backlight_intel_notebook

#!/bin/bash -e

usage() {
    cat << EOF
Usage: backlight_intel_notebook
Set the brightness using the "intel_backlight" kernel module interface. Useful
when "xbacklight" does not work. Options are equivalent to the same as
xbacklight offers but following double-dashed format for long options.

If no option is given the argument is passed on as a raw brightness selection
value.

Options:
 -v, --verbose                        execute with verbose output
 -h, -?, --help                       display this help
 -n, --dry-run                        execute in dry-run mode
 -g, --get                            get brightness in percentage
 -s <percentage>, --set <percentage>  set brightness in percentage
 -i <percentage>, --inc <percentage>  increase brightness by percentage
 -d <percentage>, --dec <percentage>  decrease brightness by percentage

Examples:
 backlight_intel_notebook 120000
 backlight_intel_notebook --get
 backlight_intel_notebook --set 100
EOF
    exit
}

set -o pipefail

opts=$(getopt -o vhns:i:d:g --long verbose,help,dry-run,set:,inc:,dec:,get -n 'parse-options' -- "$@") || usage
eval set -- "$opts"
while true; do
  case "$1" in
    -v | --verbose ) set -x; shift ;;
    -h | --help ) usage; shift ;;
    -n | --dry-run ) dry_run=true; shift ;;
    -g | --get ) get=true; shift 2 ;;
    -s | --set ) set="$2"; shift 2 ;;
    -i | --inc ) inc="$2"; shift 2 ;;
    -d | --dec ) dec="$2"; shift 2 ;;
    -- ) shift; break ;;
    * ) break ;;
  esac
done

brightness=$(cat /sys/class/backlight/intel_backlight/brightness)
if [ -n "$get" ]; then
    echo "$brightness"
    exit 0
fi

max_brightness=$(cat /sys/class/backlight/intel_backlight/max_brightness)
if [ -n "$set" ]; then
    new_brightness=$((max_brightness * set / 100))
elif [ -n "$inc" ]; then
    new_brightness=$((brightness + max_brightness * inc / 100))
elif [ -n "$dec" ]; then
    new_brightness=$((brightness - max_brightness * dec / 100))
fi

new_brightness="${new_brightness:-${1:-"90"}}"
if [ -n "$dry_run" ]; then
    echo "$0: dry run: Would set $new_brightness"
else
    echo $new_brightness | sudo tee /sys/class/backlight/intel_backlight/brightness >/dev/null
fi