Simple NIC setup

nic.sh

#!/bin/bash

function get_ipv4 {
    ip address show ${1} | grep 'inet ' | awk '{print $2}' | cut -d/ -f1
}

function get_mac {
    ip address show ${1} | grep 'link/ether' | awk '{print $2}'
}

echo "List of network interfaces found in the system:"
for IFACE in $(ls /sys/class/net | grep -v lo); do
    echo "${IFACE} - MAC: $(get_mac ${IFACE}) - IP: $(get_ipv4 ${IFACE})"
done
echo

echo "Enter the interface name to use as primary (eg. eth2 or ens33) and press [Enter]:"
read IFACE 
cat <<EOF >/etc/network/interfaces
auto lo
iface lo inet loopback

auto ${IFACE}
iface ${IFACE} inet dhcp
iface ${IFACE} inet6 auto
EOF

echo "Restarting DHCP client..."
systemctl restart networking

echo "Done. New IP of interface ${IFACE} is $(get_ipv4 ${IFACE})"