backlight — get and set the backlight brightness.

backlight COMMAND
backlight [+|-]VALUE[%]

backlight lets you adjust the brightness of your display through the Linux sysfs.

• current — Shows the current brightness value.
• maximum — Shows the maximum brightness value that can be set.

Command names can be truncated if there's no ambiguity regarding their explicit counterpart.

A command consisting of a number, optionally followed by a percent sign, sets the brightness. If the number is prefixed by a plus or minus sign, the value is relative to the current brightness.

This will output the current brightness level as percentage:

perl -e 'print int(`backlight c` * 100 / `backlight m` + 0.5)'

This sxhkd configuration snippet will bind the brightness function keys (mostly found on laptops) to backlight:

XF86MonBrightness{Up,Down}
	backlight {+,-}5%