Mute MacOS when do not disturb is on and you're not using the computer.

turn-off-volume-on-do-not-disturb.sh

#!/bin/bash
#
# Fist check if do not disturb is on.
# Then check if screen is off, meaning you're not using the computer at that time.
# If do not disturb is on and you're not using the machine, mute the volume.

if [[ $(/usr/bin/defaults -currentHost read ~/Library/Preferences/ByHost/com.apple.notificationcenterui doNotDisturb) -eq 1
    && `echo $(/usr/sbin/ioreg -n IODisplayWrangler | grep -i IOPowerManagement | perl -pe 's/^.*DevicePowerState\"=([0-9]+).*$/\1/')/4 | bc` -eq 0 ]];
            then
                osascript -e "set Volume 0"
fi