# The Node os module

> A guide to the Node.js os module for reading information about the underlying operating system, including os.cpus(), os.freemem(), os.platform(), and os.EOL.

Author: [Flavio Copes](https://flaviocopes.com/about/) | Published: 2018-09-13 | Topics: [Node.js](https://flaviocopes.com/tags/node/) | Canonical: https://flaviocopes.com/node-module-os/

This module provides many functions that you can use to retrieve information from the underlying operating system and the computer the program runs on, and interact with it.

```js
const os = require('os')
```

There are a few useful properties that tell us some key things related to handling files:

`os.EOL` gives the line delimiter sequence. It's `\n` on Linux and macOS, and `\r\n` on Windows.

> When I say Linux and macOS I mean POSIX platforms. For simplicity I exclude other less popular operating systems Node can run on.

`os.constants.signals` tells us all the constants related to handling process signals, like SIGHUP, SIGKILL and so on.

`os.constants.errno` sets the constants for error reporting, like EADDRINUSE, EOVERFLOW and more.

You can read them all on <https://nodejs.org/api/os.html#os_signal_constants>.

Let's now see the main methods that `os` provides:

<!-- TOC -->

- [os.arch()](#osarch)
- [os.cpus()](#oscpus)
- [os.endianness()](#osendianness)
- [os.freemem()](#osfreemem)
- [os.homedir()](#oshomedir)
- [os.hostname()](#oshostname)
- [os.loadavg()](#osloadavg)
- [os.networkInterfaces()](#osnetworkinterfaces)
- [os.platform()](#osplatform)
- [os.release()](#osrelease)
- [os.tmpdir()](#ostmpdir)
- [os.totalmem()](#ostotalmem)
- [os.type()](#ostype)
- [os.uptime()](#osuptime)
- [os.userInfo()](#osuserinfo)

<!-- /TOC -->

## os.arch()

Return the string that identifies the underlying architecture, like `arm`, `x64`, `arm64`.

## os.cpus()

Return information on the CPUs available on your system.

Example:

```js
[ { model: 'Intel(R) Core(TM)2 Duo CPU     P8600  @ 2.40GHz',
    speed: 2400,
    times:
     { user: 281685380,
       nice: 0,
       sys: 187986530,
       idle: 685833750,
       irq: 0 } },
  { model: 'Intel(R) Core(TM)2 Duo CPU     P8600  @ 2.40GHz',
    speed: 2400,
    times:
     { user: 282348700,
       nice: 0,
       sys: 161800480,
       idle: 703509470,
       irq: 0 } } ]
```

## os.endianness()

Return `BE` or `LE` depending if Node was compiled with [Big Endian or Little Endian](https://en.wikipedia.org/wiki/Endianness).

## os.freemem()

Return the number of bytes that represent the free memory in the system.

## os.homedir()

Return the path to the home directory of the current user.

Example:

```js
'/Users/flavio'
```

## os.hostname()

Return the hostname.

## os.loadavg()

Return the calculation made by the operating system on the load average.

It only returns a meaningful value on Linux and macOS.

Example:

```js
[ 3.68798828125, 4.00244140625, 11.1181640625 ]
```

## os.networkInterfaces()

Returns the details of the network interfaces available on your system.

Example:

```js
{ lo0:
   [ { address: '127.0.0.1',
       netmask: '255.0.0.0',
       family: 'IPv4',
       mac: 'fe:82:00:00:00:00',
       internal: true },
     { address: '::1',
       netmask: 'ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff',
       family: 'IPv6',
       mac: 'fe:82:00:00:00:00',
       scopeid: 0,
       internal: true },
     { address: 'fe80::1',
       netmask: 'ffff:ffff:ffff:ffff::',
       family: 'IPv6',
       mac: 'fe:82:00:00:00:00',
       scopeid: 1,
       internal: true } ],
  en1:
   [ { address: 'fe82::9b:8282:d7e6:496e',
       netmask: 'ffff:ffff:ffff:ffff::',
       family: 'IPv6',
       mac: '06:00:00:02:0e:00',
       scopeid: 5,
       internal: false },
     { address: '192.168.1.38',
       netmask: '255.255.255.0',
       family: 'IPv4',
       mac: '06:00:00:02:0e:00',
       internal: false } ],
  utun0:
   [ { address: 'fe80::2513:72bc:f405:61d0',
       netmask: 'ffff:ffff:ffff:ffff::',
       family: 'IPv6',
       mac: 'fe:80:00:20:00:00',
       scopeid: 8,
       internal: false } ] }
```

## os.platform()

Return the platform that Node was compiled for:

- `darwin`
- `freebsd`
- `linux`
- `openbsd`
- `win32`
- ...more

## os.release()

Returns a string that identifies the operating system release number

## os.tmpdir()

Returns the path to the assigned temp folder.

## os.totalmem()

Returns the number of bytes that represent the total memory available in the system.

## os.type()

Identifies the operating system:

- `Linux`
- `Darwin` on macOS
- `Windows_NT` on Windows

## os.uptime()

Returns the number of seconds the computer has been running since it was last rebooted.

## os.userInfo()

Returns information about the current user