robar-brightness-server

#!/bin/sh

set -eu

__help="Usage: ${0##*/} [OPTIONS]

Display the screen brightness using robar when the ACPI sysfs directory for
screen brightness changes.

Options:
  -h, --help    display this help and exit"

while [ ! $# -eq 0 ]; do
  case "$1" in
    -h | --help)
      echo "$__help"
      exit 0
      ;;
    *)
      break;
      ;;
  esac
  shift
done

[ -z "$*" ] || { echo "Error: unexpected positional arguments: $*." && exit 1; }

while ! pgrep --exact --full "robar start" >/dev/null; do sleep 1; done

brightness_file='/sys/class/backlight/intel_backlight/brightness'
max_brightness_file='/sys/class/backlight/intel_backlight/max_brightness'
max_brightness=$(cat $max_brightness_file)
last_brightness=100

while true; do
  inotifywait --quiet --monitor --event close_write /sys/class/backlight/intel_backlight/brightness | while read -r; do
    brightness=$(cat $brightness_file)
    if [ "$last_brightness" -ne "$brightness" ]; then
      echo "default $((brightness * 100 / max_brightness))"
      last_brightness=$brightness
    fi
  done | robar show-stream
done