OK, so not truly a one-liner, but a nice quick-n-dirty way to get a count of all active AZs for each region for your AWS account.
echo -e "$(tput bold)Region | # AZs$(tput sgr0)"
for region in $(aws ec2 describe-regions | jq -r '.Regions[].RegionName'); do
num_azs=$(aws ec2 describe-availability-zones --region ${region} | jq -r '.AvailabilityZones | length')
printf '%-15s | %5s\n' ${region} ${num_azs}
done
This requires jq
and the AWS CLI to be installed.