OS Module

📦 The `os` Module

os is a built-in Node.js module that gives you information about the computer your code is running on — the operating system, CPU, memory, and more. It's read-only: you use it to check system info, not change it.

const os = require('os');

🖥️ Platform & System Type

console.log(os.platform()); // 'win32', 'darwin', or 'linux'
console.log(os.type());     // 'Windows_NT', 'Darwin', or 'Linux'
console.log(os.arch());     // 'x64', 'arm64', etc.
console.log(os.release());  // OS version number

platform() gives a short OS code — 'win32' for Windows, 'darwin' for Mac, 'linux' for Linux.
type() gives the OS's internal kernel name instead — useful when platform() isn't specific enough.
arch() tells you the CPU architecture — matters if your app depends on native binaries.
release() gives the OS version, e.g. a specific Windows build or macOS version number.

⚙️ CPU Info

console.log(os.cpus());

Output (shortened):

[
  {
    model: 'Apple M2',
    speed: 3200,
    times: { user: 123456, nice: 0, sys: 45678, idle: 987654, irq: 0 }
  },
  // ...one entry per CPU core
]

cpus() returns an array with one object per core — model name, clock speed, and time spent in each state.
os.cpus().length is a quick way to get the number of cores available.

💾 Memory Info

console.log(os.totalmem()); // total RAM, in bytes
console.log(os.freemem());  // free RAM, in bytes

Both return raw bytes, so they're usually converted to something readable:

const totalGB = (os.totalmem() / (1024 ** 3)).toFixed(2);
const freeGB = (os.freemem() / (1024 ** 3)).toFixed(2);
console.log(`${freeGB} GB free of ${totalGB} GB total`);

Handy for scripts that need to check available memory before doing something heavy, or for a status dashboard.

👤 User & Home Info

console.log(os.homedir());  // '/Users/bhaskar' or 'C:\\Users\\Bhaskar'
console.log(os.hostname()); // the computer's network name
console.log(os.userInfo()); // { username, uid, gid, shell, homedir }

homedir() gives the current user's home folder — useful for finding config files that live outside your project.
hostname() returns the machine's name on the network.
userInfo() bundles several user details into one object, including the OS username running the script.

⏱️ Uptime

const seconds = os.uptime();
const hours = (seconds / 3600).toFixed(1);
console.log(`System has been up for ${hours} hours`);

uptime() returns how long the machine has been running, in seconds since it was last started — not how long your script has been running.

↩️ Line Endings

console.log(os.EOL === '\n'); // true on Mac/Linux, false on Windows

os.EOL is the correct line-break character for the current OS — \n on Mac/Linux, \r\n on Windows.
Use it instead of hardcoding \n when writing text files, so line breaks stay correct across platforms.

💡 Why Use `os`?

Lets your app adapt to the machine it's running on — different file paths, different CPU counts, different line endings.
Common uses: system-info dashboards, performance/logging tools, cross-platform CLI apps, and scripts that scale their work based on available CPU cores or memory.

const os = require('os');

console.log(`Platform: ${os.platform()}`);
console.log(`CPU cores: ${os.cpus().length}`);
console.log(`Free memory: ${(os.freemem() / (1024 ** 3)).toFixed(2)} GB`);

📦 The os Module