It's OS specific. `killall Firefox` is a good place to start.

On Mar 30, 2009, at 11:49 PM, Eric Milford wrote:

> I am working on a scraper that blows up if an instance of Firefox is
> already running (launched via Firewatir) so I want to put in code that
> first checks for any existing Firefox processes and issues a kill to
> their PIDs.
>
> I'm really new to Ruby -- how can I best accomplish this?  Thanks.
> -- 
> Posted via http://www.ruby-forum.com/.
>