Everytime your dynamic IP changes you get a slack notification. How cool is that!

current-dyn-ip.sh

#!/bin/bash
# author: Timo Stankowitz <timo.stankowitz@gmail.com>
# create date: 2017-11-17
# last change: 2018-02-13
# version 3

# everytime your dynamic ip changes you get a notification to your slack channel
# with the current dynamic ip of your router

# create a cronjob and let the script execute every 5 minutes

# replace with your data
slackURL='https://hooks.slack.com/services/XXX/YYY/ZZZ1'
DIGITALOCEAN_TOKEN='XXXYYYZZZ'
tempfile="/tmp/current-ip.txt"

# get your current public IP via my PHP script 
currentIP=$(curl -s http://ip.brainoftimo.com/cli.php)


function writeIP() {
    # write current IP into tempfile
    echo "$currentIP" > $tempfile 
}

function sendToSlack() {
   curl -X POST --data-urlencode 'payload={
      "channel": "dynamic_ip", 
      "username": "dynamic IP Bot",
      "icon_emoji": ":nerd_face:", 
      "text": "'"$1"'"
   }' $slackURL
}

# check if tempfile exists
test -f $tempfile
if [ $? != "0" ]; then
    # create file and write ip
    touch $tempfile
    writeIP
    sendToSlack "Du führst das Script das erste mal aus.\nDeine aktuelle IP lautet: *$currentIP*"
fi

# read "old" IP from file
oldIP=$(head -n1 $tempfile)

# compare the addresses and send a message if a change took place
if [ "$oldIP" != "$currentIP" ]; then
    # your ip has change
    sendToSlack "Deine dynamische IP Adresse hat sich geändert.\nZuvor hattest du die Adress ~$oldIP~. \nNun hast du die IP Adresse *$currentIP*"
    # write the new IP into the temp file.
    writeIP
    # replace with your domain
    curl -s -H "Authorization: Bearer $DIGITALOCEAN_TOKEN" -X PUT -H "Content-Type: application/json" -d '{"data":"'"$currentIP"'"}' https://api.digitalocean.com/v2/domains/example.com/records/XXYYZZ >> /tmp/curl_DO_Status
fi