#!/usr/bin/perl -w
# pipe1 - bidirectional communication using two pipe pairs
#         designed for the socketpair-challenged
use IO::Handle;     # thousands of lines just for autoflush :-(
use IO::Select;     # thousands of lines just for autoflush :-(
pipe(PARENT_RDR, CHILD_WTR);                # XXX: failure?
pipe(CHILD_RDR,  PARENT_WTR);               # XXX: failure?
CHILD_WTR->autoflush(1);
PARENT_WTR->autoflush(1);


$sel = new IO::Select( PARENT_RDR );

if ($pid = fork) {
   close PARENT_RDR; close PARENT_WTR;
   print CHILD_WTR "Parent Pid $$ is sending this\n";
   chomp($line = <CHILD_RDR>);
   print "Parent Pid $$ just read this: `$line'\n";
   close CHILD_RDR; close CHILD_WTR;
   waitpid($pid,0);
} else {
   die "cannot fork: $!" unless defined $pid;
   close CHILD_RDR; close CHILD_WTR;

   print PARENT_WTR "Before: Child Pid $$ is sending this\n";
   while(@ready = $sel->can_read) {
      foreach $fh (@ready) {
         chomp($line = <$fh>);
         print "Child Pid $$ just read this: `$line'\n";
      }
   }
   print PARENT_WTR "After: Child Pid $$ is sending this\n";
   close PARENT_RDR; close PARENT_WTR;
   exit;
}