I\'m on a mac, doing:
rails server
I get:
2010-12-17 12:35:15] INFO WEBrick 1.3.1
[2010-12-17 12:35:15] INFO ruby 1.8.7 (
For anyone stumbling across this question that is not on a Mac: assuming you know that your server is running on port 3000, you can do this in one shot by executing the following:
fuser -k 3000/tcp
But as Toby has mentioned, the implementation of fuser in Mac OS is rather primitive and this command will not work on mac.