CGI "uninitialized value" question

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

Greetings monks,

So, I've never written a CGI before, and I'm trying to get my feet wet, so to speak. In playing around with CGI, I've discovered something that I find a bit wierd. First the code:

#!/usr/bin/perl -w

use strict;
use CGI qw/:standard/;

print header();
print start_html("This is a test");
print start_form();
print end_form();
[download]

Pretty standard, eh? Well, when I run this, I get the following output:

Content-Type: text/html; charset=ISO-8859-1


<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE html
        PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
         "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en-US" xml:lang="en-U
+S"><head><title>This is a test</title>
</head><body>
Use of uninitialized value in length at (eval 9) line 11.
<form method="post" action="/test.pl" enctype="application/x-www-form-
+urlencoded">
[download]

Notice the "uninitialized value" warning. From what I've been able to ascertain, the trouble starts with the start_form sub. I looked at the documentation for CGI, and it seems like it is reasonable to call start_form sans arguments. Also, I looked at CGI.pm's source, specifically at the startform sub. I'm able to clear the warning if I provide a query string, or if I provide an action to the subroutine. Perhaps I'm making too much out of it, but I would like this to run clean under warnings. Any insight would be appreciated.

</form>

thanks in advance,
thor

Comment on CGI "uninitialized value" question Select or Download Code

Replies are listed 'Best First'.
Re: CGI "uninitialized value" question by Roger (Parson) on Dec 09, 2003 at 05:15 UTC
That bit of code worked for me under Perl 5.6.1 with an older version of the CGI library. However when I ran it under 5.8 with new CGI library, I get the warnings messages. It turns out that you need to define the 'action' for the form to get rid of the error message. Could be a bug in the new version of CGI module, but then again you should really define the action to be taken when submitting the form. `#!/usr/bin/perl -w use strict; use CGI qw/:standard/; print header(); print start_html("This is a test"); print start_form(-action=>"/cgi-bin/test.pl", -method=>"GET"); print end_form();` [download]	[reply] [d/l]
Re: Re: CGI "uninitialized value" question by thor (Priest) on Dec 09, 2003 at 05:23 UTC
I would agree that providing an action would be a reasonable fix, except that the documentation says that it provides a reasonable default. I consider this a bug unless there's compeling evidence to the contrary... thor	[reply]
Re: Re: Re: CGI "uninitialized value" question by Roger (Parson) on Dec 09, 2003 at 05:27 UTC
Well, I guess the documentation has to define what is a reasonable default. From what I saw in the OP, he you got `action="/test.pl"` as a default, which would not work if the script was stored under "/cgi-bin".	[reply] [d/l]
Re: Re: Re: Re: CGI "uninitialized value" question by rdfield (Priest) on Dec 09, 2003 at 09:42 UTC
Re: CGI "uninitialized value" question by Anonymous Monk on Dec 09, 2003 at 13:13 UTC
When you run the script from the command line, $ENV{QUERY_STRING} is not necessarily defined. startform() refers to QUERY_STRING if the action is unspecified. Also, don't forget print end_html();	[reply]
Re: CGI "uninitialized value" question by pg (Canon) on Dec 09, 2003 at 05:15 UTC
Tried your code with Perl 5.8.0 on win98, couldn't repeat the warning message you mentioned.	[reply]
Re: CGI "uninitialized value" question by Anonymous Monk on May 08, 2004 at 09:59 UTC
This bug is fixed in CGI.pm version 3.05. In this part of CGI.pm: `1721c1643 < if (exists $ENV{QUERY_STRING} && length($ENV{QUERY_STRING})>0 +) { --- > if (length($ENV{QUERY_STRING})>0) {` [download]	[reply] [d/l]


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