Undefined value as a symbol reference

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

Forgive me brothers, it has been a long time since I last sought your wisdom.

I am working on a socket server to monitor remote machines, and I thought that it would be nice to write a pair of functions, writeClient and writeLog. writeLog appears to be working just fine. However, writeClient throws

Can't use an undefined value at ./myPerlServ.pl line 150.

Here are some of the relevant pieces of code:

    my $client;

    while ( $client = $server->accept() ) {
        ...
        writeClient("I'm trying to do something, really!");
    }

    ...

sub writeClient {
    ### Read args, take first arg and use it, dump the rest
    my ( $message, @junk ) = @_;

    my $clientMessage = "$message\r\n";
    print $client $clientMessage;
}
[download]

I'm curious, do I need to pass $client into writeClient and then dereference it? (References in Perl confuse me a great deal sometimes.) Or is there something else that I am completely missing?

If you make something idiot-proof, eventually someone will make a better idiot.
I am that better idiot.

Comment on Undefined value as a symbol reference Download Code

Replies are listed 'Best First'.
(z) Re: Undefined value as a symbol reference by zigdon (Deacon) on Mar 11, 2003 at 13:45 UTC
You're trying to print to the filehandle $client, but it's not defined in writeClient, is it? or is that 'my' not bound by any codeblock? Easy way out - Add a line before the 'print': `warn "client not defined!" and return unless defined $client;` [download] -- zigdon	[reply] [d/l]
Re: Undefined value as a symbol reference by robartes (Priest) on Mar 11, 2003 at 13:47 UTC
`$client` might be out of scope in sub writeClient. In fact, the fact that the `my $client` is indented further than the writeClient sub is, kind of hints that way. CU Robartes-	[reply] [d/l] [select]
Re: Undefined value as a symbol reference by peschkaj (Pilgrim) on Mar 11, 2003 at 13:58 UTC
I think you've both hit the nail on the head. Although writeClient is being called from within the while loop, where $client is a valid variable, $client isn't in scope in writeClient. I failed to realize that I needed to to pass the handle into the subroutine. Once I did that everything worked like a charm. Thank you both If you make something idiot-proof, eventually someone will make a better idiot. I am that better idiot.	[reply]


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