Getting rid of an uninitialized warning

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

Hello Monks,

I have a Perl-CGI code, and when it's run, everything looks fine. But I checked out the error_log and found:

[Thu Jun 23 16:28:09 2011] [error] [client ::1] Use of uninitialized value $c_enabling in string eq at /Library/WebServer/CGI-Executables/myfulltextsearch2011.cgi line 53, <IRVF> line 289.

This was caused by this line of code:

 my $c_enabling = param('enabling')
...
if ($c_enabling eq 'on')
[download]

I got rid of it by putting this line in between:

$c_enabling='';

Which is obviously not practical (in the case that the param was chosen). How can I permanently fix this? Is it part of the HTML?

Comment on Getting rid of an uninitialized warning Select or Download Code

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Re: Getting rid of an uninitialized warning by Sandy (Curate) on Jun 23, 2011 at 20:50 UTC
Replace `my $c_enabling = param('enabling');` [download] with `my $c_enabling = param('enabling') \|\| '';` [download] If $c_enabling can never have '0' as a valid input; otherwise `my $c_enabling = param('enabling'); $c_enabling = '' unless defined $c_enabling;` [download]	[reply] [d/l] [select]
Re^2: Getting rid of an uninitialized warning by jonc (Beadle) on Jun 23, 2011 at 21:06 UTC
Thanks a lot, that was the problem, it was aloud to have a 0 input, but I didn't know how to check that easily. I had tried the defined check, but it didn't work. I really hope this can't backfire, since I just put it everywhere...	[reply]
Re: Getting rid of an uninitialized warning by ikegami (Patriarch) on Jun 23, 2011 at 21:03 UTC
Correct me if I'm wrong, but I believe `enabling` can either be present with value '`on`' or absent. If so, the provided solutions are overkill and all you need is `my $c_enabling = param('enabling') ... if ($c_enabling)` [download]	[reply] [d/l] [select]
Re^2: Getting rid of an uninitialized warning by jonc (Beadle) on Jun 23, 2011 at 21:08 UTC
Ah, I see, just check if there is a value there. Genius. Thanks! Re-phrased Question: Are there any possible negative outcomes from using the methods presented by others, where the conditional statement includes "the defined -or operator"?	[reply]
Re^3: Getting rid of an uninitialized warning by ikegami (Patriarch) on Jun 23, 2011 at 22:04 UTC
I don't understand the question.	[reply]
Re: Getting rid of an uninitialized warning by ww (Archbishop) on Jun 23, 2011 at 20:56 UTC
What you've told us leaves me less than confident that I understand what the actual problem is. See I know what I mean. Why don't you?. But here are a few WAGs/WAIs: Make the parameter required (since it appears the log tells you that some visitor missed a checkbox, input field or some such) in the html. Consider using CGI::Validate or Params::Validate Move your `$c_enabling='';` above (eg, before) the code you've shown (and move the `my` to the same line and put a test of the parameter's existance ahead of line 1 along code to tell the user than the param must be supplied, at which point `$c_enabling` won't be uninitialized and the visitor will be cautioned against omitting a field. Of course, if I've mis-diagnosed your problem, the above may be mere garbage....	[reply] [d/l] [select]
Re^2: Getting rid of an uninitialized warning by jonc (Beadle) on Jun 23, 2011 at 21:13 UTC
Sorry, I will try and be more clear from now on. Thanks for letting me know.	[reply]
Re: Getting rid of an uninitialized warning by wind (Priest) on Jun 23, 2011 at 20:55 UTC
The Defined-Or operator // is what you want: `my $c_enabling = param('enabling') // '';` [download]	[reply] [d/l]


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