Exchange capslock and left-ctrl using xmodmap

remove Lock = Caps_Lock
remove Control = Control_L
keysym Caps_Lock = Control_L
keysym Control_L = Caps_Lock
add Lock = Caps_Lock
add Control = Control_L

Save in a normal file, then:

$ xmodmap ./caps-ctrl

Or save as a shell script:

xmodmap -e "remove Lock = Caps_Lock"
xmodmap -e "remove Control = Control_L"
xmodmap -e "keysym Caps_Lock = Control_L"
xmodmap -e "keysym Control_L = Caps_Lock"
xmodmap -e "add Lock = Caps_Lock"
xmodmap -e "add Control = Control_L"

That's pretty cool for *nix working, like shell control & emacs & vim and so forth.