Simple hdmi activate script

This is a simple script I bound to ‘meta+F7’ to activate a second hdmi display I am using:

<pre lang="shell">
INTERNAL=eDP1
EXTERNAL=HDMI2
LOCK=/tmp/${EXTERNAL}.on

disper -l | grep $EXTERNAL

function on {
    disper -e -d $INTERNAL,$EXTERNAL -r 1920x1080,1920x1080
    touch $LOCK
}

function off {
    disper -s -d $INTERNAL -r auto
    rm -f $LOCK
}

if [ $? -eq 1 ]; then #there is no EXTERNAL, run single command
    off
elif [ -f $LOCK ]; then
    off
else
    on
fi