Dynamic Dns update script to update DigitalOcean DNS Zone record

update_do_ip.sh

#!/bin/bash

DNS_FILE="$HOME/.my_public_ip"
SUCCESS="200"
DO_API_KEY=""
DO_DOMAIN=""
DO_DNS_RECORD_ID=""

#- Get public ip
ip=$(curl --silent api.ipify.org)
ret=$?

if [ $ret -eq 0 ]; then
  #- Read previous ip from file
  [ -e "$DNS_FILE" ] && old_ip=$(< "$DNS_FILE" )

  #- Update DigitalOcean DNS record if new record differs from previous record
  if [ "$ip" != "$old_ip" ]; then
    #- Update DigitalOceans DNS Record
    result=$(curl \
      --silent \
      --output /dev/null \
      -w %{http_code} \
      -H "Authorization: Bearer $DO_API_KEY" \
      -H "Content-Type: application/json" \
      -d "{\"data\": \"$ip\"}" \
      -X PUT "https://api.digitalocean.com/v2/domains/$DO_DOMAIN/records/$DO_DNS_RECORD_ID")
    ret=$?
    if [ $ret -eq 0 ]; then

      if [ "$result" == "$SUCCESS" ]; then
        #- Persist new record to file
        echo "$ip" > "$DNS_FILE"
        logger "$0 - Public ip changed: DNS record updated to $ip"
        exit 0
      else
        logger "$0 - Updating DNS record failed with HTTP error code: $result"
        exit 1
      fi
    else
      logger "$0 - Updating public ip failed with curl error code: $ret"
      exit 1
    fi
  fi

  logger "$0 - Public ip unchanged: $ip"
  exit 0
else
  logger "$0 - Retrievieng public ip failed with curl error code: $ret"
  exit 1
fi