os.EOL#

• Type:<string>

The operating system-specific end-of-line marker.

• \n on POSIX
• \r\n on Windows

os.availableParallelism()#

• Returns:<integer>

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'suv_available_parallelism().

os.arch()#

• Returns:<string>

Returns the operating system CPU architecture for which the Node.js binary wascompiled. Possible values are'arm','arm64','ia32','loong64','mips','mipsel','ppc64','riscv64','s390x', and'x64'.

The return value is equivalent toprocess.arch.

os.constants#

• Type:<Object>

Contains commonly used operating system-specific constants for error codes,process signals, and so on. The specific constants defined are described inOS constants.

os.cpus()#

• Returns:<Object[]>

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<string>
• 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.

[  {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,    },  },]copy

nice values are POSIX-only. On Windows, thenice values of all processorsare always 0.

os.cpus().length should not be used to calculate the amount of parallelismavailable to an application. Useos.availableParallelism() for this purpose.

os.devNull#

• Type:<string>

The platform-specific file path of the null device.

• \\.\nul on Windows
• /dev/null on POSIX

os.endianness()#

• Returns:<string>

Returns a string identifying the endianness of the CPU for which the Node.jsbinary was compiled.

Possible values are'BE' for big endian and'LE' for little endian.

os.freemem()#

• Returns:<integer>

Returns the amount of free system memory in bytes as an integer.

os.getPriority([pid])#

• pid<integer> The process ID to retrieve scheduling priority for.Default:0.
• Returns:<integer>

Returns the scheduling priority for the process specified bypid. Ifpid isnot provided or is0, the priority of the current process is returned.

os.homedir()#

• Returns:<string>

Returns the string path of the current user's home directory.

On POSIX, it uses the$HOME environment variable if defined. Otherwise ituses theeffective UID to look up the user's home directory.

On Windows, it uses theUSERPROFILE environment variable if defined.Otherwise it uses the path to the profile directory of the current user.

os.hostname()#

• Returns:<string>

Returns the host name of the operating system as a string.

os.loadavg()#

• Returns:<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 operatingsystem and expressed as a fractional number.

The load average is a Unix-specific concept. On Windows, the return value isalways[0, 0, 0].

os.machine()#

• Returns:<string>

Returns the machine type as a string, such asarm,arm64,aarch64,mips,mips64,ppc64,ppc64le,s390x,i386,i686,x86_64.

On POSIX systems, the machine type is determined by callinguname(3). On Windows,RtlGetVersion() is used, and if it is notavailable,GetVersionExW() will be used. Seehttps://en.wikipedia.org/wiki/Uname#Examples for more information.

os.networkInterfaces()#

• Returns:<Object>

Returns an object containing network interfaces that have been assigned anetwork address.

Each key on the returned object identifies a network interface. The associatedvalue 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> EitherIPv4 orIPv6
• mac<string> The MAC address of the network interface
• internal<boolean>true if the network interface is a loopback orsimilar interface that is not remotely accessible; otherwisefalse
• scopeid<number> The numeric IPv6 scope ID (only specified whenfamilyisIPv6)
• cidr<string> The assigned IPv4 or IPv6 address with the routing prefixin CIDR notation. If thenetmask is invalid, this property is settonull.

{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'    }  ]}copy

os.platform()#

• Returns:<string>

Returns a string identifying the operating system platform for whichthe 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 toprocess.platform.

The value'android' may also be returned if Node.js is built on the Androidoperating system.Android support is experimental.

os.release()#

• Returns:<string>

Returns the operating system as a string.

On POSIX systems, the operating system release is determined by callinguname(3). On Windows,GetVersionExW() is used. Seehttps://en.wikipedia.org/wiki/Uname#Examples for more information.

os.setPriority([pid, ]priority)#

• pid<integer> The process ID to set scheduling priority for.Default:0.
• priority<integer> The scheduling priority to assign to the process.

Attempts to set the scheduling priority for the process specified bypid. Ifpid is not provided or is0, the process ID of the current process is used.

Thepriority input must be an integer between-20 (high priority) and19(low priority). Due to differences between Unix priority levels and Windowspriority classes,priority is mapped to one of six priority constants inos.constants.priority. When retrieving a process priority level, this rangemapping may cause the return value to be slightly different on Windows. To avoidconfusion, setpriority to one of the priority constants.

On Windows, setting priority toPRIORITY_HIGHEST requires elevated userprivileges. Otherwise the set priority will be silently reduced toPRIORITY_HIGH.

os.tmpdir()#

• Returns:<string>

Returns the operating system's default directory for temporary files as astring.

On Windows, the result can be overridden byTEMP andTMP environment variables, andTEMP takes precedence overTMP. If neither is set, it defaults to%SystemRoot%\tempor%windir%\temp.

On non-Windows platforms,TMPDIR,TMP andTEMP environment variables will be checkedto override the result of this method, in the described order. If none of them is set, itdefaults to/tmp.

Some operating system distributions would either configureTMPDIR (non-Windows) orTEMP andTMP (Windows) by default without additional configurations by the systemadministrators. The result ofos.tmpdir() typically reflects the system preferenceunless it's explicitly overridden by the users.

os.totalmem()#

• Returns:<integer>

Returns the total amount of system memory in bytes as an integer.

os.type()#

• Returns:<string>

Returns the operating system name as returned byuname(3). For example, itreturns'Linux' on Linux,'Darwin' on macOS, and'Windows_NT' on Windows.

Seehttps://en.wikipedia.org/wiki/Uname#Examples for additional informationabout the output of runninguname(3) on various operating systems.

os.uptime()#

• Returns:<integer>

Returns the system uptime in number of seconds.

os.userInfo([options])#

• options<Object>
  • encoding<string> Character encoding used to interpret resulting strings.Ifencoding is set to'buffer', theusername,shell, andhomedirvalues will beBuffer instances.Default:'utf8'.
• Returns:<Object>

Returns information about the currently effective user. On POSIX platforms,this is typically a subset of the password file. The returned object includestheusername,uid,gid,shell, andhomedir. On Windows, theuid andgid fields are-1, andshell isnull.

The value ofhomedir returned byos.userInfo() is provided by the operatingsystem. This differs from the result ofos.homedir(), which queriesenvironment variables for the home directory before falling back to theoperating system response.

Throws aSystemError if a user has nousername orhomedir.

os.version()#

• Returns:<string>

Returns a string identifying the kernel version.

On POSIX systems, the operating system release is determined by callinguname(3). On Windows,RtlGetVersion() is used, and if it is notavailable,GetVersionExW() will be used. Seehttps://en.wikipedia.org/wiki/Uname#Examples for more information.

OS constants#

The following constants are exported byos.constants.

Not all constants will be available on every operating system.