Nagios host and service notifications via Telegram bot without installing any messy scripts.
Message @BotFather in your Telegram app. Write down your bots access token, which is something like '53355511:AaFnF2Xnt1-RjGMaQZ_412tvp-_e12312KQ'. When using the token, you add 'bot' in-front of the token to complete it, turning the access token into 'bot53355511:AaFnF2Xnt1-RjGMaQZ_412tvp-_e12312KQ'.
Next, type /setprivacy to @BotFather and set DISABLE for your bot.
Select 'Info' on your group name in your Telegram app and invite the bot. Make sure you are admin of the group or there may be issues.
As yourself, write something in the group.
Fetch events from your bot by running:
curl -Lk -i -X GET https://api.telegram.org/botACCESSTOKEN-GIVEN-FROM-BOTFATHER/getUpdates
Output will be something like:
"message":{"message_id":14,"from":{"id":300920731,"is_bot":false,"first_name":"Your","last_name":"Name","language_code":"en-US"},"chat":{"id":-123456789,"title":"My fancy Telegram group","type":"supergroup"},"date":1520901132,"text":"I like beer"}}]}
Copy and save "chat" id, which in above example is -123456789.
Copy the custom notifications commands from here: https://github.com/mglantz/nagios-telegram-notification/blob/master/command.cfg and replace the chat_id value with above and replace botREPLACEME with your full access token.