How can you tell if someone is online or not?

[Skieth]

WELLLLLLL I was making this script, and part of it tells if someone is online or not, ok here is what I mean:

In your account.ini file there is a header called Friends and in that a variable called F1 like this

[stats or whatever]
blah=lame
nonsexeh=1
[Friends]
F1=Jim

ok Jim is a players name, how can I tell if Jim is online or not? (like have it say 1 if he is or 0 if he isn't or something like that)

Much appreciated =3 (this is going to become a really cool friends list script =D)