exec return values

Is there a set list of return values/error codes returned by exec? I am running this command on a windows box and getting the following error: exec ("net use /delete i: /y", $output, $ret);

print_r ($output);    // Array()

echo "Return: $ret"; // Return: 2 I tested this statement with the mapped drive (i:) created and without it. I get the same result. Now this exec statement is just one example, but are there generic return values or is it based solely on the command being sent to exec? I have RTFM (hopefully well enough) and STFW, but have not been fruitful in my searches. =/ Thanks, ~Philip "Personally, most of my web applications do not have to factor 13.7 billion years of space drift in to the calculations, so PHP's rand function has been great for me..." ~S. Johnson