Command to check for network connection

Hi, I'm trying to figure out how to write a script to check if the wifi has connected, and if so perform some tasks (like launching Thunderbird minimised and so on). I've found out how to add a script to startup, and I'm happy to have a go at writing the script (have beginners guide, will travel...), but I'm stumped about what command I might use to check for internet connection, and what output I should check for from it. Any handy advice?

Thanks in advance, Mark

 

Guess you could modify the script this guy shows here ...

http://ubuntuforums.org/showthread.php?t=731251

Cheers.

 

Excellent, thank you.

 

While searching for something else, I also found an elegant solution to this in this thread: viewtopic.php?f=5&t=4629&hilit=ssh#p30761

But learning a bit about scripting was worthwhile anyway!