How to get the unused or free IPs on linux machine?

 Inline format of the script:

lsof -nl >/tmp/lsof.log;rm -rf ~/freeIPs.log; for ip in `ip add list|grep -v "127.0.0\|::1\|0.0.0.0\|00:00:"|cut -d" " -f6|cut -d"/" -f1|grep -v qdisc|awk 'NF'`;do grep $ip /tmp/lsof.log > /dev/null; if [ $? != 0 ]; then echo $ip >> ~/freeIPs.log; fi; done; rm -rf /tmp/lsof.log;echo "Total IPs:`ip add list|grep -v "127.0.0\|::1\|0.0.0.0\|00:00:"|cut -d" " -f6|cut -d"/" -f1|grep -v qdisc|awk 'NF'|wc -l`"; echo "Free IPs:`wc -l ~/freeIPs.log`";

Script:

 lsof -nl >/tmp/lsof.log
 rm -rf ~/freeIPs.log
 for ip in `ip add list|grep -v "127.0.0\|::1\|0.0.0.0\|00:00:"|cut -d" " -f6|cut -d"/" -f1|grep -v qdisc|awk 'NF'`
 do 
     grep $ip /tmp/lsof.log > /dev/null
     if [ $? != 0 ]
    then 
          echo $ip >> ~/freeIPs.log
    fi
 done
 rm -rf  /tmp/lsof.log
 echo "Total IPs:`ip add list|grep -v "127.0.0\|::1\|0.0.0.0\|00:00:"|cut -d" " -f6|cut -d"/" -f1|grep -v qdisc|awk 'NF'|wc -l`";
 echo "Free IPs:`wc   -l ~/freeIPs.log`";