Delete Default VPCs in AWS

delete_default_vpc.sh

#!/bin/bash
set -euo pipefail

# Will only action if DRY_RUN=false
DRY_RUN=${DRY_RUN:=true}

# Will delete in the following regions
regions=(
  ap-southeast-2
  # ap-southeast-4
)

# get_subnets $vpc_id
get_subnets() {
  local vpc_id=$1; shift
  aws ec2 describe-subnets --filter Name=vpc-id,Values="${vpc_id}" \
    | jq -r '.Subnets[].SubnetId'
}

# get_igw $vpc_id
get_igw() {
  local vpc_id=$1; shift
  aws ec2 describe-internet-gateways --filter Name=attachment.vpc-id,Values="${vpc_id}" \
    | jq -r '.InternetGateways[].InternetGatewayId'
}

# delete_subnets ..$subnet_id
delete_subnets() {
  for id in "$@"; do
    if [ "${DRY_RUN}" == "false" ]; then
      echo "Deleting Subnet ${id} in ${AWS_REGION}"
      aws ec2 delete-subnet --subnet-id=${id}
    else
      echo "Would delete subnet ${id} in ${AWS_REGION}"
    fi
  done
}

# delete_igw $vpc_id ..$igw_id
delete_igw() {
  vpc_id=$1; shift
  for igw_id in "$@"; do
    n_attachments=$(aws ec2 describe-internet-gateways --filter Name=attachment.vpc-id,Values="${vpc_id}" \
      | jq ".InternetGateways[] | select(.InternetGatewayId == \"${igw_id}\") | .Attachments | length")
    if [[ ${n_attachments} == 1 ]]; then
      if [ "${DRY_RUN}" == "false" ]; then
        echo "Detaching IGW ${igw_id} from ${vpc_id}"
        aws ec2 detach-internet-gateway --internet-gateway-id=${igw_id} --vpc-id="${vpc_id}"
      else
        echo "Would detach IGW ${igw_id} from ${vpc_id} in ${AWS_REGION}"
      fi
    fi
    if [ "${DRY_RUN}" == "false" ]; then
      echo "Deleting IGW ${igw_id}"
      aws ec2 delete-internet-gateway --internet-gateway-id=${igw_id}
    else
      echo "Would delete IGW ${igw_id} in ${AWS_REGION}"
    fi
  done
}

# delete_vpc $vpc_id
delete_vpc() {
  local id=$1; shift
  if [ "${DRY_RUN}" == "false" ]; then
    echo "Deleting default VPC ${id} in ${AWS_REGION}"
    aws ec2 delete-vpc --vpc-id "${vpc_id}"
  else
    echo "Would delete default VPC ${id} in ${AWS_REGION}"
  fi
}

for region in "${regions[@]}"; do
  (
    export AWS_REGION=${region}
    default_vpc_id=$(aws ec2 describe-vpcs | jq -r '.Vpcs[] | select(.IsDefault) | .VpcId')
    test -z "{$default_vpc_id}" && {
      echo "No default VPC found in ${AWS_REGION}"
      exit 0
    }

    delete_subnets $(get_subnets "${default_vpc_id}")
    delete_igw "${default_vpc_id}" $(get_igw "${default_vpc_id}")
    delete_vpc "${default_vpc_id}"
  )
done