A bash script to notify changes of your ip address with an email

checkip.sh

#!/bin/bash
# Run this script in the background with './checkip.sh >/dev/null 2>&1 &'
# mail or mailx have to be configured by placing a .mailrc file in
# your home directory.

# The file where the current ip is saved
IPFILE='ipfile'
# Change this with your own email
MAILTO='example@example.com'

while true; do
  newip=$(dig +short myip.opendns.com @resolver1.opendns.com)
  oldip=$(cat $ipfile)
  
  if [[ "$newip" != "$oldip" ]]; then
    echo "The new ip is $newip"
    echo $newip | mail -s 'Your ip has changed' $MAILTO
    echo $newip >$IPFILE
  fi
  sleep 30
  
done