function run_command($working_dir, $cmd, $args, $error_out = NULL)
{
// change dir and execute
$previous_dir = getcwd();
$command = SystemUtil::build_command($cmd, $args, $error_out);
if ($working_dir) {
chdir($working_dir);
}
system($command, $retval);
chdir($previous_dir);
return $retval == 0;
}
