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

• right click: turn off backlight
• scroll: increase/decrease the brightness in percentage steps according to STEP_SIZE

These tools from the xorg-suite are needed:

• xorg-xbacklight
• xorg-xset

You 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.