#!/bin/sh

# set backlight brightness level

current=$(cat /sys/class/backlight/intel_backlight/brightness)

if test -z "$1"; then
  echo "$current"
  exit 0
fi

case "$1" in
'+' | '-')
  if test -z "$2"; then
    echo "missing increment"
    exit 1
  fi
  new="$((current $1 $2))"
;;
*)
  echo "invalid argument '$1'"
  exit 1
;;
esac

echo "current: $new"
echo "$new" > /sys/class/backlight/intel_backlight/brightness