Environment Variables

Overview

The Price Tracker Bot uses environment variables to securely manage sensitive configuration data. All environment variables are loaded from a .env file in the project root.

Loading Configuration

The bot uses the dotenv package to load environment variables:

index.mjs (lines 5-8)

import dotenv from "dotenv";

dotenv.config();

This must be called before accessing any environment variables to ensure they’re available.

Required Variables

TELEGRAM_TOKEN

string

required

The authentication token for your Telegram bot. This is the only required environment variable.

The TELEGRAM_TOKEN is mandatory and validates on startup:

index.mjs (lines 11-15)

const TELEGRAM_TOKEN = process.env.TELEGRAM_TOKEN;
if (!TELEGRAM_TOKEN) {
  console.error("❌ TELEGRAM_TOKEN no definido en .env");
  process.exit(1);
}

Token Format: A string like 123456789:ABCdefGHIjklMNOpqrsTUVwxyz-1234567890

The bot will immediately exit with an error if TELEGRAM_TOKEN is not defined. This prevents running without authentication.

Getting Your Telegram Bot Token

Step 1: Contact BotFather

Telegram’s @BotFather manages all bot creation and token generation.

Open Telegram and search for @BotFather
Start a conversation by clicking Start or sending /start

Step 2: Create a New Bot

Send the /newbot command to BotFather:

/newbot

BotFather will guide you through the creation process:

Choose a name: The display name for your bot (e.g., “Price Tracker Bot”)
Choose a username: Must end in bot (e.g., my_price_tracker_bot)

Usernames must be unique across all Telegram bots. If your choice is taken, try adding numbers or underscores.

Step 3: Receive Your Token

Upon successful creation, BotFather sends a message containing:

Done! Congratulations on your new bot. You will find it at t.me/your_bot_username.

Use this token to access the HTTP API:
123456789:ABCdefGHIjklMNOpqrsTUVwxyz-1234567890

Keep your token secure and store it safely, it can be used by anyone to control your bot.

Keep your token secret! Anyone with access to your token can control your bot. Never commit it to version control or share it publicly.

Step 4: Add Token to .env File

Copy the token and add it to your .env file:

.env

TELEGRAM_TOKEN=123456789:ABCdefGHIjklMNOpqrsTUVwxyz-1234567890

Token Usage in Code

The token is used to initialize the Telegram bot instance:

index.mjs (line 17)

const bot = new TelegramBot(TELEGRAM_TOKEN, { polling: true });

Configuration options:

polling: true - Enables long polling to receive updates from Telegram

Polling is ideal for development and simple deployments. For production at scale, consider using webhooks instead.

Optional Variables

While the bot currently only requires TELEGRAM_TOKEN, you may want to add additional environment variables for customization:

Suggested Optional Variables

TELEGRAM_TOKEN=your_token_here

The extended configuration example shows potential future enhancements. Currently, only TELEGRAM_TOKEN is used by the bot.

Security Best Practices

1. Never Commit Secrets

Add .env to your .gitignore:

.gitignore

# Environment variables
.env
.env.local
.env.*.local

# Data files
prices.json
prices.backup.*.json

2. Use Environment-Specific Files

For multiple environments, use separate env files:

.env.development    # Development tokens
.env.production     # Production tokens
.env.test          # Test tokens

Load the appropriate file based on your environment:

import dotenv from "dotenv";

const envFile = process.env.NODE_ENV === 'production' 
  ? '.env.production' 
  : '.env.development';

dotenv.config({ path: envFile });

3. Restrict File Permissions

Limit who can read your .env file:

# Owner read/write only
chmod 600 .env

# Verify permissions
ls -la .env
# Should show: -rw------- (600)

4. Rotate Tokens Regularly

Periodically regenerate your bot token:

Open @BotFather
Send /mybots
Select your bot
Choose API Token → Revoke current token
Update .env with the new token

Revoking your token immediately invalidates the old one. Update your .env file before restarting the bot.

Token Validation

Testing Your Token

Verify your token is valid before starting the bot:

curl https://api.telegram.org/bot<YOUR_TOKEN>/getMe

A valid token returns:

{
  "ok": true,
  "result": {
    "id": 123456789,
    "is_bot": true,
    "first_name": "Price Tracker Bot",
    "username": "my_price_tracker_bot"
  }
}

An invalid token returns:

{
  "ok": false,
  "error_code": 401,
  "description": "Unauthorized"
}

Common Token Issues

Issue	Symptom	Solution
Missing token	Bot exits: “TELEGRAM_TOKEN no definido”	Add token to `.env` file
Invalid format	Bot fails to connect	Verify token format from BotFather
Revoked token	API returns 401 Unauthorized	Generate new token via BotFather
Extra whitespace	Connection errors	Remove spaces around token in `.env`

Environment Variable Precedence

When using multiple configuration sources, variables are loaded in this order (later sources override earlier ones):

System environment variables
.env file variables
.env.local file variables (if using)

For local development, create a .env.local file that overrides .env. Add .env.local to .gitignore to keep personal settings private.

Deployment Considerations

Docker

When deploying with Docker, pass environment variables via docker-compose:

docker-compose.yml

version: '3.8'
services:
  price-tracker:
    build: .
    environment:
      - TELEGRAM_TOKEN=${TELEGRAM_TOKEN}
    volumes:
      - ./data:/app/data
    restart: unless-stopped

Then create a .env file alongside docker-compose.yml:

.env

TELEGRAM_TOKEN=your_token_here

Cloud Platforms

For cloud deployments, use the platform’s secret management: Heroku:

heroku config:set TELEGRAM_TOKEN=your_token_here

AWS:

aws ssm put-parameter \
  --name /price-tracker/telegram-token \
  --value "your_token_here" \
  --type SecureString

Railway/Render: Use the dashboard to add environment variables in the service settings.

Cloud platforms typically inject environment variables directly into the runtime, so you don’t need a .env file in production.

Troubleshooting

Bot Can’t Find .env File

Symptom: “TELEGRAM_TOKEN no definido” despite having .env file Solutions:

Verify .env is in the same directory as index.mjs
Check file is named exactly .env (not env.txt or .env.txt)
Ensure no UTF-8 BOM or special characters in the file

Token Not Loading

Symptom: Token is in .env but bot says it’s undefined Solutions:

Check for spaces: Use TELEGRAM_TOKEN=value not TELEGRAM_TOKEN = value
Verify no quotes needed: TELEGRAM_TOKEN=123:ABC not TELEGRAM_TOKEN="123:ABC"
Ensure dotenv.config() is called before accessing variables

Multiple Bots on Same Server

Symptom: Need to run multiple bot instances Solution: Use separate directories with individual .env files:

project/
├── bot1/
│   ├── .env          # Token for bot 1
│   ├── index.mjs
│   └── prices.json
└── bot2/
    ├── .env          # Token for bot 2
    ├── index.mjs
    └── prices.json

Getting Started

Features

Commands

Configuration

Technical Details

Support

Overview

Loading Configuration

Required Variables

TELEGRAM_TOKEN

Getting Your Telegram Bot Token

Step 1: Contact BotFather

Step 2: Create a New Bot

Step 3: Receive Your Token

Step 4: Add Token to .env File

Token Usage in Code

Optional Variables

Suggested Optional Variables

Security Best Practices

1. Never Commit Secrets

2. Use Environment-Specific Files

3. Restrict File Permissions

4. Rotate Tokens Regularly

Token Validation

Testing Your Token

Common Token Issues

Environment Variable Precedence

Deployment Considerations

Docker

Cloud Platforms

Troubleshooting

Bot Can’t Find .env File

Token Not Loading

Multiple Bots on Same Server

Next Steps

Setup Guide

Scheduling

Build docs developers (and LLMs) love

Getting Started

Features

Commands

Configuration

Technical Details

Support

​Overview

​Loading Configuration

​Required Variables

​TELEGRAM_TOKEN

​Getting Your Telegram Bot Token

​Step 1: Contact BotFather

​Step 2: Create a New Bot

​Step 3: Receive Your Token

​Step 4: Add Token to .env File

​Token Usage in Code

​Optional Variables

​Suggested Optional Variables

​Security Best Practices

​1. Never Commit Secrets

​2. Use Environment-Specific Files

​3. Restrict File Permissions

​4. Rotate Tokens Regularly

​Token Validation

​Testing Your Token

​Common Token Issues

​Environment Variable Precedence

​Deployment Considerations

​Docker

​Cloud Platforms

​Troubleshooting

​Bot Can’t Find .env File

​Token Not Loading

​Multiple Bots on Same Server

​Next Steps

Setup Guide

Scheduling

Build docs developers (and LLMs) love

Overview

Loading Configuration

Required Variables

TELEGRAM_TOKEN

Getting Your Telegram Bot Token

Step 1: Contact BotFather

Step 2: Create a New Bot

Step 3: Receive Your Token

Step 4: Add Token to .env File

Token Usage in Code

Optional Variables

Suggested Optional Variables

Security Best Practices

1. Never Commit Secrets

2. Use Environment-Specific Files

3. Restrict File Permissions

4. Rotate Tokens Regularly

Token Validation

Testing Your Token

Common Token Issues

Environment Variable Precedence

Deployment Considerations

Docker

Cloud Platforms

Troubleshooting

Bot Can’t Find .env File

Token Not Loading

Multiple Bots on Same Server

Next Steps