Ubuntu – Turn the Caps Lock LED on, while keep Caps Lock status is off

capslockkeyboard

I have a magicforce smart 68 kb now and it would look better if the Caps Lock LED would emit light too.

I do not even has a Caps Lock function on that button, because I have switched it with the left Control, and made that to be a compose key for the international layout. I was searching and trying some stuff but nothing has worked so far.

tl;dr: How do I turn on the Caps Lock LED without enabling Caps Lock?

Best Answer

You can get a list of all controllable LEDs by checking the content of the virtual directory /sys/class/leds:

$ ls /sys/class/leds/
input5::capslock  input5::numlock  input5::scrolllock

On my system, there are only the three keyboard LEDs. If your output looks different, make sure you use the correct names instead below!

Each file is a symbolic link to a directory holding several properties of that LED:

$ ls '/sys/class/leds/input5::capslock'
brightness  device  max_brightness  power  subsystem  trigger  uevent

The only thing which is important for us is the brightness file content.

0 means the LED is off.
1 means the LED is on. (Assuming the max_brightness file holds the value 1 - on special keyboards the LED might maybe support multiple brightness values?)

We get the current LED state by checking the brightness file's content (it's currently off):

$ cat '/sys/class/leds/input5::capslock/brightness' 
0

To switch the LED on, we must set that file's content to 1:

$ echo 1 | sudo tee '/sys/class/leds/input5::capslock/brightness'
1

To switch the LED on during every boot, you might want to append the command below to your /etc/rc.local script. It will be executed as root, therefore we don't need the sudo tee but can use Bash output redirection:

$ echo 1 > '/sys/class/leds/input5::capslock/brightness'

Related Solutions

Ubuntu – How to turn off Caps Lock (the lock, not the key) by command line

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 display\n");
        return 2;
    }
    Bool sent = XkbLockModifiers(display, XkbUseCoreKbd, LockMask, 0);
    if (!sent) {
        fprintf(stderr, "Couldn't send LatchLockState\n");
        return 1;
    }
#ifdef REPORT_STATE
    XkbStateRec xkb_state;
    Status status = XkbGetState(display, XkbUseCoreKbd, &xkb_state);
    if (status) {
        fprintf(stderr, "XkbGetState returned %d\n", status);
        return 1;
    }
    printf("state.group=%02x\n", xkb_state.group);
    printf("state.locked_group=%02x\n", xkb_state.locked_group);
    printf("state.base_group=%02x\n", xkb_state.base_group);
    printf("state.latched_group=%02x\n", xkb_state.latched_group);
    printf("state.mods=%02x\n", xkb_state.mods);
    printf("state.base_mods=%02x\n", xkb_state.base_mods);
    printf("state.latched_mods=%02x\n", xkb_state.latched_mods);
    printf("state.locked_mods=%02x\n", xkb_state.locked_mods);
    printf("state.compat_state=%02x\n", xkb_state.compat_state);
    printf("state.grab_mods=%02x\n", xkb_state.grab_mods);
    printf("state.compat_grab_mods=%02x\n", xkb_state.compat_grab_mods);
    printf("state.lookup_mods=%02x\n", xkb_state.lookup_mods);
    printf("state.compat_lookup_mods=%02x\n", xkb_state.compat_lookup_mods);
    printf("state.ptr_buttons=%02x\n", xkb_state.ptr_buttons);
#endif
    int err = XCloseDisplay(display);
    if (err) {
        fprintf(stderr, "XCloseDisplay returned %d\n", 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.

Ubuntu – Why are the Caps Lock and Num lock indicators not working on the keyboard

The problem is because of the inappropriate driver used. Ubuntu's default drivers might not suite your keyboard. If You have a dual boot use the keyboard on windows to confirm it is because of Ubuntu only. If yes then you will have to try additional drivers that might be provided by Manufacturer or Download from Internet. There is a additional driver option for Ubuntu in the dash. Use it to solve your problem.

Best Answer

Related Solutions

Ubuntu – How to turn off Caps Lock (the lock, not the key) by command line

Ubuntu – Why are the Caps Lock and Num lock indicators not working on the keyboard

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