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data-id="wasi" class="interior"> 971cb0ef41Sopenharmony_ci <header class="header"> 981cb0ef41Sopenharmony_ci <div class="header-container"> 991cb0ef41Sopenharmony_ci <h1>Node.js v18.20.1 documentation</h1> 1001cb0ef41Sopenharmony_ci <button class="theme-toggle-btn" id="theme-toggle-btn" title="Toggle dark mode/light mode" aria-label="Toggle dark mode/light mode" hidden> 1011cb0ef41Sopenharmony_ci <svg xmlns="http://www.w3.org/2000/svg" class="icon dark-icon" height="24" width="24"> 1021cb0ef41Sopenharmony_ci <path fill="none" d="M0 0h24v24H0z" /> 1031cb0ef41Sopenharmony_ci <path d="M11.1 12.08c-2.33-4.51-.5-8.48.53-10.07C6.27 2.2 1.98 6.59 1.98 12c0 .14.02.28.02.42.62-.27 1.29-.42 2-.42 1.66 0 3.18.83 4.1 2.15A4.01 4.01 0 0111 18c0 1.52-.87 2.83-2.12 3.51.98.32 2.03.5 3.11.5 3.5 0 6.58-1.8 8.37-4.52-2.36.23-6.98-.97-9.26-5.41z"/> 1041cb0ef41Sopenharmony_ci <path d="M7 16h-.18C6.4 14.84 5.3 14 4 14c-1.66 0-3 1.34-3 3s1.34 3 3 3h3c1.1 0 2-.9 2-2s-.9-2-2-2z"/> 1051cb0ef41Sopenharmony_ci </svg> 1061cb0ef41Sopenharmony_ci <svg xmlns="http://www.w3.org/2000/svg" class="icon light-icon" height="24" width="24"> 1071cb0ef41Sopenharmony_ci <path d="M0 0h24v24H0z" fill="none" /> 1081cb0ef41Sopenharmony_ci <path d="M6.76 4.84l-1.8-1.79-1.41 1.41 1.79 1.79 1.42-1.41zM4 10.5H1v2h3v-2zm9-9.95h-2V3.5h2V.55zm7.45 3.91l-1.41-1.41-1.79 1.79 1.41 1.41 1.79-1.79zm-3.21 13.7l1.79 1.8 1.41-1.41-1.8-1.79-1.4 1.4zM20 10.5v2h3v-2h-3zm-8-5c-3.31 0-6 2.69-6 6s2.69 6 6 6 6-2.69 6-6-2.69-6-6-6zm-1 16.95h2V19.5h-2v2.95zm-7.45-3.91l1.41 1.41 1.79-1.8-1.41-1.41-1.79 1.8z"/> 1091cb0ef41Sopenharmony_ci </svg> 1101cb0ef41Sopenharmony_ci </button> 1111cb0ef41Sopenharmony_ci </div> 1121cb0ef41Sopenharmony_ci <div id="gtoc"> 1131cb0ef41Sopenharmony_ci <ul> 1141cb0ef41Sopenharmony_ci <li class="pinned-header">Node.js v18.20.1</li> 1151cb0ef41Sopenharmony_ci 1161cb0ef41Sopenharmony_ci <li class="picker-header"> 1171cb0ef41Sopenharmony_ci <a href="#"> 1181cb0ef41Sopenharmony_ci <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 1191cb0ef41Sopenharmony_ci Table of contents 1201cb0ef41Sopenharmony_ci </a> 1211cb0ef41Sopenharmony_ci 1221cb0ef41Sopenharmony_ci <div class="picker"><div class="toc"><ul> 1231cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#webassembly-system-interface-wasi">WebAssembly System Interface (WASI)</a></span> 1241cb0ef41Sopenharmony_ci<ul> 1251cb0ef41Sopenharmony_ci<li><a href="#class-wasi">Class: <code>WASI</code></a> 1261cb0ef41Sopenharmony_ci<ul> 1271cb0ef41Sopenharmony_ci<li><a href="#new-wasioptions"><code>new WASI([options])</code></a></li> 1281cb0ef41Sopenharmony_ci<li><a href="#wasistartinstance"><code>wasi.start(instance)</code></a></li> 1291cb0ef41Sopenharmony_ci<li><a href="#wasiinitializeinstance"><code>wasi.initialize(instance)</code></a></li> 1301cb0ef41Sopenharmony_ci<li><a href="#wasiwasiimport"><code>wasi.wasiImport</code></a></li> 1311cb0ef41Sopenharmony_ci</ul> 1321cb0ef41Sopenharmony_ci</li> 1331cb0ef41Sopenharmony_ci</ul> 1341cb0ef41Sopenharmony_ci</li> 1351cb0ef41Sopenharmony_ci</ul></div></div> 1361cb0ef41Sopenharmony_ci </li> 1371cb0ef41Sopenharmony_ci 1381cb0ef41Sopenharmony_ci 1391cb0ef41Sopenharmony_ci <li class="picker-header"> 1401cb0ef41Sopenharmony_ci <a href="#"> 1411cb0ef41Sopenharmony_ci <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 1421cb0ef41Sopenharmony_ci Index 1431cb0ef41Sopenharmony_ci </a> 1441cb0ef41Sopenharmony_ci 1451cb0ef41Sopenharmony_ci <div class="picker"><ul> 1461cb0ef41Sopenharmony_ci<li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> 1471cb0ef41Sopenharmony_ci<li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> 1481cb0ef41Sopenharmony_ci 1491cb0ef41Sopenharmony_ci <li> 1501cb0ef41Sopenharmony_ci <a href="index.html">Index</a> 1511cb0ef41Sopenharmony_ci </li> 1521cb0ef41Sopenharmony_ci </ul> 1531cb0ef41Sopenharmony_ci 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class="nav-https-github-com-nodejs-node">Code repository and issue tracker</a></li> 2201cb0ef41Sopenharmony_ci</ul></div> 2211cb0ef41Sopenharmony_ci </li> 2221cb0ef41Sopenharmony_ci 2231cb0ef41Sopenharmony_ci 2241cb0ef41Sopenharmony_ci <li class="picker-header"> 2251cb0ef41Sopenharmony_ci <a href="#"> 2261cb0ef41Sopenharmony_ci <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 2271cb0ef41Sopenharmony_ci Other versions 2281cb0ef41Sopenharmony_ci </a> 2291cb0ef41Sopenharmony_ci <div class="picker"><ol id="alt-docs"><li><a href="https://nodejs.org/docs/latest-v21.x/api/wasi.html">21.x</a></li> 2301cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v20.x/api/wasi.html">20.x <b>LTS</b></a></li> 2311cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v19.x/api/wasi.html">19.x</a></li> 2321cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v18.x/api/wasi.html">18.x <b>LTS</b></a></li> 2331cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v17.x/api/wasi.html">17.x</a></li> 2341cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v16.x/api/wasi.html">16.x</a></li> 2351cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v15.x/api/wasi.html">15.x</a></li> 2361cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v14.x/api/wasi.html">14.x</a></li> 2371cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v13.x/api/wasi.html">13.x</a></li> 2381cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v12.x/api/wasi.html">12.x</a></li></ol></div> 2391cb0ef41Sopenharmony_ci </li> 2401cb0ef41Sopenharmony_ci 2411cb0ef41Sopenharmony_ci <li class="picker-header"> 2421cb0ef41Sopenharmony_ci <a href="#"> 2431cb0ef41Sopenharmony_ci <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 2441cb0ef41Sopenharmony_ci Options 2451cb0ef41Sopenharmony_ci </a> 2461cb0ef41Sopenharmony_ci 2471cb0ef41Sopenharmony_ci <div class="picker"> 2481cb0ef41Sopenharmony_ci <ul> 2491cb0ef41Sopenharmony_ci <li> 2501cb0ef41Sopenharmony_ci <a href="all.html">View on single page</a> 2511cb0ef41Sopenharmony_ci </li> 2521cb0ef41Sopenharmony_ci <li> 2531cb0ef41Sopenharmony_ci <a href="wasi.json">View as JSON</a> 2541cb0ef41Sopenharmony_ci </li> 2551cb0ef41Sopenharmony_ci <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/main/doc/api/wasi.md">Edit on GitHub</a></li> 2561cb0ef41Sopenharmony_ci </ul> 2571cb0ef41Sopenharmony_ci </div> 2581cb0ef41Sopenharmony_ci </li> 2591cb0ef41Sopenharmony_ci </ul> 2601cb0ef41Sopenharmony_ci </div> 2611cb0ef41Sopenharmony_ci <hr> 2621cb0ef41Sopenharmony_ci </header> 2631cb0ef41Sopenharmony_ci 2641cb0ef41Sopenharmony_ci <details id="toc" open><summary>Table of contents</summary><ul> 2651cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#webassembly-system-interface-wasi">WebAssembly System Interface (WASI)</a></span> 2661cb0ef41Sopenharmony_ci<ul> 2671cb0ef41Sopenharmony_ci<li><a href="#class-wasi">Class: <code>WASI</code></a> 2681cb0ef41Sopenharmony_ci<ul> 2691cb0ef41Sopenharmony_ci<li><a href="#new-wasioptions"><code>new WASI([options])</code></a></li> 2701cb0ef41Sopenharmony_ci<li><a href="#wasistartinstance"><code>wasi.start(instance)</code></a></li> 2711cb0ef41Sopenharmony_ci<li><a href="#wasiinitializeinstance"><code>wasi.initialize(instance)</code></a></li> 2721cb0ef41Sopenharmony_ci<li><a href="#wasiwasiimport"><code>wasi.wasiImport</code></a></li> 2731cb0ef41Sopenharmony_ci</ul> 2741cb0ef41Sopenharmony_ci</li> 2751cb0ef41Sopenharmony_ci</ul> 2761cb0ef41Sopenharmony_ci</li> 2771cb0ef41Sopenharmony_ci</ul></details> 2781cb0ef41Sopenharmony_ci 2791cb0ef41Sopenharmony_ci <div id="apicontent"> 2801cb0ef41Sopenharmony_ci <h2>WebAssembly System Interface (WASI)<span><a class="mark" href="#webassembly-system-interface-wasi" id="webassembly-system-interface-wasi">#</a></span><a aria-hidden="true" class="legacy" id="wasi_webassembly_system_interface_wasi"></a></h2> 2811cb0ef41Sopenharmony_ci 2821cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 2831cb0ef41Sopenharmony_ci<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v18.20.1/lib/wasi.js">lib/wasi.js</a></p> 2841cb0ef41Sopenharmony_ci<p>The WASI API provides an implementation of the <a href="https://wasi.dev/">WebAssembly System Interface</a> 2851cb0ef41Sopenharmony_cispecification. WASI gives sandboxed WebAssembly applications access to the 2861cb0ef41Sopenharmony_ciunderlying operating system via a collection of POSIX-like functions.</p> 2871cb0ef41Sopenharmony_ci 2881cb0ef41Sopenharmony_ci<pre class="with-49-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { readFile } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:fs/promises'</span>; 2891cb0ef41Sopenharmony_ci<span class="hljs-keyword">import</span> { <span class="hljs-variable constant_">WASI</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'wasi'</span>; 2901cb0ef41Sopenharmony_ci<span class="hljs-keyword">import</span> { argv, env } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2911cb0ef41Sopenharmony_ci 2921cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> wasi = <span class="hljs-keyword">new</span> <span class="hljs-title function_">WASI</span>({ 2931cb0ef41Sopenharmony_ci <span class="hljs-attr">args</span>: argv, 2941cb0ef41Sopenharmony_ci env, 2951cb0ef41Sopenharmony_ci <span class="hljs-attr">preopens</span>: { 2961cb0ef41Sopenharmony_ci <span class="hljs-string">'/sandbox'</span>: <span class="hljs-string">'/some/real/path/that/wasm/can/access'</span>, 2971cb0ef41Sopenharmony_ci }, 2981cb0ef41Sopenharmony_ci}); 2991cb0ef41Sopenharmony_ci 3001cb0ef41Sopenharmony_ci<span class="hljs-comment">// Some WASI binaries require:</span> 3011cb0ef41Sopenharmony_ci<span class="hljs-comment">// const importObject = { wasi_unstable: wasi.wasiImport };</span> 3021cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> importObject = { <span class="hljs-attr">wasi_snapshot_preview1</span>: wasi.<span class="hljs-property">wasiImport</span> }; 3031cb0ef41Sopenharmony_ci 3041cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> wasm = <span class="hljs-keyword">await</span> <span class="hljs-title class_">WebAssembly</span>.<span class="hljs-title function_">compile</span>( 3051cb0ef41Sopenharmony_ci <span class="hljs-keyword">await</span> <span class="hljs-title function_">readFile</span>(<span class="hljs-keyword">new</span> <span class="hljs-title function_">URL</span>(<span class="hljs-string">'./demo.wasm'</span>, <span class="hljs-keyword">import</span>.<span class="hljs-property">meta</span>.<span class="hljs-property">url</span>)), 3061cb0ef41Sopenharmony_ci); 3071cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> instance = <span class="hljs-keyword">await</span> <span class="hljs-title class_">WebAssembly</span>.<span class="hljs-title function_">instantiate</span>(wasm, importObject); 3081cb0ef41Sopenharmony_ci 3091cb0ef41Sopenharmony_ciwasi.<span class="hljs-title function_">start</span>(instance);</code><code class="language-js cjs"><span class="hljs-meta">'use strict'</span>; 3101cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> { readFile } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:fs/promises'</span>); 3111cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> { <span class="hljs-variable constant_">WASI</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'wasi'</span>); 3121cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> { argv, env } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3131cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> { join } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:path'</span>); 3141cb0ef41Sopenharmony_ci 3151cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> wasi = <span class="hljs-keyword">new</span> <span class="hljs-title function_">WASI</span>({ 3161cb0ef41Sopenharmony_ci <span class="hljs-attr">args</span>: argv, 3171cb0ef41Sopenharmony_ci env, 3181cb0ef41Sopenharmony_ci <span class="hljs-attr">preopens</span>: { 3191cb0ef41Sopenharmony_ci <span class="hljs-string">'/sandbox'</span>: <span class="hljs-string">'/some/real/path/that/wasm/can/access'</span>, 3201cb0ef41Sopenharmony_ci }, 3211cb0ef41Sopenharmony_ci}); 3221cb0ef41Sopenharmony_ci 3231cb0ef41Sopenharmony_ci<span class="hljs-comment">// Some WASI binaries require:</span> 3241cb0ef41Sopenharmony_ci<span class="hljs-comment">// const importObject = { wasi_unstable: wasi.wasiImport };</span> 3251cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> importObject = { <span class="hljs-attr">wasi_snapshot_preview1</span>: wasi.<span class="hljs-property">wasiImport</span> }; 3261cb0ef41Sopenharmony_ci 3271cb0ef41Sopenharmony_ci(<span class="hljs-keyword">async</span> () => { 3281cb0ef41Sopenharmony_ci <span class="hljs-keyword">const</span> wasm = <span class="hljs-keyword">await</span> <span class="hljs-title class_">WebAssembly</span>.<span class="hljs-title function_">compile</span>( 3291cb0ef41Sopenharmony_ci <span class="hljs-keyword">await</span> <span class="hljs-title function_">readFile</span>(<span class="hljs-title function_">join</span>(__dirname, <span class="hljs-string">'demo.wasm'</span>)), 3301cb0ef41Sopenharmony_ci ); 3311cb0ef41Sopenharmony_ci <span class="hljs-keyword">const</span> instance = <span class="hljs-keyword">await</span> <span class="hljs-title class_">WebAssembly</span>.<span class="hljs-title function_">instantiate</span>(wasm, importObject); 3321cb0ef41Sopenharmony_ci 3331cb0ef41Sopenharmony_ci wasi.<span class="hljs-title function_">start</span>(instance); 3341cb0ef41Sopenharmony_ci})();</code><button class="copy-button">copy</button></pre> 3351cb0ef41Sopenharmony_ci<p>To run the above example, create a new WebAssembly text format file named 3361cb0ef41Sopenharmony_ci<code>demo.wat</code>:</p> 3371cb0ef41Sopenharmony_ci<pre><code class="language-text">(module 3381cb0ef41Sopenharmony_ci ;; Import the required fd_write WASI function which will write the given io vectors to stdout 3391cb0ef41Sopenharmony_ci ;; The function signature for fd_write is: 3401cb0ef41Sopenharmony_ci ;; (File Descriptor, *iovs, iovs_len, nwritten) -> Returns number of bytes written 3411cb0ef41Sopenharmony_ci (import "wasi_snapshot_preview1" "fd_write" (func $fd_write (param i32 i32 i32 i32) (result i32))) 3421cb0ef41Sopenharmony_ci 3431cb0ef41Sopenharmony_ci (memory 1) 3441cb0ef41Sopenharmony_ci (export "memory" (memory 0)) 3451cb0ef41Sopenharmony_ci 3461cb0ef41Sopenharmony_ci ;; Write 'hello world\n' to memory at an offset of 8 bytes 3471cb0ef41Sopenharmony_ci ;; Note the trailing newline which is required for the text to appear 3481cb0ef41Sopenharmony_ci (data (i32.const 8) "hello world\n") 3491cb0ef41Sopenharmony_ci 3501cb0ef41Sopenharmony_ci (func $main (export "_start") 3511cb0ef41Sopenharmony_ci ;; Creating a new io vector within linear memory 3521cb0ef41Sopenharmony_ci (i32.store (i32.const 0) (i32.const 8)) ;; iov.iov_base - This is a pointer to the start of the 'hello world\n' string 3531cb0ef41Sopenharmony_ci (i32.store (i32.const 4) (i32.const 12)) ;; iov.iov_len - The length of the 'hello world\n' string 3541cb0ef41Sopenharmony_ci 3551cb0ef41Sopenharmony_ci (call $fd_write 3561cb0ef41Sopenharmony_ci (i32.const 1) ;; file_descriptor - 1 for stdout 3571cb0ef41Sopenharmony_ci (i32.const 0) ;; *iovs - The pointer to the iov array, which is stored at memory location 0 3581cb0ef41Sopenharmony_ci (i32.const 1) ;; iovs_len - We're printing 1 string stored in an iov - so one. 3591cb0ef41Sopenharmony_ci (i32.const 20) ;; nwritten - A place in memory to store the number of bytes written 3601cb0ef41Sopenharmony_ci ) 3611cb0ef41Sopenharmony_ci drop ;; Discard the number of bytes written from the top of the stack 3621cb0ef41Sopenharmony_ci ) 3631cb0ef41Sopenharmony_ci)</code> <button class="copy-button">copy</button></pre> 3641cb0ef41Sopenharmony_ci<p>Use <a href="https://github.com/WebAssembly/wabt">wabt</a> to compile <code>.wat</code> to <code>.wasm</code></p> 3651cb0ef41Sopenharmony_ci<pre><code class="language-console"><span class="hljs-meta prompt_">$ </span><span class="language-bash">wat2wasm demo.wat</span></code> <button class="copy-button">copy</button></pre> 3661cb0ef41Sopenharmony_ci<section><h3>Class: <code>WASI</code><span><a class="mark" href="#class-wasi" id="class-wasi">#</a></span><a aria-hidden="true" class="legacy" id="wasi_class_wasi"></a></h3> 3671cb0ef41Sopenharmony_ci<div class="api_metadata"> 3681cb0ef41Sopenharmony_ci<span>Added in: v13.3.0, v12.16.0</span> 3691cb0ef41Sopenharmony_ci</div> 3701cb0ef41Sopenharmony_ci<p>The <code>WASI</code> class provides the WASI system call API and additional convenience 3711cb0ef41Sopenharmony_cimethods for working with WASI-based applications. Each <code>WASI</code> instance 3721cb0ef41Sopenharmony_cirepresents a distinct sandbox environment. For security purposes, each <code>WASI</code> 3731cb0ef41Sopenharmony_ciinstance must have its command-line arguments, environment variables, and 3741cb0ef41Sopenharmony_cisandbox directory structure configured explicitly.</p> 3751cb0ef41Sopenharmony_ci<h4><code>new WASI([options])</code><span><a class="mark" href="#new-wasioptions" id="new-wasioptions">#</a></span><a aria-hidden="true" class="legacy" id="wasi_new_wasi_options"></a></h4> 3761cb0ef41Sopenharmony_ci<div class="api_metadata"> 3771cb0ef41Sopenharmony_ci<span>Added in: v13.3.0, v12.16.0</span> 3781cb0ef41Sopenharmony_ci</div> 3791cb0ef41Sopenharmony_ci<ul> 3801cb0ef41Sopenharmony_ci<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 3811cb0ef41Sopenharmony_ci<ul> 3821cb0ef41Sopenharmony_ci<li><code>args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" class="type"><Array></a> An array of strings that the WebAssembly application will 3831cb0ef41Sopenharmony_cisee as command-line arguments. The first argument is the virtual path to the 3841cb0ef41Sopenharmony_ciWASI command itself. <strong>Default:</strong> <code>[]</code>.</li> 3851cb0ef41Sopenharmony_ci<li><code>env</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> An object similar to <code>process.env</code> that the WebAssembly 3861cb0ef41Sopenharmony_ciapplication will see as its environment. <strong>Default:</strong> <code>{}</code>.</li> 3871cb0ef41Sopenharmony_ci<li><code>preopens</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> This object represents the WebAssembly application's 3881cb0ef41Sopenharmony_cisandbox directory structure. The string keys of <code>preopens</code> are treated as 3891cb0ef41Sopenharmony_cidirectories within the sandbox. The corresponding values in <code>preopens</code> are 3901cb0ef41Sopenharmony_cithe real paths to those directories on the host machine.</li> 3911cb0ef41Sopenharmony_ci<li><code>returnOnExit</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> By default, WASI applications terminate the Node.js 3921cb0ef41Sopenharmony_ciprocess via the <code>__wasi_proc_exit()</code> function. Setting this option to <code>true</code> 3931cb0ef41Sopenharmony_cicauses <code>wasi.start()</code> to return the exit code rather than terminate the 3941cb0ef41Sopenharmony_ciprocess. <strong>Default:</strong> <code>false</code>.</li> 3951cb0ef41Sopenharmony_ci<li><code>stdin</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The file descriptor used as standard input in the 3961cb0ef41Sopenharmony_ciWebAssembly application. <strong>Default:</strong> <code>0</code>.</li> 3971cb0ef41Sopenharmony_ci<li><code>stdout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The file descriptor used as standard output in the 3981cb0ef41Sopenharmony_ciWebAssembly application. <strong>Default:</strong> <code>1</code>.</li> 3991cb0ef41Sopenharmony_ci<li><code>stderr</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The file descriptor used as standard error in the 4001cb0ef41Sopenharmony_ciWebAssembly application. <strong>Default:</strong> <code>2</code>.</li> 4011cb0ef41Sopenharmony_ci</ul> 4021cb0ef41Sopenharmony_ci</li> 4031cb0ef41Sopenharmony_ci</ul> 4041cb0ef41Sopenharmony_ci<h4><code>wasi.start(instance)</code><span><a class="mark" href="#wasistartinstance" id="wasistartinstance">#</a></span><a aria-hidden="true" class="legacy" id="wasi_wasi_start_instance"></a></h4> 4051cb0ef41Sopenharmony_ci<div class="api_metadata"> 4061cb0ef41Sopenharmony_ci<span>Added in: v13.3.0, v12.16.0</span> 4071cb0ef41Sopenharmony_ci</div> 4081cb0ef41Sopenharmony_ci<ul> 4091cb0ef41Sopenharmony_ci<li><code>instance</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Instance" class="type"><WebAssembly.Instance></a></li> 4101cb0ef41Sopenharmony_ci</ul> 4111cb0ef41Sopenharmony_ci<p>Attempt to begin execution of <code>instance</code> as a WASI command by invoking its 4121cb0ef41Sopenharmony_ci<code>_start()</code> export. If <code>instance</code> does not contain a <code>_start()</code> export, or if 4131cb0ef41Sopenharmony_ci<code>instance</code> contains an <code>_initialize()</code> export, then an exception is thrown.</p> 4141cb0ef41Sopenharmony_ci<p><code>start()</code> requires that <code>instance</code> exports a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Memory"><code>WebAssembly.Memory</code></a> named 4151cb0ef41Sopenharmony_ci<code>memory</code>. If <code>instance</code> does not have a <code>memory</code> export an exception is thrown.</p> 4161cb0ef41Sopenharmony_ci<p>If <code>start()</code> is called more than once, an exception is thrown.</p> 4171cb0ef41Sopenharmony_ci<h4><code>wasi.initialize(instance)</code><span><a class="mark" href="#wasiinitializeinstance" id="wasiinitializeinstance">#</a></span><a aria-hidden="true" class="legacy" id="wasi_wasi_initialize_instance"></a></h4> 4181cb0ef41Sopenharmony_ci<div class="api_metadata"> 4191cb0ef41Sopenharmony_ci<span>Added in: v14.6.0, v12.19.0</span> 4201cb0ef41Sopenharmony_ci</div> 4211cb0ef41Sopenharmony_ci<ul> 4221cb0ef41Sopenharmony_ci<li><code>instance</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Instance" class="type"><WebAssembly.Instance></a></li> 4231cb0ef41Sopenharmony_ci</ul> 4241cb0ef41Sopenharmony_ci<p>Attempt to initialize <code>instance</code> as a WASI reactor by invoking its 4251cb0ef41Sopenharmony_ci<code>_initialize()</code> export, if it is present. If <code>instance</code> contains a <code>_start()</code> 4261cb0ef41Sopenharmony_ciexport, then an exception is thrown.</p> 4271cb0ef41Sopenharmony_ci<p><code>initialize()</code> requires that <code>instance</code> exports a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Memory"><code>WebAssembly.Memory</code></a> named 4281cb0ef41Sopenharmony_ci<code>memory</code>. If <code>instance</code> does not have a <code>memory</code> export an exception is thrown.</p> 4291cb0ef41Sopenharmony_ci<p>If <code>initialize()</code> is called more than once, an exception is thrown.</p> 4301cb0ef41Sopenharmony_ci<h4><code>wasi.wasiImport</code><span><a class="mark" href="#wasiwasiimport" id="wasiwasiimport">#</a></span><a aria-hidden="true" class="legacy" id="wasi_wasi_wasiimport"></a></h4> 4311cb0ef41Sopenharmony_ci<div class="api_metadata"> 4321cb0ef41Sopenharmony_ci<span>Added in: v13.3.0, v12.16.0</span> 4331cb0ef41Sopenharmony_ci</div> 4341cb0ef41Sopenharmony_ci<ul> 4351cb0ef41Sopenharmony_ci<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 4361cb0ef41Sopenharmony_ci</ul> 4371cb0ef41Sopenharmony_ci<p><code>wasiImport</code> is an object that implements the WASI system call API. This object 4381cb0ef41Sopenharmony_cishould be passed as the <code>wasi_snapshot_preview1</code> import during the instantiation 4391cb0ef41Sopenharmony_ciof a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Instance"><code>WebAssembly.Instance</code></a>.</p></section> 4401cb0ef41Sopenharmony_ci <!-- API END --> 4411cb0ef41Sopenharmony_ci </div> 4421cb0ef41Sopenharmony_ci </div> 4431cb0ef41Sopenharmony_ci </div> 4441cb0ef41Sopenharmony_ci</body> 4451cb0ef41Sopenharmony_ci</html> 446