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Always Looping

by jesuashok (Curate)
on Mar 27, 2006 at 07:07 UTC ( #539380=perlquestion: print w/replies, xml ) Need Help??

jesuashok has asked for the wisdom of the Perl Monks concerning the following question:

Hi All

I apreciate if anybody help me in this little problem... I just want to store an image from a url in a variable, but sometimes anything go wrong, and the routine can't open the i create this code:

$size = 0; use LWP::Simple; while ($size == 0) { my $data2 = LWP::Simple::get $site; my $size = length($data2); print "$size\n"; }

My wish is that, when the image are really stored in variable $data, the loop stop, and the programe continue... but my problem is that the loop is continually looping..

Somebody can help me?

"Keep pouring your ideas"

Replies are listed 'Best First'.
Re: Always Looping
by Corion (Patriarch) on Mar 27, 2006 at 07:12 UTC

    The problem is that you are not using strict, or rather, you are not Coping With Scoping. You actually have two variables $size - one, the global $size which you set to 0 at the top of your program, and another, $size, which you declare in the loop and set it to the length of your data. You should do away with the inner my and the script should work:

    use strict; use LWP::Simple; my $size; my $data2; while (! length $data2) { $data2 = LWP::Simple::get($site); if (! length $data2) { warn "Couldn't get a response from '$site', sleeping"; sleep 5; # give the website some time }: }; ...
      I'd always try to avoid a loop which could continue to fail like this. What if the file is deleted? You'll be looping forever.
      use strict; use LWP::Simple; my $data = ""; my $try_count = 0; while ($try_count++ < 5) { $data = LWP::Simple::get('http://somedomain/'); last if defined $data; print "were is this file?\n"; sleep(5); };
      I also changed the criteria for success to check for 'definedness', because the LWP::Simple::get() function will explictly return undef if it fails.
      my name's not Keith, and I'm not reasonable.

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