Displays and sets backlight level for intel laptops. Tested with xubuntu 16.04.

backlight.sh

#!/usr/bin/env sh

if [ -n "$1" ]; then
  sudo su -c "echo $1 >/sys/class/backlight/intel_backlight/brightness"
else
  cat /sys/class/backlight/intel_backlight/brightness
fi

black.sh

#!/usr/bin/env bash

original_backlight=$(backlight)
backlight 0
touch /tmp/blackscreen
while [ -f /tmp/blackscreen ]; do
  read -t 1 && rm /tmp/blackscreen
  sudo -v
done
backlight $original_backlight