#!/usr/bin/bash
for process in $(pgrep -t $(cat /sys/class/tty/tty0/active));
do 
    display=$(awk -v RS='\0' -F= '$1=="DISPLAY" {print $2}' /proc/$process/environ 2>/dev/null); 
    [[ -n $display ]] && break; 
done;
echo $display
