runit-scripts/boot-services/09-brightness.sh

# shellcheck shell=sh

(
: "${BRIGHTNESS_DEV:=/sys/class/backlight/intel_backlight}"
: "${BRIGHTNESS_SAVE:=/var/cache/brightness}"

[ -r "${BRIGHTNESS_SAVE}" ] || exit

read -r brightness < "${BRIGHTNESS_SAVE}"
[ "${brightness}" -gt 100 ] || exit

msg 'restoring brightness'
[ -w "${BRIGHTNESS_DEV}/brightness" ] \
	&& printf '%d' "${brightness}" > "${BRIGHTNESS_DEV}/brightness" \
	|| error 'unable to restore brightness' \
		"(failed to write to '${BRIGHTNESS_DEV}/brightness')"
) &