App restart after update

[Bill Vlahos]

My application can update itself by downloading and placing the new  
version in the appropriate spot. To utilize the new version the user  
has to quit the old version and relaunch it which brings up the new  
version.

An example of this is Firefox which downloads the new file, expands  
it, quits the running application, and then relaunches the new one  
(and I presume deletes the old version).

Quitting the application after the download is easy but how do I have  
the computer automatically relaunch it?

I would need this for Macintosh and Windows and Linux.

Bill Vlahos