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<li><span class="stability_2"><a href="#os">OS</a></span>
<ul>
<li><a href="#oseol"><code>os.EOL</code></a></li>
<li><a href="#osavailableparallelism"><code>os.availableParallelism()</code></a></li>
<li><a href="#osarch"><code>os.arch()</code></a></li>
<li><a href="#osconstants"><code>os.constants</code></a></li>
<li><a href="#oscpus"><code>os.cpus()</code></a></li>
<li><a href="#osdevnull"><code>os.devNull</code></a></li>
<li><a href="#osendianness"><code>os.endianness()</code></a></li>
<li><a href="#osfreemem"><code>os.freemem()</code></a></li>
<li><a href="#osgetprioritypid"><code>os.getPriority([pid])</code></a></li>
<li><a href="#oshomedir"><code>os.homedir()</code></a></li>
<li><a href="#oshostname"><code>os.hostname()</code></a></li>
<li><a href="#osloadavg"><code>os.loadavg()</code></a></li>
<li><a href="#osmachine"><code>os.machine()</code></a></li>
<li><a href="#osnetworkinterfaces"><code>os.networkInterfaces()</code></a></li>
<li><a href="#osplatform"><code>os.platform()</code></a></li>
<li><a href="#osrelease"><code>os.release()</code></a></li>
<li><a href="#ossetprioritypid-priority"><code>os.setPriority([pid, ]priority)</code></a></li>
<li><a href="#ostmpdir"><code>os.tmpdir()</code></a></li>
<li><a href="#ostotalmem"><code>os.totalmem()</code></a></li>
<li><a href="#ostype"><code>os.type()</code></a></li>
<li><a href="#osuptime"><code>os.uptime()</code></a></li>
<li><a href="#osuserinfooptions"><code>os.userInfo([options])</code></a></li>
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<li><a href="#os-constants">OS constants</a>
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<li><a href="#signal-constants">Signal constants</a></li>
<li><a href="#error-constants">Error constants</a>
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<li><a href="#posix-error-constants">POSIX error constants</a></li>
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<li><a href="#dlopen-constants">dlopen constants</a></li>
<li><a href="#priority-constants">Priority constants</a></li>
<li><a href="#libuv-constants">libuv constants</a></li>
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<li><a href="https://nodejs.org/docs/latest-v16.x/api/os.html">16.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v15.x/api/os.html">15.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v14.x/api/os.html">14.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v13.x/api/os.html">13.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v12.x/api/os.html">12.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v11.x/api/os.html">11.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v10.x/api/os.html">10.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v9.x/api/os.html">9.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v8.x/api/os.html">8.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v7.x/api/os.html">7.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v6.x/api/os.html">6.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v5.x/api/os.html">5.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v4.x/api/os.html">4.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v0.12.x/api/os.html">0.12.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v0.10.x/api/os.html">0.10.x</a></li></ol></div>
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<details role="navigation" id="toc" open><summary>Table of contents</summary><ul>
<li><span class="stability_2"><a href="#os">OS</a></span>
<ul>
<li><a href="#oseol"><code>os.EOL</code></a></li>
<li><a href="#osavailableparallelism"><code>os.availableParallelism()</code></a></li>
<li><a href="#osarch"><code>os.arch()</code></a></li>
<li><a href="#osconstants"><code>os.constants</code></a></li>
<li><a href="#oscpus"><code>os.cpus()</code></a></li>
<li><a href="#osdevnull"><code>os.devNull</code></a></li>
<li><a href="#osendianness"><code>os.endianness()</code></a></li>
<li><a href="#osfreemem"><code>os.freemem()</code></a></li>
<li><a href="#osgetprioritypid"><code>os.getPriority([pid])</code></a></li>
<li><a href="#oshomedir"><code>os.homedir()</code></a></li>
<li><a href="#oshostname"><code>os.hostname()</code></a></li>
<li><a href="#osloadavg"><code>os.loadavg()</code></a></li>
<li><a href="#osmachine"><code>os.machine()</code></a></li>
<li><a href="#osnetworkinterfaces"><code>os.networkInterfaces()</code></a></li>
<li><a href="#osplatform"><code>os.platform()</code></a></li>
<li><a href="#osrelease"><code>os.release()</code></a></li>
<li><a href="#ossetprioritypid-priority"><code>os.setPriority([pid, ]priority)</code></a></li>
<li><a href="#ostmpdir"><code>os.tmpdir()</code></a></li>
<li><a href="#ostotalmem"><code>os.totalmem()</code></a></li>
<li><a href="#ostype"><code>os.type()</code></a></li>
<li><a href="#osuptime"><code>os.uptime()</code></a></li>
<li><a href="#osuserinfooptions"><code>os.userInfo([options])</code></a></li>
<li><a href="#osversion"><code>os.version()</code></a></li>
<li><a href="#os-constants">OS constants</a>
<ul>
<li><a href="#signal-constants">Signal constants</a></li>
<li><a href="#error-constants">Error constants</a>
<ul>
<li><a href="#posix-error-constants">POSIX error constants</a></li>
<li><a href="#windows-specific-error-constants">Windows-specific error constants</a></li>
</ul>
</li>
<li><a href="#dlopen-constants">dlopen constants</a></li>
<li><a href="#priority-constants">Priority constants</a></li>
<li><a href="#libuv-constants">libuv constants</a></li>
</ul>
</li>
</ul>
</li>
</ul></details>
<div role="main" id="apicontent">
<h2>OS<span><a class="mark" href="#os" id="os">#</a></span><a aria-hidden="true" class="legacy" id="os_os"></a></h2>
<p></p><div class="api_stability api_stability_2"><a href="documentation.html#stability-index">Stability: 2</a> - Stable</div><p></p>
<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v20.18.0/lib/os.js">lib/os.js</a></p>
<p>The <code>node:os</code> module provides operating system-related utility methods and
properties. It can be accessed using:</p>
<pre class="with-30-chars"><input class="js-flavor-toggle" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> os <span class="hljs-keyword">from</span> <span class="hljs-string">'node:os'</span>;</code><code class="language-js cjs"><span class="hljs-keyword">const</span> os = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:os'</span>);</code><button class="copy-button">copy</button></pre>
<section><h3><code>os.EOL</code><span><a class="mark" href="#oseol" id="oseol">#</a></span><a aria-hidden="true" class="legacy" id="os_os_eol"></a></h3>
<div class="api_metadata">
<span>Added in: v0.7.8</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>The operating system-specific end-of-line marker.</p>
<ul>
<li><code>\n</code> on POSIX</li>
<li><code>\r\n</code> on Windows</li>
</ul>
</section><section><h3><code>os.availableParallelism()</code><span><a class="mark" href="#osavailableparallelism" id="osavailableparallelism">#</a></span><a aria-hidden="true" class="legacy" id="os_os_availableparallelism"></a></h3>
<div class="api_metadata">
<span>Added in: v19.4.0, v18.14.0</span>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Returns an estimate of the default amount of parallelism a program should use.
Always returns a value greater than zero.</p>
<p>This function is a small wrapper about libuv's <a href="https://docs.libuv.org/en/v1.x/misc.html#c.uv_available_parallelism"><code>uv_available_parallelism()</code></a>.</p>
</section><section><h3><code>os.arch()</code><span><a class="mark" href="#osarch" id="osarch">#</a></span><a aria-hidden="true" class="legacy" id="os_os_arch"></a></h3>
<div class="api_metadata">
<span>Added in: v0.5.0</span>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>Returns the operating system CPU architecture for which the Node.js binary was
compiled. Possible values are <code>'arm'</code>, <code>'arm64'</code>, <code>'ia32'</code>, <code>'loong64'</code>,
<code>'mips'</code>, <code>'mipsel'</code>, <code>'ppc'</code>, <code>'ppc64'</code>, <code>'riscv64'</code>, <code>'s390'</code>, <code>'s390x'</code>,
and <code>'x64'</code>.</p>
<p>The return value is equivalent to <a href="process.html#processarch"><code>process.arch</code></a>.</p>
</section><section><h3><code>os.constants</code><span><a class="mark" href="#osconstants" id="osconstants">#</a></span><a aria-hidden="true" class="legacy" id="os_os_constants"></a></h3>
<div class="api_metadata">
<span>Added in: v6.3.0</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li>
</ul>
<p>Contains commonly used operating system-specific constants for error codes,
process signals, and so on. The specific constants defined are described in
<a href="#os-constants">OS constants</a>.</p>
</section><section><h3><code>os.cpus()</code><span><a class="mark" href="#oscpus" id="oscpus">#</a></span><a aria-hidden="true" class="legacy" id="os_os_cpus"></a></h3>
<div class="api_metadata">
<span>Added in: v0.3.3</span>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a></li>
</ul>
<p>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
<code>/proc</code> file system is unavailable.</p>
<p>The properties included on each object include:</p>
<ul>
<li><code>model</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
<li><code>speed</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> (in MHz)</li>
<li><code>times</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
<ul>
<li><code>user</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of milliseconds the CPU has spent in user mode.</li>
<li><code>nice</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of milliseconds the CPU has spent in nice mode.</li>
<li><code>sys</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of milliseconds the CPU has spent in sys mode.</li>
<li><code>idle</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of milliseconds the CPU has spent in idle mode.</li>
<li><code>irq</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of milliseconds the CPU has spent in irq mode.</li>
</ul>
</li>
</ul>
<!-- eslint-disable @stylistic/js/semi -->
<pre><code class="language-js">[
{
<span class="hljs-attr">model</span>: <span class="hljs-string">'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz'</span>,
<span class="hljs-attr">speed</span>: <span class="hljs-number">2926</span>,
<span class="hljs-attr">times</span>: {
<span class="hljs-attr">user</span>: <span class="hljs-number">252020</span>,
<span class="hljs-attr">nice</span>: <span class="hljs-number">0</span>,
<span class="hljs-attr">sys</span>: <span class="hljs-number">30340</span>,
<span class="hljs-attr">idle</span>: <span class="hljs-number">1070356870</span>,
<span class="hljs-attr">irq</span>: <span class="hljs-number">0</span>,
},
},
{
<span class="hljs-attr">model</span>: <span class="hljs-string">'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz'</span>,
<span class="hljs-attr">speed</span>: <span class="hljs-number">2926</span>,
<span class="hljs-attr">times</span>: {
<span class="hljs-attr">user</span>: <span class="hljs-number">306960</span>,
<span class="hljs-attr">nice</span>: <span class="hljs-number">0</span>,
<span class="hljs-attr">sys</span>: <span class="hljs-number">26980</span>,
<span class="hljs-attr">idle</span>: <span class="hljs-number">1071569080</span>,
<span class="hljs-attr">irq</span>: <span class="hljs-number">0</span>,
},
},
{
<span class="hljs-attr">model</span>: <span class="hljs-string">'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz'</span>,
<span class="hljs-attr">speed</span>: <span class="hljs-number">2926</span>,
<span class="hljs-attr">times</span>: {
<span class="hljs-attr">user</span>: <span class="hljs-number">248450</span>,
<span class="hljs-attr">nice</span>: <span class="hljs-number">0</span>,
<span class="hljs-attr">sys</span>: <span class="hljs-number">21750</span>,
<span class="hljs-attr">idle</span>: <span class="hljs-number">1070919370</span>,
<span class="hljs-attr">irq</span>: <span class="hljs-number">0</span>,
},
},
{
<span class="hljs-attr">model</span>: <span class="hljs-string">'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz'</span>,
<span class="hljs-attr">speed</span>: <span class="hljs-number">2926</span>,
<span class="hljs-attr">times</span>: {
<span class="hljs-attr">user</span>: <span class="hljs-number">256880</span>,
<span class="hljs-attr">nice</span>: <span class="hljs-number">0</span>,
<span class="hljs-attr">sys</span>: <span class="hljs-number">19430</span>,
<span class="hljs-attr">idle</span>: <span class="hljs-number">1070905480</span>,
<span class="hljs-attr">irq</span>: <span class="hljs-number">20</span>,
},
},
]</code> <button class="copy-button">copy</button></pre>
<p><code>nice</code> values are POSIX-only. On Windows, the <code>nice</code> values of all processors
are always 0.</p>
<p><code>os.cpus().length</code> should not be used to calculate the amount of parallelism
available to an application. Use
<a href="#osavailableparallelism"><code>os.availableParallelism()</code></a> for this purpose.</p>
</section><section><h3><code>os.devNull</code><span><a class="mark" href="#osdevnull" id="osdevnull">#</a></span><a aria-hidden="true" class="legacy" id="os_os_devnull"></a></h3>
<div class="api_metadata">
<span>Added in: v16.3.0, v14.18.0</span>
</div>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>The platform-specific file path of the null device.</p>
<ul>
<li><code>\\.\nul</code> on Windows</li>
<li><code>/dev/null</code> on POSIX</li>
</ul>
</section><section><h3><code>os.endianness()</code><span><a class="mark" href="#osendianness" id="osendianness">#</a></span><a aria-hidden="true" class="legacy" id="os_os_endianness"></a></h3>
<div class="api_metadata">
<span>Added in: v0.9.4</span>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>Returns a string identifying the endianness of the CPU for which the Node.js
binary was compiled.</p>
<p>Possible values are <code>'BE'</code> for big endian and <code>'LE'</code> for little endian.</p>
</section><section><h3><code>os.freemem()</code><span><a class="mark" href="#osfreemem" id="osfreemem">#</a></span><a aria-hidden="true" class="legacy" id="os_os_freemem"></a></h3>
<div class="api_metadata">
<span>Added in: v0.3.3</span>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Returns the amount of free system memory in bytes as an integer.</p>
</section><section><h3><code>os.getPriority([pid])</code><span><a class="mark" href="#osgetprioritypid" id="osgetprioritypid">#</a></span><a aria-hidden="true" class="legacy" id="os_os_getpriority_pid"></a></h3>
<div class="api_metadata">
<span>Added in: v10.10.0</span>
</div>
<ul>
<li><code>pid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The process ID to retrieve scheduling priority for.
<strong>Default:</strong> <code>0</code>.</li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Returns the scheduling priority for the process specified by <code>pid</code>. If <code>pid</code> is
not provided or is <code>0</code>, the priority of the current process is returned.</p>
</section><section><h3><code>os.homedir()</code><span><a class="mark" href="#oshomedir" id="oshomedir">#</a></span><a aria-hidden="true" class="legacy" id="os_os_homedir"></a></h3>
<div class="api_metadata">
<span>Added in: v2.3.0</span>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>Returns the string path of the current user's home directory.</p>
<p>On POSIX, it uses the <code>$HOME</code> environment variable if defined. Otherwise it
uses the <a href="https://en.wikipedia.org/wiki/User_identifier#Effective_user_ID">effective UID</a> to look up the user's home directory.</p>
<p>On Windows, it uses the <code>USERPROFILE</code> environment variable if defined.
Otherwise it uses the path to the profile directory of the current user.</p>
</section><section><h3><code>os.hostname()</code><span><a class="mark" href="#oshostname" id="oshostname">#</a></span><a aria-hidden="true" class="legacy" id="os_os_hostname"></a></h3>
<div class="api_metadata">
<span>Added in: v0.3.3</span>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>Returns the host name of the operating system as a string.</p>
</section><section><h3><code>os.loadavg()</code><span><a class="mark" href="#osloadavg" id="osloadavg">#</a></span><a aria-hidden="true" class="legacy" id="os_os_loadavg"></a></h3>
<div class="api_metadata">
<span>Added in: v0.3.3</span>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number[]></a></li>
</ul>
<p>Returns an array containing the 1, 5, and 15 minute load averages.</p>
<p>The load average is a measure of system activity calculated by the operating
system and expressed as a fractional number.</p>
<p>The load average is a Unix-specific concept. On Windows, the return value is
always <code>[0, 0, 0]</code>.</p>
</section><section><h3><code>os.machine()</code><span><a class="mark" href="#osmachine" id="osmachine">#</a></span><a aria-hidden="true" class="legacy" id="os_os_machine"></a></h3>
<div class="api_metadata">
<span>Added in: v18.9.0, v16.18.0</span>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>Returns the machine type as a string, such as <code>arm</code>, <code>arm64</code>, <code>aarch64</code>,
<code>mips</code>, <code>mips64</code>, <code>ppc64</code>, <code>ppc64le</code>, <code>s390</code>, <code>s390x</code>, <code>i386</code>, <code>i686</code>, <code>x86_64</code>.</p>
<p>On POSIX systems, the machine type is determined by calling
<a href="https://linux.die.net/man/3/uname"><code>uname(3)</code></a>. On Windows, <code>RtlGetVersion()</code> is used, and if it is not
available, <code>GetVersionExW()</code> will be used. See
<a href="https://en.wikipedia.org/wiki/Uname#Examples">https://en.wikipedia.org/wiki/Uname#Examples</a> for more information.</p>
</section><section><h3><code>os.networkInterfaces()</code><span><a class="mark" href="#osnetworkinterfaces" id="osnetworkinterfaces">#</a></span><a aria-hidden="true" class="legacy" id="os_os_networkinterfaces"></a></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tbody><tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.4.0</td>
<td><p>The <code>family</code> property now returns a string instead of a number.</p></td></tr>
<tr><td>v18.0.0</td>
<td><p>The <code>family</code> property now returns a number instead of a string.</p></td></tr>
<tr><td>v0.6.0</td>
<td><p><span>Added in: v0.6.0</span></p></td></tr>
</tbody></table>
</details>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li>
</ul>
<p>Returns an object containing network interfaces that have been assigned a
network address.</p>
<p>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.</p>
<p>The properties available on the assigned network address object include:</p>
<ul>
<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The assigned IPv4 or IPv6 address</li>
<li><code>netmask</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The IPv4 or IPv6 network mask</li>
<li><code>family</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Either <code>IPv4</code> or <code>IPv6</code></li>
<li><code>mac</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The MAC address of the network interface</li>
<li><code>internal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> <code>true</code> if the network interface is a loopback or
similar interface that is not remotely accessible; otherwise <code>false</code></li>
<li><code>scopeid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The numeric IPv6 scope ID (only specified when <code>family</code>
is <code>IPv6</code>)</li>
<li><code>cidr</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The assigned IPv4 or IPv6 address with the routing prefix
in CIDR notation. If the <code>netmask</code> is invalid, this property is set
to <code>null</code>.</li>
</ul>
<!-- eslint-skip -->
<pre><code class="language-js">{
<span class="hljs-attr">lo</span>: [
{
<span class="hljs-attr">address</span>: <span class="hljs-string">'127.0.0.1'</span>,
<span class="hljs-attr">netmask</span>: <span class="hljs-string">'255.0.0.0'</span>,
<span class="hljs-attr">family</span>: <span class="hljs-string">'IPv4'</span>,
<span class="hljs-attr">mac</span>: <span class="hljs-string">'00:00:00:00:00:00'</span>,
<span class="hljs-attr">internal</span>: <span class="hljs-literal">true</span>,
<span class="hljs-attr">cidr</span>: <span class="hljs-string">'127.0.0.1/8'</span>
},
{
<span class="hljs-attr">address</span>: <span class="hljs-string">'::1'</span>,
<span class="hljs-attr">netmask</span>: <span class="hljs-string">'ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff'</span>,
<span class="hljs-attr">family</span>: <span class="hljs-string">'IPv6'</span>,
<span class="hljs-attr">mac</span>: <span class="hljs-string">'00:00:00:00:00:00'</span>,
<span class="hljs-attr">scopeid</span>: <span class="hljs-number">0</span>,
<span class="hljs-attr">internal</span>: <span class="hljs-literal">true</span>,
<span class="hljs-attr">cidr</span>: <span class="hljs-string">'::1/128'</span>
}
],
<span class="hljs-attr">eth0</span>: [
{
<span class="hljs-attr">address</span>: <span class="hljs-string">'192.168.1.108'</span>,
<span class="hljs-attr">netmask</span>: <span class="hljs-string">'255.255.255.0'</span>,
<span class="hljs-attr">family</span>: <span class="hljs-string">'IPv4'</span>,
<span class="hljs-attr">mac</span>: <span class="hljs-string">'01:02:03:0a:0b:0c'</span>,
<span class="hljs-attr">internal</span>: <span class="hljs-literal">false</span>,
<span class="hljs-attr">cidr</span>: <span class="hljs-string">'192.168.1.108/24'</span>
},
{
<span class="hljs-attr">address</span>: <span class="hljs-string">'fe80::a00:27ff:fe4e:66a1'</span>,
<span class="hljs-attr">netmask</span>: <span class="hljs-string">'ffff:ffff:ffff:ffff::'</span>,
<span class="hljs-attr">family</span>: <span class="hljs-string">'IPv6'</span>,
<span class="hljs-attr">mac</span>: <span class="hljs-string">'01:02:03:0a:0b:0c'</span>,
<span class="hljs-attr">scopeid</span>: <span class="hljs-number">1</span>,
<span class="hljs-attr">internal</span>: <span class="hljs-literal">false</span>,
<span class="hljs-attr">cidr</span>: <span class="hljs-string">'fe80::a00:27ff:fe4e:66a1/64'</span>
}
]
}</code> <button class="copy-button">copy</button></pre>
</section><section><h3><code>os.platform()</code><span><a class="mark" href="#osplatform" id="osplatform">#</a></span><a aria-hidden="true" class="legacy" id="os_os_platform"></a></h3>
<div class="api_metadata">
<span>Added in: v0.5.0</span>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>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 <code>'aix'</code>, <code>'darwin'</code>, <code>'freebsd'</code>,<code>'linux'</code>,
<code>'openbsd'</code>, <code>'sunos'</code>, and <code>'win32'</code>.</p>
<p>The return value is equivalent to <a href="process.html#processplatform"><code>process.platform</code></a>.</p>
<p>The value <code>'android'</code> may also be returned if Node.js is built on the Android
operating system. <a href="https://github.com/nodejs/node/blob/HEAD/BUILDING.md#android">Android support is experimental</a>.</p>
</section><section><h3><code>os.release()</code><span><a class="mark" href="#osrelease" id="osrelease">#</a></span><a aria-hidden="true" class="legacy" id="os_os_release"></a></h3>
<div class="api_metadata">
<span>Added in: v0.3.3</span>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>Returns the operating system as a string.</p>
<p>On POSIX systems, the operating system release is determined by calling
<a href="https://linux.die.net/man/3/uname"><code>uname(3)</code></a>. On Windows, <code>GetVersionExW()</code> is used. See
<a href="https://en.wikipedia.org/wiki/Uname#Examples">https://en.wikipedia.org/wiki/Uname#Examples</a> for more information.</p>
</section><section><h3><code>os.setPriority([pid, ]priority)</code><span><a class="mark" href="#ossetprioritypid-priority" id="ossetprioritypid-priority">#</a></span><a aria-hidden="true" class="legacy" id="os_os_setpriority_pid_priority"></a></h3>
<div class="api_metadata">
<span>Added in: v10.10.0</span>
</div>
<ul>
<li><code>pid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The process ID to set scheduling priority for.
<strong>Default:</strong> <code>0</code>.</li>
<li><code>priority</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The scheduling priority to assign to the process.</li>
</ul>
<p>Attempts to set the scheduling priority for the process specified by <code>pid</code>. If
<code>pid</code> is not provided or is <code>0</code>, the process ID of the current process is used.</p>
<p>The <code>priority</code> input must be an integer between <code>-20</code> (high priority) and <code>19</code>
(low priority). Due to differences between Unix priority levels and Windows
priority classes, <code>priority</code> is mapped to one of six priority constants in
<code>os.constants.priority</code>. When retrieving a process priority level, this range
mapping may cause the return value to be slightly different on Windows. To avoid
confusion, set <code>priority</code> to one of the priority constants.</p>
<p>On Windows, setting priority to <code>PRIORITY_HIGHEST</code> requires elevated user
privileges. Otherwise the set priority will be silently reduced to
<code>PRIORITY_HIGH</code>.</p>
</section><section><h3><code>os.tmpdir()</code><span><a class="mark" href="#ostmpdir" id="ostmpdir">#</a></span><a aria-hidden="true" class="legacy" id="os_os_tmpdir"></a></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tbody><tr><th>Version</th><th>Changes</th></tr>
<tr><td>v2.0.0</td>
<td><p>This function is now cross-platform consistent and no longer returns a path with a trailing slash on any platform.</p></td></tr>
<tr><td>v0.9.9</td>
<td><p><span>Added in: v0.9.9</span></p></td></tr>
</tbody></table>
</details>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>Returns the operating system's default directory for temporary files as a
string.</p>
<p>On Windows, the result can be overridden by <code>TEMP</code> and <code>TMP</code> environment variables, and
<code>TEMP</code> takes precedence over <code>TMP</code>. If neither is set, it defaults to <code>%SystemRoot%\temp</code>
or <code>%windir%\temp</code>.</p>
<p>On non-Windows platforms, <code>TMPDIR</code>, <code>TMP</code> and <code>TEMP</code> environment variables will be checked
to override the result of this method, in the described order. If none of them is set, it
defaults to <code>/tmp</code>.</p>
<p>Some operating system distributions would either configure <code>TMPDIR</code> (non-Windows) or
<code>TEMP</code> and <code>TMP</code> (Windows) by default without additional configurations by the system
administrators. The result of <code>os.tmpdir()</code> typically reflects the system preference
unless it's explicitly overridden by the users.</p>
</section><section><h3><code>os.totalmem()</code><span><a class="mark" href="#ostotalmem" id="ostotalmem">#</a></span><a aria-hidden="true" class="legacy" id="os_os_totalmem"></a></h3>
<div class="api_metadata">
<span>Added in: v0.3.3</span>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Returns the total amount of system memory in bytes as an integer.</p>
</section><section><h3><code>os.type()</code><span><a class="mark" href="#ostype" id="ostype">#</a></span><a aria-hidden="true" class="legacy" id="os_os_type"></a></h3>
<div class="api_metadata">
<span>Added in: v0.3.3</span>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>Returns the operating system name as returned by <a href="https://linux.die.net/man/3/uname"><code>uname(3)</code></a>. For example, it
returns <code>'Linux'</code> on Linux, <code>'Darwin'</code> on macOS, and <code>'Windows_NT'</code> on Windows.</p>
<p>See <a href="https://en.wikipedia.org/wiki/Uname#Examples">https://en.wikipedia.org/wiki/Uname#Examples</a> for additional information
about the output of running <a href="https://linux.die.net/man/3/uname"><code>uname(3)</code></a> on various operating systems.</p>
</section><section><h3><code>os.uptime()</code><span><a class="mark" href="#osuptime" id="osuptime">#</a></span><a aria-hidden="true" class="legacy" id="os_os_uptime"></a></h3>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tbody><tr><th>Version</th><th>Changes</th></tr>
<tr><td>v10.0.0</td>
<td><p>The result of this function no longer contains a fraction component on Windows.</p></td></tr>
<tr><td>v0.3.3</td>
<td><p><span>Added in: v0.3.3</span></p></td></tr>
</tbody></table>
</details>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li>
</ul>
<p>Returns the system uptime in number of seconds.</p>
</section><section><h3><code>os.userInfo([options])</code><span><a class="mark" href="#osuserinfooptions" id="osuserinfooptions">#</a></span><a aria-hidden="true" class="legacy" id="os_os_userinfo_options"></a></h3>
<div class="api_metadata">
<span>Added in: v6.0.0</span>
</div>
<ul>
<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
<ul>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Character encoding used to interpret resulting strings.
If <code>encoding</code> is set to <code>'buffer'</code>, the <code>username</code>, <code>shell</code>, and <code>homedir</code>
values will be <code>Buffer</code> instances. <strong>Default:</strong> <code>'utf8'</code>.</li>
</ul>
</li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li>
</ul>
<p>Returns information about the currently effective user. On POSIX platforms,
this is typically a subset of the password file. The returned object includes
the <code>username</code>, <code>uid</code>, <code>gid</code>, <code>shell</code>, and <code>homedir</code>. On Windows, the <code>uid</code> and
<code>gid</code> fields are <code>-1</code>, and <code>shell</code> is <code>null</code>.</p>
<p>The value of <code>homedir</code> returned by <code>os.userInfo()</code> is provided by the operating
system. This differs from the result of <code>os.homedir()</code>, which queries
environment variables for the home directory before falling back to the
operating system response.</p>
<p>Throws a <a href="errors.html#class-systemerror"><code>SystemError</code></a> if a user has no <code>username</code> or <code>homedir</code>.</p>
</section><section><h3><code>os.version()</code><span><a class="mark" href="#osversion" id="osversion">#</a></span><a aria-hidden="true" class="legacy" id="os_os_version"></a></h3>
<div class="api_metadata">
<span>Added in: v13.11.0, v12.17.0</span>
</div>
<ul>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>Returns a string identifying the kernel version.</p>
<p>On POSIX systems, the operating system release is determined by calling
<a href="https://linux.die.net/man/3/uname"><code>uname(3)</code></a>. On Windows, <code>RtlGetVersion()</code> is used, and if it is not
available, <code>GetVersionExW()</code> will be used. See
<a href="https://en.wikipedia.org/wiki/Uname#Examples">https://en.wikipedia.org/wiki/Uname#Examples</a> for more information.</p>
</section><section><h3>OS constants<span><a class="mark" href="#os-constants" id="os-constants">#</a></span><a aria-hidden="true" class="legacy" id="os_os_constants_1"></a></h3>
<p>The following constants are exported by <code>os.constants</code>.</p>
<p>Not all constants will be available on every operating system.</p>
<h4>Signal constants<span><a class="mark" href="#signal-constants" id="signal-constants">#</a></span><a aria-hidden="true" class="legacy" id="os_signal_constants"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tbody><tr><th>Version</th><th>Changes</th></tr>
<tr><td>v5.11.0</td>
<td><p>Added support for <code>SIGINFO</code>.</p></td></tr>
</tbody></table>
</details>
</div>
<p>The following signal constants are exported by <code>os.constants.signals</code>.</p>
<table>
<tbody><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>
<td>Sent to indicate when a user wishes to interrupt a process
(<kbd>Ctrl</kbd>+<kbd>C</kbd>).</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>
<td>Sent to a process when an exception has occurred.</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>
<td>Sent to a process to notify that it has performed an illegal arithmetic
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>
</tbody></table>
<h4>Error constants<span><a class="mark" href="#error-constants" id="error-constants">#</a></span><a aria-hidden="true" class="legacy" id="os_error_constants"></a></h4>
<p>The following error constants are exported by <code>os.constants.errno</code>.</p>
<h5>POSIX error constants<span><a class="mark" href="#posix-error-constants" id="posix-error-constants">#</a></span><a aria-hidden="true" class="legacy" id="os_posix_error_constants"></a></h5>
<table>
<tbody><tr>
<th>Constant</th>
<th>Description</th>
</tr>
<tr>
<td><code>E2BIG</code></td>
<td>Indicates that the list of arguments is longer than expected.</td>
</tr>
<tr>
<td><code>EACCES</code></td>
<td>Indicates that the operation did not have sufficient permissions.</td>
</tr>
<tr>
<td><code>EADDRINUSE</code></td>
<td>Indicates that the network address is already in use.</td>
</tr>
<tr>
<td><code>EADDRNOTAVAIL</code></td>
<td>Indicates that the network address is currently unavailable for
use.</td>
</tr>
<tr>
<td><code>EAFNOSUPPORT</code></td>
<td>Indicates that the network address family is not supported.</td>
</tr>
<tr>
<td><code>EAGAIN</code></td>
<td>Indicates that there is no data available and to try the
operation again later.</td>
</tr>
<tr>
<td><code>EALREADY</code></td>
<td>Indicates that the socket already has a pending connection in
progress.</td>
</tr>
<tr>
<td><code>EBADF</code></td>
<td>Indicates that a file descriptor is not valid.</td>
</tr>
<tr>
<td><code>EBADMSG</code></td>
<td>Indicates an invalid data message.</td>
</tr>
<tr>
<td><code>EBUSY</code></td>
<td>Indicates that a device or resource is busy.</td>
</tr>
<tr>
<td><code>ECANCELED</code></td>
<td>Indicates that an operation was canceled.</td>
</tr>
<tr>
<td><code>ECHILD</code></td>
<td>Indicates that there are no child processes.</td>
</tr>
<tr>
<td><code>ECONNABORTED</code></td>
<td>Indicates that the network connection has been aborted.</td>
</tr>
<tr>
<td><code>ECONNREFUSED</code></td>
<td>Indicates that the network connection has been refused.</td>
</tr>
<tr>
<td><code>ECONNRESET</code></td>
<td>Indicates that the network connection has been reset.</td>
</tr>
<tr>
<td><code>EDEADLK</code></td>
<td>Indicates that a resource deadlock has been avoided.</td>
</tr>
<tr>
<td><code>EDESTADDRREQ</code></td>
<td>Indicates that a destination address is required.</td>
</tr>
<tr>
<td><code>EDOM</code></td>
<td>Indicates that an argument is out of the domain of the function.</td>
</tr>
<tr>
<td><code>EDQUOT</code></td>
<td>Indicates that the disk quota has been exceeded.</td>
</tr>
<tr>
<td><code>EEXIST</code></td>
<td>Indicates that the file already exists.</td>
</tr>
<tr>
<td><code>EFAULT</code></td>
<td>Indicates an invalid pointer address.</td>
</tr>
<tr>
<td><code>EFBIG</code></td>
<td>Indicates that the file is too large.</td>
</tr>
<tr>
<td><code>EHOSTUNREACH</code></td>
<td>Indicates that the host is unreachable.</td>
</tr>
<tr>
<td><code>EIDRM</code></td>
<td>Indicates that the identifier has been removed.</td>
</tr>
<tr>
<td><code>EILSEQ</code></td>
<td>Indicates an illegal byte sequence.</td>
</tr>
<tr>
<td><code>EINPROGRESS</code></td>
<td>Indicates that an operation is already in progress.</td>
</tr>
<tr>
<td><code>EINTR</code></td>
<td>Indicates that a function call was interrupted.</td>
</tr>
<tr>
<td><code>EINVAL</code></td>
<td>Indicates that an invalid argument was provided.</td>
</tr>
<tr>
<td><code>EIO</code></td>
<td>Indicates an otherwise unspecified I/O error.</td>
</tr>
<tr>
<td><code>EISCONN</code></td>
<td>Indicates that the socket is connected.</td>
</tr>
<tr>
<td><code>EISDIR</code></td>
<td>Indicates that the path is a directory.</td>
</tr>
<tr>
<td><code>ELOOP</code></td>
<td>Indicates too many levels of symbolic links in a path.</td>
</tr>
<tr>
<td><code>EMFILE</code></td>
<td>Indicates that there are too many open files.</td>
</tr>
<tr>
<td><code>EMLINK</code></td>
<td>Indicates that there are too many hard links to a file.</td>
</tr>
<tr>
<td><code>EMSGSIZE</code></td>
<td>Indicates that the provided message is too long.</td>
</tr>
<tr>
<td><code>EMULTIHOP</code></td>
<td>Indicates that a multihop was attempted.</td>
</tr>
<tr>
<td><code>ENAMETOOLONG</code></td>
<td>Indicates that the filename is too long.</td>
</tr>
<tr>
<td><code>ENETDOWN</code></td>
<td>Indicates that the network is down.</td>
</tr>
<tr>
<td><code>ENETRESET</code></td>
<td>Indicates that the connection has been aborted by the network.</td>
</tr>
<tr>
<td><code>ENETUNREACH</code></td>
<td>Indicates that the network is unreachable.</td>
</tr>
<tr>
<td><code>ENFILE</code></td>
<td>Indicates too many open files in the system.</td>
</tr>
<tr>
<td><code>ENOBUFS</code></td>
<td>Indicates that no buffer space is available.</td>
</tr>
<tr>
<td><code>ENODATA</code></td>
<td>Indicates that no message is available on the stream head read
queue.</td>
</tr>
<tr>
<td><code>ENODEV</code></td>
<td>Indicates that there is no such device.</td>
</tr>
<tr>
<td><code>ENOENT</code></td>
<td>Indicates that there is no such file or directory.</td>
</tr>
<tr>
<td><code>ENOEXEC</code></td>
<td>Indicates an exec format error.</td>
</tr>
<tr>
<td><code>ENOLCK</code></td>
<td>Indicates that there are no locks available.</td>
</tr>
<tr>
<td><code>ENOLINK</code></td>
<td>Indications that a link has been severed.</td>
</tr>
<tr>
<td><code>ENOMEM</code></td>
<td>Indicates that there is not enough space.</td>
</tr>
<tr>
<td><code>ENOMSG</code></td>
<td>Indicates that there is no message of the desired type.</td>
</tr>
<tr>
<td><code>ENOPROTOOPT</code></td>
<td>Indicates that a given protocol is not available.</td>
</tr>
<tr>
<td><code>ENOSPC</code></td>
<td>Indicates that there is no space available on the device.</td>
</tr>
<tr>
<td><code>ENOSR</code></td>
<td>Indicates that there are no stream resources available.</td>
</tr>
<tr>
<td><code>ENOSTR</code></td>
<td>Indicates that a given resource is not a stream.</td>
</tr>
<tr>
<td><code>ENOSYS</code></td>
<td>Indicates that a function has not been implemented.</td>
</tr>
<tr>
<td><code>ENOTCONN</code></td>
<td>Indicates that the socket is not connected.</td>
</tr>
<tr>
<td><code>ENOTDIR</code></td>
<td>Indicates that the path is not a directory.</td>
</tr>
<tr>
<td><code>ENOTEMPTY</code></td>
<td>Indicates that the directory is not empty.</td>
</tr>
<tr>
<td><code>ENOTSOCK</code></td>
<td>Indicates that the given item is not a socket.</td>
</tr>
<tr>
<td><code>ENOTSUP</code></td>
<td>Indicates that a given operation is not supported.</td>
</tr>
<tr>
<td><code>ENOTTY</code></td>
<td>Indicates an inappropriate I/O control operation.</td>
</tr>
<tr>
<td><code>ENXIO</code></td>
<td>Indicates no such device or address.</td>
</tr>
<tr>
<td><code>EOPNOTSUPP</code></td>
<td>Indicates that an operation is not supported on the socket. Although
<code>ENOTSUP</code> and <code>EOPNOTSUPP</code> have the same value
on Linux, according to POSIX.1 these error values should be distinct.)</td>
</tr>
<tr>
<td><code>EOVERFLOW</code></td>
<td>Indicates that a value is too large to be stored in a given data
type.</td>
</tr>
<tr>
<td><code>EPERM</code></td>
<td>Indicates that the operation is not permitted.</td>
</tr>
<tr>
<td><code>EPIPE</code></td>
<td>Indicates a broken pipe.</td>
</tr>
<tr>
<td><code>EPROTO</code></td>
<td>Indicates a protocol error.</td>
</tr>
<tr>
<td><code>EPROTONOSUPPORT</code></td>
<td>Indicates that a protocol is not supported.</td>
</tr>
<tr>
<td><code>EPROTOTYPE</code></td>
<td>Indicates the wrong type of protocol for a socket.</td>
</tr>
<tr>
<td><code>ERANGE</code></td>
<td>Indicates that the results are too large.</td>
</tr>
<tr>
<td><code>EROFS</code></td>
<td>Indicates that the file system is read only.</td>
</tr>
<tr>
<td><code>ESPIPE</code></td>
<td>Indicates an invalid seek operation.</td>
</tr>
<tr>
<td><code>ESRCH</code></td>
<td>Indicates that there is no such process.</td>
</tr>
<tr>
<td><code>ESTALE</code></td>
<td>Indicates that the file handle is stale.</td>
</tr>
<tr>
<td><code>ETIME</code></td>
<td>Indicates an expired timer.</td>
</tr>
<tr>
<td><code>ETIMEDOUT</code></td>
<td>Indicates that the connection timed out.</td>
</tr>
<tr>
<td><code>ETXTBSY</code></td>
<td>Indicates that a text file is busy.</td>
</tr>
<tr>
<td><code>EWOULDBLOCK</code></td>
<td>Indicates that the operation would block.</td>
</tr>
<tr>
<td><code>EXDEV</code></td>
<td>Indicates an improper link.</td>
</tr>
</tbody></table>
<h5>Windows-specific error constants<span><a class="mark" href="#windows-specific-error-constants" id="windows-specific-error-constants">#</a></span><a aria-hidden="true" class="legacy" id="os_windows_specific_error_constants"></a></h5>
<p>The following error codes are specific to the Windows operating system.</p>
<table>
<tbody><tr>
<th>Constant</th>
<th>Description</th>
</tr>
<tr>
<td><code>WSAEINTR</code></td>
<td>Indicates an interrupted function call.</td>
</tr>
<tr>
<td><code>WSAEBADF</code></td>
<td>Indicates an invalid file handle.</td>
</tr>
<tr>
<td><code>WSAEACCES</code></td>
<td>Indicates insufficient permissions to complete the operation.</td>
</tr>
<tr>
<td><code>WSAEFAULT</code></td>
<td>Indicates an invalid pointer address.</td>
</tr>
<tr>
<td><code>WSAEINVAL</code></td>
<td>Indicates that an invalid argument was passed.</td>
</tr>
<tr>
<td><code>WSAEMFILE</code></td>
<td>Indicates that there are too many open files.</td>
</tr>
<tr>
<td><code>WSAEWOULDBLOCK</code></td>
<td>Indicates that a resource is temporarily unavailable.</td>
</tr>
<tr>
<td><code>WSAEINPROGRESS</code></td>
<td>Indicates that an operation is currently in progress.</td>
</tr>
<tr>
<td><code>WSAEALREADY</code></td>
<td>Indicates that an operation is already in progress.</td>
</tr>
<tr>
<td><code>WSAENOTSOCK</code></td>
<td>Indicates that the resource is not a socket.</td>
</tr>
<tr>
<td><code>WSAEDESTADDRREQ</code></td>
<td>Indicates that a destination address is required.</td>
</tr>
<tr>
<td><code>WSAEMSGSIZE</code></td>
<td>Indicates that the message size is too long.</td>
</tr>
<tr>
<td><code>WSAEPROTOTYPE</code></td>
<td>Indicates the wrong protocol type for the socket.</td>
</tr>
<tr>
<td><code>WSAENOPROTOOPT</code></td>
<td>Indicates a bad protocol option.</td>
</tr>
<tr>
<td><code>WSAEPROTONOSUPPORT</code></td>
<td>Indicates that the protocol is not supported.</td>
</tr>
<tr>
<td><code>WSAESOCKTNOSUPPORT</code></td>
<td>Indicates that the socket type is not supported.</td>
</tr>
<tr>
<td><code>WSAEOPNOTSUPP</code></td>
<td>Indicates that the operation is not supported.</td>
</tr>
<tr>
<td><code>WSAEPFNOSUPPORT</code></td>
<td>Indicates that the protocol family is not supported.</td>
</tr>
<tr>
<td><code>WSAEAFNOSUPPORT</code></td>
<td>Indicates that the address family is not supported.</td>
</tr>
<tr>
<td><code>WSAEADDRINUSE</code></td>
<td>Indicates that the network address is already in use.</td>
</tr>
<tr>
<td><code>WSAEADDRNOTAVAIL</code></td>
<td>Indicates that the network address is not available.</td>
</tr>
<tr>
<td><code>WSAENETDOWN</code></td>
<td>Indicates that the network is down.</td>
</tr>
<tr>
<td><code>WSAENETUNREACH</code></td>
<td>Indicates that the network is unreachable.</td>
</tr>
<tr>
<td><code>WSAENETRESET</code></td>
<td>Indicates that the network connection has been reset.</td>
</tr>
<tr>
<td><code>WSAECONNABORTED</code></td>
<td>Indicates that the connection has been aborted.</td>
</tr>
<tr>
<td><code>WSAECONNRESET</code></td>
<td>Indicates that the connection has been reset by the peer.</td>
</tr>
<tr>
<td><code>WSAENOBUFS</code></td>
<td>Indicates that there is no buffer space available.</td>
</tr>
<tr>
<td><code>WSAEISCONN</code></td>
<td>Indicates that the socket is already connected.</td>
</tr>
<tr>
<td><code>WSAENOTCONN</code></td>
<td>Indicates that the socket is not connected.</td>
</tr>
<tr>
<td><code>WSAESHUTDOWN</code></td>
<td>Indicates that data cannot be sent after the socket has been
shutdown.</td>
</tr>
<tr>
<td><code>WSAETOOMANYREFS</code></td>
<td>Indicates that there are too many references.</td>
</tr>
<tr>
<td><code>WSAETIMEDOUT</code></td>
<td>Indicates that the connection has timed out.</td>
</tr>
<tr>
<td><code>WSAECONNREFUSED</code></td>
<td>Indicates that the connection has been refused.</td>
</tr>
<tr>
<td><code>WSAELOOP</code></td>
<td>Indicates that a name cannot be translated.</td>
</tr>
<tr>
<td><code>WSAENAMETOOLONG</code></td>
<td>Indicates that a name was too long.</td>
</tr>
<tr>
<td><code>WSAEHOSTDOWN</code></td>
<td>Indicates that a network host is down.</td>
</tr>
<tr>
<td><code>WSAEHOSTUNREACH</code></td>
<td>Indicates that there is no route to a network host.</td>
</tr>
<tr>
<td><code>WSAENOTEMPTY</code></td>
<td>Indicates that the directory is not empty.</td>
</tr>
<tr>
<td><code>WSAEPROCLIM</code></td>
<td>Indicates that there are too many processes.</td>
</tr>
<tr>
<td><code>WSAEUSERS</code></td>
<td>Indicates that the user quota has been exceeded.</td>
</tr>
<tr>
<td><code>WSAEDQUOT</code></td>
<td>Indicates that the disk quota has been exceeded.</td>
</tr>
<tr>
<td><code>WSAESTALE</code></td>
<td>Indicates a stale file handle reference.</td>
</tr>
<tr>
<td><code>WSAEREMOTE</code></td>
<td>Indicates that the item is remote.</td>
</tr>
<tr>
<td><code>WSASYSNOTREADY</code></td>
<td>Indicates that the network subsystem is not ready.</td>
</tr>
<tr>
<td><code>WSAVERNOTSUPPORTED</code></td>
<td>Indicates that the <code>winsock.dll</code> version is out of
range.</td>
</tr>
<tr>
<td><code>WSANOTINITIALISED</code></td>
<td>Indicates that successful WSAStartup has not yet been performed.</td>
</tr>
<tr>
<td><code>WSAEDISCON</code></td>
<td>Indicates that a graceful shutdown is in progress.</td>
</tr>
<tr>
<td><code>WSAENOMORE</code></td>
<td>Indicates that there are no more results.</td>
</tr>
<tr>
<td><code>WSAECANCELLED</code></td>
<td>Indicates that an operation has been canceled.</td>
</tr>
<tr>
<td><code>WSAEINVALIDPROCTABLE</code></td>
<td>Indicates that the procedure call table is invalid.</td>
</tr>
<tr>
<td><code>WSAEINVALIDPROVIDER</code></td>
<td>Indicates an invalid service provider.</td>
</tr>
<tr>
<td><code>WSAEPROVIDERFAILEDINIT</code></td>
<td>Indicates that the service provider failed to initialized.</td>
</tr>
<tr>
<td><code>WSASYSCALLFAILURE</code></td>
<td>Indicates a system call failure.</td>
</tr>
<tr>
<td><code>WSASERVICE_NOT_FOUND</code></td>
<td>Indicates that a service was not found.</td>
</tr>
<tr>
<td><code>WSATYPE_NOT_FOUND</code></td>
<td>Indicates that a class type was not found.</td>
</tr>
<tr>
<td><code>WSA_E_NO_MORE</code></td>
<td>Indicates that there are no more results.</td>
</tr>
<tr>
<td><code>WSA_E_CANCELLED</code></td>
<td>Indicates that the call was canceled.</td>
</tr>
<tr>
<td><code>WSAEREFUSED</code></td>
<td>Indicates that a database query was refused.</td>
</tr>
</tbody></table>
<h4>dlopen constants<span><a class="mark" href="#dlopen-constants" id="dlopen-constants">#</a></span><a aria-hidden="true" class="legacy" id="os_dlopen_constants"></a></h4>
<p>If available on the operating system, the following constants
are exported in <code>os.constants.dlopen</code>. See <a href="http://man7.org/linux/man-pages/man3/dlopen.3.html"><code>dlopen(3)</code></a> for detailed
information.</p>
<table>
<tbody><tr>
<th>Constant</th>
<th>Description</th>
</tr>
<tr>
<td><code>RTLD_LAZY</code></td>
<td>Perform lazy binding. Node.js sets this flag by default.</td>
</tr>
<tr>
<td><code>RTLD_NOW</code></td>
<td>Resolve all undefined symbols in the library before dlopen(3)
returns.</td>
</tr>
<tr>
<td><code>RTLD_GLOBAL</code></td>
<td>Symbols defined by the library will be made available for symbol
resolution of subsequently loaded libraries.</td>
</tr>
<tr>
<td><code>RTLD_LOCAL</code></td>
<td>The converse of <code>RTLD_GLOBAL</code>. This is the default behavior
if neither flag is specified.</td>
</tr>
<tr>
<td><code>RTLD_DEEPBIND</code></td>
<td>Make a self-contained library use its own symbols in preference to
symbols from previously loaded libraries.</td>
</tr>
</tbody></table>
<h4>Priority constants<span><a class="mark" href="#priority-constants" id="priority-constants">#</a></span><a aria-hidden="true" class="legacy" id="os_priority_constants"></a></h4>
<div class="api_metadata">
<span>Added in: v10.10.0</span>
</div>
<p>The following process scheduling constants are exported by
<code>os.constants.priority</code>.</p>
<table>
<tbody><tr>
<th>Constant</th>
<th>Description</th>
</tr>
<tr>
<td><code>PRIORITY_LOW</code></td>
<td>The lowest process scheduling priority. This corresponds to
<code>IDLE_PRIORITY_CLASS</code> on Windows, and a nice value of
<code>19</code> on all other platforms.</td>
</tr>
<tr>
<td><code>PRIORITY_BELOW_NORMAL</code></td>
<td>The process scheduling priority above <code>PRIORITY_LOW</code> and
below <code>PRIORITY_NORMAL</code>. This corresponds to
<code>BELOW_NORMAL_PRIORITY_CLASS</code> on Windows, and a nice value of
<code>10</code> on all other platforms.</td>
</tr>
<tr>
<td><code>PRIORITY_NORMAL</code></td>
<td>The default process scheduling priority. This corresponds to
<code>NORMAL_PRIORITY_CLASS</code> on Windows, and a nice value of
<code>0</code> on all other platforms.</td>
</tr>
<tr>
<td><code>PRIORITY_ABOVE_NORMAL</code></td>
<td>The process scheduling priority above <code>PRIORITY_NORMAL</code> and
below <code>PRIORITY_HIGH</code>. This corresponds to
<code>ABOVE_NORMAL_PRIORITY_CLASS</code> on Windows, and a nice value of
<code>-7</code> on all other platforms.</td>
</tr>
<tr>
<td><code>PRIORITY_HIGH</code></td>
<td>The process scheduling priority above <code>PRIORITY_ABOVE_NORMAL</code>
and below <code>PRIORITY_HIGHEST</code>. This corresponds to
<code>HIGH_PRIORITY_CLASS</code> on Windows, and a nice value of
<code>-14</code> on all other platforms.</td>
</tr>
<tr>
<td><code>PRIORITY_HIGHEST</code></td>
<td>The highest process scheduling priority. This corresponds to
<code>REALTIME_PRIORITY_CLASS</code> on Windows, and a nice value of
<code>-20</code> on all other platforms.</td>
</tr>
</tbody></table>
<h4>libuv constants<span><a class="mark" href="#libuv-constants" id="libuv-constants">#</a></span><a aria-hidden="true" class="legacy" id="os_libuv_constants"></a></h4>
<table>
<tbody><tr>
<th>Constant</th>
<th>Description</th>
</tr>
<tr>
<td><code>UV_UDP_REUSEADDR</code></td>
<td></td>
</tr>
</tbody></table></section>
<!-- API END -->
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