OVH dynhost (DynDNS clone) update script

#!/usr/bin/env bash
# /path/to/dyndns-update.sh

# 1. Create a credentials file in the same folder with this script named 
# dyndns-update.sh_EXAMPLE.COM.creds.txt 
# with user credentials, such as 
# example.com-username:USER-PASSWORD
# 
# 2. Try this at least once. The output of curl commands tells if update is successful, not necessary or if something was wrong.
# sudo sh /path/to/dyndns-update.sh
#
# 3. Run this as a cronjob
# $ sudo crontab -e
# and add something like this to your crontab (this checks IP every 10 mins):
# */10 * * * * sh /path/to/dyndns-update.sh EXAMPLE.COM

# Disable to get less output:
DEBUG=1

USER_ID=$(id -u)
if [ "$USER_ID" -ne "0" ]; then
  echo This script must be run as a root.
  exit 0
fi

DOMAIN=$1
if [ -z "$DOMAIN" ]; then
  echo "Usage: "
  echo "${0} example.com"
  exit 1
fi

SCRIPT=`realpath $0`
SCRIPT_FOLDER=$(dirname $SCRIPT)
SCRIPT_NAME=$(basename $SCRIPT)

DOMAIN_IP=$(host $DOMAIN |awk '{print $4}' | xargs)
PUBLIC_IP=$(curl --silent https://ipinfo.io/ip | xargs)

if [ "$DOMAIN_IP" != "$PUBLIC_IP" ]; then
  echo -n "Domain ${DOMAIN} public IP is ${DOMAIN_IP}. "
  echo "Your local IP is ${PUBLIC_IP}, so DynHost needs updating. "
  FILE="${SCRIPT_FOLDER}/${SCRIPT_NAME}_${DOMAIN}.creds.txt "
  # Reads the 1st line of a file $FILE  into a PASS varible.
  read -r PASS < $FILE
  if [ -z "$PASS" ]; then
    echo "No password (tried $FILE), exiting!"
    exit 1;
  fi
  [ ! -z "$DEBUG" ] && [ "$DEBUG" -ne "0" ] && echo "Next (with creds):" "https://www.ovh.com/nic/update?system=dyndns&hostname=${DOMAIN}&myip=${PUBLIC_IP}"
  curl --silent --user "${PASS}"                       "https://www.ovh.com/nic/update?system=dyndns&hostname=${DOMAIN}&myip=${PUBLIC_IP}"
elif [ ! -z "$DEBUG" ] && [ "$DEBUG" -ne "0" ]; then
  echo  "Domain ${DOMAIN} public IP is ${DOMAIN_IP}."
  echo "Your local IP is ${PUBLIC_IP}."
  echo "Domain ${DOMAIN} IP still ok."
fi