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From: rm55+@andrew.cmu.edu (Rudolph T. Maceyko)
Newsgroups: comp.lang.perl
Subject: PERL mucks with "magic number?"
Message-ID: <saFPa1u00WB70wDoQn@andrew.cmu.edu>
Date: 7 May 90 18:08:01 GMT
Organization: Carnegie Mellon, Pittsburgh, PA
Lines: 32

Hi.  I'm trying to use PERL in a multiple-machine (VAX, rt, sun)
environment, same OS, though (Andrew, if you know it).  Anyway,
because of symlink resolution and kernel limits on #! pathnames, my
PERL scripts began with

#!/bin/csh -f

eval "exec /usr/contributed/bin/perl -S $0 $*"
	if $running_under_some_shell;

Well, after patchlevel 15 was installed, all of my scripts began to
hang, without doing anything (i.e., no output).  I have nothing to do
with installing PERL here, by the way.  Anyway, it seems that PERL is
looking at the "magic number" when it shouldn't be.  Actually, it's
not only LOOKING, but EXECUTING the pathname as if it were the KERNEL!
#!/bin/csh -fx reports an infinite loop of exec'king.

What reasoning was behind this change, or, if it wasn't changed, why
isn't this implemented intuitively (kernel looks at magic number, PERL
ignores it -- it's a comment)?  Anyway, the change occurred after an
upgrade from 8 to 15.  The "fix" is to remove the #! altogether and
let the evel "exec ..." / if $running_under_some_shell; do its trick
from the shell.  Still PERL shouldn't play with the #! line -- how
does it know when to stop?

Rudy
 
+---------+
: +-----+ : Rudy Maceyko
: : +-+ : : rm55+@andrew.cmu.edu
: : : +-+ : rtmst@unix.cis.pitt.edu
+-+ +-+-+-+