title: Listen to a background process in vala
body: <p>I have a command I want to listen to in the background <code>Process.spawn_command_line_async</code> is what I want but I can't work out how to then listen to the response. The command will output lines when something needs updating and I then need to parse that line and run a function accordingly. The process won't end until stopped, so will need to be listened to as it's running.</p>