ref: 114f10337b032b3cf907247e66bc4794b1e7f1a9
dir: /sys/src/cmd/bitsy/light.rc/
#!/bin/rc
#master file is /sys/src/cmd/bitsy/light.rc
switch($1){
case on
echo -n 2 1 0x80 > /dev/backlight
case off
echo -n 2 0 0x80 > /dev/backlight
case auto
echo -n 1 1 0x80 > /dev/backlight
case *
echo -n 2 1 $1 > /dev/backlight
}