I have a very simple task that I am trying to accomplish. I have a child process that gets forked from a parent. The child runs an infinite loop. In each loop iteration I want it to check a value being set in the parent. If the parent value changes I want it to exit the loop. I am on Win32 Activeperl so please no %SIG solutions unless you know of some that work. Here is my current code:

use strict;
$|++;

my $stream = *STDOUT;
my $thingy = [ "\\", "|", "/", "-" ];
my $rate = 0.175;
my $step = 0;
my $spin_stop = 0;

FORK: 
{
   if( my $code_pid = fork() ) {

       sleep(5); 
       $spin_stop = 1;
   }
   elsif( defined $code_pid ) {

       print "Process executing..";
       _spin();
       exit 0;
   }   
   elsif( $! =~ /No more process/ ) {  

       sleep 2;
       redo FORK;
   }
   else { 

       die "ERROR: can't fork! $!";
   }
}

print "\nProcess Complete\n";

sub _spin {

   SPIN: while(1) {
      my $old_fh = select($stream);
      local $| = 1;
      print $stream $$thingy[$step],
      chr(8) x length($$thingy[$step]);
      select($old_fh);

      $step = ( $step+1 > $#$thingy ? 0 : $step+1 );

      select(undef,undef,undef, $rate);
      last SPIN if($spin_stop == 1);
   }

   return;
}

[download]

Obviously the $spin_stop variable in the forked child seems to have no relationship whatsoever to the $spin_stop in the parent process, but you can see what I am trying to do.

In reply to Child reading from Parent by icius

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