Reassociate AWS EIP (needs awscli, jq and the corresponding iam permissions)

associate_ip.sh

#!/bin/bash
# Helper Functions
get_instance_region() {
    if [ -z "$AWS_REGION" ]; then
        AWS_REGION=$(curl -s http://169.254.169.254/latest/dynamic/instance-identity/document \
            | grep -i region \
            | awk -F\" '{print $4}')
    fi

    echo $AWS_REGION
}

AWS_CLI="aws --region $(get_instance_region)"
get_instance_id() {
    curl -s http://169.254.169.254/latest/meta-data/instance-id
    return $?
}

INSTANCE_ID=$(get_instance_id)
if [ $? != 0 -o -z "$INSTANCE_ID" ]; then
    error_exit "Unable to get this instance's ID; cannot continue."
fi

AWS_CLI="aws --region $(get_instance_region)"
EIP_ALLOCATION=$YOUR-EIP-ALLOCATION-HERE

associate_ip() {
    $AWS_CLI ec2 associate-address --instance-id $INSTANCE_ID --allocation-id $EIP_ALLOCATION
}


check_association() {
  $AWS_CLI ec2 describe-addresses --allocation-ids $EIP_ALLOCATION | jq '.Addresses[].InstanceId' --raw-output
  return $?
  echo $?
}

CURRENT_INSTANCE=$(check_association)

echo "$EIP_ALLOCATION is currently associated to $CURRENT_INSTANCE, we are Instance $INSTANCE_ID"
if [ "$CURRENT_INSTANCE" == "$INSTANCE_ID" ]; then
    echo "EIP is already associated to this instance"
        exit 1
    else
    echo "ok, will reassociate"
fi
associate_ip