Show the screen brightness value given by xbacklight.
Clicking uses xset to turn off the backlight, scrolling increases or decreases
the brightness.

Example i3blocks configuration:
[backlight]
command=$SCRIPT_DIR/backlight
label=☀
interval=20
#STEP_SIZE=5
#USE_SUDO=0
STEP_SIZEThese tools from the xorg-suite are needed:
xorg-xbacklightxorg-xsetYou need to allow the user to change the brightness (only if you want to use scrolling). If you don't have the proper permissions, you will get an error like
$ xbacklight -inc 5
/usr/bin/xbacklight: [Errno 13] Permission denied: '/sys/class/backlight/intel_backlight/brightness'
One option is to create a udev rule.
Another option is to allow the user to execute xbacklight without a password using the
sudoers file.
For the user <user> it would be something like
<user> ALL=(ALL) NOPASSWD: /usr/bin/xbacklight
Then use USE_SUDO=1 in the configuration of this block.