check_generic is the Nagios plugin you always needed but never wrote
It executes any command (line) and compares the output against arbitrary numerical or string expressions. Allowed is everything known from perl. Also performance data can be gathered using check_generic.
If you are not a command line wizard up to now: you will be one very soon!
Writing a plugin is sometimes boring and for 90% the same procedure: create a structure to deal with the command line options, perform an operation and report the results. The only thing changing is the command to be executed to gather data.
This plugin will let you concentrate on the bare minimum: define a command (chain) to gather data and specify some thresholds to interprete this data. Thats all. The rest is to be done by the plugin.