Node.js OS Module

Importing the os Module

The os module is part of Node's standard library, so it requires no installation. It exposes a mix of methods and read-only properties that describe the current machine.

const os = require('os');

console.log('Platform:', os.platform());
console.log('Architecture:', os.arch());
console.log('Hostname:', os.hostname());

Identifying the Platform

os.platform() returns a short string identifying the operating system, such as 'win32' for Windows, 'darwin' for macOS, or 'linux' for Linux distributions. This is useful for writing cross-platform scripts that need to branch on OS-specific behavior, such as path separators or shell commands.

const os = require('os');

function getShellCommand() {
  switch (os.platform()) {
    case 'win32':
      return 'dir';
    case 'darwin':
    case 'linux':
      return 'ls -la';
    default:
      throw new Error(`Unsupported platform: ${os.platform()}`);
  }
}

console.log('Command to run:', getShellCommand());

Inspecting CPU Information

os.cpus() returns an array with one entry per logical CPU core, each containing the model name, clock speed in MHz, and time spent in different CPU states (user, nice, sys, idle, irq). This is commonly used to size worker pools or thread counts based on available hardware.

const os = require('os');

const cpus = os.cpus();
console.log('Number of logical cores:', cpus.length);
console.log('CPU model:', cpus[0].model);
console.log('Clock speed (MHz):', cpus[0].speed);

Checking Memory

os.totalmem() and os.freemem() both return byte counts describing the machine's total installed RAM and currently available RAM. Dividing by 1024 three times converts bytes to gigabytes for human-readable output.

const os = require('os');

function bytesToGB(bytes) {
  return (bytes / (1024 ** 3)).toFixed(2);
}

const total = os.totalmem();
const free = os.freemem();
const usedPercent = (((total - free) / total) * 100).toFixed(1);

console.log(`Total memory: ${bytesToGB(total)} GB`);
console.log(`Free memory: ${bytesToGB(free)} GB`);
console.log(`Memory in use: ${usedPercent}%`);

User and Directory Information

os.homedir() returns the current user's home directory path, and os.tmpdir() returns the operating system's default directory for temporary files — both are cross-platform, so you never need to hardcode paths like /home/user or C:\Users\name.

const os = require('os');
const path = require('path');

const configPath = path.join(os.homedir(), '.myapp', 'config.json');
console.log('Config will be stored at:', configPath);