#!/usr/bin/perl

package threads::system;

require Exporter;
@ISA = qw{Exporter};
@EXPORT_OK = qw{system};

use threads::shared;
use IO::Handle;
use strict; use warnings;

pipe my ($crh, $cwh) or die "Could not pipe: $!";  # Command string read/write handles
pipe my ($erh, $ewh) or die "Could not pipe: $!";  # Exit status read/write handles
$cwh->autoflush(1); $ewh->autoflush(1);

my $sync : shared;

my $child = fork;
die "Could not fork: $!" if $child < 0;
unless ($child) {  # We are the child (daemon) - we handle system() calls for our parent
	close $erh; close $cwh;
	while (<$crh>) {  # Read commands to exec
		my $child = fork;
		die "Could not fork: $!" if $child < 0;
		unless ($child) {  # We are the child - we exec() for our parent
			exec $_; exit $!;
		} else {  # Parent - communicate our child's failure with our own parent
			while (my $pid = waitpid $child, 0) {  # Is all this really needed?
				if ($pid < 0) { die "Error: waitpid: $!" }
				elsif ($pid == 0) { next }
				else { print $ewh $?, "\n"; last }  # Tell parent!
			}
		}
	}
	# Decide: is the following a feature or a bug?
	exit;  # Should never happen, unless client does system(undef), or something
} else {  # Parent
	close $ewh; close $crh;
}

sub system {
	lock($sync);
	my $string = shift;  # TODO: Accept a full list
	print $cwh $string, "\n" or die "Could not write: $!";
	return <$erh>;
}

1

##</code><code>##

#!/usr/bin/perl

use threads::system qw{system};

use strict; use warnings;

my $code = system("ls -al /etc");
print "Exited with code: $code\n";