Emacs: bind smth to right Alt key

I want to bind Right-Alt key to toggle-input-method function and Left-Alt to Meta. B开发者_开发百科ut Emacs identify both Alt keys as Meta. How can I get Emacs to distinguish between the Alt buttons?

os: Ubuntu

Assuming you are using GNOME, you can check what is your Alt key behavior in System -> Preferences -> Keyboard -> Layout tab -> Option button -> Alt\Win key behavior and make some tests if there is an option satisfying you.

Also quite much depends on keyboard layout you are using - you can look at xkeycaps - GUI for xmodmap, which controls key mappings in X - and check if Left / Right Alt is assigned to Meta.