Node.js module

os

The 'node:os' module provides operating system-related utility methods and properties, such as CPU architecture, memory usage, uptime, user information, network interfaces, and platform details.

It is useful for gathering runtime environment data and making OS-specific decisions.

Works in Bun

Fully implemented. 100% of Node.js's test suite passes.

namespace constants
- namespace dlopen
  const RTLD_DEEPBIND: number
  const RTLD_GLOBAL: number
  const RTLD_LAZY: number
  const RTLD_LOCAL: number
  const RTLD_NOW: number
- namespace errno
  const E2BIG: number
  const EACCES: number
  const EADDRINUSE: number
  const EADDRNOTAVAIL: number
  const EAFNOSUPPORT: number
  const EAGAIN: number
  const EALREADY: number
  const EBADF: number
  const EBADMSG: number
  const EBUSY: number
  const ECANCELED: number
  const ECHILD: number
  const ECONNABORTED: number
  const ECONNREFUSED: number
  const ECONNRESET: number
  const EDEADLK: number
  const EDESTADDRREQ: number
  const EDOM: number
  const EDQUOT: number
  const EEXIST: number
  const EFAULT: number
  const EFBIG: number
  const EHOSTUNREACH: number
  const EIDRM: number
  const EILSEQ: number
  const EINPROGRESS: number
  const EINTR: number
  const EINVAL: number
  const EIO: number
  const EISCONN: number
  const EISDIR: number
  const ELOOP: number
  const EMFILE: number
  const EMLINK: number
  const EMSGSIZE: number
  const EMULTIHOP: number
  const ENAMETOOLONG: number
  const ENETDOWN: number
  const ENETRESET: number
  const ENETUNREACH: number
  const ENFILE: number
  const ENOBUFS: number
  const ENODATA: number
  const ENODEV: number
  const ENOENT: number
  const ENOEXEC: number
  const ENOLCK: number
  const ENOLINK: number
  const ENOMEM: number
  const ENOMSG: number
  const ENOPROTOOPT: number
  const ENOSPC: number
  const ENOSR: number
  const ENOSTR: number
  const ENOSYS: number
  const ENOTCONN: number
  const ENOTDIR: number
  const ENOTEMPTY: number
  const ENOTSOCK: number
  const ENOTSUP: number
  const ENOTTY: number
  const ENXIO: number
  const EOPNOTSUPP: number
  const EOVERFLOW: number
  const EPERM: number
  const EPIPE: number
  const EPROTO: number
  const EPROTONOSUPPORT: number
  const EPROTOTYPE: number
  const ERANGE: number
  const EROFS: number
  const ESPIPE: number
  const ESRCH: number
  const ESTALE: number
  const ETIME: number
  const ETIMEDOUT: number
  const ETXTBSY: number
  const EWOULDBLOCK: number
  const EXDEV: number
  const WSA_E_CANCELLED: number
  const WSA_E_NO_MORE: number
  const WSAEACCES: number
  const WSAEADDRINUSE: number
  const WSAEADDRNOTAVAIL: number
  const WSAEAFNOSUPPORT: number
  const WSAEALREADY: number
  const WSAEBADF: number
  const WSAECANCELLED: number
  const WSAECONNABORTED: number
  const WSAECONNREFUSED: number
  const WSAECONNRESET: number
  const WSAEDESTADDRREQ: number
  const WSAEDISCON: number
  const WSAEDQUOT: number
  const WSAEFAULT: number
  const WSAEHOSTDOWN: number
  const WSAEHOSTUNREACH: number
  const WSAEINPROGRESS: number
  const WSAEINTR: number
  const WSAEINVAL: number
  const WSAEINVALIDPROCTABLE: number
  const WSAEINVALIDPROVIDER: number
  const WSAEISCONN: number
  const WSAELOOP: number
  const WSAEMFILE: number
  const WSAEMSGSIZE: number
  const WSAENAMETOOLONG: number
  const WSAENETDOWN: number
  const WSAENETRESET: number
  const WSAENETUNREACH: number
  const WSAENOBUFS: number
  const WSAENOMORE: number
  const WSAENOPROTOOPT: number
  const WSAENOTCONN: number
  const WSAENOTEMPTY: number
  const WSAENOTSOCK: number
  const WSAEOPNOTSUPP: number
  const WSAEPFNOSUPPORT: number
  const WSAEPROCLIM: number
  const WSAEPROTONOSUPPORT: number
  const WSAEPROTOTYPE: number
  const WSAEPROVIDERFAILEDINIT: number
  const WSAEREFUSED: number
  const WSAEREMOTE: number
  const WSAESHUTDOWN: number
  const WSAESOCKTNOSUPPORT: number
  const WSAESTALE: number
  const WSAETIMEDOUT: number
  const WSAETOOMANYREFS: number
  const WSAEUSERS: number
  const WSAEWOULDBLOCK: number
  const WSANOTINITIALISED: number
  const WSASERVICE_NOT_FOUND: number
  const WSASYSCALLFAILURE: number
  const WSASYSNOTREADY: number
  const WSATYPE_NOT_FOUND: number
  const WSAVERNOTSUPPORTED: number
- namespace priority
  const PRIORITY_ABOVE_NORMAL: number
  const PRIORITY_BELOW_NORMAL: number
  const PRIORITY_HIGH: number
  const PRIORITY_HIGHEST: number
  const PRIORITY_LOW: number
  const PRIORITY_NORMAL: number
- namespace signals
- const signals: SignalConstants
- const UV_UDP_REUSEADDR: number
const devNull: string
const EOL: string
The operating system-specific end-of-line marker.

on POSIX
\r
on Windows
function arch(): string;
Returns the operating system CPU architecture for which the Node.js binary was compiled. Possible values are 'arm', 'arm64', 'ia32', 'loong64', 'mips', 'mipsel', 'ppc', 'ppc64', 'riscv64', 's390', 's390x', and 'x64'.
The return value is equivalent to process.arch.
function availableParallelism(): number;
Returns an estimate of the default amount of parallelism a program should use. Always returns a value greater than zero.
This function is a small wrapper about libuv's uv_available_parallelism().
function cpus(): CpuInfo[];
Returns an array of objects containing information about each logical CPU core. The array will be empty if no CPU information is available, such as if the /proc file system is unavailable.
The properties included on each object include:
[ { model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz', speed: 2926, times: { user: 252020, nice: 0, sys: 30340, idle: 1070356870, irq: 0, }, }, { model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz', speed: 2926, times: { user: 306960, nice: 0, sys: 26980, idle: 1071569080, irq: 0, }, }, { model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz', speed: 2926, times: { user: 248450, nice: 0, sys: 21750, idle: 1070919370, irq: 0, }, }, { model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz', speed: 2926, times: { user: 256880, nice: 0, sys: 19430, idle: 1070905480, irq: 20, }, }, ]
nice values are POSIX-only. On Windows, the nice values of all processors are always 0.
os.cpus().length should not be used to calculate the amount of parallelism available to an application. Use availableParallelism for this purpose.
function endianness(): 'BE' | 'LE';
Returns a string identifying the endianness of the CPU for which the Node.js binary was compiled.
Possible values are 'BE' for big endian and 'LE' for little endian.
function freemem(): number;
Returns the amount of free system memory in bytes as an integer.
function getPriority(
pid?: number
): number;
Returns the scheduling priority for the process specified by pid. If pid is not provided or is 0, the priority of the current process is returned.
@param pid
The process ID to retrieve scheduling priority for.
function homedir(): string;
Returns the string path of the current user's home directory.
On POSIX, it uses the $HOME environment variable if defined. Otherwise it uses the effective UID to look up the user's home directory.
On Windows, it uses the USERPROFILE environment variable if defined. Otherwise it uses the path to the profile directory of the current user.
function hostname(): string;
Returns the host name of the operating system as a string.
function loadavg(): number[];
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.
The load average is a Unix-specific concept. On Windows, the return value is always [0, 0, 0].
function machine(): string;
Returns the machine type as a string, such as arm, arm64, aarch64, mips, mips64, ppc64, ppc64le, s390, s390x, i386, i686, x86_64.
On POSIX systems, the machine type is determined by calling uname(3). On Windows, RtlGetVersion() is used, and if it is not available, GetVersionExW() will be used. See https://en.wikipedia.org/wiki/Uname#Examples for more information.
function networkInterfaces(): Dict<NetworkInterfaceInfo[]>;
Returns an object containing 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:
{ lo: [ { address: '127.0.0.1', netmask: '255.0.0.0', family: 'IPv4', mac: '00:00:00:00:00:00', internal: true, cidr: '127.0.0.1/8' }, { address: '::1', netmask: 'ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff', family: 'IPv6', mac: '00:00:00:00:00:00', scopeid: 0, internal: true, cidr: '::1/128' } ], eth0: [ { address: '192.168.1.108', netmask: '255.255.255.0', family: 'IPv4', mac: '01:02:03:0a:0b:0c', internal: false, cidr: '192.168.1.108/24' }, { address: 'fe80::a00:27ff:fe4e:66a1', netmask: 'ffff:ffff:ffff:ffff::', family: 'IPv6', mac: '01:02:03:0a:0b:0c', scopeid: 1, internal: false, cidr: 'fe80::a00:27ff:fe4e:66a1/64' } ] }
function platform(): Platform;
Returns a string identifying the operating system platform for which the Node.js binary was compiled. The value is set at compile time. Possible values are 'aix', 'darwin', 'freebsd', 'linux', 'openbsd', 'sunos', and 'win32'.
The return value is equivalent to process.platform.
The value 'android' may also be returned if Node.js is built on the Android operating system. Android support is experimental.
function release(): string;
Returns the operating system as a string.
On POSIX systems, the operating system release is determined by calling uname(3). On Windows, GetVersionExW() is used. See https://en.wikipedia.org/wiki/Uname#Examples for more information.
function setPriority(
priority: number
): void;
Attempts to set the scheduling priority for the process specified by pid. If pid is not provided or is 0, the process ID of the current process is used.
The priority input must be an integer between -20 (high priority) and 19 (low priority). Due to differences between Unix priority levels and Windows priority classes, priority is mapped to one of six priority constants in os.constants.priority. When retrieving a process priority level, this range mapping may cause the return value to be slightly different on Windows. To avoid confusion, set priority to one of the priority constants.
On Windows, setting priority to PRIORITY_HIGHEST requires elevated user privileges. Otherwise the set priority will be silently reduced to PRIORITY_HIGH.
@param priority
The scheduling priority to assign to the process.
function setPriority(
pid: number,
priority: number
): void;
Attempts to set the scheduling priority for the process specified by pid. If pid is not provided or is 0, the process ID of the current process is used.
The priority input must be an integer between -20 (high priority) and 19 (low priority). Due to differences between Unix priority levels and Windows priority classes, priority is mapped to one of six priority constants in os.constants.priority. When retrieving a process priority level, this range mapping may cause the return value to be slightly different on Windows. To avoid confusion, set priority to one of the priority constants.
On Windows, setting priority to PRIORITY_HIGHEST requires elevated user privileges. Otherwise the set priority will be silently reduced to PRIORITY_HIGH.
@param pid
The process ID to set scheduling priority for.
@param priority
The scheduling priority to assign to the process.
function tmpdir(): string;
Returns the operating system's default directory for temporary files as a string.
function totalmem(): number;
Returns the total amount of system memory in bytes as an integer.
function type(): string;
Returns the operating system name as returned by uname(3). For example, it returns 'Linux' on Linux, 'Darwin' on macOS, and 'Windows_NT' on Windows.
See https://en.wikipedia.org/wiki/Uname#Examples for additional information about the output of running uname(3) on various operating systems.
function uptime(): number;
Returns the system uptime in number of seconds.
function userInfo(
options: { encoding: 'buffer' }
): UserInfo<Buffer<ArrayBufferLike>>;
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 environment variables for the home directory before falling back to the operating system response.
Throws a SystemError if a user has no username or homedir.
function userInfo(
options?: { encoding: BufferEncoding }
): UserInfo<string>;
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 environment variables for the home directory before falling back to the operating system response.
Throws a SystemError if a user has no username or homedir.
function version(): string;
Returns a string identifying the kernel version.
On POSIX systems, the operating system release is determined by calling uname(3). On Windows, RtlGetVersion() is used, and if it is not available, GetVersionExW() will be used. See https://en.wikipedia.org/wiki/Uname#Examples for more information.

Type definitions

interface CpuInfo
- model: string
- speed: number
- times: { idle: number; irq: number; nice: number; sys: number; user: number }
interface NetworkInterfaceBase
- address: string
- cidr: null | string
- internal: boolean
- mac: string
- netmask: string
interface NetworkInterfaceInfoIPv4
- address: string
- cidr: null | string
- family: 'IPv4'
- internal: boolean
- mac: string
- netmask: string
- scopeid?: undefined
interface NetworkInterfaceInfoIPv6
- address: string
- cidr: null | string
- family: 'IPv6'
- internal: boolean
- mac: string
- netmask: string
- scopeid: number
interface UserInfo<T>
- gid: number
- homedir: T
- shell: null | T
- uid: number
- username: T
type NetworkInterfaceInfo = NetworkInterfaceInfoIPv4 | NetworkInterfaceInfoIPv6
type SignalConstants = { [K in NodeJS.Signals]: number }

os

namespace constants

namespace dlopen

namespace errno

namespace priority

namespace signals

Type definitions

interface CpuInfo

interface NetworkInterfaceBase

interface NetworkInterfaceInfoIPv4

interface NetworkInterfaceInfoIPv6

interface UserInfo<T>