updated docs

launch.py

@@ -876,7 +876,9 @@ if __name__ == '__main__':
                         default=False, help='Sort pbs file list. Default=False')
     parser.add_argument('--crontab', action='store_true', dest='crontab',
                         default=False, help='Crontab mode. Implies --cache, '
-                        'and not compatible with --node. Default=False')
+                        'and not compatible with --node. When all jobs are '
+                        'done, crontab -r will remove all the user\' current '
+                        'crontab jobs. Default=False')
     parser.add_argument('--debug', action='store_true', dest='debug',
                         default=False, help='Debug print statements. Default=False')
     (options, args) = parser.parse_args()