Get IP4s of Google's servers' to, for example, whitelist them for accessing own services

get_googles_ips.sh

#!/bin/sh -e

get_ip4s () {
  dig +short txt $1 | grep -Eo '(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)(/(3[0-2]|[1-2][0-9]|[1-9])?)?' | tr '\n' ','
}

echo -n $(get_ip4s _netblocks.google.com)
# `_netblocks2.google.com` returns only IPv6 addresses, so we can skip it
#echo -n $(get_ip4s _netblocks2.google.com)
echo -n $(get_ip4s _netblocks3.google.com)
echo -n $(get_ip4s _netblocks4.google.com)
echo ""