So I'm trying to create a combination of keys to generate ISO keys for the Portuguese layout, the key in question is the , pressing it will normally generate the character, + Shift will generate the > character. So I'm trying to create a combination using xmodmap , and I want this to work for all the programs. I've been searching on Google and came up with this example for Control + P = Up : xmodmap -e "keycode 33 = p P Up" keycode 33 matches p , so where does Control come up in that command? What I want is: map Control + , to > map Control + . to