dynamicDnsNamecheap

#!/bin/bash

# Author: Mike Slinn mslinn@mslinn.com
# Modified from AWS version (dynameicDnsAws) 2022-06-30
# Added auth subdomain 2022-08-18
# See https://www.namecheap.com/support/knowledgebase/article.aspx/36/11/how-do-i-start-using-dynamic-dns/

export SAVE_FILE_NAME="$HOME/.dynamicDns"

function help {
  echo "$( basename $0 ) - Maintains three Namecheap dynamic DNS records: the apex domain, www and auth.

Saves data in '$SAVE_FILE_NAME'

Syntax:
  $( basename $0) [OPTIONS] DOMAIN PASSWORD

OPTIONS:
  -v Verbose mode

Example usage:
  $( basename $0) mydomain.com  asdfasdfasdfasdfasdf
  $( basename $0) -v mydomain.com asdfasdfasdfasdf

"
  exit 1
}

function upsert {
  curl "https://dynamicdns.park-your-domain.com/update?host=@&domain=$DOMAIN&password=$PASSWORD&ip=$IP"
  curl "https://dynamicdns.park-your-domain.com/update?host=auth&domain=$DOMAIN&password=$PASSWORD&ip=$IP"
  curl "https://dynamicdns.park-your-domain.com/update?host=www&domain=$DOMAIN&password=$PASSWORD&ip=$IP"
  echo "$IP" > "$SAVE_FILE_NAME"
  echo ""
}

if [ "$1" == -v ]; then
  export VERBOSE=true
  shift
fi

if [ -z "$2" ]; then help; fi

set -e

export DOMAIN="$1"
export PASSWORD="$2"
export IP="$( dig +short myip.opendns.com @resolver1.opendns.com )"

if [ ! -f "$SAVE_FILE_NAME" ]; then
  if [ "$VERBOSE" ]; then echo "Creating $SAVE_FILE_NAME"; fi
  upsert;
elif [ "$( cat "$SAVE_FILE_NAME" )" != "$IP" ]; then
  if [ "$VERBOSE" ]; then
    echo "Updating $SAVE_FILE_NAME"
    echo "'$IP' was not equal to '$( cat "$SAVE_FILE_NAME" )'"
  fi
  upsert;
else
  if [ "$VERBOSE" ]; then echo "No change necessary for $SAVE_FILE_NAME"; fi
fi