#!/usr/bin/perl
# Fig. 18.11: fig18_11.pl
# Using pipe to communicate with child processes.

use warnings;
use strict;
use IO::Handle;

pipe( CHILDINPUT, PARENTOUTPUT );
pipe( PARENTINPUT, CHILDOUTPUT );

PARENTOUTPUT->autoflush( 1 );
CHILDOUTPUT->autoflush( 1 );
STDOUT->autoflush( 1 );

if ( my $pid = fork() ) {

   for ( 1 .. 10 ) {
      print( PARENTOUTPUT "$_\n" );
      print( "I said $_, " );
      chomp( my $response = <PARENTINPUT> );
      print( "and he said $response!\n" );
   }
   
   close( PARENTOUTPUT ) or 
      die( "Cannot close PARENTOUTPUT: $!" );
   close( PARENTINPUT ) or
      die( "Cannot close PARENTINPUT: $!" );
}
elsif ( defined( $pid ) ) {
   close( PARENTOUTPUT ) or
      die( "Cannot close PARENTOUTPUT: $!" );
   close( PARENTINPUT ) or
      die( "Cannot close PARENTINPUT: $!" );

   while ( <CHILDINPUT> ) {
      chomp();
      print( CHILDOUTPUT $_ * 20, "\n" );
   }

   close( CHILDOUTPUT ) or
      die( "Cannot close CHILDOUTPUT: $!" );
   close( CHILDINPUT ) or
      die( "Cannot close CHILDINPUT: $!" );
   exit();
}
else {
   die( "Fork did not work" );
}

print( "And that is the end of the conversation.\n" );

###########################################################################
#  (C) Copyright 2001 by Deitel & Associates, Inc. and Prentice Hall.     #
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