bright

#!/usr/bin/env bash

TYPE=$1

MAX_BRIGHT=$(cat /sys/class/backlight/intel_backlight/max_brightness | xargs echo)
MIN_BRIGHT=$(echo "$MAX_BRIGHT * 0.08" | bc)

BRIGHT=$(cat /sys/class/backlight/intel_backlight/brightness | xargs echo)
STEP=$(echo "$MAX_BRIGHT * 0.05" | bc)

if [ ! -w "/sys/class/backlight/intel_backlight/brightness" ]
    then
    echo "'/sys/class/backlight/intel_backlight/brightness' is not writable!"
    echo "Please execute 'sudo chmod o+w /sys/class/backlight/intel_backlight/brightness'"
    echo "so that you can use this script without super user privileges."
    exit 1
fi


if [ "$TYPE" = "down" ]
    then
    NEW_BRIGHT=$(echo "scale=0; ($BRIGHT - $STEP) / 1" | bc)
elif [ "$TYPE" = "up" ]
    then
    NEW_BRIGHT=$(echo "scale=0; ($BRIGHT + $STEP) / 1" | bc)
else
    echo "Usage syntax: bright (up|down)"
    exit 1
fi

if (( $(echo "$NEW_BRIGHT <= $MIN_BRIGHT" | bc -l) )) && [ "$TYPE" != "up" ]
    then
	echo "Impossible to decrease bright. It is already in the min level."
	exit 1
fi

if (( $(echo "$NEW_BRIGHT >= $MAX_BRIGHT" | bc -l) )) && [ "$TYPE" != "down" ]
    then
    echo "Impossible to increase bright. It is already in the max level."
    exit 1
fi

PERC_BRIGHT_ORIG=$(echo $(( 100 * $BRIGHT / $MAX_BRIGHT )) )
PERC_BRIGHT=$(echo $(( 100 * $NEW_BRIGHT / $MAX_BRIGHT )) )

echo "$NEW_BRIGHT" | tee /sys/class/backlight/intel_backlight/brightness
echo "Bright changed from $PERC_BRIGHT_ORIG% to $PERC_BRIGHT%."