notify-tg for ssh

notify-tg.sh

#!/bin/bash

# 0. prerequisites:
#    register bot and get access token
#    message /newbot to @BotFather
#    enter bot name
#    save token received from @BotFather
#    send message to your newly created bot
#    find out chat_id with
#    curl -s https://api.telegram.org/bot${TOKEN}/getUpdates \
#       | jq '.result[].message.chat.id' | uniq
#
# 1. put this script in ~/.ssh/backchannel/notify-tg.sh 
#
# 2. start http server for backchannel
#    cat <<EOF > ~/.config/systemd/user/ssh-tg.service
#    [Unit]
#    Description=ssh backchannel
#    [Service]
#    Type=simple
#    Restart=always
#    ExecStart=/bin/sh -c 'cat ~/.ssh/backchannel/notify-tg.sh | nc -q 0 -l localhost -p 40000'
#    [Install]
#    WantedBy=default.target
#    EOF
#    
#    systemctl --user enable ssh-tg.service
#    systemctl --user start ssh-tg.service
#
# 3. ssh with remote forwarding to some host
#    ssh -R 40000:127.0.0.1:40000 some.server
#
# 4. on some.server source notify-tg.sh script fetched through backchannel
#    source <(curl -s http://localhost:40000/notify-tg.sh)
#
# 5. now you can use notify-tg without actually having the script on the server
#
# 6. to make things easier, add forwarding to .ssh/config and sourcing to .bashrc
#
# ps. I know, there are other ways to do this, but they may require enabling features in sshd
# and that is not always possible.

function notify-tg {
    TOKEN=your:token
    CHAT_ID=your_id

    CURL='curl -s -G --data-urlencode'
    DEST="https://api.telegram.org/bot${TOKEN}/sendMessage?chat_id=${CHAT_ID}"
    if [ "$1" = '-l' ]; then
        while read line; do
            $CURL "text=${line}" $DEST > /dev/null
        done
    else
        $CURL "text@-" $DEST > /dev/null
    fi
}