#!/bin/bash
DIR="/sys/class/backlight/"
if [[ -d "${DIR}acpi_video0" ]]; then
   DIR="${DIR}acpi_video0"
elif [[ -d "${DIR}intel_backlight" ]]; then
   DIR="${DIR}intel_backlight"
fi
cat "${DIR}/brightness" "${DIR}/max_brightness" | gawk '
    NR==1 { cbr=$1 }
    NR==2 { mbr=$1 }
    END { printf("%d%", cbr/mbr*100) }
'