BASH Script to keep Route53 updated with your current external IP address

update-route53.sh

#!/bin/bash

# (optional) You might need to set your PATH variable at the top here
# depending on how you run this script
# PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
# Hosted Zone ID e.g. BJBK35SKMM9OE
ZONEID=(
    "ZONEID-0"
    "ZONEID-1"
    "ZONEID-2"
    "ZONEID-3"
)

# The CNAME you want to update e.g. hello.example.com
RECORDSET=(
    "RECORDSET-0"
    "RECORDSET-1"
    "RECORDSET-2"
    "RECORDSET-3"
)

# More advanced options below
# The Time-To-Live of this recordset
TTL=300
# Change this if you want
COMMENT="Auto updating @ `date`"
# Change to AAAA if using an IPv6 address
TYPE="A"

# Get current dir
# (from http://stackoverflow.com/a/246128/920350)
DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
LOGFILE="$DIR/update-route53-log"
IPFILE="$DIR/update-route53-ip"

# Get the external IP address from OpenDNS (more reliable than other providers)
IP=`dig +short myip.opendns.com @resolver1.opendns.com`

function valid_ip()
{
    local  ip=$1
    local  stat=1

    if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
        OIFS=$IFS
        IFS='.'
        ip=($ip)
        IFS=$OIFS
        [[ ${ip[0]} -le 255 && ${ip[1]} -le 255 \
            && ${ip[2]} -le 255 && ${ip[3]} -le 255 ]]
        stat=$?
    fi
    return $stat
}

# Log and exit if IP is invalid
if ! valid_ip $IP; then
    echo "$(date -R) Invalid IP address: $IP" >> "$LOGFILE"
    exit 1
fi

# Check if the IP file exists and creates one if it doesn't
if [ ! -f "$IPFILE" ]
    then
    touch "$IPFILE"
fi

# Log and exit if IP matches current IP address stored in IPFILE
# Else update IP address on amazon.com and log to file
if grep -Fxq "$IP" "$IPFILE"; then
    # code if found
    echo "$(date -R) IP is still $IP. Exiting" >> "$LOGFILE"
    exit 0
else
    echo "$(date -R) IP has changed to $IP" >> "$LOGFILE"
    zn_iter=0
    zn_list_length=${#ZONEID[@]};
    for zone in "${ZONEID[@]}";
    do
        # Fill a temp file with valid JSON
        TMPFILE=$(mktemp /tmp/temporary-file.XXXXXXXX)
        cat > ${TMPFILE} << EOF
        {
        "Comment":"$COMMENT",
        "Changes":[
            {
            "Action":"UPSERT",
            "ResourceRecordSet":{
                "ResourceRecords":[
                {
                    "Value":"$IP"
                }
                ],
                "Name":"${RECORDSET[$zn_iter]}",
                "Type":"$TYPE",
                "TTL":$TTL
            }
            }
        ]
        }
EOF

        # Update the Hosted Zone record
        aws route53 change-resource-record-sets \
            --hosted-zone-id $zone \
            --change-batch file://"$TMPFILE" >> "$LOGFILE"
        zn_iter=$(( $zn_iter + 1 ));
        echo "" >> "$LOGFILE"

        # Clean up
        rm $TMPFILE
    done
    # All Done - cache the IP address for next time
    echo "$IP" > "$IPFILE"
fi