#!/usr/local/bin/perl
use strict;
use warnings;
use POSIX ":sys_wait_h";

$|++;   # away with buffering

# stringref read_a_file( string filename)
sub read_a_file
{
    my $fn = shift;
    local $/ = undef;
    open FILE, $fn or return undef;
    my $text = <FILE>;
    close FILE or return undef;
    return \$text;
}

# int system2( string cmdline,
# 				stringref retmsg,
# 				stringref stdoutttxr,
# 				stringref stderrtxr)
sub system2
{
	my $er = shift;
	my $cmd = shift;
	my $stdouttxr = shift;
	my $stderrtxr = shift;
	my $retval;

	my $stdoutfn = '/tmp/teststdout';
	my $stderrfn = '/tmp/teststderr';

	unlink ($stdoutfn) if (-e $stdoutfn);
	unlink ($stderrfn) if (-e $stderrfn);
	my $pid = fork();
	if ($pid < 0) {
		$$er .= "Forking failed with return code $pid.";
		return $pid;
	} elsif ($pid == 0) {
		# CHILD
use POSIX qw(setsid);
		setsid() or die "Can't start a new session: $!";
		chdir('/');
		$SIG{HUP} = 'IGNORE';
		umask 0033;
		close STDIN or die;
		close STDOUT or die;
		close STDERR or die;
		open(STDIN, '</dev/null') or die;
		open(STDOUT, ">$stdoutfn") or die;
		open(STDERR, ">$stderrfn") or die;

		my @argv = split(/ /, $cmd);
		exec( @argv);
	}
    my $wpid = waitpid($pid,0);
	my $normalexit = WIFEXITED(${^CHILD_ERROR_NATIVE});

	if ($normalexit) {
		$retval = WEXITSTATUS(${^CHILD_ERROR_NATIVE});
	} else {
		if (WIFSIGNALED(${^CHILD_ERROR_NATIVE})) {
			$$er .= "Child terminated due to signal";
			if (WTERMSIG(${^CHILD_ERROR_NATIVE})) {
				$$er .= ": SIGTERM";
			}
		}
	}
	if (-e $stdoutfn) {
		if (-s $stdoutfn) {
			my $s = read_a_file($stdoutfn);
			die if (not defined $s);
			$$$stdouttxr = $s;
		}
		unlink ($stdoutfn);
	}
	if (-e $stderrfn) {
		if (-s $stderrfn) {
			my $s = read_a_file($stderrfn);
			die if (not defined $s);
			$$$stderrtxr = $s;
		}
		unlink ($stderrfn);
	}

	return $retval;
}

sub main
{
	my $er = '';
	my $cmd = '/path_to_a_out/a.out';
	my $stdouttxr = undef;
	my $stderrtxr = undef;

	my $ret = system2($cmd,\$er,\$stdouttxr,\$stderrtxr);
	if (defined $ret) {
		print "return value = '$ret'\n";
	} else {
		print "return value = undef\n";
	}
	if ($er ne '') {
		print "Error text: '$er'\n";
	} else {
		print "No error text!\n";
	}
	if (defined $stdouttxr) {
		print "STDOUT: '$$$stdouttxr'\n";
	} else {
		print "No stdout output!\n";
	}
	if (defined $stderrtxr) {
		print "STDERR: '$$$stderrtxr'\n";
	} else {
		print "No stderr output!\n";
	}

	return 0;
}

exit main();