os
The node:os module provides operating system-related utility methods and properties. It can be accessed using:
import os from 'node:os';
Usage in Deno
import * as mod from "node:os";
function arch
Usage in Deno
import { arch } from "node:os";
arch(): stringReturns 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.
Return Type
string function availableParallelism
Usage in Deno
import { availableParallelism } from "node:os";
availableParallelism(): numberReturns 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().
Return Type
number function cpus
Usage in Deno
import { cpus } from "node:os";
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.
Return Type
CpuInfo[] function endianness
Usage in Deno
import { endianness } from "node:os";
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.
Return Type
"BE" | "LE" function freemem
Usage in Deno
import { freemem } from "node:os";
freemem(): numberReturns the amount of free system memory in bytes as an integer.
Return Type
number function getPriority
Usage in Deno
import { getPriority } from "node:os";
getPriority(pid?: number): numberReturns 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.
Parameters
pid: number = 0 The process ID to retrieve scheduling priority for.
Return Type
number function homedir
Usage in Deno
import { homedir } from "node:os";
homedir(): stringReturns 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.
Return Type
string function hostname
Usage in Deno
import { hostname } from "node:os";
hostname(): stringReturns the host name of the operating system as a string.
Return Type
string function loadavg
Usage in Deno
import { loadavg } from "node:os";
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].
Return Type
number[] function machine
Usage in Deno
import { machine } from "node:os";
machine(): stringReturns 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.
Return Type
string function networkInterfaces
Usage in Deno
import { networkInterfaces } from "node:os";
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'
}
]
}
Return Type
Dict<NetworkInterfaceInfo[]> function platform
Usage in Deno
import { platform } from "node:os";
platform(): PlatformReturns 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.
Return Type
Platform function release
Usage in Deno
import { release } from "node:os";
release(): stringReturns 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.
Return Type
string function setPriority
Usage in Deno
import { setPriority } from "node:os";
Overload 1
setPriority(priority: number): voidAttempts 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.
Parameters
priority: number The scheduling priority to assign to the process.
Return Type
void Overload 2
setPriority(
pid: number,
priority: number,
): voidParameters
pid: number priority: number Return Type
void function tmpdir
Usage in Deno
import { tmpdir } from "node:os";
tmpdir(): stringReturns the operating system's default directory for temporary files as a string.
Return Type
string function totalmem
Usage in Deno
import { totalmem } from "node:os";
totalmem(): numberReturns the total amount of system memory in bytes as an integer.
Return Type
number function type
Usage in Deno
import { type } from "node:os";
type(): stringReturns 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.
Return Type
string function uptime
Usage in Deno
import { uptime } from "node:os";
uptime(): numberReturns the system uptime in number of seconds.
Return Type
number function userInfo
Usage in Deno
import { userInfo } from "node:os";
Overload 1
userInfo(options: { encoding: "buffer"; }): UserInfo<Buffer>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.
Parameters
options: { encoding: "buffer"; } Return Type
UserInfo<Buffer> Overload 2
function version
Usage in Deno
import { version } from "node:os";
version(): stringReturns 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.
Return Type
string interface CpuInfo
Usage in Deno
import { type CpuInfo } from "node:os";
interface NetworkInterfaceInfoIPv4
Usage in Deno
import { type NetworkInterfaceInfoIPv4 } from "node:os";
interface NetworkInterfaceInfoIPv6
Usage in Deno
import { type NetworkInterfaceInfoIPv6 } from "node:os";
namespace constants
Usage in Deno
import { constants } from "node:os";
Namespaces
Variables
namespace constants.dlopen
Usage in Deno
import { constants } from "node:os";
Variables
namespace constants.errno
Usage in Deno
import { constants } from "node:os";
Variables
namespace constants.priority
Usage in Deno
import { constants } from "node:os";
Variables
namespace constants.signals
Usage in Deno
import { constants } from "node:os";
variable constants.signals
Type
type alias NetworkInterfaceInfo
Usage in Deno
import { type NetworkInterfaceInfo } from "node:os";
Definition
type alias SignalConstants
Usage in Deno
import { type SignalConstants } from "node:os";
Definition
[key in Signals]: number variable constants.dlopen.RTLD_DEEPBIND
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.dlopen.RTLD_GLOBAL
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.EADDRNOTAVAIL
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.EAFNOSUPPORT
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.ECONNABORTED
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.ECONNREFUSED
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.EDESTADDRREQ
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.EHOSTUNREACH
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.ENAMETOOLONG
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.EPROTONOSUPPORT
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSA_E_CANCELLED
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSA_E_NO_MORE
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAEADDRINUSE
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAEADDRNOTAVAIL
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAEAFNOSUPPORT
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAECANCELLED
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAECONNABORTED
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAECONNREFUSED
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAECONNRESET
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAEDESTADDRREQ
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAEHOSTDOWN
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAEHOSTUNREACH
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAEINPROGRESS
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAEINVALIDPROCTABLE
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAEINVALIDPROVIDER
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAENAMETOOLONG
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAENETRESET
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAENETUNREACH
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAENOPROTOOPT
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAENOTEMPTY
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAEOPNOTSUPP
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAEPFNOSUPPORT
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAEPROTONOSUPPORT
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAEPROTOTYPE
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAEPROVIDERFAILEDINIT
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAESHUTDOWN
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAESOCKTNOSUPPORT
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAETIMEDOUT
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAETOOMANYREFS
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAEWOULDBLOCK
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSANOTINITIALISED
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSASERVICE_NOT_FOUND
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSASYSCALLFAILURE
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSASYSNOTREADY
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSATYPE_NOT_FOUND
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.errno.WSAVERNOTSUPPORTED
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.priority.PRIORITY_ABOVE_NORMAL
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.priority.PRIORITY_BELOW_NORMAL
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.priority.PRIORITY_HIGH
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.priority.PRIORITY_HIGHEST
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.priority.PRIORITY_LOW
Usage in Deno
import { constants } from "node:os";
Type
number variable constants.priority.PRIORITY_NORMAL
Usage in Deno
import { constants } from "node:os";
Type
number variable EOL
Usage in Deno
import { EOL } from "node:os";
The operating system-specific end-of-line marker.
-
\non POSIX -
\r\non Windows
Type
string
© 2018–2025 the Deno authors
Licensed under the MIT License.
https://docs.deno.com/api/node/os
