Cloudflare as Dynamic DNS

lwp-cloudflare-dyndns.sh

#!/bin/bash
# Cloudflare as Dynamic DNS
# From: https://letswp.io/cloudflare-as-dynamic-dns-raspberry-pi/
# Based on: https://gist.github.com/benkulbertis/fff10759c2391b6618dd/
# Original non-RPi article: https://phillymesh.net/2016/02/23/setting-up-dynamic-dns-for-your-registered-domain-through-cloudflare/

# Update these with real values
auth_email="[email protected]"
auth_key="global_api_key_goes_here" 
zone_name="example.com"
record_name="home.example.com"

# Don't touch these
ip=$(curl -s http://ipv4.icanhazip.com)
ip_file="ip.txt"
id_file="cloudflare.ids"
log_file="cloudflare.log"

# Keep files in the same folder when run from cron
current="$(pwd)"
cd "$(dirname "$(readlink -f "$0")")"

log() {
    if [ "$1" ]; then
        echo -e "[$(date)] - $1" >> $log_file
    fi
}

log "Check Initiated"

if [ -f $ip_file ]; then
    old_ip=$(cat $ip_file)
    if [ $ip == $old_ip ]; then
        log "IP has not changed."
        exit 0
    fi
fi

if [ -f $id_file ] && [ $(wc -l $id_file | cut -d " " -f 1) == 2 ]; then
    zone_identifier=$(head -1 $id_file)
    record_identifier=$(tail -1 $id_file)
else
    zone_identifier=$(curl -s -X GET "https://api.cloudflare.com/client/v4/zones?name=$zone_name" -H "X-Auth-Email: $auth_email" -H "X-Auth-Key: $auth_key" -H "Content-Type: application/json" | grep -Po '(?<="id":")[^"]*' | head -1 )
    record_identifier=$(curl -s -X GET "https://api.cloudflare.com/client/v4/zones/$zone_identifier/dns_records?name=$record_name" -H "X-Auth-Email: $auth_email" -H "X-Auth-Key: $auth_key" -H "Content-Type: application/json"  | grep -Po '(?<="id":")[^"]*')
    echo "$zone_identifier" > $id_file
    echo "$record_identifier" >> $id_file
fi

update=$(curl -s -X PUT "https://api.cloudflare.com/client/v4/zones/$zone_identifier/dns_records/$record_identifier" -H "X-Auth-Email: $auth_email" -H "X-Auth-Key: $auth_key" -H "Content-Type: application/json" --data "{\"id\":\"$zone_identifier\",\"type\":\"A\",\"name\":\"$record_name\",\"content\":\"$ip\"}")

if [[ $update == *"\"success\":false"* ]]; then
    message="API UPDATE FAILED. DUMPING RESULTS:\n$update"
    log "$message"
    echo -e "$message"
    exit 1 
else
    message="IP changed to: $ip"
    echo "$ip" > $ip_file
    log "$message"
    echo "$message"
fi

I implemented logrotate. This will rotate the log files each day for 7 days before deleting the oldest one. Then you don't have a giant growing log file for eternity. Before running the program:

sudo mkdir /var/log/cloudflare
sudo chown $USER:$USER /var/log/cloudflare/
touch /var/log/cloudflare/cloudflare.log
nano /etc/logrotate.d/cloudflare

Enter in /etc/logrotate.d/cloudflare file:

/var/log/cloudflare/cloudflare.log {
	rotate 7
	daily
}

Save the file. Then change directory back to where this script (lwp-cloudflare-dyndns.sh) is located. For me, ~/cloudflare. Finally:
ln -s cloudflare.log /var/log/cloudflare/cloudflare.log