Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!convex!usenet
From: tchrist@convex.COM (Tom Christiansen)
Newsgroups: comp.lang.perl
Subject: Re: turning on warnings from within a script
Message-ID: <1991May11.183203.5273@convex.com>
Date: 11 May 91 18:32:03 GMT
References: <1991May11.154445.655@batcomputer.tn.cornell.edu>
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Reply-To: tchrist@convex.COM (Tom Christiansen)
Organization: CONVEX Software Development, Richardson, TX
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From the keyboard of lijewski@theory.tn.cornell.edu (Mike Lijewski):
:Is there any way to turn on the "-w" switch from within Perl?  What I
:would like to be able to do is turn on the "-w" switch from inside of
:a Perl script, depending on the options I pass to the script.
:Specifically, if I put some debugging code in my script, which I
:toggle with a "-d" switch, I would like to enable Perl's warning
:messages as well.  I don't like running with "-w" enabled since Perl
:warns about some things which are perfectly legal.

The writeable $^W variable contains the value of the -w switch in 4.0
version of perl.  For example, the first assignment here gives a warning,
but the second one doesn't.

    $ = 1;		# enable -w
    $a = $b[$i];	# generate warning
    $ = 0;		# disable -w
    $c = $d[$i];	# remain silent

Note that this only applies the run-time warnings, not compile-time 
ones (unless you're in an eval and thus compiling).   This means 
that you won't get "Possible typo" messages, but you will get 
"uninitialized variable" messages.

--tom
--
Tom Christiansen		tchrist@convex.com	convex!tchrist
		"So much mail, so little time."