#!/bin/bash
s='Mozilla/4.5 (X1; Linux x86_64) AppleWebKit/534.34 (KHTML, Gecko) Qt/4.8.1 Safari/53'
echo $s | grep -o '([^()]*)' | head -1
IyEvYmluL2Jhc2gKCnM9J01vemlsbGEvNC41IChYMTsgTGludXggeDg2XzY0KSBBcHBsZVdlYktpdC81MzQuMzQgKEtIVE1MLCBHZWNrbykgUXQvNC44LjEgU2FmYXJpLzUzJwplY2hvICRzIHwgZ3JlcCAtbyAnKFteKCldKiknIHwgaGVhZCAtMQ==