How do I turn off Caps Lock (the lock, not the key) by command line?

Question

For some reason my laptop is stuck in Caps Lock. I have the Caps Lock key mapped by xmodmap to hyper_l, so I don't have a caps_lock key to turn it off. Is there a way I can turn it off by command line? It would be nice if I could reset the lock state without resetting my computer, especially for future reference. This has happened before, but I would like to know now how to do it properly this time.

Answer 1

I don't know of any command line tool for that in Ubuntu. (For Num Lock, there is numlockx .) Here's a one-liner that you can copy-paste into a terminal window:

python -c 'from ctypes import *; X11 = cdll.LoadLibrary("libX11.so.6"); display = X11.XOpenDisplay(None); X11.XkbLockModifiers(display, c_uint(0x0100), c_uint(2), c_uint(0)); X11.XCloseDisplay(display)'

Here it is again in a more expanded form. We use the Python ctypes library to call C functions from the X library directly. The function XkbLockModifiers changes the state of the keyboard locks, on the core keyboard (XkbUseCoreKbd = 0x0100), affecting Caps Lock (2), setting it to 0 (off).

#!/usr/bin/env python
from ctypes import *
X11 = cdll.LoadLibrary("libX11.so.6")
display = X11.XOpenDisplay(None)
X11.XkbLockModifiers(display, c_uint(0x0100), c_uint(2), c_uint(0))
X11.XCloseDisplay(display)

If you have a stuck modifier, change 2 to the mask of the modifiers you want to turn off. The modifiers are 1=Shift, 2=Lock (Caps Lock), 4=Control, 8=Mod1, 16=Mod2, 32=Mod3, 64=Mod4, 128=Mod5. Run xmodmap -pm to see what Mod1 through Mod5 correspond to. For example, to turn off all modifiers, call X11.XkbLockModifiers(display, c_uint(0x0100), c_uint(255), c_uint(0)). To turn on Num Lock which is on Mod2 and at the same time turn off Caps Lock, call X11.XkbLockModifiers(display, c_uint(0x0100), c_uint(2 | 16), c_uint(16)).

Also possibly of interest is a way to temporarily ignore Caps Lock:

xkbset nullify lock

After this, Caps Lock will effectively be permanently off, until you reenable it with xkbset nullify -lock.