#!/bin/bash

listBacklight=`ls /sys/class/backlight`

if [ $# -gt 1 ] ; then
    echo "light2 [VALUE]"
    exit
fi
if [ -z "$1" ] ; then
    val=150
else
    val="$1"
fi

if [ -n "$listBacklight" ] ; then
    for backlight in "$listBacklight"
    do
        echo "${val}" | $right tee "/sys/class/backlight/${backlight}/brightness" 2>&1 /dev/null
    done
else
    echo 'No backlight detected'
fi