The parent pid sends a string to the child pid, which the child prints out. The child then sleeps for 2 seconds before sending a string to the parent. Instead of locking up completaly the parent prints "Waiting...\n" until there is input for it to read.
I wrote this to encorperate it into a larger Tk script which I don't want freezing when it forks off to download information.
NOTE: This does not work on Windows (hence the name "Unix Sockets")!
The code is a based on of "pipe2" from perlipc. See also: IO::Socket, IO::Select, and perlipc.
#!/usr/bin/perl -w
use strict;
use Socket;
use IO::Socket;
use IO::Select;
socketpair(CHILD, PARENT, AF_UNIX, SOCK_STREAM, PF_UNSPEC)
or die "socketpair: $!";
CHILD->autoflush(1);
PARENT->autoflush(1);
my $pid;
my $s = IO::Select->new();
$s->add(\*CHILD);
if ( $pid = fork ) {
close PARENT;
print CHILD "Parent Pid $$ is sending this\n";
#chomp(my $line = <CHILD>);
my $line;
while ( 1 ) {
if ( $s->can_read(0) ) {
foreach my $handle ( $s->can_read(0) ) {
recv($handle, $line, 1024, 0);
}
last;
}
print "Waiting...\n";
}
chomp $line;
print "Parent Pid $$ just read this: '$line'\n";
close CHILD;
waitpid($pid, 0);
} else {
die "cannot fork: $!" unless defined $pid;
close CHILD;
chomp(my $line = <PARENT>);
print "Child Pid $$ just read this: '$line'\n";
sleep 2;
print PARENT "Child Pid $$ is sending this\n";
close PARENT;
exit;
}
