#include <CoreFoundation/CoreFoundation.h>
     int main(int argc, char ** argv)
          {
           CFMessagePortRef port = CFMessagePortCreateRemote(NULL, CFSTR("com.apple.loginwindow.notify"));
           CFMessagePortSendRequest(port, 500, 0, 0, 0, 0, 0);
           CFRelease(port);
           return 0;
          }