• https://linuxscriptshub.com/send-telegram-message-linux-scripts/
• From BotFather to 'Hello World'
• Bash Script to Send a Message in Telegram from your Terminal!
• Telegram Bot - how to get a group chat id?

BotFather

/newbot

choose name: Val spec N

choose username: ValspecNbot

...
You will find it at t.me/Valspec2bot
...
Use this token to access the HTTP API:
823268117438:AAE5W1PlK3ex0udwaQeznHG5ejsQNXc-J58
...

/start
...

https://api.telegram.org/bot823268117438:AAE5W1PlK3ex0udwaQeznHG5ejsQNXc-J58/getUpdates
...
        "chat": {
          "id": 1776721761
...

$ cat send-to-telegram.sh

#!/bin/sh

[ "$1" ] && MESSAGE=$1 || MESSAGE="Hello, world!"
#MESSAGE=$(cat)

 TOKEN="768604181156:AAGB1Qwvd-DAPhFbQiMKR3InggtIvPPEtT8"
CHAT_ID="1776721761"
curl -s -X POST https://api.telegram.org/bot$TOKEN/sendMessage -d chat_id=$CHAT_ID -d text="$MESSAGE"

$ time make buildworld; /home/val/send-to-telegram.sh FINISH

• Использование pam_exec для регистрации подключений

debian:~# chmod 700 /usr/local/bin/send-to-telegram.sh