The `os` module provides a number of operating system-related utility methods.

It can be accessed using:

```js

const os = require('os');

```

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A string constant defining the operating system-specific end-of-line marker:

* `\n` on POSIX

* `\r\n` on Windows

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The `os.arch()` method returns a string identifying the operating system CPU

architecture *for which the Node.js binary was compiled*.

The current possible values are: `'arm'`, `'arm64'`, `'ia32'`, `'mips'`,

`'mipsel'`, `'ppc'`, `'ppc64'`, `'s390'`, `'s390x'`, `'x32'`, `'x64'`, and

`'x86'`.

Equivalent to [`process.arch`][].

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* {Object}

Returns an object containing commonly used operating system specific constants

for error codes, process signals, and so on. The specific constants currently

defined are described in [OS Constants][].

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* Returns: {Array}

The `os.cpus()` method returns an array of objects containing information about

each CPU/core installed.

The properties included on each object include:

* `speed` {number} (in MHz)

* `times` {Object}

* `user` {number} The number of milliseconds the CPU has spent in user mode.

* `nice` {number} The number of milliseconds the CPU has spent in nice mode.

* `sys` {number} The number of milliseconds the CPU has spent in sys mode.

* `idle` {number} The number of milliseconds the CPU has spent in idle mode.

* `irq` {number} The number of milliseconds the CPU has spent in irq mode.

For example:

[

{

model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',

times: {

user: 252020,

nice: 0,

sys: 30340,

idle: 1070356870,

irq: 0

}

},

{

model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',

times: {

user: 306960,

nice: 0,

sys: 26980,

idle: 1071569080,

irq: 0

}

},

{

model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',

times: {

user: 248450,

nice: 0,

sys: 21750,

idle: 1070919370,

irq: 0

}

},

{

model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',

times: {

user: 256880,

nice: 0,

sys: 19430,

idle: 1070905480,

irq: 20

}

},

{

model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',

times: {

user: 511580,

nice: 20,

sys: 40900,

idle: 1070842510,

irq: 0

}

},

{

model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',

times: {

user: 291660,

nice: 0,

sys: 34360,

idle: 1070888000,

irq: 10

}

},

{

model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',

times: {

user: 308260,

nice: 0,

sys: 55410,

idle: 1071129970,

irq: 880

}

},

{

model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',

times: {

user: 266450,

nice: 1480,

sys: 34920,

idle: 1072572010,

irq: 30

}

}

]

all processors are always 0.

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The `os.endianness()` method returns a string identifying the endianness of the

CPU *for which the Node.js binary was compiled*.

Possible values are:

* `'BE'` for big endian

* `'LE'` for little endian.

## os.freemem()

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The `os.freemem()` method returns the amount of free system memory in bytes as

an integer.

## os.homedir()

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The `os.homedir()` method returns the home directory of the current user as a

string.

## os.hostname()

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The `os.hostname()` method returns the hostname of the operating system as a

string.

## os.loadavg()

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* Returns: {Array}

The `os.loadavg()` method returns an array containing the 1, 5, and 15 minute

load averages.

The load average is a measure of system activity, calculated by the operating

system and expressed as a fractional number. As a rule of thumb, the load

average should ideally be less than the number of logical CPUs in the system.

The load average is a UNIX-specific concept with no real equivalent on

Windows platforms. On Windows, the return value is always `[0, 0, 0]`.

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* Returns: {Object}

The `os.networkInterfaces()` method returns an object containing only network

interfaces that have been assigned a network address.

Each key on the returned object identifies a network interface. The associated

value is an array of objects that each describe an assigned network address.

The properties available on the assigned network address object include:

* `address` {string} The assigned IPv4 or IPv6 address

* `netmask` {string} The IPv4 or IPv6 network mask

* `family` {string} Either `IPv4` or `IPv6`

* `mac` {string} The MAC address of the network interface

* `internal` {boolean} `true` if the network interface is a loopback or

similar interface that is not remotely accessible; otherwise `false`

* `scopeid` {number} The numeric IPv6 scope ID (only specified when `family`

is `IPv6`)

{

lo: [

{

address: '127.0.0.1',

netmask: '255.0.0.0',

family: 'IPv4',

mac: '00:00:00:00:00:00',

internal: true

},

{

address: '::1',

netmask: 'ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff',

family: 'IPv6',

mac: '00:00:00:00:00:00',

internal: true

}

],

eth0: [

{

address: '192.168.1.108',

netmask: '255.255.255.0',

family: 'IPv4',

mac: '01:02:03:0a:0b:0c',

internal: false

},

{

address: 'fe80::a00:27ff:fe4e:66a1',

netmask: 'ffff:ffff:ffff:ffff::',

family: 'IPv6',

mac: '01:02:03:0a:0b:0c',

internal: false

}

]

}

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The `os.platform()` method returns a string identifying the operating system

platform as set during compile time of Node.js.

Currently possible values are:

* `'aix'`

* `'darwin'`

* `'freebsd'`

* `'linux'`

* `'openbsd'`

* `'sunos'`

* `'win32'`

Equivalent to [`process.platform`][].

*Note*: The value `'android'` may also be returned if the Node.js is built on

the Android operating system. However, Android support in Node.js is considered

to be experimental at this time.

## os.release()

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The `os.release()` method returns a string identifying the operating system

release.

*Note*: On POSIX systems, the operating system release is determined by calling

uname(3). On Windows, `GetVersionExW()` is used. Please see

https://en.wikipedia.org/wiki/Uname#Examples for more information.

## os.tmpdir()

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returns a path with a trailing slash on any platform

The `os.tmpdir()` method returns a string specifying the operating system's

default directory for temporary files.

## os.totalmem()

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The `os.totalmem()` method returns the total amount of system memory in bytes

as an integer.

## os.type()

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`'Windows_NT'` on Windows.

Please see https://en.wikipedia.org/wiki/Uname#Examples for additional

information about the output of running uname(3) on various operating systems.

## os.uptime()

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The `os.uptime()` method returns the system uptime in number of seconds.

*Note*: Within Node.js' internals, this number is represented as a `double`.

However, fractional seconds are not returned and the value can typically be

treated as an integer.

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* `options` {Object}

If `encoding` is set to `'buffer'`, the `username`, `shell`, and `homedir`

values will be `Buffer` instances. (Default: 'utf8')

The `os.userInfo()` method returns information about the currently effective

user -- on POSIX platforms, this is typically a subset of the password file. The

returned object includes the `username`, `uid`, `gid`, `shell`, and `homedir`.

On Windows, the `uid` and `gid` fields are `-1`, and `shell` is `null`.

The value of `homedir` returned by `os.userInfo()` is provided by the operating

system. This differs from the result of `os.homedir()`, which queries several

environment variables for the home directory before falling back to the

operating system response.

## OS Constants

The following constants are exported by `os.constants`. **Note:** Not all

constants will be available on every operating system.

### Signal Constants

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The following signal constants are exported by `os.constants.signals`:

<table>

<tr>

<th>Constant</th>

<th>Description</th>

</tr>

<tr>

<td><code>SIGHUP</code></td>

<td>Sent to indicate when a controlling terminal is closed or a parent

process exits.</td>

</tr>

<tr>

<td><code>SIGINT</code></td>

(`(Ctrl+C)`).</td>

</tr>

<tr>

<td><code>SIGQUIT</code></td>

<td>Sent to indicate when a user wishes to terminate a process and perform a

core dump.</td>

</tr>

<tr>

<td><code>SIGILL</code></td>

<td>Sent to a process to notify that it has attempted to perform an illegal,

malformed, unknown or privileged instruction.</td>

</tr>

<tr>

<td><code>SIGTRAP</code></td>

</tr>

<tr>

<td><code>SIGABRT</code></td>

<td>Sent to a process to request that it abort.</td>

</tr>

<tr>

<td><code>SIGIOT</code></td>

<td>Synonym for <code>SIGABRT</code></td>

</tr>

<tr>

<td><code>SIGBUS</code></td>

<td>Sent to a process to notify that it has caused a bus error.</td>

</tr>

<tr>

<td><code>SIGFPE</code></td>

operation.</td>

</tr>

<tr>

<td><code>SIGKILL</code></td>

<td>Sent to a process to terminate it immediately.</td>

</tr>

<tr>

<td><code>SIGUSR1</code> <code>SIGUSR2</code></td>

<td>Sent to a process to identify user-defined conditions.</td>

</tr>

<tr>

<td><code>SIGSEGV</code></td>

<td>Sent to a process to notify of a segmentation fault.</td>

</tr>

<tr>

<td><code>SIGPIPE</code></td>

<td>Sent to a process when it has attempted to write to a disconnected

pipe.</td>

</tr>

<tr>

<td><code>SIGALRM</code></td>

<td>Sent to a process when a system timer elapses.</td>

</tr>

<tr>

<td><code>SIGTERM</code></td>

<td>Sent to a process to request termination.</td>

</tr>

<tr>

<td><code>SIGCHLD</code></td>

<td>Sent to a process when a child process terminates.</td>

</tr>

<tr>

<td><code>SIGSTKFLT</code></td>

<td>Sent to a process to indicate a stack fault on a coprocessor.</td>

</tr>

<tr>

<td><code>SIGCONT</code></td>

<td>Sent to instruct the operating system to continue a paused process.</td>

</tr>

<tr>

<td><code>SIGSTOP</code></td>

<td>Sent to instruct the operating system to halt a process.</td>

</tr>

<tr>

<td><code>SIGTSTP</code></td>

<td>Sent to a process to request it to stop.</td>

</tr>

<tr>

<td><code>SIGBREAK</code></td>

<td>Sent to indicate when a user wishes to interrupt a process.</td>

</tr>

<tr>

<td><code>SIGTTIN</code></td>

<td>Sent to a process when it reads from the TTY while in the

background.</td>

</tr>

<tr>

<td><code>SIGTTOU</code></td>

<td>Sent to a process when it writes to the TTY while in the

background.</td>

</tr>

<tr>

<td><code>SIGURG</code></td>

<td>Sent to a process when a socket has urgent data to read.</td>

</tr>

<tr>

<td><code>SIGXCPU</code></td>

<td>Sent to a process when it has exceeded its limit on CPU usage.</td>

</tr>

<tr>

<td><code>SIGXFSZ</code></td>

<td>Sent to a process when it grows a file larger than the maximum

allowed.</td>

</tr>

<tr>

<td><code>SIGVTALRM</code></td>

<td>Sent to a process when a virtual timer has elapsed.</td>

</tr>

<tr>

<td><code>SIGPROF</code></td>

<td>Sent to a process when a system timer has elapsed.</td>

</tr>

<tr>

<td><code>SIGWINCH</code></td>

<td>Sent to a process when the controlling terminal has changed its

size.</td>

</tr>

<tr>

<td><code>SIGIO</code></td>

<td>Sent to a process when I/O is available.</td>

</tr>

<tr>

<td><code>SIGPOLL</code></td>

<td>Synonym for <code>SIGIO</code></td>

</tr>

<tr>

<td><code>SIGLOST</code></td>

<td>Sent to a process when a file lock has been lost.</td>

</tr>

<tr>

<td><code>SIGPWR</code></td>

<td>Sent to a process to notify of a power failure.</td>

</tr>

<tr>

<td><code>SIGINFO</code></td>

<td>Synonym for <code>SIGPWR</code></td>

</tr>

<tr>

<td><code>SIGSYS</code></td>

<td>Sent to a process to notify of a bad argument.</td>

</tr>

<tr>

<td><code>SIGUNUSED</code></td>

<td>Synonym for <code>SIGSYS</code></td>

</tr>

</table>

### Error Constants

The following error constants are exported by `os.constants.errno`:

#### POSIX Error Constants