Strange (for me) behavior of Parallel::ForkManager

[Sterh]

Hello Perl Monks

Could you please help me with what I am doing wrong

use Parallel::ForkManager;

my $manager = new Parallel::ForkManager( 20 );

while (<LIST>){
     $manager->start and next;
        my @array = split( /\s+/, $_ );
    print "ip ? $array[1]\n";
    unless ($p->ping($array[1])) {next; print "line\n"} etc...

}
 
      
print "flag\n";
       
$manager->finish(\&next);

 print "flag2 \n";

Everything works, but script prints out "flag" , but not "flag2". Please help me figure out how to go further. Thanks D

[ikegami]

$manager->finish(\&next); is exit(\&next). Aside from the fact that the argument makes no sense, you're exiting the child at the wrong spot. When that child is done processing a line, it needs to exit by calling finish.

use Parallel::ForkManager;

my $manager = new Parallel::ForkManager( 20 );

while (<LIST>){
    $manager->start and next;

    my (..., $ip, ...) = split( /\s+/, $_ );
    print "ip ? $ip\n";
          
    $manager->finish() if !$p->ping($ip);

    ...

    $manager->finish();
}
 
print "flag\n";

[Sterh]

And it still executes everything , but does not exit the loop...:(

[mbethke]

That's expected behavior---finish() is not supposed to return. But why would you want to pass in a code reference as a return code? None of the example code I've looked at does that.

In any case I what you need to do is call finish() within the loop:

while (<LIST>){
    $manager->start and next;
    my @array = split( /\s+/, $_ );
    # do child stuff
    $manager->finish;
}

[Sterh]

It works , but how to make it go out of the loop?

[mbethke]

If you need to leave early, you can use "last". Otherwise it will just read to EOF and then quit.

[ikegami]

There's only one process that loops. It loops until it reaches the end of the file, at which point it continues after the loop.