I was responding to Steve Donovan's message about lua-ex. See http://lua-users.org/lists/lua-l/2009-06/msg00135.html.The process exit code is the return value from the process object's wait() function: exitcode = proc:wait()I'm not sure I understand... popen() doesn't return a process object, it returns a file handle. Also, I don't see wait() or a process object in the lua docs anyplace. Is it part of an add-on module? I don't think there's any concept of process in ANSI-C, which is what the un-adorned lua interpreter targets.