Hi i'm learning english and i wanna know the difference among as long as, but, except and barring to refer to exception..
like "all they go "but, as long as, barring" except her.. : ) ! ^^

As long as isn't really used for exceptions.
Well, maybe in things like "You can have ice cream as long as you eat your veggies." Then it's a little like saying "You can have ice cream if you eat your veggies"

But 
"You can have ice cream, but you need to eat your veggies first."

Except
"Everyone can have ice cream, except for Gally"

Barring
I'm not really sure about this one...

Um, I hope this helps!