For the sake of providing another option, you could use the ip addr command this way to get the IP address:

ip addr show eth0 | grep "inet" | awk '{print $2}' | cut -d/ -f1

• ip addr show eth0 shows information about eth0


• grep "inet" only shows the line that has the IPv4 address (if you wanted the IPv6 address, change it to "inet6")


• awk '{print $2}' prints on the second field, which has the ipaddress/mask, example 172.20.20.15/25


• cut -d/ -f1 only takes the IP address portion.

In a script:

#!/bin/bash

theIPaddress=$(ip addr show eth0 | grep "inet" | awk '{print $2}' | cut -d/ -f1)