I know I can use f9 to access the developer console but that's not what I'm trying to do. How do I get the output of the output?
If you're referring to the game's server log, you can click the "Server log" tab in the f9 console, or you can use "LogService" which you can use to get server logs from the game. If you're talking about something else, it would help if you elaborated a bit more.
Wiki page for LogService: http://wiki.roblox.com/index.php?title=LogService