Backlight control with smooth transitions

blutil

#!/usr/bin/env bash

adjust() {
  delay=0.01

  bl_base=$2
  cur_br=$(cat $bl_base/brightness)
  min_br=0
  max_br=$(cat $bl_base/max_brightness)

  case $1 in
    up)
      adj_br=$(($cur_br + 10))
      ;;
    down)
      adj_br=$(($cur_br - 10))
      ;;
    min)
      adj_br=$min_br
      ;;
    mid)
      adj_br=$((($max_br+ $min_br) / 2))
      ;;
    max)
      adj_br=$max_br
      ;;
  esac

  if [[ $cur_br -eq $adj_br ]]
  then
    echo $adj_br > $bl_base/brightness
  elif [[ $cur_br -lt $adj_br ]]
  then
    for i in $(seq $cur_br $adj_br)
    do
      echo $i > $bl_base/brightness
      sleep $delay
    done
  elif [[ $cur_br -gt $adj_br ]]
  then
    for i in $(seq $cur_br -1 $adj_br)
    do
      echo $i > $bl_base/brightness
      sleep $delay
    done
  fi
}

usage() {
  echo "Usage: [bl | kb] [min | mid | max | up | down]"
  exit 1
}

case $1 in
  bl | kb)
    if [[ $1 == "bl" ]]
    then
      bl_base=/sys/class/backlight/acpi_video0
    elif [[ $1 == "kb" ]]
    then
      bl_base=/sys/class/leds/smc::kbd_backlight
    fi
    shift
    ;&
  min | mid | max | up | down)
    if [[ -z $bl_base ]]
    then
      usage
    fi
    adjust $1 $bl_base
    ;;
  *)
    usage
    ;;
esac