Perl Advent Calendar 2008-12-15

Merry fork()ing Christmas

by Jerrad Pierce

Santa's a busy guy with a lot on his mind, and can never quite remember how to invoke fork…"RTFM!" you say? Did I mention he was a busy guy? Instead, this cookie-thieving B&E artist—just kidding Nick, honest!—relies upon a little bit of syntactic sugar known as ForkBlock, which actually makes things a bit clearer too:

mod15.pl

   1 use ForkBlock ':all';
   2 
   3 #'Dumb' so that the parent can carry-on afterwards & show us another way
   4 DumbFork {
   5     Parent \&manager,
   6     Child  \&worker
   7 };
   8 
   9 #OR
  10 Fork {
  11     Parent {
  12       my $kid = $_[0];   #Not meant to condone infanticide
  13       local $SIG{ALRM} = sub { kill(9, $kid); sleep 2; exit };
  14       alarm(2);
  15 
  16       print "Work work work\n" while(1);
  17     }
  18     Child {
  19       print "I want toys!\n" while(1);
  20     }
  21 };
  22 
  23 
  24 sub manager{
  25   my $employee = $_[0];
  26   local $SIG{ALRM} = sub { kill(9, $employee); sleep 2; die };
  27   alarm(2);
  28 
  29   #Eval required to trap die, so signal handler can punt us,
  30   #and we can fall out to second invocation form.
  31   eval{ print "Work harder not smarter\n" while(1) };
  32 }
  33 
  34 sub worker{
  35   print "Work work work\n" while(1);
  36 }

Published 2008-12-24