OS X: Find Network Gateway using the Comand Line
This is a bit more complex than it should be; I was hoping networksetup would make this easier but, alas. Using netstat -nr appears to be the best way to find your gateway from the command line:
netstat -nr | grep '^default' | awk '{ print $2 }'
If you haven't played around with networksetup, I recommend checking out networksetup -getinfo "Airport" and networksetup -listnetworkserviceorder.