Google Cloud, Amazon AWS, and Microsoft Azure publish their IP ranges for their cloud platforms.
Amazon:
https://ip-ranges.amazonaws.com/ip-ranges.json
one-liner:
curl https://ip-ranges.amazonaws.com/ip-ranges.json | grep 'ip_prefix' | cut -d '"' -f 4
Microsoft Azure:
https://www.microsoft.com/en-gb/download/details.aspx?id=41653
one-liner:
cat PublicIPs_20190401.xml | grep 'IpRange Subnet='| cut -d '"' -f2
Google Cloud:
DNS txt records for: _cloud-netblocks.googleusercontent.com
one-liner:
for netblock in $(dig txt _cloud-netblocks.googleusercontent.com +short | tr " " "\n" | grep include | cut -f 2 -d :); do dig txt +short $netblock; done | tr " " "\n" | grep ip4: | cut -d ':' -f2
