creating an error message

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

I am writting a user logon page, and want to add an error check to it so that if the username or password field are left blank an error message is printed to the screen. I have been trying the following ways of doing this

   if($username eq null) {

                display_error_message();
       }
[download]

This is bringing back an internal software error. Can anybody see why this is happening? Thanks

Comment on creating an error message Download Code

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Re: creating an error message by rhesa (Vicar) on Dec 10, 2006 at 19:41 UTC
`null` is not a Perl keyword. You probably want `if( !defined $username )` or `if( $username !~ /\S/ )`. Or maybe both. Also don't forget to print a http header before printing any content.	[reply] [d/l] [select]
Re: creating an error message by Old_Gray_Bear (Bishop) on Dec 10, 2006 at 22:31 UTC
You might want to consider adding one more line to your code: `use warnings;` [download] If you do, you will get the following message: `Unquoted string "null" may clash with future reserved word at line ... +."` [download] I'd personally make it two lines: `use strict; use warnings;` [download] ---- I Go Back to Sleep, Now. OGB	[reply] [d/l] [select]
Re: creating an error message by PockMonk (Beadle) on Dec 10, 2006 at 20:25 UTC
If this is a CGI app or similar, adding the following at the top of your script will help in returning more detailed errors for problems such as this than simply "500 internal server error": `#!/usr/bin/perl -w # as normal use strict; use warnings; use CGI::Carp "fatalsToBrowser";` [download] Dan	[reply] [d/l]
Re: creating an error message by Joost (Canon) on Dec 10, 2006 at 19:53 UTC
This is bringing back an internal software error. Can anybody see why this is happening? I'm assuming you mean "internal server error" - go look in the logs. As mentioned null isn't a perl keyword, so this will only work if you have a null() function defined. Also, you probably want to use defined instead. "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply]
Re: creating an error message by ysth (Canon) on Dec 10, 2006 at 20:30 UTC
The "internal software error" probably means your perl program threw an error, the text of which ended up in the server's error log. If you have no access to the error log (for any reasonable development environment, you really should) see CGI::Carp.	[reply]