#!/bin/bash
# this script and "currentIP.txt" must be in the same directory
# run "(hostname -I) > currentIP.txt" in bash before running this script the first time
ip_rightNow=$(hostname -I)

ip_prev=$(cat currentIP.txt)

if [[ "$ip_rightNow" != "$ip_prev" ]]; then
    echo $ip_rightNow > currentIP.txt
    scp currentIP.txt user@XXX.XXX.XXX.XXX:/path/to/directory
fi

# above depends on ssh key authentication (no passphrase on key)
# can add this to crontab to run every Y minutes with:
#   */Y * * * * /path/to/updateIP.sh