How to test for uninitialized value

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How to test for uninitialized value

Before the script blows up

runner

1:51 am on Oct 25, 2006 (gmt 0)

I can't remember how to test a scalar to see if it is uninitialized before being used. I am writing a cgi script in perl and in the development process I have found a place where it is possible for a particular scalar $article to be uninitialized. I want to test for this condition so it can be corrected before the scalar is used somewhere and blows chunks.

I've done this before but I can't remember what I did. I've googled and searched but I guess I'm not using the correct search words. I'm getting really frustrated!

runner

1:56 am on Oct 25, 2006 (gmt 0)

I think I'll give the variable a default value and then check to see if it is still set to that value before I use it.

runner

1:59 am on Oct 25, 2006 (gmt 0)

Darn, that won't work...

runner

2:14 am on Oct 25, 2006 (gmt 0)

OK I found it!

{
no warnings 'uninitialized';
if ( CGI::param('name') ) {
print "Hello, " . CGI::param('name');
}
else {
print "Hi there.";
}
}

wruppert

3:32 am on Oct 25, 2006 (gmt 0)

The "defined" function tests for uninitialized vars -

$var = '' unless defined $var;

$var ¦¦= '';

if (!defined($var) {do stuff}

perl_diver

4:51 pm on Oct 25, 2006 (gmt 0)

for form data you not only want to check if it's defined but also if it's valid. If all you do is check to see if it's defined a person can enter something as useful as a single space character in the form widget and your script will accept that as the value.