A very useful command line tool for listening to OSC messages is oscdump, part of the liblo package. To listen to OSC messages on port 9000 with oscdump, simply type this command into a terminal window:

oscdump 9000

Included in the liblo package is another utility called oscsend. For example, to send the OSM a CV message on channel A (with default settings in AP mode) you can issue this command:

oscsend 8000 /osm/a/cv f 0.5

To find out more about these commands type in man oscsend or man oscdump in a terminal window.