#!/bin/bash
eth="$(ip -4 addr show eth0 | grep -oP '(?<=inet\s)\d+(\.\d+){3}')"
wlp="$(ip -4 addr show wlan0 | grep -oP '(?<=inet\s)\d+(\.\d+){3}')"

if [[ $(echo $eth | wc -c) -gt 1 ]]
then
    echo "$eth"
    exit;
fi

echo "$wlp"