Process and Environment Variables

The process object provides runtime information about your Node.js app.

Environment Variables

const dbHost = process.env.DB_HOST || 'localhost';
const port = process.env.PORT || 3000;
const nodeEnv = process.env.NODE_ENV || 'development';

console.log(`Running in ${nodeEnv} mode`);
console.log(`Database: ${dbHost}`);
console.log(`Port: ${port}`);

Using .env Files

npm install dotenv

# .env
DB_HOST=localhost
DB_USER=admin
DB_PASS=secret123
PORT=3000

require('dotenv').config();

const dbConfig = {
  host: process.env.DB_HOST,
  user: process.env.DB_USER,
  password: process.env.DB_PASS
};

Process Information

console.log(process.version);
console.log(process.platform);
console.log(process.arch);
console.log(process.cwd());
console.log(process.pid);
console.log(process.uptime());

Output:

v18.17.0
linux
x64
/home/user/project
12345
45.234

Memory Usage

const used = process.memoryUsage();

console.log({
  rss: `${Math.round(used.rss / 1024 / 1024)} MB`,
  heapUsed: `${Math.round(used.heapUsed / 1024 / 1024)} MB`,
  heapTotal: `${Math.round(used.heapTotal / 1024 / 1024)} MB`
});

Real Example: Health Check

const express = require('express');
const app = express();

app.get('/health', (req, res) => {
  const health = {
    uptime: process.uptime(),
    timestamp: Date.now(),
    memory: process.memoryUsage(),
    version: process.version,
    status: 'ok'
  };
  
  res.json(health);
});

app.listen(3000);

Graceful Shutdown

const express = require('express');
const mongoose = require('mongoose');
const app = express();

const server = app.listen(3000);

process.on('SIGTERM', () => {
  console.log('SIGTERM received, closing server...');
  
  server.close(() => {
    console.log('Server closed');
    
    mongoose.connection.close(false, () => {
      console.log('MongoDB closed');
      process.exit(0);
    });
  });
});

Command Line Arguments

console.log(process.argv);

node app.js --port 3000 --env production

Output:

[
  '/usr/bin/node',
  '/path/to/app.js',
  '--port',
  '3000',
  '--env',
  'production'
]

Exit Process

if (!process.env.API_KEY) {
  console.error('API_KEY is required');
  process.exit(1);
}

Key Takeaway

Use process.env for configuration. Monitor memory with memoryUsage(). Handle SIGTERM for graceful shutdown. Use dotenv for environment variables.