Cloudflare API v4 Dynamic DNS Update in Bash

cloudflare-update-record.service

[Unit]
Description=Update a DNS record using Cloudflare DDNS service
After=network.target

[Install]
WantedBy=multi-user.target

[Service]
StandardOutput=journal
StandardError=journal

# CHANGE THESE VALUES
User=username
ExecStart=/home/username/cloudflare-update-record/cloudflare-update-record.sh
WorkingDirectory=/home/username/cloudflare-update-record/
Environment="CLOUDFLARE_AUTH_EMAIL=username@example.org" "CLOUDFLARE_API_KEY=1234567890ABCDEF"
Environment="CLOUDFLARE_ZONE_NAME=example.org" "CLOUDFLARE_RECORD_NAME=example.org"

cloudflare-update-record.sh

#!/bin/bash

# CHANGE THESE
auth_email="$CLOUDFLARE_AUTH_EMAIL"
auth_key="$CLOUDFLARE_API_KEY"
zone_name="$CLOUDFLARE_ZONE_NAME"
record_name="$CLOUDFLARE_RECORD_NAME"

# MAYBE CHANGE THESE
ip=$(curl -s http://ipv4.icanhazip.com)
ip_file="ip.txt"
id_file="cloudflare.ids"

# LOGGER
log() {
    if [ "$1" ]; then
        echo "$1" | systemd-cat -p info --identifier=cloudflare-update-record
    fi
}

# SCRIPT START
log "Check Initiated"

if [ -f $ip_file ]; then
    old_ip=$(cat $ip_file)
    if [ $ip == $old_ip ]; then
        echo "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

cloudflare-update-record.timer

[Unit]
Description=Update a DNS record every minute via Cloudflare DDNS service

[Timer]
OnBootSec=1min
OnUnitActiveSec=1min
AccuracySec=1s

[Install]
WantedBy=timers.target