12 Aug 2014

Changing IP Octets with Bash

I have program at work which needs to create a UDP multicast address from a server’s IP address. This process basically just entails replacing the first IP octet with “239”. In order to be able to do this I wrote the following. There is probably a much neater and more efficient way of doing this and I would love to hear it:

MCAST_IP=$(echo ${SERVER_IP} | cut -d. -f2-4)
MCAST_IP=$(echo "239."${META_MCAST_IP})