turn screen brightness down automatically?

[TheRedFox]

I remember in Xubuntu, when the laptop got unplugged, the screen brightness would go down. Any idea what sort of command they used to do that? I have mine (using ACPI event) underclock to 600MHz CPU and 90MHz GPU when unplugged, but it would be nice if I could lower the screen brightness too. It doesn't matter that much, but if anyone happens to know, it'd be appreciated.
Thank you!

[uux]

There is a command line utility called xbacklight. Support for changing the brightness using xbacklight varies between drivers, though. Another possibility is one of the many knobs under /sys or /proc.

Is it possible what you saw was the Display brightness setting in the BIOS? If it's set to High, then you won't notice a change when unplugging the power cable. If it is set to Normal, the display will dim a bit regardless of the OS.

[TheRedFox]

I figured out that I can echo level + a number (0-7) to /proc/acpi/ibm/brightness
(as in "echo level 3 > /proc/acpi/ibm/brightness"). wow, Linux is pretty advanced!
now I have it set to do the following whenever the cord is unplugged:
cpufreq-set -f 600
rovclock -c 90 -m 100
echo level 3 > /proc/acpi/ibm/brightness

then when it becomes plugged in:
cpufreq-set -g ondemand
rovclock -c 144 -m 144
echo level 7 > /proc/acpi/ibm/brightness

I think the /proc folder might be one of my favorite aspects of Linux. well I guess just the everything being a file, in general.