Dynamic DNS Updater

#!/bin/bash

FORCE=false

TO="user@yahoo.com"
FROM=user@yahoo.com

HOSTNAME="@"
DOMAINS=( 
      "site1.com"
	  "site2.com"
)
 
PASSWORDS=( 
        "xxx"
	    "xxx"
)


BASE_URL="https://dynamicdns.park-your-domain.com/update"
TMP_FILE=/tmp/dyndns_mail.txt

EMAIL_BODY=""
LOG=""

function log(){
  echo $1
  LOG+="$1\n"
}

function sendEmail(){

  SUBJECT="$1"

  echo "Subject: $SUBJECT" > $TMP_FILE
  echo "From: $FROM" >> $TMP_FILE
  echo "To: $TO" >> $TMP_FILE
  echo "" >> $TMP_FILE
  echo -e $LOG >> $TMP_FILE
  echo "" >> $TMP_FILE
  if [ -f ./site.output ]; then
    cat ./site.output >> $TMP_FILE
    rm ./site.output
  fi
  cat $TMP_FILE |sendmail -t
  rm $TMP_FILE
}

log "-- Dynamic Ip Address Updater --"
log " "

CURRENT_IP=$(curl -s 'https://api.ipify.org')
if [[ $CURRENT_IP =~ ^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
  log "CUR IP: $CURRENT_IP"
else
  log "--> Failed to determine current IP"
  sendEmail "Dynamic DNS Update Failure"
  exit
fi

DNS_IP=$(dig +short jmehan.com @resolver1.opendns.com)
if [[ $DNS_IP =~ ^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
  log "DNS IP: $DNS_IP"
  log " "
else
  log "--> Failed to determine DNS IP for ${DOMAINS[$index]}"
  sendEmail "Dynamic DNS Update Failure"
  exit 1
fi

NEEDS_UPDATING=false
FAILURE=false

log "Verifying Domain IPs"
for index in "${!DOMAINS[@]}"
do
    if [ "$DNS_IP" != "$CURRENT_IP" ] || [ $FORCE == true ]; then
      NEEDS_UPDATING=true 
      URL="${BASE_URL}?host=$HOSTNAME&domain=${DOMAINS[$index]}&password=${PASSWORDS[$index]}" 
      status_code=$(curl --write-out %{http_code} --silent --output site.output $URL)
      if [[ "$status_code" -ne 200 ]] ; then
        log "--> Error: StatusCode: $status_code"
        sendEmail "Dynamic DNS Update Failure" 
        exit 1
      fi
      success=$(cat site.output |grep "<ErrCount>0</ErrCount>" |wc -l)
      if [[ "$success" -eq 1 ]] ; then
        log "- SUCCESS [ $DNS_IP -> $CURRENT_IP ] ${DOMAINS[$index]}"
      else
        FAILURE=true
        log "- FAILED  ${DOMAINS[$index]}"
        sendEmail "Dynamic DNS Update Failure" 
      fi
    fi
done

if [ $NEEDS_UPDATING == true ]; then
  if [ $FAILURE == false ]; then
    log "Done"
    sendEmail "Dynamic DNS Updated" 
  fi
else
   log "- Nothing to Update"
   log "Done"
fi