Re: non-determinate program execution in perl

[Ken Irving <fnkci@uaf.edu>]

> On 8/30/05, Donald Perkovich <donp@mindspring.com> wrote:
> 
>     I have a perl program that runs every hour that scans a POP3 maildrop.
>     About once every other day the program fails and I get this error:
> 
>     Can't call method "user" on an undefined value at
>     /home/user/bin/fetch- headers.pl line 40.
> 
>     It appears to me that the hash isn't being properly initialized.
>     Here is the code that initializes the hash.  None of these values
>     are changed in the program once they are set.
> 
>     my %pop = (
>          server => 'pop.example.org',
>          port   =>  110,
>          user   => 'someuser@example.org',
>          pass   => 'asswordpay',
>          dir    => '/home/user/mail'
>     );
> 
>     Here is Line 40.
> 
>     $server->user($pop{user}) || die;
> 
>     My questions are:
>     (1) Is there a better way to initialize the hash?
>     (2) Could this be a fault in perl itself?
>     (3) Is it something else entirely?
> 
>     Don

Here $server is a perl object, and user() a method with $pop{user} 
as its argument.  From the error message the $server object is not
being initialized, and this would be somewhere else in the code, not
shown here.

If the code works most of the time, the failure is probably due to 
some problem connecting to the server, but the code (sigh) continues
to run past the actual failure and the error message is generated 
later.  Better would be to place some sort of error checking at the
point where $server is initialized, and die with a more meaningful
message.

-- 
Ken Irving, fnkci@uaf.edu