Cloudflare API v4 Dynamic DNS Update in sh(For ASUS Merlin)

ddns-start.sh

#!/bin/bash

# https://github.com/RMerl/asuswrt-merlin/wiki/Custom-DDNS
# CHANGE THESE
auth_email="user@example.com"
auth_key="c2547eb745079dac9320b638f5e225cf483cc5cfdda41" # found in cloudflare account settings
zone_name="example.com"
record_names="*.a.example.com"
record_names="$record_names a.example.com"

ip=$(curl -s https://ipv4.icanhazip.com)

for record_name in $record_names; do
  # compatible with grep without perl support
  zone_identifier=$(curl -s -X GET "https://api.cloudflare.com/client/v4/zones?name=$zone_name" -H "X-Auth-Email: $auth_email" -H "X-Auth-Key: $auth_key" -H "Content-Type: application/json" | grep -o '"id":"[0-9a-z]*"' | grep -o '"[0-9a-f]*"' | grep -o '[0-9a-f]*' | head -1 )
  record_identifier=$(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 -o '"id":"[0-9a-z]*"' | grep -o '"[0-9a-f]*"' | grep -o '[0-9a-f]*')

  curl -fs -o /dev/null -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: $auth_key" \
       -H "Content-Type: application/json" \
       --data "{\"type\":\"A\",\"name\":\"$record_name\",\"content\":\"$ip\",\"proxied\":false}"
done

if [ $? -eq 0 ]; then
  /sbin/ddns_custom_updated 1
else
  /sbin/ddns_custom_updated 0
fi