trigger call shell script

Hi,

I'm thinking of having a trigger launch a java program.
My plan is to make the trigger execute a command line java class, basically
the trigger should type this into the console:

'java DoWork 1403'

Where 'DoWork' is the name of my java class that takes a command line
argument 'itemid' which is 1403 in this case.

Can command line programs/scripts be called from Postgresql functions?
Can anyone provide example code for making the Postgresql function that
executes a command line statement?

Thanks, Kenneth.