check if IP address matches last know IP, do something if it doesn't.

checkip.sh

#!/bin/bash
# Get current IP

ip_address=$(curl icanhazip.com)

echo $ip_address
# Check if IP Address matches last known IP

FILE=/home/pi/scripts/ip.txt

old_ip=$(cat $FILE)

if [[ "$old_ip" != "$ip_address" ]];then
	echo "Run a script"
fi
echo $ip_address > $FILE