It reports any errors to standard error, including errors reported by the Click module. Read the router configuration to transform from file . The default is the standard input. If you supply this option, the new configuration will only be installed if it initializes correctly. If it fails, the old configuration will continue to route packets without interruption.
Lower numbers have higher priority.
If a Click kernel module is installed, write its load map to standard output. This can make it easier to debug kernel panics. Print usage information and exit. Print the version number and some quickie warranty information and exit.