On IP Change

README.md

ON IP CHANGE

Installation

# Copy files into /usr/local/bin/on-ip-change.sh and /etc/systemd/system/on-ip-change.service
mkdir -p /usr/local/var/on-ip-change/scripts
sudo systemctl enable on-ip-change.service
sudo systemctl start on-ip-change.service
# Add your scripts to /usr/local/var/on-ip-change/scripts

# Follow logs ...
sudo journalctl -f -u on-ip-change

example-script.sh

#!/usr/bin/env bash

# copy to /usr/local/var/on-ip-change/scripts/example-script.sh

# echo new ip address
echo $1

on-ip-change.service

[Unit]
Description=Run scripts when IP changes
Requires=network.target

[Service]
ExecStart=/usr/local/bin/on-ip-change.sh /usr/local/var/on-ip-change/scripts 30
Restart=on-failure

[Install]
WantedBy=multi-user.target

on-ip-change.sh

#!/usr/bin/env bash

# run all *.sh scripts when IP changes
scripts_dir="$1"

# run IP detection every n seconds
check_interval_sec=$2

current_ip=""
while true; do
  # get current ip and verify syntax
  new_ip=$(dig +short myip.opendns.com @resolver1.opendns.com)
  if [[ ! "$new_ip" =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
    echo "Invalid IP returned $new_ip"
  else
    # check if ip has changed
    if [[ "$new_ip" != "$current_ip" ]]; then
      current_ip="$new_ip"
      echo "--> New IP $new_ip"

      # run scripts
      for file in $scripts_dir/*.sh; do
        echo "--> $file"
        ( $file "$new_ip" )
        echo
      done
    fi
  fi 
  
  # wait until next check  
  sleep $check_interval_sec
done