backlight controller in Archlinux

gistfile1.txt

#!/usr/sbin/env bash
set -exuo pipefail

# Backlight controller

# IMPORTANT!!
# YOU MUST RUN THESE TWO COMMANDS AFTER EVERY REBOOT SINCE I FIND A PROPER SOLUTION.
# # chown root:user sys/class/backlight/intel_backlight/max_brightness
# # chmod 664 sys/class/backlight/intel_backlight/max_brightness

# USAGE:
# backlightc.sh command step
#                 |      |
# inc: increase <-|      |-> inc/dec step lenght
# dec: decrease <-|

max_backlight=$(< /sys/class/backlight/intel_backlight/max_brightness)
min_backlight=0
brightness="/sys/class/backlight/intel_backlight/brightness"
current_backlight=$(< ${brightness})
step=${2}

function decrease() {
    current_backlight=$((current_backlight - step))
    if [[ ${current_backlight} -le ${min_backlight} ]]; then
        current_backlight=1
    fi
    tee "${brightness}" <<< ${current_backlight}
}

function increase() {
    current_backlight=$((current_backlight + step))
    if [[ ${current_backlight} -gt ${max_backlight} ]]; then
        current_backlight=${max_backlight}
    fi
    tee "${brightness}" <<< "${current_backlight}"
}

case $1 in
    inc)
        increase
        exit 0;;
    dec)
        decrease
        exit 0;;
    *)
        echo "${current_backlight}";;
esac