re: best way to communicate between 2 applications

["Garth's KidStuff" <garthskidstuff gmail com>]

More details:
I'm running a large application written in gtkmm on an Ubuntu (8.1 or 9.04)
machine.  I'd like to know when a usb device has been attached or detached.
 Some other kind people on this list pointed me to udev for the usb event
handling, and told me how I could run a little program when udev detected an
event, so the missing piece is how does this little udev app tell the first
application that something has happened?
Thanks!

-- 
Garth Upshaw
Garth's KidStuff