Send a signal to a process.
kill [options] process_id
-signum (where signum is a number or name) sends the specified signal.
-l lists the signal names and numbers.
The kill command sends a signal to a process. Typically, the signal is meant to terminate the process. For example, kill -9 123 terminates the process with ID 123. To see process IDs, use the ps command. To see a list of signal names and numbers, type kill -l (that's a lowercase 'L').