Bsrgvty

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.

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)).

Here's a C version if you want to make a small binary instead of invoking Python. Compile with gcc -O -Wall -o caps_lock_off caps_lock_off.c -lX11, with the packages build-essentials and libx11-dev installed.

#include <stdio.h>
#include <X11/X.h>
#include <X11/XKBlib.h>
int main()

 Display *display = XOpenDisplay(NULL);
 if (display == NULL) 
 fprintf(stderr, "Couldn't open displayn");
 return 2;
 
 Bool sent = XkbLockModifiers(display, XkbUseCoreKbd, LockMask, 0);
 if (!sent) 
 fprintf(stderr, "Couldn't send LatchLockStaten");
 return 1;
 
#ifdef REPORT_STATE
 XkbStateRec xkb_state;
 Status status = XkbGetState(display, XkbUseCoreKbd, &xkb_state);
 if (status) 
 fprintf(stderr, "XkbGetState returned %dn", status);
 return 1;
 
 printf("state.group=%02xn", xkb_state.group);
 printf("state.locked_group=%02xn", xkb_state.locked_group);
 printf("state.base_group=%02xn", xkb_state.base_group);
 printf("state.latched_group=%02xn", xkb_state.latched_group);
 printf("state.mods=%02xn", xkb_state.mods);
 printf("state.base_mods=%02xn", xkb_state.base_mods);
 printf("state.latched_mods=%02xn", xkb_state.latched_mods);
 printf("state.locked_mods=%02xn", xkb_state.locked_mods);
 printf("state.compat_state=%02xn", xkb_state.compat_state);
 printf("state.grab_mods=%02xn", xkb_state.grab_mods);
 printf("state.compat_grab_mods=%02xn", xkb_state.compat_grab_mods);
 printf("state.lookup_mods=%02xn", xkb_state.lookup_mods);
 printf("state.compat_lookup_mods=%02xn", xkb_state.compat_lookup_mods);
 printf("state.ptr_buttons=%02xn", xkb_state.ptr_buttons);
#endif
 int err = XCloseDisplay(display);
 if (err) 
 fprintf(stderr, "XCloseDisplay returned %dn", err);
 return 1;
 
 return 0;

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.

X automation tools could be used for sending the required key events.

Note:

This solution needs you to tape the correct password, if your
CAPS is currently active: open office writer, write password there,
change the letter case, copy it, then paste it to password dialog.

If that previous step is not possible or doesn't work, Go with Gilles' answer / python script. It does not need to install any additional tool, it uses only python & libX11 shared lib which are pre-installed.

Using xdotool

1. 
   

   Install it

   
   
   

   sudo apt-get install xdotool
   

   
   


2. 
   

   Send a CAPS down/up event

   
   
   

   xdotool key Caps_Lock
   

   
   

Another tool is xte

1. 
   

   Install it

   
   
   

   sudo apt-get install xautomation
   

   
   


2. 
   

   Send a CAPS lock down/up event

   
   
   

   xte "key Caps_Lock"
   

   
   

References:

• Ubuntu Forums: Caps lock inverted


• man xdotool


• man xte

As for Gilles python version not working in newer ubuntus, setting the correct return for the open display seems to do the trick:

#! /usr/bin/env python

from ctypes import *
import subprocess

class Display(Structure):
 """ opaque struct """

X11 = cdll.LoadLibrary("libX11.so.6")
X11.XOpenDisplay.restype = POINTER(Display)

display = X11.XOpenDisplay(c_int(0))
X11.XkbLockModifiers(display, c_uint(0x0100), c_uint(2), c_uint(0))
X11.XCloseDisplay(display)

(Code adapted from https://stackoverflow.com/questions/29638210/how-can-i-use-python-xlib-to-generate-a-single-keypress)

If you can't access CAPS because you remapped it in .bashrc, like I did, then simply switching to a virtual terminal (alt+ctl+fN) and then switching back worked for me.