Ping to HOST and if it fails return a message through Telegram

telegram-ping.sh

#!/usr/bin/env bash
#shellcheck disable=SC2034
#
# CONFIG
#

# IP or HOSTNAME to ping
# IP o host al que hacer ping
# HOST="192.168.33.1"

# Message if fails
# Mensaje si falla
FAILURE_MESSAGE="Telegram PING to \`%s\` failed"

# Time between pings in secs
# Tiempo entre pings en segundos
PING_TIME=5

# Number of tries
# Número de reintentos
PING_RETRIES=3

# Telegram
# BOT_API_KEY=""
# BOT_CHAT_ID=""
# BOT_VIM_NAME=""

# Other
PATH_LOG="$HOME/telegram-ping.log"
CURRENT_DATE="$(date)"
PING_CMD=(ping -c 2 -i 5 -o)

_log() {
  touch "$PATH_LOG"
  if [[ -w "$PATH_LOG" ]] && [[ -t 0 ]]; then
    [[ $# -gt 0 ]] && printf "%s\n" "$@" >> "$PATH_LOG"
  elif [[ -w "$PATH_LOG" ]] && [[ ! -t 0 ]]; then
    [[ $# -gt 0 ]] && echo "$*" >> "$PATH_LOG"
    echo "$(< /dev/stdin)" >> "$PATH_LOG"
  elif [[ -t 0 ]]; then
    [[ $# -gt 0 ]] && printf "%s\n" "$@"
  else
    [[ $# -gt 0 ]] && echo "$*"
    echo "$(< /dev/stdin)"
  fi
}
 
#
# DO THE WORK
#
if [[ -z "${HOST:-}" || -z "${FAILURE_MESSAGE:-}" ]]; then
  echo "Empty host or message" | _log "Configuration error"
else
  RETRIES=0
  FAILED=true
  while [[ $RETRIES -lt ${PING_RETRIES:-2} ]]; do
    RETRIES=$(( RETRIES + 1 ))

    _log "Ping retry $RETRIES to host: $HOST"

    if "${PING_CMD[@]}" "$HOST" &>/dev/null; then
      FAILED=false
      break
    fi

    sleep "${PING_TIME}s"
  done

  if ${FAILED:-}; then
    #shellcheck disable=SC2059
    message="$(printf "$FAILURE_MESSAGE" "$HOST")"
    _log "Ping to \`$HOST\` failed"
    data=$(curl --silent "https://api.telegram.org/bot${BOT_API_KEY}/sendMessage" --data-urlencode "chat_id=${BOT_CHAT_ID}" --data-urlencode "text=$message")
    [[ $(echo "$data" | jq -r '.ok') != "true" ]] && _log "Fail to send telegram message"
  else
    _log "Ping to \`$HOST\` sucess"
  fi
fi

Uncomment or comment the variables if you you want to have static values, if not, use ENV vars like:

HOST="192.168.0.1" BOT_API_KEY="myapi" BOT_CHAT_ID="chat id" BOT_VIM_NAME="bot name" ./telegram-ping.sh