Shell Programming and Scripting

Hi guys, i am having some mine bash script which print only ip addresses

Code:

echo "Interfaces IP addresses:"
ip -o addr | awk '!/^[0-9]*: ?lo|link\/ether/ {print $2" "$4}'
echo -n "enter range of IPs(192.168.0.1-254)[ENTER]: "
read range
nmap -oG - $range >/home/test/Desktop/SCAN
cat /home/test/Desktop/SCAN |grep Up | awk -F " " '{print $2}' > /home/test/Desktop/SCAN2
echo "IPs in range $range:"
cat /home/test/Desktop/SCAN2

I know want to give a little more. I have some devices with same mac addresses, and if all my pc in networks begin with ff:aa mac, how can i add some maybe question: Do you want scan all devices or PCs, and if user press 2, it will nmap only devices with mac address that starts with ff:aa