Re: Use of uninitialized value in open second time but not first.

Excellent suggestions, monks.

I don't really see the problem in the same way, however. If the problem is here:

 my $output; # this value is unintialized
 open my $old_stdout, '>&=', \*STDOUT;
 close STDOUT;
 # Use of uninitialized value in open at the following line
 open STDOUT, '>', \$output;
[download]

It's not an issue of 'spitting warnings at the second opening of a memory file'. $output really is uninitialized, and STDOUT, when its called, is already initialized. So it actually spits a warning the first time.

What I'm trying to say is that the warning is thrown more or less as expected. It's been pointed out that setting $output='' will fix the problem. Also... turning off 'use warnings' would probably silence it, but I wouldn't know because I never turn off warnings.

I hope this helps.

Bro. Doug :wq

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Re^2: Use of uninitialized value in open second time but not first. by kyle (Abbot) on Mar 31, 2007 at 19:33 UTC
So it actually spits a warning the first time. Where does that warning go? It's not on my screen when I run it. As I see it, `$output` is uninitialized both times, but the warning is not printed the first time. I'm confused also because what I pass to open is a reference to `$output` which is always a real value regardless of whether `$output` is initialized or not.	[reply] [d/l] [select]
Re^3: Use of uninitialized value in open second time but not first. by Bro. Doug (Monk) on Apr 01, 2007 at 16:29 UTC
I see where I went wrong. To give a more concise answer to this question, I got the code to run and saw the results just as you reported. So I started experimenting. I noticed there are a lot of operations on references happening here, which makes me leery when you're mucking with global symbols (STDOUT, for instance). So I took $output and gave it persistence in scope: `our $output ; # changed 'my' to 'our'` [download] The problem went away. By the way, I agree with the monks who suggested using select(). Peace, monks. Bro. Doug :wq	[reply] [d/l]