote:
> I'm not sure what you're trying to do.

  I've elaborated in response to Robert.  Does that clarify?

> Is it something like this?
> caller:
>     #!/usr/bin/perl -w
>     system (shift, $0) if @ARGV;
>
> processor:
>     #!/usr/bin/perl -w
>     system ('cat', shift) if @ARGV;
> % caller processor

  (I guess I never noticed that @_, on entry to a program,
refers to @ARGV.)

  Well, the result I need is to have the reference to the
processor occur in the caller, rather than in the invocation
of the caller.  That's easy to fix in your proposal.

  I suppose, then, that the crux of your suggestion is that
I pass the caller's name explicitly as an argument to the
processor, rather than attempting to have it implicit in the
calling mechanism the OS and perl is (might be) supporting.

  Since the implicit passing of the script's name, that the
shebang mechanism implements, isn't available to a script
that's targeting another shebanged script, I have to
mention the caller's name explicitly in the caller's code
anyway, to use the exec() feature (or, in your suggestion,
the system call).  Therefore, there's no payoff in trying to
avoid passing it explicitly as an argument.

  Good observation!  I was so fixated on the idea of making
things implicit, that I missed that point.  Now, my tst00
file could look like:

#!/usr/bin/perl -w
$IFH=shift;
print "tst00: processing $IFH\n";
open IFH;while(<IFH>){print;};close IFH;
1;

and my tst02 file looks like:

#!/usr/bin/perl -w
exec 'tst00',$0;
__END__
more stuff
and even more stuff

so that tst02 asks tst00 to look back at itself.  My purpose
here is to have other stuff in tst02 after the exec line, and
to have tst00 do other things to tst02 than just print it.

  Now, how do I get the effects of the exec line (and the
__END__ line) in tst02 up into the line above (the shebang
line)?  Maybe the shebang line will need to bring in a
package that takes care of everything before the rest of
tst02 ever gets to perl's compiler.  A source filter, or
something arcane like that?

  Thanks, Hao!  You've moved me onward and upward into even
more trouble.

            regards,  -- John Kirk
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