Control the backlight brightness.
I had some problems with xbacklight
in combination with the proprietary nvidia driver, so I wrote a replacement.
make
sudo make install
sudo make uninstall
$ backlight_control
Usage: backlight_control [+|-]<value>
Examples:
backlight_control +10
backlight_control -10
backlight_control 50
backlight_control +n
increases brightness by n%
backlight_control -n
decreases brightness by n%
backlight_control n
sets the brightness to n%