exit isn't killing children

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

exit(0) isn't killing the children in this. On the first connect, it creates a new child (I assume,) says "Hi!", then does nothing. The process still has two threads even after it would appear that the child would be exitting. What am I doing wrong? (The while loop was originally from the Cougar book but has since been chopped down to the bare minimums.)

my $listener = IO::Socket::INET->new(LocalPort => 12345,
                                     Listen => 1) || die "Cannot creat
+e socket\n";

while ($client = $listener->accept()) {
    $pid = fork();
    die "Cannot fork: $!" unless defined($pid);
    if ($pid == 0) { 
         print "Hi!";
         exit(0);
    }
}
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Re: exit isn't killing children by chromatic (Archbishop) on Dec 16, 2002 at 03:00 UTC
As the documentation for fork states, you probably need to wait on the child processes (not threads; be careful with the terminology): If you "fork" without ever waiting on your children, you will accumulate zombies. On some systems, you can avoid this by setting "$SIG{CHLD}" to "IGNORE". See also the perlipc manpage for more examples of forking and reaping moribund children.	[reply]
Re: exit isn't killing children by pg (Canon) on Dec 16, 2002 at 03:30 UTC
Not a direct solution for your problem, but I noticed something that you might want to improve for a better style, and to show a clear understanding of socket programming. In the child process, $listener is not useful at all, so the child process should close it after being forked. Don't worry, this will not close the $listener in the parent process. Similarly, $client is not useful in the parent process, so the parent process should close each instance of $client, after it forked the child process for that particular $client. Again, don't worry, this will not close the $client in the child process.	[reply]
Re: exit isn't killing children by VSarkiss (Monsignor) on Dec 16, 2002 at 03:21 UTC
exit(0) isn't killing the children in this. `exit` never kills children. It tells the current process to go away. What am I doing wrong? It's impossible to answer that without knowing what you're trying to do. As you correctly noted, this program accepts a connection, then does nothing. But your note sounds like you were expecting it to do something else. What were you expecting? If you describe that more fully, it'll be a lot easier to help.	[reply] [d/l]