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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_2"><a href="#child-process">Child process</a></span> 1241cb0ef41Sopenharmony_ci<ul> 1251cb0ef41Sopenharmony_ci<li><a href="#asynchronous-process-creation">Asynchronous process creation</a> 1261cb0ef41Sopenharmony_ci<ul> 1271cb0ef41Sopenharmony_ci<li><a href="#spawning-bat-and-cmd-files-on-windows">Spawning <code>.bat</code> and <code>.cmd</code> files on Windows</a></li> 1281cb0ef41Sopenharmony_ci<li><a href="#child_processexeccommand-options-callback"><code>child_process.exec(command[, options][, callback])</code></a></li> 1291cb0ef41Sopenharmony_ci<li><a href="#child_processexecfilefile-args-options-callback"><code>child_process.execFile(file[, args][, options][, callback])</code></a></li> 1301cb0ef41Sopenharmony_ci<li><a href="#child_processforkmodulepath-args-options"><code>child_process.fork(modulePath[, args][, options])</code></a></li> 1311cb0ef41Sopenharmony_ci<li><a href="#child_processspawncommand-args-options"><code>child_process.spawn(command[, args][, options])</code></a> 1321cb0ef41Sopenharmony_ci<ul> 1331cb0ef41Sopenharmony_ci<li><a href="#optionsdetached"><code>options.detached</code></a></li> 1341cb0ef41Sopenharmony_ci<li><a href="#optionsstdio"><code>options.stdio</code></a></li> 1351cb0ef41Sopenharmony_ci</ul> 1361cb0ef41Sopenharmony_ci</li> 1371cb0ef41Sopenharmony_ci</ul> 1381cb0ef41Sopenharmony_ci</li> 1391cb0ef41Sopenharmony_ci<li><a href="#synchronous-process-creation">Synchronous process creation</a> 1401cb0ef41Sopenharmony_ci<ul> 1411cb0ef41Sopenharmony_ci<li><a href="#child_processexecfilesyncfile-args-options"><code>child_process.execFileSync(file[, args][, options])</code></a></li> 1421cb0ef41Sopenharmony_ci<li><a href="#child_processexecsynccommand-options"><code>child_process.execSync(command[, options])</code></a></li> 1431cb0ef41Sopenharmony_ci<li><a href="#child_processspawnsynccommand-args-options"><code>child_process.spawnSync(command[, args][, options])</code></a></li> 1441cb0ef41Sopenharmony_ci</ul> 1451cb0ef41Sopenharmony_ci</li> 1461cb0ef41Sopenharmony_ci<li><a href="#class-childprocess">Class: <code>ChildProcess</code></a> 1471cb0ef41Sopenharmony_ci<ul> 1481cb0ef41Sopenharmony_ci<li><a href="#event-close">Event: <code>'close'</code></a></li> 1491cb0ef41Sopenharmony_ci<li><a href="#event-disconnect">Event: <code>'disconnect'</code></a></li> 1501cb0ef41Sopenharmony_ci<li><a href="#event-error">Event: <code>'error'</code></a></li> 1511cb0ef41Sopenharmony_ci<li><a href="#event-exit">Event: <code>'exit'</code></a></li> 1521cb0ef41Sopenharmony_ci<li><a href="#event-message">Event: <code>'message'</code></a></li> 1531cb0ef41Sopenharmony_ci<li><a href="#event-spawn">Event: <code>'spawn'</code></a></li> 1541cb0ef41Sopenharmony_ci<li><a href="#subprocesschannel"><code>subprocess.channel</code></a> 1551cb0ef41Sopenharmony_ci<ul> 1561cb0ef41Sopenharmony_ci<li><a href="#subprocesschannelref"><code>subprocess.channel.ref()</code></a></li> 1571cb0ef41Sopenharmony_ci<li><a href="#subprocesschannelunref"><code>subprocess.channel.unref()</code></a></li> 1581cb0ef41Sopenharmony_ci</ul> 1591cb0ef41Sopenharmony_ci</li> 1601cb0ef41Sopenharmony_ci<li><a href="#subprocessconnected"><code>subprocess.connected</code></a></li> 1611cb0ef41Sopenharmony_ci<li><a href="#subprocessdisconnect"><code>subprocess.disconnect()</code></a></li> 1621cb0ef41Sopenharmony_ci<li><a href="#subprocessexitcode"><code>subprocess.exitCode</code></a></li> 1631cb0ef41Sopenharmony_ci<li><a href="#subprocesskillsignal"><code>subprocess.kill([signal])</code></a></li> 1641cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#subprocesssymboldispose"><code>subprocess[Symbol.dispose]()</code></a></span></li> 1651cb0ef41Sopenharmony_ci<li><a href="#subprocesskilled"><code>subprocess.killed</code></a></li> 1661cb0ef41Sopenharmony_ci<li><a href="#subprocesspid"><code>subprocess.pid</code></a></li> 1671cb0ef41Sopenharmony_ci<li><a href="#subprocessref"><code>subprocess.ref()</code></a></li> 1681cb0ef41Sopenharmony_ci<li><a href="#subprocesssendmessage-sendhandle-options-callback"><code>subprocess.send(message[, sendHandle[, options]][, callback])</code></a> 1691cb0ef41Sopenharmony_ci<ul> 1701cb0ef41Sopenharmony_ci<li><a href="#example-sending-a-server-object">Example: sending a server object</a></li> 1711cb0ef41Sopenharmony_ci<li><a href="#example-sending-a-socket-object">Example: sending a socket object</a></li> 1721cb0ef41Sopenharmony_ci</ul> 1731cb0ef41Sopenharmony_ci</li> 1741cb0ef41Sopenharmony_ci<li><a href="#subprocesssignalcode"><code>subprocess.signalCode</code></a></li> 1751cb0ef41Sopenharmony_ci<li><a href="#subprocessspawnargs"><code>subprocess.spawnargs</code></a></li> 1761cb0ef41Sopenharmony_ci<li><a href="#subprocessspawnfile"><code>subprocess.spawnfile</code></a></li> 1771cb0ef41Sopenharmony_ci<li><a href="#subprocessstderr"><code>subprocess.stderr</code></a></li> 1781cb0ef41Sopenharmony_ci<li><a href="#subprocessstdin"><code>subprocess.stdin</code></a></li> 1791cb0ef41Sopenharmony_ci<li><a href="#subprocessstdio"><code>subprocess.stdio</code></a></li> 1801cb0ef41Sopenharmony_ci<li><a href="#subprocessstdout"><code>subprocess.stdout</code></a></li> 1811cb0ef41Sopenharmony_ci<li><a href="#subprocessunref"><code>subprocess.unref()</code></a></li> 1821cb0ef41Sopenharmony_ci</ul> 1831cb0ef41Sopenharmony_ci</li> 1841cb0ef41Sopenharmony_ci<li><a href="#maxbuffer-and-unicode"><code>maxBuffer</code> and Unicode</a></li> 1851cb0ef41Sopenharmony_ci<li><a href="#shell-requirements">Shell requirements</a></li> 1861cb0ef41Sopenharmony_ci<li><a href="#default-windows-shell">Default Windows shell</a></li> 1871cb0ef41Sopenharmony_ci<li><a href="#advanced-serialization">Advanced serialization</a></li> 1881cb0ef41Sopenharmony_ci</ul> 1891cb0ef41Sopenharmony_ci</li> 1901cb0ef41Sopenharmony_ci</ul></div></div> 1911cb0ef41Sopenharmony_ci </li> 1921cb0ef41Sopenharmony_ci 1931cb0ef41Sopenharmony_ci 1941cb0ef41Sopenharmony_ci <li class="picker-header"> 1951cb0ef41Sopenharmony_ci <a href="#"> 1961cb0ef41Sopenharmony_ci <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 1971cb0ef41Sopenharmony_ci Index 1981cb0ef41Sopenharmony_ci </a> 1991cb0ef41Sopenharmony_ci 2001cb0ef41Sopenharmony_ci <div class="picker"><ul> 2011cb0ef41Sopenharmony_ci<li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> 2021cb0ef41Sopenharmony_ci<li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> 2031cb0ef41Sopenharmony_ci 2041cb0ef41Sopenharmony_ci <li> 2051cb0ef41Sopenharmony_ci <a href="index.html">Index</a> 2061cb0ef41Sopenharmony_ci </li> 2071cb0ef41Sopenharmony_ci </ul> 2081cb0ef41Sopenharmony_ci 2091cb0ef41Sopenharmony_ci<hr class="line"> 2101cb0ef41Sopenharmony_ci<ul> 2111cb0ef41Sopenharmony_ci<li><a href="assert.html" class="nav-assert">Assertion testing</a></li> 2121cb0ef41Sopenharmony_ci<li><a href="async_context.html" class="nav-async_context">Asynchronous context tracking</a></li> 2131cb0ef41Sopenharmony_ci<li><a href="async_hooks.html" class="nav-async_hooks">Async hooks</a></li> 2141cb0ef41Sopenharmony_ci<li><a href="buffer.html" class="nav-buffer">Buffer</a></li> 2151cb0ef41Sopenharmony_ci<li><a href="addons.html" class="nav-addons">C++ addons</a></li> 2161cb0ef41Sopenharmony_ci<li><a href="n-api.html" class="nav-n-api">C/C++ addons with Node-API</a></li> 2171cb0ef41Sopenharmony_ci<li><a href="embedding.html" class="nav-embedding">C++ embedder API</a></li> 2181cb0ef41Sopenharmony_ci<li><a href="child_process.html" class="nav-child_process active">Child processes</a></li> 2191cb0ef41Sopenharmony_ci<li><a href="cluster.html" class="nav-cluster">Cluster</a></li> 2201cb0ef41Sopenharmony_ci<li><a href="cli.html" class="nav-cli">Command-line 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2761cb0ef41Sopenharmony_ci </li> 2771cb0ef41Sopenharmony_ci 2781cb0ef41Sopenharmony_ci 2791cb0ef41Sopenharmony_ci <li class="picker-header"> 2801cb0ef41Sopenharmony_ci <a href="#"> 2811cb0ef41Sopenharmony_ci <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 2821cb0ef41Sopenharmony_ci Other versions 2831cb0ef41Sopenharmony_ci </a> 2841cb0ef41Sopenharmony_ci <div class="picker"><ol id="alt-docs"><li><a href="https://nodejs.org/docs/latest-v21.x/api/child_process.html">21.x</a></li> 2851cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v20.x/api/child_process.html">20.x <b>LTS</b></a></li> 2861cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v19.x/api/child_process.html">19.x</a></li> 2871cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v18.x/api/child_process.html">18.x <b>LTS</b></a></li> 2881cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v17.x/api/child_process.html">17.x</a></li> 2891cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v16.x/api/child_process.html">16.x</a></li> 2901cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v15.x/api/child_process.html">15.x</a></li> 2911cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v14.x/api/child_process.html">14.x</a></li> 2921cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v13.x/api/child_process.html">13.x</a></li> 2931cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v12.x/api/child_process.html">12.x</a></li> 2941cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v11.x/api/child_process.html">11.x</a></li> 2951cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v10.x/api/child_process.html">10.x</a></li> 2961cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v9.x/api/child_process.html">9.x</a></li> 2971cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v8.x/api/child_process.html">8.x</a></li> 2981cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v7.x/api/child_process.html">7.x</a></li> 2991cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v6.x/api/child_process.html">6.x</a></li> 3001cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v5.x/api/child_process.html">5.x</a></li> 3011cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v4.x/api/child_process.html">4.x</a></li> 3021cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v0.12.x/api/child_process.html">0.12.x</a></li> 3031cb0ef41Sopenharmony_ci<li><a href="https://nodejs.org/docs/latest-v0.10.x/api/child_process.html">0.10.x</a></li></ol></div> 3041cb0ef41Sopenharmony_ci </li> 3051cb0ef41Sopenharmony_ci 3061cb0ef41Sopenharmony_ci <li class="picker-header"> 3071cb0ef41Sopenharmony_ci <a href="#"> 3081cb0ef41Sopenharmony_ci <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 3091cb0ef41Sopenharmony_ci Options 3101cb0ef41Sopenharmony_ci </a> 3111cb0ef41Sopenharmony_ci 3121cb0ef41Sopenharmony_ci <div class="picker"> 3131cb0ef41Sopenharmony_ci <ul> 3141cb0ef41Sopenharmony_ci <li> 3151cb0ef41Sopenharmony_ci <a href="all.html">View on single page</a> 3161cb0ef41Sopenharmony_ci </li> 3171cb0ef41Sopenharmony_ci <li> 3181cb0ef41Sopenharmony_ci <a href="child_process.json">View as JSON</a> 3191cb0ef41Sopenharmony_ci </li> 3201cb0ef41Sopenharmony_ci <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/main/doc/api/child_process.md">Edit on GitHub</a></li> 3211cb0ef41Sopenharmony_ci </ul> 3221cb0ef41Sopenharmony_ci </div> 3231cb0ef41Sopenharmony_ci </li> 3241cb0ef41Sopenharmony_ci </ul> 3251cb0ef41Sopenharmony_ci </div> 3261cb0ef41Sopenharmony_ci <hr> 3271cb0ef41Sopenharmony_ci </header> 3281cb0ef41Sopenharmony_ci 3291cb0ef41Sopenharmony_ci <details id="toc" open><summary>Table of contents</summary><ul> 3301cb0ef41Sopenharmony_ci<li><span class="stability_2"><a href="#child-process">Child process</a></span> 3311cb0ef41Sopenharmony_ci<ul> 3321cb0ef41Sopenharmony_ci<li><a href="#asynchronous-process-creation">Asynchronous process creation</a> 3331cb0ef41Sopenharmony_ci<ul> 3341cb0ef41Sopenharmony_ci<li><a href="#spawning-bat-and-cmd-files-on-windows">Spawning <code>.bat</code> and <code>.cmd</code> files on Windows</a></li> 3351cb0ef41Sopenharmony_ci<li><a href="#child_processexeccommand-options-callback"><code>child_process.exec(command[, options][, callback])</code></a></li> 3361cb0ef41Sopenharmony_ci<li><a href="#child_processexecfilefile-args-options-callback"><code>child_process.execFile(file[, args][, options][, callback])</code></a></li> 3371cb0ef41Sopenharmony_ci<li><a href="#child_processforkmodulepath-args-options"><code>child_process.fork(modulePath[, args][, options])</code></a></li> 3381cb0ef41Sopenharmony_ci<li><a href="#child_processspawncommand-args-options"><code>child_process.spawn(command[, args][, options])</code></a> 3391cb0ef41Sopenharmony_ci<ul> 3401cb0ef41Sopenharmony_ci<li><a href="#optionsdetached"><code>options.detached</code></a></li> 3411cb0ef41Sopenharmony_ci<li><a href="#optionsstdio"><code>options.stdio</code></a></li> 3421cb0ef41Sopenharmony_ci</ul> 3431cb0ef41Sopenharmony_ci</li> 3441cb0ef41Sopenharmony_ci</ul> 3451cb0ef41Sopenharmony_ci</li> 3461cb0ef41Sopenharmony_ci<li><a href="#synchronous-process-creation">Synchronous process creation</a> 3471cb0ef41Sopenharmony_ci<ul> 3481cb0ef41Sopenharmony_ci<li><a href="#child_processexecfilesyncfile-args-options"><code>child_process.execFileSync(file[, args][, options])</code></a></li> 3491cb0ef41Sopenharmony_ci<li><a href="#child_processexecsynccommand-options"><code>child_process.execSync(command[, options])</code></a></li> 3501cb0ef41Sopenharmony_ci<li><a href="#child_processspawnsynccommand-args-options"><code>child_process.spawnSync(command[, args][, options])</code></a></li> 3511cb0ef41Sopenharmony_ci</ul> 3521cb0ef41Sopenharmony_ci</li> 3531cb0ef41Sopenharmony_ci<li><a href="#class-childprocess">Class: <code>ChildProcess</code></a> 3541cb0ef41Sopenharmony_ci<ul> 3551cb0ef41Sopenharmony_ci<li><a href="#event-close">Event: <code>'close'</code></a></li> 3561cb0ef41Sopenharmony_ci<li><a href="#event-disconnect">Event: <code>'disconnect'</code></a></li> 3571cb0ef41Sopenharmony_ci<li><a href="#event-error">Event: <code>'error'</code></a></li> 3581cb0ef41Sopenharmony_ci<li><a href="#event-exit">Event: <code>'exit'</code></a></li> 3591cb0ef41Sopenharmony_ci<li><a href="#event-message">Event: <code>'message'</code></a></li> 3601cb0ef41Sopenharmony_ci<li><a href="#event-spawn">Event: <code>'spawn'</code></a></li> 3611cb0ef41Sopenharmony_ci<li><a href="#subprocesschannel"><code>subprocess.channel</code></a> 3621cb0ef41Sopenharmony_ci<ul> 3631cb0ef41Sopenharmony_ci<li><a href="#subprocesschannelref"><code>subprocess.channel.ref()</code></a></li> 3641cb0ef41Sopenharmony_ci<li><a href="#subprocesschannelunref"><code>subprocess.channel.unref()</code></a></li> 3651cb0ef41Sopenharmony_ci</ul> 3661cb0ef41Sopenharmony_ci</li> 3671cb0ef41Sopenharmony_ci<li><a href="#subprocessconnected"><code>subprocess.connected</code></a></li> 3681cb0ef41Sopenharmony_ci<li><a href="#subprocessdisconnect"><code>subprocess.disconnect()</code></a></li> 3691cb0ef41Sopenharmony_ci<li><a href="#subprocessexitcode"><code>subprocess.exitCode</code></a></li> 3701cb0ef41Sopenharmony_ci<li><a href="#subprocesskillsignal"><code>subprocess.kill([signal])</code></a></li> 3711cb0ef41Sopenharmony_ci<li><span class="stability_1"><a href="#subprocesssymboldispose"><code>subprocess[Symbol.dispose]()</code></a></span></li> 3721cb0ef41Sopenharmony_ci<li><a href="#subprocesskilled"><code>subprocess.killed</code></a></li> 3731cb0ef41Sopenharmony_ci<li><a href="#subprocesspid"><code>subprocess.pid</code></a></li> 3741cb0ef41Sopenharmony_ci<li><a href="#subprocessref"><code>subprocess.ref()</code></a></li> 3751cb0ef41Sopenharmony_ci<li><a href="#subprocesssendmessage-sendhandle-options-callback"><code>subprocess.send(message[, sendHandle[, options]][, callback])</code></a> 3761cb0ef41Sopenharmony_ci<ul> 3771cb0ef41Sopenharmony_ci<li><a href="#example-sending-a-server-object">Example: sending a server object</a></li> 3781cb0ef41Sopenharmony_ci<li><a href="#example-sending-a-socket-object">Example: sending a socket object</a></li> 3791cb0ef41Sopenharmony_ci</ul> 3801cb0ef41Sopenharmony_ci</li> 3811cb0ef41Sopenharmony_ci<li><a href="#subprocesssignalcode"><code>subprocess.signalCode</code></a></li> 3821cb0ef41Sopenharmony_ci<li><a href="#subprocessspawnargs"><code>subprocess.spawnargs</code></a></li> 3831cb0ef41Sopenharmony_ci<li><a href="#subprocessspawnfile"><code>subprocess.spawnfile</code></a></li> 3841cb0ef41Sopenharmony_ci<li><a href="#subprocessstderr"><code>subprocess.stderr</code></a></li> 3851cb0ef41Sopenharmony_ci<li><a href="#subprocessstdin"><code>subprocess.stdin</code></a></li> 3861cb0ef41Sopenharmony_ci<li><a href="#subprocessstdio"><code>subprocess.stdio</code></a></li> 3871cb0ef41Sopenharmony_ci<li><a href="#subprocessstdout"><code>subprocess.stdout</code></a></li> 3881cb0ef41Sopenharmony_ci<li><a href="#subprocessunref"><code>subprocess.unref()</code></a></li> 3891cb0ef41Sopenharmony_ci</ul> 3901cb0ef41Sopenharmony_ci</li> 3911cb0ef41Sopenharmony_ci<li><a href="#maxbuffer-and-unicode"><code>maxBuffer</code> and Unicode</a></li> 3921cb0ef41Sopenharmony_ci<li><a href="#shell-requirements">Shell requirements</a></li> 3931cb0ef41Sopenharmony_ci<li><a href="#default-windows-shell">Default Windows shell</a></li> 3941cb0ef41Sopenharmony_ci<li><a href="#advanced-serialization">Advanced serialization</a></li> 3951cb0ef41Sopenharmony_ci</ul> 3961cb0ef41Sopenharmony_ci</li> 3971cb0ef41Sopenharmony_ci</ul></details> 3981cb0ef41Sopenharmony_ci 3991cb0ef41Sopenharmony_ci <div id="apicontent"> 4001cb0ef41Sopenharmony_ci <h2>Child process<span><a class="mark" href="#child-process" id="child-process">#</a></span><a aria-hidden="true" class="legacy" id="child_process_child_process"></a></h2> 4011cb0ef41Sopenharmony_ci 4021cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_2"><a href="documentation.html#stability-index">Stability: 2</a> - Stable</div><p></p> 4031cb0ef41Sopenharmony_ci<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v18.20.1/lib/child_process.js">lib/child_process.js</a></p> 4041cb0ef41Sopenharmony_ci<p>The <code>node:child_process</code> module provides the ability to spawn subprocesses in 4051cb0ef41Sopenharmony_cia manner that is similar, but not identical, to <a href="http://man7.org/linux/man-pages/man3/popen.3.html"><code>popen(3)</code></a>. This capability 4061cb0ef41Sopenharmony_ciis primarily provided by the <a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a> function:</p> 4071cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 4081cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> ls = <span class="hljs-title function_">spawn</span>(<span class="hljs-string">'ls'</span>, [<span class="hljs-string">'-lh'</span>, <span class="hljs-string">'/usr'</span>]); 4091cb0ef41Sopenharmony_ci 4101cb0ef41Sopenharmony_cils.<span class="hljs-property">stdout</span>.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 4111cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`stdout: <span class="hljs-subst">${data}</span>`</span>); 4121cb0ef41Sopenharmony_ci}); 4131cb0ef41Sopenharmony_ci 4141cb0ef41Sopenharmony_cils.<span class="hljs-property">stderr</span>.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 4151cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`stderr: <span class="hljs-subst">${data}</span>`</span>); 4161cb0ef41Sopenharmony_ci}); 4171cb0ef41Sopenharmony_ci 4181cb0ef41Sopenharmony_cils.<span class="hljs-title function_">on</span>(<span class="hljs-string">'close'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 4191cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`child process exited with code <span class="hljs-subst">${code}</span>`</span>); 4201cb0ef41Sopenharmony_ci});</code> <button class="copy-button">copy</button></pre> 4211cb0ef41Sopenharmony_ci<p>By default, pipes for <code>stdin</code>, <code>stdout</code>, and <code>stderr</code> are established between 4221cb0ef41Sopenharmony_cithe parent Node.js process and the spawned subprocess. These pipes have 4231cb0ef41Sopenharmony_cilimited (and platform-specific) capacity. If the subprocess writes to 4241cb0ef41Sopenharmony_cistdout in excess of that limit without the output being captured, the 4251cb0ef41Sopenharmony_cisubprocess blocks waiting for the pipe buffer to accept more data. This is 4261cb0ef41Sopenharmony_ciidentical to the behavior of pipes in the shell. Use the <code>{ stdio: 'ignore' }</code> 4271cb0ef41Sopenharmony_cioption if the output will not be consumed.</p> 4281cb0ef41Sopenharmony_ci<p>The command lookup is performed using the <code>options.env.PATH</code> environment 4291cb0ef41Sopenharmony_civariable if <code>env</code> is in the <code>options</code> object. Otherwise, <code>process.env.PATH</code> is 4301cb0ef41Sopenharmony_ciused. If <code>options.env</code> is set without <code>PATH</code>, lookup on Unix is performed 4311cb0ef41Sopenharmony_cion a default search path search of <code>/usr/bin:/bin</code> (see your operating system's 4321cb0ef41Sopenharmony_cimanual for execvpe/execvp), on Windows the current processes environment 4331cb0ef41Sopenharmony_civariable <code>PATH</code> is used.</p> 4341cb0ef41Sopenharmony_ci<p>On Windows, environment variables are case-insensitive. Node.js 4351cb0ef41Sopenharmony_cilexicographically sorts the <code>env</code> keys and uses the first one that 4361cb0ef41Sopenharmony_cicase-insensitively matches. Only first (in lexicographic order) entry will be 4371cb0ef41Sopenharmony_cipassed to the subprocess. This might lead to issues on Windows when passing 4381cb0ef41Sopenharmony_ciobjects to the <code>env</code> option that have multiple variants of the same key, such as 4391cb0ef41Sopenharmony_ci<code>PATH</code> and <code>Path</code>.</p> 4401cb0ef41Sopenharmony_ci<p>The <a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a> method spawns the child process asynchronously, 4411cb0ef41Sopenharmony_ciwithout blocking the Node.js event loop. The <a href="#child_processspawnsynccommand-args-options"><code>child_process.spawnSync()</code></a> 4421cb0ef41Sopenharmony_cifunction provides equivalent functionality in a synchronous manner that blocks 4431cb0ef41Sopenharmony_cithe event loop until the spawned process either exits or is terminated.</p> 4441cb0ef41Sopenharmony_ci<p>For convenience, the <code>node:child_process</code> module provides a handful of 4451cb0ef41Sopenharmony_cisynchronous and asynchronous alternatives to <a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a> and 4461cb0ef41Sopenharmony_ci<a href="#child_processspawnsynccommand-args-options"><code>child_process.spawnSync()</code></a>. Each of these alternatives are implemented on 4471cb0ef41Sopenharmony_citop of <a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a> or <a href="#child_processspawnsynccommand-args-options"><code>child_process.spawnSync()</code></a>.</p> 4481cb0ef41Sopenharmony_ci<ul> 4491cb0ef41Sopenharmony_ci<li><a href="#child_processexeccommand-options-callback"><code>child_process.exec()</code></a>: spawns a shell and runs a command within that 4501cb0ef41Sopenharmony_cishell, passing the <code>stdout</code> and <code>stderr</code> to a callback function when 4511cb0ef41Sopenharmony_cicomplete.</li> 4521cb0ef41Sopenharmony_ci<li><a href="#child_processexecfilefile-args-options-callback"><code>child_process.execFile()</code></a>: similar to <a href="#child_processexeccommand-options-callback"><code>child_process.exec()</code></a> except 4531cb0ef41Sopenharmony_cithat it spawns the command directly without first spawning a shell by 4541cb0ef41Sopenharmony_cidefault.</li> 4551cb0ef41Sopenharmony_ci<li><a href="#child_processforkmodulepath-args-options"><code>child_process.fork()</code></a>: spawns a new Node.js process and invokes a 4561cb0ef41Sopenharmony_cispecified module with an IPC communication channel established that allows 4571cb0ef41Sopenharmony_cisending messages between parent and child.</li> 4581cb0ef41Sopenharmony_ci<li><a href="#child_processexecsynccommand-options"><code>child_process.execSync()</code></a>: a synchronous version of 4591cb0ef41Sopenharmony_ci<a href="#child_processexeccommand-options-callback"><code>child_process.exec()</code></a> that will block the Node.js event loop.</li> 4601cb0ef41Sopenharmony_ci<li><a href="#child_processexecfilesyncfile-args-options"><code>child_process.execFileSync()</code></a>: a synchronous version of 4611cb0ef41Sopenharmony_ci<a href="#child_processexecfilefile-args-options-callback"><code>child_process.execFile()</code></a> that will block the Node.js event loop.</li> 4621cb0ef41Sopenharmony_ci</ul> 4631cb0ef41Sopenharmony_ci<p>For certain use cases, such as automating shell scripts, the 4641cb0ef41Sopenharmony_ci<a href="#synchronous-process-creation">synchronous counterparts</a> may be more convenient. In many cases, however, 4651cb0ef41Sopenharmony_cithe synchronous methods can have significant impact on performance due to 4661cb0ef41Sopenharmony_cistalling the event loop while spawned processes complete.</p> 4671cb0ef41Sopenharmony_ci<section><h3>Asynchronous process creation<span><a class="mark" href="#asynchronous-process-creation" id="asynchronous-process-creation">#</a></span><a aria-hidden="true" class="legacy" id="child_process_asynchronous_process_creation"></a></h3> 4681cb0ef41Sopenharmony_ci<p>The <a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a>, <a href="#child_processforkmodulepath-args-options"><code>child_process.fork()</code></a>, <a href="#child_processexeccommand-options-callback"><code>child_process.exec()</code></a>, 4691cb0ef41Sopenharmony_ciand <a href="#child_processexecfilefile-args-options-callback"><code>child_process.execFile()</code></a> methods all follow the idiomatic asynchronous 4701cb0ef41Sopenharmony_ciprogramming pattern typical of other Node.js APIs.</p> 4711cb0ef41Sopenharmony_ci<p>Each of the methods returns a <a href="#class-childprocess"><code>ChildProcess</code></a> instance. These objects 4721cb0ef41Sopenharmony_ciimplement the Node.js <a href="events.html#class-eventemitter"><code>EventEmitter</code></a> API, allowing the parent process to 4731cb0ef41Sopenharmony_ciregister listener functions that are called when certain events occur during 4741cb0ef41Sopenharmony_cithe life cycle of the child process.</p> 4751cb0ef41Sopenharmony_ci<p>The <a href="#child_processexeccommand-options-callback"><code>child_process.exec()</code></a> and <a href="#child_processexecfilefile-args-options-callback"><code>child_process.execFile()</code></a> methods 4761cb0ef41Sopenharmony_ciadditionally allow for an optional <code>callback</code> function to be specified that is 4771cb0ef41Sopenharmony_ciinvoked when the child process terminates.</p> 4781cb0ef41Sopenharmony_ci<h4>Spawning <code>.bat</code> and <code>.cmd</code> files on Windows<span><a class="mark" href="#spawning-bat-and-cmd-files-on-windows" id="spawning-bat-and-cmd-files-on-windows">#</a></span><a aria-hidden="true" class="legacy" id="child_process_spawning_bat_and_cmd_files_on_windows"></a></h4> 4791cb0ef41Sopenharmony_ci<p>The importance of the distinction between <a href="#child_processexeccommand-options-callback"><code>child_process.exec()</code></a> and 4801cb0ef41Sopenharmony_ci<a href="#child_processexecfilefile-args-options-callback"><code>child_process.execFile()</code></a> can vary based on platform. On Unix-type 4811cb0ef41Sopenharmony_cioperating systems (Unix, Linux, macOS) <a href="#child_processexecfilefile-args-options-callback"><code>child_process.execFile()</code></a> can be 4821cb0ef41Sopenharmony_cimore efficient because it does not spawn a shell by default. On Windows, 4831cb0ef41Sopenharmony_cihowever, <code>.bat</code> and <code>.cmd</code> files are not executable on their own without a 4841cb0ef41Sopenharmony_citerminal, and therefore cannot be launched using <a href="#child_processexecfilefile-args-options-callback"><code>child_process.execFile()</code></a>. 4851cb0ef41Sopenharmony_ciWhen running on Windows, <code>.bat</code> and <code>.cmd</code> files can be invoked using 4861cb0ef41Sopenharmony_ci<a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a> with the <code>shell</code> option set, with 4871cb0ef41Sopenharmony_ci<a href="#child_processexeccommand-options-callback"><code>child_process.exec()</code></a>, or by spawning <code>cmd.exe</code> and passing the <code>.bat</code> or 4881cb0ef41Sopenharmony_ci<code>.cmd</code> file as an argument (which is what the <code>shell</code> option and 4891cb0ef41Sopenharmony_ci<a href="#child_processexeccommand-options-callback"><code>child_process.exec()</code></a> do). In any case, if the script filename contains 4901cb0ef41Sopenharmony_cispaces it needs to be quoted.</p> 4911cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-comment">// On Windows Only...</span> 4921cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> { spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 4931cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> bat = <span class="hljs-title function_">spawn</span>(<span class="hljs-string">'cmd.exe'</span>, [<span class="hljs-string">'/c'</span>, <span class="hljs-string">'my.bat'</span>]); 4941cb0ef41Sopenharmony_ci 4951cb0ef41Sopenharmony_cibat.<span class="hljs-property">stdout</span>.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 4961cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(data.<span class="hljs-title function_">toString</span>()); 4971cb0ef41Sopenharmony_ci}); 4981cb0ef41Sopenharmony_ci 4991cb0ef41Sopenharmony_cibat.<span class="hljs-property">stderr</span>.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 5001cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(data.<span class="hljs-title function_">toString</span>()); 5011cb0ef41Sopenharmony_ci}); 5021cb0ef41Sopenharmony_ci 5031cb0ef41Sopenharmony_cibat.<span class="hljs-title function_">on</span>(<span class="hljs-string">'exit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 5041cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Child exited with code <span class="hljs-subst">${code}</span>`</span>); 5051cb0ef41Sopenharmony_ci});</code> <button class="copy-button">copy</button></pre> 5061cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-comment">// OR...</span> 5071cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> { exec, spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 5081cb0ef41Sopenharmony_ci<span class="hljs-title function_">exec</span>(<span class="hljs-string">'my.bat'</span>, <span class="hljs-function">(<span class="hljs-params">err, stdout, stderr</span>) =></span> { 5091cb0ef41Sopenharmony_ci <span class="hljs-keyword">if</span> (err) { 5101cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(err); 5111cb0ef41Sopenharmony_ci <span class="hljs-keyword">return</span>; 5121cb0ef41Sopenharmony_ci } 5131cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(stdout); 5141cb0ef41Sopenharmony_ci}); 5151cb0ef41Sopenharmony_ci 5161cb0ef41Sopenharmony_ci<span class="hljs-comment">// Script with spaces in the filename:</span> 5171cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> bat = <span class="hljs-title function_">spawn</span>(<span class="hljs-string">'"my script.cmd"'</span>, [<span class="hljs-string">'a'</span>, <span class="hljs-string">'b'</span>], { <span class="hljs-attr">shell</span>: <span class="hljs-literal">true</span> }); 5181cb0ef41Sopenharmony_ci<span class="hljs-comment">// or:</span> 5191cb0ef41Sopenharmony_ci<span class="hljs-title function_">exec</span>(<span class="hljs-string">'"my script.cmd" a b'</span>, <span class="hljs-function">(<span class="hljs-params">err, stdout, stderr</span>) =></span> { 5201cb0ef41Sopenharmony_ci <span class="hljs-comment">// ...</span> 5211cb0ef41Sopenharmony_ci});</code> <button class="copy-button">copy</button></pre> 5221cb0ef41Sopenharmony_ci<h4><code>child_process.exec(command[, options][, callback])</code><span><a class="mark" href="#child_processexeccommand-options-callback" id="child_processexeccommand-options-callback">#</a></span><a aria-hidden="true" class="legacy" id="child_process_child_process_exec_command_options_callback"></a></h4> 5231cb0ef41Sopenharmony_ci<div class="api_metadata"> 5241cb0ef41Sopenharmony_ci<details class="changelog"><summary>History</summary> 5251cb0ef41Sopenharmony_ci<table> 5261cb0ef41Sopenharmony_ci<tbody><tr><th>Version</th><th>Changes</th></tr> 5271cb0ef41Sopenharmony_ci<tr><td>v15.4.0</td> 5281cb0ef41Sopenharmony_ci<td><p>AbortSignal support was added.</p></td></tr> 5291cb0ef41Sopenharmony_ci<tr><td>v16.4.0, v14.18.0</td> 5301cb0ef41Sopenharmony_ci<td><p>The <code>cwd</code> option can be a WHATWG <code>URL</code> object using <code>file:</code> protocol.</p></td></tr> 5311cb0ef41Sopenharmony_ci<tr><td>v8.8.0</td> 5321cb0ef41Sopenharmony_ci<td><p>The <code>windowsHide</code> option is supported now.</p></td></tr> 5331cb0ef41Sopenharmony_ci<tr><td>v0.1.90</td> 5341cb0ef41Sopenharmony_ci<td><p><span>Added in: v0.1.90</span></p></td></tr> 5351cb0ef41Sopenharmony_ci</tbody></table> 5361cb0ef41Sopenharmony_ci</details> 5371cb0ef41Sopenharmony_ci</div> 5381cb0ef41Sopenharmony_ci<ul> 5391cb0ef41Sopenharmony_ci<li><code>command</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The command to run, with space-separated arguments.</li> 5401cb0ef41Sopenharmony_ci<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 5411cb0ef41Sopenharmony_ci<ul> 5421cb0ef41Sopenharmony_ci<li><code>cwd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="url.html#the-whatwg-url-api" class="type"><URL></a> Current working directory of the child process. 5431cb0ef41Sopenharmony_ci<strong>Default:</strong> <code>process.cwd()</code>.</li> 5441cb0ef41Sopenharmony_ci<li><code>env</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Environment key-value pairs. <strong>Default:</strong> <code>process.env</code>.</li> 5451cb0ef41Sopenharmony_ci<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> <strong>Default:</strong> <code>'utf8'</code></li> 5461cb0ef41Sopenharmony_ci<li><code>shell</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Shell to execute the command with. See 5471cb0ef41Sopenharmony_ci<a href="#shell-requirements">Shell requirements</a> and <a href="#default-windows-shell">Default Windows shell</a>. <strong>Default:</strong> 5481cb0ef41Sopenharmony_ci<code>'/bin/sh'</code> on Unix, <code>process.env.ComSpec</code> on Windows.</li> 5491cb0ef41Sopenharmony_ci<li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> allows aborting the child process using an 5501cb0ef41Sopenharmony_ciAbortSignal.</li> 5511cb0ef41Sopenharmony_ci<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> <strong>Default:</strong> <code>0</code></li> 5521cb0ef41Sopenharmony_ci<li><code>maxBuffer</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Largest amount of data in bytes allowed on stdout or 5531cb0ef41Sopenharmony_cistderr. If exceeded, the child process is terminated and any output is 5541cb0ef41Sopenharmony_citruncated. See caveat at <a href="#maxbuffer-and-unicode"><code>maxBuffer</code> and Unicode</a>. 5551cb0ef41Sopenharmony_ci<strong>Default:</strong> <code>1024 * 1024</code>.</li> 5561cb0ef41Sopenharmony_ci<li><code>killSignal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <strong>Default:</strong> <code>'SIGTERM'</code></li> 5571cb0ef41Sopenharmony_ci<li><code>uid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the user identity of the process (see <a href="http://man7.org/linux/man-pages/man2/setuid.2.html"><code>setuid(2)</code></a>).</li> 5581cb0ef41Sopenharmony_ci<li><code>gid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the group identity of the process (see <a href="http://man7.org/linux/man-pages/man2/setgid.2.html"><code>setgid(2)</code></a>).</li> 5591cb0ef41Sopenharmony_ci<li><code>windowsHide</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Hide the subprocess console window that would 5601cb0ef41Sopenharmony_cinormally be created on Windows systems. <strong>Default:</strong> <code>false</code>.</li> 5611cb0ef41Sopenharmony_ci</ul> 5621cb0ef41Sopenharmony_ci</li> 5631cb0ef41Sopenharmony_ci<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> called with the output when process terminates. 5641cb0ef41Sopenharmony_ci<ul> 5651cb0ef41Sopenharmony_ci<li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 5661cb0ef41Sopenharmony_ci<li><code>stdout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#class-buffer" class="type"><Buffer></a></li> 5671cb0ef41Sopenharmony_ci<li><code>stderr</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#class-buffer" class="type"><Buffer></a></li> 5681cb0ef41Sopenharmony_ci</ul> 5691cb0ef41Sopenharmony_ci</li> 5701cb0ef41Sopenharmony_ci<li>Returns: <a href="child_process.html#class-childprocess" class="type"><ChildProcess></a></li> 5711cb0ef41Sopenharmony_ci</ul> 5721cb0ef41Sopenharmony_ci<p>Spawns a shell then executes the <code>command</code> within that shell, buffering any 5731cb0ef41Sopenharmony_cigenerated output. The <code>command</code> string passed to the exec function is processed 5741cb0ef41Sopenharmony_cidirectly by the shell and special characters (vary based on 5751cb0ef41Sopenharmony_ci<a href="https://en.wikipedia.org/wiki/List_of_command-line_interpreters">shell</a>) 5761cb0ef41Sopenharmony_cineed to be dealt with accordingly:</p> 5771cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { exec } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 5781cb0ef41Sopenharmony_ci 5791cb0ef41Sopenharmony_ci<span class="hljs-title function_">exec</span>(<span class="hljs-string">'"/path/to/test file/test.sh" arg1 arg2'</span>); 5801cb0ef41Sopenharmony_ci<span class="hljs-comment">// Double quotes are used so that the space in the path is not interpreted as</span> 5811cb0ef41Sopenharmony_ci<span class="hljs-comment">// a delimiter of multiple arguments.</span> 5821cb0ef41Sopenharmony_ci 5831cb0ef41Sopenharmony_ci<span class="hljs-title function_">exec</span>(<span class="hljs-string">'echo "The \\$HOME variable is $HOME"'</span>); 5841cb0ef41Sopenharmony_ci<span class="hljs-comment">// The $HOME variable is escaped in the first instance, but not in the second.</span></code> <button class="copy-button">copy</button></pre> 5851cb0ef41Sopenharmony_ci<p><strong>Never pass unsanitized user input to this function. Any input containing shell 5861cb0ef41Sopenharmony_cimetacharacters may be used to trigger arbitrary command execution.</strong></p> 5871cb0ef41Sopenharmony_ci<p>If a <code>callback</code> function is provided, it is called with the arguments 5881cb0ef41Sopenharmony_ci<code>(error, stdout, stderr)</code>. On success, <code>error</code> will be <code>null</code>. On error, 5891cb0ef41Sopenharmony_ci<code>error</code> will be an instance of <a href="errors.html#class-error"><code>Error</code></a>. The <code>error.code</code> property will be 5901cb0ef41Sopenharmony_cithe exit code of the process. By convention, any exit code other than <code>0</code> 5911cb0ef41Sopenharmony_ciindicates an error. <code>error.signal</code> will be the signal that terminated the 5921cb0ef41Sopenharmony_ciprocess.</p> 5931cb0ef41Sopenharmony_ci<p>The <code>stdout</code> and <code>stderr</code> arguments passed to the callback will contain the 5941cb0ef41Sopenharmony_cistdout and stderr output of the child process. By default, Node.js will decode 5951cb0ef41Sopenharmony_cithe output as UTF-8 and pass strings to the callback. The <code>encoding</code> option 5961cb0ef41Sopenharmony_cican be used to specify the character encoding used to decode the stdout and 5971cb0ef41Sopenharmony_cistderr output. If <code>encoding</code> is <code>'buffer'</code>, or an unrecognized character 5981cb0ef41Sopenharmony_ciencoding, <code>Buffer</code> objects will be passed to the callback instead.</p> 5991cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { exec } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 6001cb0ef41Sopenharmony_ci<span class="hljs-title function_">exec</span>(<span class="hljs-string">'cat *.js missing_file | wc -l'</span>, <span class="hljs-function">(<span class="hljs-params">error, stdout, stderr</span>) =></span> { 6011cb0ef41Sopenharmony_ci <span class="hljs-keyword">if</span> (error) { 6021cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`exec error: <span class="hljs-subst">${error}</span>`</span>); 6031cb0ef41Sopenharmony_ci <span class="hljs-keyword">return</span>; 6041cb0ef41Sopenharmony_ci } 6051cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`stdout: <span class="hljs-subst">${stdout}</span>`</span>); 6061cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`stderr: <span class="hljs-subst">${stderr}</span>`</span>); 6071cb0ef41Sopenharmony_ci});</code> <button class="copy-button">copy</button></pre> 6081cb0ef41Sopenharmony_ci<p>If <code>timeout</code> is greater than <code>0</code>, the parent will send the signal 6091cb0ef41Sopenharmony_ciidentified by the <code>killSignal</code> property (the default is <code>'SIGTERM'</code>) if the 6101cb0ef41Sopenharmony_cichild runs longer than <code>timeout</code> milliseconds.</p> 6111cb0ef41Sopenharmony_ci<p>Unlike the <a href="http://man7.org/linux/man-pages/man3/exec.3.html"><code>exec(3)</code></a> POSIX system call, <code>child_process.exec()</code> does not replace 6121cb0ef41Sopenharmony_cithe existing process and uses a shell to execute the command.</p> 6131cb0ef41Sopenharmony_ci<p>If this method is invoked as its <a href="util.html#utilpromisifyoriginal"><code>util.promisify()</code></a>ed version, it returns 6141cb0ef41Sopenharmony_cia <code>Promise</code> for an <code>Object</code> with <code>stdout</code> and <code>stderr</code> properties. The returned 6151cb0ef41Sopenharmony_ci<code>ChildProcess</code> instance is attached to the <code>Promise</code> as a <code>child</code> property. In 6161cb0ef41Sopenharmony_cicase of an error (including any error resulting in an exit code other than 0), a 6171cb0ef41Sopenharmony_cirejected promise is returned, with the same <code>error</code> object given in the 6181cb0ef41Sopenharmony_cicallback, but with two additional properties <code>stdout</code> and <code>stderr</code>.</p> 6191cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:util'</span>); 6201cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> exec = util.<span class="hljs-title function_">promisify</span>(<span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>).<span class="hljs-property">exec</span>); 6211cb0ef41Sopenharmony_ci 6221cb0ef41Sopenharmony_ci<span class="hljs-keyword">async</span> <span class="hljs-keyword">function</span> <span class="hljs-title function_">lsExample</span>(<span class="hljs-params"></span>) { 6231cb0ef41Sopenharmony_ci <span class="hljs-keyword">const</span> { stdout, stderr } = <span class="hljs-keyword">await</span> <span class="hljs-title function_">exec</span>(<span class="hljs-string">'ls'</span>); 6241cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'stdout:'</span>, stdout); 6251cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">'stderr:'</span>, stderr); 6261cb0ef41Sopenharmony_ci} 6271cb0ef41Sopenharmony_ci<span class="hljs-title function_">lsExample</span>();</code> <button class="copy-button">copy</button></pre> 6281cb0ef41Sopenharmony_ci<p>If the <code>signal</code> option is enabled, calling <code>.abort()</code> on the corresponding 6291cb0ef41Sopenharmony_ci<code>AbortController</code> is similar to calling <code>.kill()</code> on the child process except 6301cb0ef41Sopenharmony_cithe error passed to the callback will be an <code>AbortError</code>:</p> 6311cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { exec } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 6321cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> controller = <span class="hljs-keyword">new</span> <span class="hljs-title class_">AbortController</span>(); 6331cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> { signal } = controller; 6341cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> child = <span class="hljs-title function_">exec</span>(<span class="hljs-string">'grep ssh'</span>, { signal }, <span class="hljs-function">(<span class="hljs-params">error</span>) =></span> { 6351cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(error); <span class="hljs-comment">// an AbortError</span> 6361cb0ef41Sopenharmony_ci}); 6371cb0ef41Sopenharmony_cicontroller.<span class="hljs-title function_">abort</span>();</code> <button class="copy-button">copy</button></pre> 6381cb0ef41Sopenharmony_ci<h4><code>child_process.execFile(file[, args][, options][, callback])</code><span><a class="mark" href="#child_processexecfilefile-args-options-callback" id="child_processexecfilefile-args-options-callback">#</a></span><a aria-hidden="true" class="legacy" id="child_process_child_process_execfile_file_args_options_callback"></a></h4> 6391cb0ef41Sopenharmony_ci<div class="api_metadata"> 6401cb0ef41Sopenharmony_ci<details class="changelog"><summary>History</summary> 6411cb0ef41Sopenharmony_ci<table> 6421cb0ef41Sopenharmony_ci<tbody><tr><th>Version</th><th>Changes</th></tr> 6431cb0ef41Sopenharmony_ci<tr><td>v16.4.0, v14.18.0</td> 6441cb0ef41Sopenharmony_ci<td><p>The <code>cwd</code> option can be a WHATWG <code>URL</code> object using <code>file:</code> protocol.</p></td></tr> 6451cb0ef41Sopenharmony_ci<tr><td>v15.4.0, v14.17.0</td> 6461cb0ef41Sopenharmony_ci<td><p>AbortSignal support was added.</p></td></tr> 6471cb0ef41Sopenharmony_ci<tr><td>v8.8.0</td> 6481cb0ef41Sopenharmony_ci<td><p>The <code>windowsHide</code> option is supported now.</p></td></tr> 6491cb0ef41Sopenharmony_ci<tr><td>v0.1.91</td> 6501cb0ef41Sopenharmony_ci<td><p><span>Added in: v0.1.91</span></p></td></tr> 6511cb0ef41Sopenharmony_ci</tbody></table> 6521cb0ef41Sopenharmony_ci</details> 6531cb0ef41Sopenharmony_ci</div> 6541cb0ef41Sopenharmony_ci<ul> 6551cb0ef41Sopenharmony_ci<li><code>file</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The name or path of the executable file to run.</li> 6561cb0ef41Sopenharmony_ci<li><code>args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> List of string arguments.</li> 6571cb0ef41Sopenharmony_ci<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 6581cb0ef41Sopenharmony_ci<ul> 6591cb0ef41Sopenharmony_ci<li><code>cwd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="url.html#the-whatwg-url-api" class="type"><URL></a> Current working directory of the child process.</li> 6601cb0ef41Sopenharmony_ci<li><code>env</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Environment key-value pairs. <strong>Default:</strong> <code>process.env</code>.</li> 6611cb0ef41Sopenharmony_ci<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> <strong>Default:</strong> <code>'utf8'</code></li> 6621cb0ef41Sopenharmony_ci<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> <strong>Default:</strong> <code>0</code></li> 6631cb0ef41Sopenharmony_ci<li><code>maxBuffer</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Largest amount of data in bytes allowed on stdout or 6641cb0ef41Sopenharmony_cistderr. If exceeded, the child process is terminated and any output is 6651cb0ef41Sopenharmony_citruncated. See caveat at <a href="#maxbuffer-and-unicode"><code>maxBuffer</code> and Unicode</a>. 6661cb0ef41Sopenharmony_ci<strong>Default:</strong> <code>1024 * 1024</code>.</li> 6671cb0ef41Sopenharmony_ci<li><code>killSignal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <strong>Default:</strong> <code>'SIGTERM'</code></li> 6681cb0ef41Sopenharmony_ci<li><code>uid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the user identity of the process (see <a href="http://man7.org/linux/man-pages/man2/setuid.2.html"><code>setuid(2)</code></a>).</li> 6691cb0ef41Sopenharmony_ci<li><code>gid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the group identity of the process (see <a href="http://man7.org/linux/man-pages/man2/setgid.2.html"><code>setgid(2)</code></a>).</li> 6701cb0ef41Sopenharmony_ci<li><code>windowsHide</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Hide the subprocess console window that would 6711cb0ef41Sopenharmony_cinormally be created on Windows systems. <strong>Default:</strong> <code>false</code>.</li> 6721cb0ef41Sopenharmony_ci<li><code>windowsVerbatimArguments</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> No quoting or escaping of arguments is 6731cb0ef41Sopenharmony_cidone on Windows. Ignored on Unix. <strong>Default:</strong> <code>false</code>.</li> 6741cb0ef41Sopenharmony_ci<li><code>shell</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If <code>true</code>, runs <code>command</code> inside of a shell. Uses 6751cb0ef41Sopenharmony_ci<code>'/bin/sh'</code> on Unix, and <code>process.env.ComSpec</code> on Windows. A different 6761cb0ef41Sopenharmony_cishell can be specified as a string. See <a href="#shell-requirements">Shell requirements</a> and 6771cb0ef41Sopenharmony_ci<a href="#default-windows-shell">Default Windows shell</a>. <strong>Default:</strong> <code>false</code> (no shell).</li> 6781cb0ef41Sopenharmony_ci<li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> allows aborting the child process using an 6791cb0ef41Sopenharmony_ciAbortSignal.</li> 6801cb0ef41Sopenharmony_ci</ul> 6811cb0ef41Sopenharmony_ci</li> 6821cb0ef41Sopenharmony_ci<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Called with the output when process terminates. 6831cb0ef41Sopenharmony_ci<ul> 6841cb0ef41Sopenharmony_ci<li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 6851cb0ef41Sopenharmony_ci<li><code>stdout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#class-buffer" class="type"><Buffer></a></li> 6861cb0ef41Sopenharmony_ci<li><code>stderr</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#class-buffer" class="type"><Buffer></a></li> 6871cb0ef41Sopenharmony_ci</ul> 6881cb0ef41Sopenharmony_ci</li> 6891cb0ef41Sopenharmony_ci<li>Returns: <a href="child_process.html#class-childprocess" class="type"><ChildProcess></a></li> 6901cb0ef41Sopenharmony_ci</ul> 6911cb0ef41Sopenharmony_ci<p>The <code>child_process.execFile()</code> function is similar to <a href="#child_processexeccommand-options-callback"><code>child_process.exec()</code></a> 6921cb0ef41Sopenharmony_ciexcept that it does not spawn a shell by default. Rather, the specified 6931cb0ef41Sopenharmony_ciexecutable <code>file</code> is spawned directly as a new process making it slightly more 6941cb0ef41Sopenharmony_ciefficient than <a href="#child_processexeccommand-options-callback"><code>child_process.exec()</code></a>.</p> 6951cb0ef41Sopenharmony_ci<p>The same options as <a href="#child_processexeccommand-options-callback"><code>child_process.exec()</code></a> are supported. Since a shell is 6961cb0ef41Sopenharmony_cinot spawned, behaviors such as I/O redirection and file globbing are not 6971cb0ef41Sopenharmony_cisupported.</p> 6981cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { execFile } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 6991cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> child = <span class="hljs-title function_">execFile</span>(<span class="hljs-string">'node'</span>, [<span class="hljs-string">'--version'</span>], <span class="hljs-function">(<span class="hljs-params">error, stdout, stderr</span>) =></span> { 7001cb0ef41Sopenharmony_ci <span class="hljs-keyword">if</span> (error) { 7011cb0ef41Sopenharmony_ci <span class="hljs-keyword">throw</span> error; 7021cb0ef41Sopenharmony_ci } 7031cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(stdout); 7041cb0ef41Sopenharmony_ci});</code> <button class="copy-button">copy</button></pre> 7051cb0ef41Sopenharmony_ci<p>The <code>stdout</code> and <code>stderr</code> arguments passed to the callback will contain the 7061cb0ef41Sopenharmony_cistdout and stderr output of the child process. By default, Node.js will decode 7071cb0ef41Sopenharmony_cithe output as UTF-8 and pass strings to the callback. The <code>encoding</code> option 7081cb0ef41Sopenharmony_cican be used to specify the character encoding used to decode the stdout and 7091cb0ef41Sopenharmony_cistderr output. If <code>encoding</code> is <code>'buffer'</code>, or an unrecognized character 7101cb0ef41Sopenharmony_ciencoding, <code>Buffer</code> objects will be passed to the callback instead.</p> 7111cb0ef41Sopenharmony_ci<p>If this method is invoked as its <a href="util.html#utilpromisifyoriginal"><code>util.promisify()</code></a>ed version, it returns 7121cb0ef41Sopenharmony_cia <code>Promise</code> for an <code>Object</code> with <code>stdout</code> and <code>stderr</code> properties. The returned 7131cb0ef41Sopenharmony_ci<code>ChildProcess</code> instance is attached to the <code>Promise</code> as a <code>child</code> property. In 7141cb0ef41Sopenharmony_cicase of an error (including any error resulting in an exit code other than 0), a 7151cb0ef41Sopenharmony_cirejected promise is returned, with the same <code>error</code> object given in the 7161cb0ef41Sopenharmony_cicallback, but with two additional properties <code>stdout</code> and <code>stderr</code>.</p> 7171cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:util'</span>); 7181cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> execFile = util.<span class="hljs-title function_">promisify</span>(<span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>).<span class="hljs-property">execFile</span>); 7191cb0ef41Sopenharmony_ci<span class="hljs-keyword">async</span> <span class="hljs-keyword">function</span> <span class="hljs-title function_">getVersion</span>(<span class="hljs-params"></span>) { 7201cb0ef41Sopenharmony_ci <span class="hljs-keyword">const</span> { stdout } = <span class="hljs-keyword">await</span> <span class="hljs-title function_">execFile</span>(<span class="hljs-string">'node'</span>, [<span class="hljs-string">'--version'</span>]); 7211cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(stdout); 7221cb0ef41Sopenharmony_ci} 7231cb0ef41Sopenharmony_ci<span class="hljs-title function_">getVersion</span>();</code> <button class="copy-button">copy</button></pre> 7241cb0ef41Sopenharmony_ci<p><strong>If the <code>shell</code> option is enabled, do not pass unsanitized user input to this 7251cb0ef41Sopenharmony_cifunction. Any input containing shell metacharacters may be used to trigger 7261cb0ef41Sopenharmony_ciarbitrary command execution.</strong></p> 7271cb0ef41Sopenharmony_ci<p>If the <code>signal</code> option is enabled, calling <code>.abort()</code> on the corresponding 7281cb0ef41Sopenharmony_ci<code>AbortController</code> is similar to calling <code>.kill()</code> on the child process except 7291cb0ef41Sopenharmony_cithe error passed to the callback will be an <code>AbortError</code>:</p> 7301cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { execFile } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 7311cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> controller = <span class="hljs-keyword">new</span> <span class="hljs-title class_">AbortController</span>(); 7321cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> { signal } = controller; 7331cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> child = <span class="hljs-title function_">execFile</span>(<span class="hljs-string">'node'</span>, [<span class="hljs-string">'--version'</span>], { signal }, <span class="hljs-function">(<span class="hljs-params">error</span>) =></span> { 7341cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(error); <span class="hljs-comment">// an AbortError</span> 7351cb0ef41Sopenharmony_ci}); 7361cb0ef41Sopenharmony_cicontroller.<span class="hljs-title function_">abort</span>();</code> <button class="copy-button">copy</button></pre> 7371cb0ef41Sopenharmony_ci<h4><code>child_process.fork(modulePath[, args][, options])</code><span><a class="mark" href="#child_processforkmodulepath-args-options" id="child_processforkmodulepath-args-options">#</a></span><a aria-hidden="true" class="legacy" id="child_process_child_process_fork_modulepath_args_options"></a></h4> 7381cb0ef41Sopenharmony_ci<div class="api_metadata"> 7391cb0ef41Sopenharmony_ci<details class="changelog"><summary>History</summary> 7401cb0ef41Sopenharmony_ci<table> 7411cb0ef41Sopenharmony_ci<tbody><tr><th>Version</th><th>Changes</th></tr> 7421cb0ef41Sopenharmony_ci<tr><td>v17.4.0, v16.14.0</td> 7431cb0ef41Sopenharmony_ci<td><p>The <code>modulePath</code> parameter can be a WHATWG <code>URL</code> object using <code>file:</code> protocol.</p></td></tr> 7441cb0ef41Sopenharmony_ci<tr><td>v16.4.0, v14.18.0</td> 7451cb0ef41Sopenharmony_ci<td><p>The <code>cwd</code> option can be a WHATWG <code>URL</code> object using <code>file:</code> protocol.</p></td></tr> 7461cb0ef41Sopenharmony_ci<tr><td>v15.13.0, v14.18.0</td> 7471cb0ef41Sopenharmony_ci<td><p>timeout was added.</p></td></tr> 7481cb0ef41Sopenharmony_ci<tr><td>v15.11.0, v14.18.0</td> 7491cb0ef41Sopenharmony_ci<td><p>killSignal for AbortSignal was added.</p></td></tr> 7501cb0ef41Sopenharmony_ci<tr><td>v15.6.0, v14.17.0</td> 7511cb0ef41Sopenharmony_ci<td><p>AbortSignal support was added.</p></td></tr> 7521cb0ef41Sopenharmony_ci<tr><td>v13.2.0, v12.16.0</td> 7531cb0ef41Sopenharmony_ci<td><p>The <code>serialization</code> option is supported now.</p></td></tr> 7541cb0ef41Sopenharmony_ci<tr><td>v8.0.0</td> 7551cb0ef41Sopenharmony_ci<td><p>The <code>stdio</code> option can now be a string.</p></td></tr> 7561cb0ef41Sopenharmony_ci<tr><td>v6.4.0</td> 7571cb0ef41Sopenharmony_ci<td><p>The <code>stdio</code> option is supported now.</p></td></tr> 7581cb0ef41Sopenharmony_ci<tr><td>v0.5.0</td> 7591cb0ef41Sopenharmony_ci<td><p><span>Added in: v0.5.0</span></p></td></tr> 7601cb0ef41Sopenharmony_ci</tbody></table> 7611cb0ef41Sopenharmony_ci</details> 7621cb0ef41Sopenharmony_ci</div> 7631cb0ef41Sopenharmony_ci<ul> 7641cb0ef41Sopenharmony_ci<li><code>modulePath</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="url.html#the-whatwg-url-api" class="type"><URL></a> The module to run in the child.</li> 7651cb0ef41Sopenharmony_ci<li><code>args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> List of string arguments.</li> 7661cb0ef41Sopenharmony_ci<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 7671cb0ef41Sopenharmony_ci<ul> 7681cb0ef41Sopenharmony_ci<li><code>cwd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="url.html#the-whatwg-url-api" class="type"><URL></a> Current working directory of the child process.</li> 7691cb0ef41Sopenharmony_ci<li><code>detached</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Prepare child to run independently of its parent 7701cb0ef41Sopenharmony_ciprocess. Specific behavior depends on the platform, see 7711cb0ef41Sopenharmony_ci<a href="#optionsdetached"><code>options.detached</code></a>).</li> 7721cb0ef41Sopenharmony_ci<li><code>env</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Environment key-value pairs. <strong>Default:</strong> <code>process.env</code>.</li> 7731cb0ef41Sopenharmony_ci<li><code>execPath</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Executable used to create the child process.</li> 7741cb0ef41Sopenharmony_ci<li><code>execArgv</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> List of string arguments passed to the executable. 7751cb0ef41Sopenharmony_ci<strong>Default:</strong> <code>process.execArgv</code>.</li> 7761cb0ef41Sopenharmony_ci<li><code>gid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the group identity of the process (see <a href="http://man7.org/linux/man-pages/man2/setgid.2.html"><code>setgid(2)</code></a>).</li> 7771cb0ef41Sopenharmony_ci<li><code>serialization</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Specify the kind of serialization used for sending 7781cb0ef41Sopenharmony_cimessages between processes. Possible values are <code>'json'</code> and <code>'advanced'</code>. 7791cb0ef41Sopenharmony_ciSee <a href="#advanced-serialization">Advanced serialization</a> for more details. <strong>Default:</strong> <code>'json'</code>.</li> 7801cb0ef41Sopenharmony_ci<li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Allows closing the child process using an 7811cb0ef41Sopenharmony_ciAbortSignal.</li> 7821cb0ef41Sopenharmony_ci<li><code>killSignal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The signal value to be used when the spawned 7831cb0ef41Sopenharmony_ciprocess will be killed by timeout or abort signal. <strong>Default:</strong> <code>'SIGTERM'</code>.</li> 7841cb0ef41Sopenharmony_ci<li><code>silent</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If <code>true</code>, stdin, stdout, and stderr of the child will be 7851cb0ef41Sopenharmony_cipiped to the parent, otherwise they will be inherited from the parent, see 7861cb0ef41Sopenharmony_cithe <code>'pipe'</code> and <code>'inherit'</code> options for <a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a>'s 7871cb0ef41Sopenharmony_ci<a href="#optionsstdio"><code>stdio</code></a> for more details. <strong>Default:</strong> <code>false</code>.</li> 7881cb0ef41Sopenharmony_ci<li><code>stdio</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" class="type"><Array></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> See <a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a>'s <a href="#optionsstdio"><code>stdio</code></a>. 7891cb0ef41Sopenharmony_ciWhen this option is provided, it overrides <code>silent</code>. If the array variant 7901cb0ef41Sopenharmony_ciis used, it must contain exactly one item with value <code>'ipc'</code> or an error 7911cb0ef41Sopenharmony_ciwill be thrown. For instance <code>[0, 1, 2, 'ipc']</code>.</li> 7921cb0ef41Sopenharmony_ci<li><code>uid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the user identity of the process (see <a href="http://man7.org/linux/man-pages/man2/setuid.2.html"><code>setuid(2)</code></a>).</li> 7931cb0ef41Sopenharmony_ci<li><code>windowsVerbatimArguments</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> No quoting or escaping of arguments is 7941cb0ef41Sopenharmony_cidone on Windows. Ignored on Unix. <strong>Default:</strong> <code>false</code>.</li> 7951cb0ef41Sopenharmony_ci<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> In milliseconds the maximum amount of time the process 7961cb0ef41Sopenharmony_ciis allowed to run. <strong>Default:</strong> <code>undefined</code>.</li> 7971cb0ef41Sopenharmony_ci</ul> 7981cb0ef41Sopenharmony_ci</li> 7991cb0ef41Sopenharmony_ci<li>Returns: <a href="child_process.html#class-childprocess" class="type"><ChildProcess></a></li> 8001cb0ef41Sopenharmony_ci</ul> 8011cb0ef41Sopenharmony_ci<p>The <code>child_process.fork()</code> method is a special case of 8021cb0ef41Sopenharmony_ci<a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a> used specifically to spawn new Node.js processes. 8031cb0ef41Sopenharmony_ciLike <a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a>, a <a href="#class-childprocess"><code>ChildProcess</code></a> object is returned. The 8041cb0ef41Sopenharmony_cireturned <a href="#class-childprocess"><code>ChildProcess</code></a> will have an additional communication channel 8051cb0ef41Sopenharmony_cibuilt-in that allows messages to be passed back and forth between the parent and 8061cb0ef41Sopenharmony_cichild. See <a href="#subprocesssendmessage-sendhandle-options-callback"><code>subprocess.send()</code></a> for details.</p> 8071cb0ef41Sopenharmony_ci<p>Keep in mind that spawned Node.js child processes are 8081cb0ef41Sopenharmony_ciindependent of the parent with exception of the IPC communication channel 8091cb0ef41Sopenharmony_cithat is established between the two. Each process has its own memory, with 8101cb0ef41Sopenharmony_citheir own V8 instances. Because of the additional resource allocations 8111cb0ef41Sopenharmony_cirequired, spawning a large number of child Node.js processes is not 8121cb0ef41Sopenharmony_cirecommended.</p> 8131cb0ef41Sopenharmony_ci<p>By default, <code>child_process.fork()</code> will spawn new Node.js instances using the 8141cb0ef41Sopenharmony_ci<a href="process.html#processexecpath"><code>process.execPath</code></a> of the parent process. The <code>execPath</code> property in the 8151cb0ef41Sopenharmony_ci<code>options</code> object allows for an alternative execution path to be used.</p> 8161cb0ef41Sopenharmony_ci<p>Node.js processes launched with a custom <code>execPath</code> will communicate with the 8171cb0ef41Sopenharmony_ciparent process using the file descriptor (fd) identified using the 8181cb0ef41Sopenharmony_cienvironment variable <code>NODE_CHANNEL_FD</code> on the child process.</p> 8191cb0ef41Sopenharmony_ci<p>Unlike the <a href="http://man7.org/linux/man-pages/man2/fork.2.html"><code>fork(2)</code></a> POSIX system call, <code>child_process.fork()</code> does not clone the 8201cb0ef41Sopenharmony_cicurrent process.</p> 8211cb0ef41Sopenharmony_ci<p>The <code>shell</code> option available in <a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a> is not supported by 8221cb0ef41Sopenharmony_ci<code>child_process.fork()</code> and will be ignored if set.</p> 8231cb0ef41Sopenharmony_ci<p>If the <code>signal</code> option is enabled, calling <code>.abort()</code> on the corresponding 8241cb0ef41Sopenharmony_ci<code>AbortController</code> is similar to calling <code>.kill()</code> on the child process except 8251cb0ef41Sopenharmony_cithe error passed to the callback will be an <code>AbortError</code>:</p> 8261cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">if</span> (process.<span class="hljs-property">argv</span>[<span class="hljs-number">2</span>] === <span class="hljs-string">'child'</span>) { 8271cb0ef41Sopenharmony_ci <span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 8281cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Hello from <span class="hljs-subst">${process.argv[<span class="hljs-number">2</span>]}</span>!`</span>); 8291cb0ef41Sopenharmony_ci }, <span class="hljs-number">1_000</span>); 8301cb0ef41Sopenharmony_ci} <span class="hljs-keyword">else</span> { 8311cb0ef41Sopenharmony_ci <span class="hljs-keyword">const</span> { fork } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 8321cb0ef41Sopenharmony_ci <span class="hljs-keyword">const</span> controller = <span class="hljs-keyword">new</span> <span class="hljs-title class_">AbortController</span>(); 8331cb0ef41Sopenharmony_ci <span class="hljs-keyword">const</span> { signal } = controller; 8341cb0ef41Sopenharmony_ci <span class="hljs-keyword">const</span> child = <span class="hljs-title function_">fork</span>(__filename, [<span class="hljs-string">'child'</span>], { signal }); 8351cb0ef41Sopenharmony_ci child.<span class="hljs-title function_">on</span>(<span class="hljs-string">'error'</span>, <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 8361cb0ef41Sopenharmony_ci <span class="hljs-comment">// This will be called with err being an AbortError if the controller aborts</span> 8371cb0ef41Sopenharmony_ci }); 8381cb0ef41Sopenharmony_ci controller.<span class="hljs-title function_">abort</span>(); <span class="hljs-comment">// Stops the child process</span> 8391cb0ef41Sopenharmony_ci}</code> <button class="copy-button">copy</button></pre> 8401cb0ef41Sopenharmony_ci<h4><code>child_process.spawn(command[, args][, options])</code><span><a class="mark" href="#child_processspawncommand-args-options" id="child_processspawncommand-args-options">#</a></span><a aria-hidden="true" class="legacy" id="child_process_child_process_spawn_command_args_options"></a></h4> 8411cb0ef41Sopenharmony_ci<div class="api_metadata"> 8421cb0ef41Sopenharmony_ci<details class="changelog"><summary>History</summary> 8431cb0ef41Sopenharmony_ci<table> 8441cb0ef41Sopenharmony_ci<tbody><tr><th>Version</th><th>Changes</th></tr> 8451cb0ef41Sopenharmony_ci<tr><td>v16.4.0, v14.18.0</td> 8461cb0ef41Sopenharmony_ci<td><p>The <code>cwd</code> option can be a WHATWG <code>URL</code> object using <code>file:</code> protocol.</p></td></tr> 8471cb0ef41Sopenharmony_ci<tr><td>v15.13.0, v14.18.0</td> 8481cb0ef41Sopenharmony_ci<td><p>timeout was added.</p></td></tr> 8491cb0ef41Sopenharmony_ci<tr><td>v15.11.0, v14.18.0</td> 8501cb0ef41Sopenharmony_ci<td><p>killSignal for AbortSignal was added.</p></td></tr> 8511cb0ef41Sopenharmony_ci<tr><td>v15.5.0, v14.17.0</td> 8521cb0ef41Sopenharmony_ci<td><p>AbortSignal support was added.</p></td></tr> 8531cb0ef41Sopenharmony_ci<tr><td>v13.2.0, v12.16.0</td> 8541cb0ef41Sopenharmony_ci<td><p>The <code>serialization</code> option is supported now.</p></td></tr> 8551cb0ef41Sopenharmony_ci<tr><td>v8.8.0</td> 8561cb0ef41Sopenharmony_ci<td><p>The <code>windowsHide</code> option is supported now.</p></td></tr> 8571cb0ef41Sopenharmony_ci<tr><td>v6.4.0</td> 8581cb0ef41Sopenharmony_ci<td><p>The <code>argv0</code> option is supported now.</p></td></tr> 8591cb0ef41Sopenharmony_ci<tr><td>v5.7.0</td> 8601cb0ef41Sopenharmony_ci<td><p>The <code>shell</code> option is supported now.</p></td></tr> 8611cb0ef41Sopenharmony_ci<tr><td>v0.1.90</td> 8621cb0ef41Sopenharmony_ci<td><p><span>Added in: v0.1.90</span></p></td></tr> 8631cb0ef41Sopenharmony_ci</tbody></table> 8641cb0ef41Sopenharmony_ci</details> 8651cb0ef41Sopenharmony_ci</div> 8661cb0ef41Sopenharmony_ci<ul> 8671cb0ef41Sopenharmony_ci<li><code>command</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The command to run.</li> 8681cb0ef41Sopenharmony_ci<li><code>args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> List of string arguments.</li> 8691cb0ef41Sopenharmony_ci<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 8701cb0ef41Sopenharmony_ci<ul> 8711cb0ef41Sopenharmony_ci<li><code>cwd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="url.html#the-whatwg-url-api" class="type"><URL></a> Current working directory of the child process.</li> 8721cb0ef41Sopenharmony_ci<li><code>env</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Environment key-value pairs. <strong>Default:</strong> <code>process.env</code>.</li> 8731cb0ef41Sopenharmony_ci<li><code>argv0</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Explicitly set the value of <code>argv[0]</code> sent to the child 8741cb0ef41Sopenharmony_ciprocess. This will be set to <code>command</code> if not specified.</li> 8751cb0ef41Sopenharmony_ci<li><code>stdio</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" class="type"><Array></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Child's stdio configuration (see 8761cb0ef41Sopenharmony_ci<a href="#optionsstdio"><code>options.stdio</code></a>).</li> 8771cb0ef41Sopenharmony_ci<li><code>detached</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Prepare child to run independently of its parent 8781cb0ef41Sopenharmony_ciprocess. Specific behavior depends on the platform, see 8791cb0ef41Sopenharmony_ci<a href="#optionsdetached"><code>options.detached</code></a>).</li> 8801cb0ef41Sopenharmony_ci<li><code>uid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the user identity of the process (see <a href="http://man7.org/linux/man-pages/man2/setuid.2.html"><code>setuid(2)</code></a>).</li> 8811cb0ef41Sopenharmony_ci<li><code>gid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the group identity of the process (see <a href="http://man7.org/linux/man-pages/man2/setgid.2.html"><code>setgid(2)</code></a>).</li> 8821cb0ef41Sopenharmony_ci<li><code>serialization</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Specify the kind of serialization used for sending 8831cb0ef41Sopenharmony_cimessages between processes. Possible values are <code>'json'</code> and <code>'advanced'</code>. 8841cb0ef41Sopenharmony_ciSee <a href="#advanced-serialization">Advanced serialization</a> for more details. <strong>Default:</strong> <code>'json'</code>.</li> 8851cb0ef41Sopenharmony_ci<li><code>shell</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If <code>true</code>, runs <code>command</code> inside of a shell. Uses 8861cb0ef41Sopenharmony_ci<code>'/bin/sh'</code> on Unix, and <code>process.env.ComSpec</code> on Windows. A different 8871cb0ef41Sopenharmony_cishell can be specified as a string. See <a href="#shell-requirements">Shell requirements</a> and 8881cb0ef41Sopenharmony_ci<a href="#default-windows-shell">Default Windows shell</a>. <strong>Default:</strong> <code>false</code> (no shell).</li> 8891cb0ef41Sopenharmony_ci<li><code>windowsVerbatimArguments</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> No quoting or escaping of arguments is 8901cb0ef41Sopenharmony_cidone on Windows. Ignored on Unix. This is set to <code>true</code> automatically 8911cb0ef41Sopenharmony_ciwhen <code>shell</code> is specified and is CMD. <strong>Default:</strong> <code>false</code>.</li> 8921cb0ef41Sopenharmony_ci<li><code>windowsHide</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Hide the subprocess console window that would 8931cb0ef41Sopenharmony_cinormally be created on Windows systems. <strong>Default:</strong> <code>false</code>.</li> 8941cb0ef41Sopenharmony_ci<li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> allows aborting the child process using an 8951cb0ef41Sopenharmony_ciAbortSignal.</li> 8961cb0ef41Sopenharmony_ci<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> In milliseconds the maximum amount of time the process 8971cb0ef41Sopenharmony_ciis allowed to run. <strong>Default:</strong> <code>undefined</code>.</li> 8981cb0ef41Sopenharmony_ci<li><code>killSignal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The signal value to be used when the spawned 8991cb0ef41Sopenharmony_ciprocess will be killed by timeout or abort signal. <strong>Default:</strong> <code>'SIGTERM'</code>.</li> 9001cb0ef41Sopenharmony_ci</ul> 9011cb0ef41Sopenharmony_ci</li> 9021cb0ef41Sopenharmony_ci<li>Returns: <a href="child_process.html#class-childprocess" class="type"><ChildProcess></a></li> 9031cb0ef41Sopenharmony_ci</ul> 9041cb0ef41Sopenharmony_ci<p>The <code>child_process.spawn()</code> method spawns a new process using the given 9051cb0ef41Sopenharmony_ci<code>command</code>, with command-line arguments in <code>args</code>. If omitted, <code>args</code> defaults 9061cb0ef41Sopenharmony_cito an empty array.</p> 9071cb0ef41Sopenharmony_ci<p><strong>If the <code>shell</code> option is enabled, do not pass unsanitized user input to this 9081cb0ef41Sopenharmony_cifunction. Any input containing shell metacharacters may be used to trigger 9091cb0ef41Sopenharmony_ciarbitrary command execution.</strong></p> 9101cb0ef41Sopenharmony_ci<p>A third argument may be used to specify additional options, with these defaults:</p> 9111cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> defaults = { 9121cb0ef41Sopenharmony_ci <span class="hljs-attr">cwd</span>: <span class="hljs-literal">undefined</span>, 9131cb0ef41Sopenharmony_ci <span class="hljs-attr">env</span>: process.<span class="hljs-property">env</span>, 9141cb0ef41Sopenharmony_ci};</code> <button class="copy-button">copy</button></pre> 9151cb0ef41Sopenharmony_ci<p>Use <code>cwd</code> to specify the working directory from which the process is spawned. 9161cb0ef41Sopenharmony_ciIf not given, the default is to inherit the current working directory. If given, 9171cb0ef41Sopenharmony_cibut the path does not exist, the child process emits an <code>ENOENT</code> error 9181cb0ef41Sopenharmony_ciand exits immediately. <code>ENOENT</code> is also emitted when the command 9191cb0ef41Sopenharmony_cidoes not exist.</p> 9201cb0ef41Sopenharmony_ci<p>Use <code>env</code> to specify environment variables that will be visible to the new 9211cb0ef41Sopenharmony_ciprocess, the default is <a href="process.html#processenv"><code>process.env</code></a>.</p> 9221cb0ef41Sopenharmony_ci<p><code>undefined</code> values in <code>env</code> will be ignored.</p> 9231cb0ef41Sopenharmony_ci<p>Example of running <code>ls -lh /usr</code>, capturing <code>stdout</code>, <code>stderr</code>, and the 9241cb0ef41Sopenharmony_ciexit code:</p> 9251cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 9261cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> ls = <span class="hljs-title function_">spawn</span>(<span class="hljs-string">'ls'</span>, [<span class="hljs-string">'-lh'</span>, <span class="hljs-string">'/usr'</span>]); 9271cb0ef41Sopenharmony_ci 9281cb0ef41Sopenharmony_cils.<span class="hljs-property">stdout</span>.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 9291cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`stdout: <span class="hljs-subst">${data}</span>`</span>); 9301cb0ef41Sopenharmony_ci}); 9311cb0ef41Sopenharmony_ci 9321cb0ef41Sopenharmony_cils.<span class="hljs-property">stderr</span>.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 9331cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`stderr: <span class="hljs-subst">${data}</span>`</span>); 9341cb0ef41Sopenharmony_ci}); 9351cb0ef41Sopenharmony_ci 9361cb0ef41Sopenharmony_cils.<span class="hljs-title function_">on</span>(<span class="hljs-string">'close'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 9371cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`child process exited with code <span class="hljs-subst">${code}</span>`</span>); 9381cb0ef41Sopenharmony_ci});</code> <button class="copy-button">copy</button></pre> 9391cb0ef41Sopenharmony_ci<p>Example: A very elaborate way to run <code>ps ax | grep ssh</code></p> 9401cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 9411cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> ps = <span class="hljs-title function_">spawn</span>(<span class="hljs-string">'ps'</span>, [<span class="hljs-string">'ax'</span>]); 9421cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> grep = <span class="hljs-title function_">spawn</span>(<span class="hljs-string">'grep'</span>, [<span class="hljs-string">'ssh'</span>]); 9431cb0ef41Sopenharmony_ci 9441cb0ef41Sopenharmony_cips.<span class="hljs-property">stdout</span>.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 9451cb0ef41Sopenharmony_ci grep.<span class="hljs-property">stdin</span>.<span class="hljs-title function_">write</span>(data); 9461cb0ef41Sopenharmony_ci}); 9471cb0ef41Sopenharmony_ci 9481cb0ef41Sopenharmony_cips.<span class="hljs-property">stderr</span>.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 9491cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`ps stderr: <span class="hljs-subst">${data}</span>`</span>); 9501cb0ef41Sopenharmony_ci}); 9511cb0ef41Sopenharmony_ci 9521cb0ef41Sopenharmony_cips.<span class="hljs-title function_">on</span>(<span class="hljs-string">'close'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 9531cb0ef41Sopenharmony_ci <span class="hljs-keyword">if</span> (code !== <span class="hljs-number">0</span>) { 9541cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`ps process exited with code <span class="hljs-subst">${code}</span>`</span>); 9551cb0ef41Sopenharmony_ci } 9561cb0ef41Sopenharmony_ci grep.<span class="hljs-property">stdin</span>.<span class="hljs-title function_">end</span>(); 9571cb0ef41Sopenharmony_ci}); 9581cb0ef41Sopenharmony_ci 9591cb0ef41Sopenharmony_cigrep.<span class="hljs-property">stdout</span>.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 9601cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(data.<span class="hljs-title function_">toString</span>()); 9611cb0ef41Sopenharmony_ci}); 9621cb0ef41Sopenharmony_ci 9631cb0ef41Sopenharmony_cigrep.<span class="hljs-property">stderr</span>.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 9641cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`grep stderr: <span class="hljs-subst">${data}</span>`</span>); 9651cb0ef41Sopenharmony_ci}); 9661cb0ef41Sopenharmony_ci 9671cb0ef41Sopenharmony_cigrep.<span class="hljs-title function_">on</span>(<span class="hljs-string">'close'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 9681cb0ef41Sopenharmony_ci <span class="hljs-keyword">if</span> (code !== <span class="hljs-number">0</span>) { 9691cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`grep process exited with code <span class="hljs-subst">${code}</span>`</span>); 9701cb0ef41Sopenharmony_ci } 9711cb0ef41Sopenharmony_ci});</code> <button class="copy-button">copy</button></pre> 9721cb0ef41Sopenharmony_ci<p>Example of checking for failed <code>spawn</code>:</p> 9731cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 9741cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> subprocess = <span class="hljs-title function_">spawn</span>(<span class="hljs-string">'bad_command'</span>); 9751cb0ef41Sopenharmony_ci 9761cb0ef41Sopenharmony_cisubprocess.<span class="hljs-title function_">on</span>(<span class="hljs-string">'error'</span>, <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 9771cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">'Failed to start subprocess.'</span>); 9781cb0ef41Sopenharmony_ci});</code> <button class="copy-button">copy</button></pre> 9791cb0ef41Sopenharmony_ci<p>Certain platforms (macOS, Linux) will use the value of <code>argv[0]</code> for the process 9801cb0ef41Sopenharmony_cititle while others (Windows, SunOS) will use <code>command</code>.</p> 9811cb0ef41Sopenharmony_ci<p>Node.js overwrites <code>argv[0]</code> with <code>process.execPath</code> on startup, so 9821cb0ef41Sopenharmony_ci<code>process.argv[0]</code> in a Node.js child process will not match the <code>argv0</code> 9831cb0ef41Sopenharmony_ciparameter passed to <code>spawn</code> from the parent. Retrieve it with the 9841cb0ef41Sopenharmony_ci<code>process.argv0</code> property instead.</p> 9851cb0ef41Sopenharmony_ci<p>If the <code>signal</code> option is enabled, calling <code>.abort()</code> on the corresponding 9861cb0ef41Sopenharmony_ci<code>AbortController</code> is similar to calling <code>.kill()</code> on the child process except 9871cb0ef41Sopenharmony_cithe error passed to the callback will be an <code>AbortError</code>:</p> 9881cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 9891cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> controller = <span class="hljs-keyword">new</span> <span class="hljs-title class_">AbortController</span>(); 9901cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> { signal } = controller; 9911cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> grep = <span class="hljs-title function_">spawn</span>(<span class="hljs-string">'grep'</span>, [<span class="hljs-string">'ssh'</span>], { signal }); 9921cb0ef41Sopenharmony_cigrep.<span class="hljs-title function_">on</span>(<span class="hljs-string">'error'</span>, <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 9931cb0ef41Sopenharmony_ci <span class="hljs-comment">// This will be called with err being an AbortError if the controller aborts</span> 9941cb0ef41Sopenharmony_ci}); 9951cb0ef41Sopenharmony_cicontroller.<span class="hljs-title function_">abort</span>(); <span class="hljs-comment">// Stops the child process</span></code> <button class="copy-button">copy</button></pre> 9961cb0ef41Sopenharmony_ci<h5><code>options.detached</code><span><a class="mark" href="#optionsdetached" id="optionsdetached">#</a></span><a aria-hidden="true" class="legacy" id="child_process_options_detached"></a></h5> 9971cb0ef41Sopenharmony_ci<div class="api_metadata"> 9981cb0ef41Sopenharmony_ci<span>Added in: v0.7.10</span> 9991cb0ef41Sopenharmony_ci</div> 10001cb0ef41Sopenharmony_ci<p>On Windows, setting <code>options.detached</code> to <code>true</code> makes it possible for the 10011cb0ef41Sopenharmony_cichild process to continue running after the parent exits. The child will have 10021cb0ef41Sopenharmony_ciits own console window. Once enabled for a child process, it cannot be 10031cb0ef41Sopenharmony_cidisabled.</p> 10041cb0ef41Sopenharmony_ci<p>On non-Windows platforms, if <code>options.detached</code> is set to <code>true</code>, the child 10051cb0ef41Sopenharmony_ciprocess will be made the leader of a new process group and session. Child 10061cb0ef41Sopenharmony_ciprocesses may continue running after the parent exits regardless of whether 10071cb0ef41Sopenharmony_cithey are detached or not. See <a href="http://man7.org/linux/man-pages/man2/setsid.2.html"><code>setsid(2)</code></a> for more information.</p> 10081cb0ef41Sopenharmony_ci<p>By default, the parent will wait for the detached child to exit. To prevent the 10091cb0ef41Sopenharmony_ciparent from waiting for a given <code>subprocess</code> to exit, use the 10101cb0ef41Sopenharmony_ci<code>subprocess.unref()</code> method. Doing so will cause the parent's event loop to not 10111cb0ef41Sopenharmony_ciinclude the child in its reference count, allowing the parent to exit 10121cb0ef41Sopenharmony_ciindependently of the child, unless there is an established IPC channel between 10131cb0ef41Sopenharmony_cithe child and the parent.</p> 10141cb0ef41Sopenharmony_ci<p>When using the <code>detached</code> option to start a long-running process, the process 10151cb0ef41Sopenharmony_ciwill not stay running in the background after the parent exits unless it is 10161cb0ef41Sopenharmony_ciprovided with a <code>stdio</code> configuration that is not connected to the parent. 10171cb0ef41Sopenharmony_ciIf the parent's <code>stdio</code> is inherited, the child will remain attached to the 10181cb0ef41Sopenharmony_cicontrolling terminal.</p> 10191cb0ef41Sopenharmony_ci<p>Example of a long-running process, by detaching and also ignoring its parent 10201cb0ef41Sopenharmony_ci<code>stdio</code> file descriptors, in order to ignore the parent's termination:</p> 10211cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 10221cb0ef41Sopenharmony_ci 10231cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> subprocess = <span class="hljs-title function_">spawn</span>(process.<span class="hljs-property">argv</span>[<span class="hljs-number">0</span>], [<span class="hljs-string">'child_program.js'</span>], { 10241cb0ef41Sopenharmony_ci <span class="hljs-attr">detached</span>: <span class="hljs-literal">true</span>, 10251cb0ef41Sopenharmony_ci <span class="hljs-attr">stdio</span>: <span class="hljs-string">'ignore'</span>, 10261cb0ef41Sopenharmony_ci}); 10271cb0ef41Sopenharmony_ci 10281cb0ef41Sopenharmony_cisubprocess.<span class="hljs-title function_">unref</span>();</code> <button class="copy-button">copy</button></pre> 10291cb0ef41Sopenharmony_ci<p>Alternatively one can redirect the child process' output into files:</p> 10301cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> fs = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:fs'</span>); 10311cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> { spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 10321cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> out = fs.<span class="hljs-title function_">openSync</span>(<span class="hljs-string">'./out.log'</span>, <span class="hljs-string">'a'</span>); 10331cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> err = fs.<span class="hljs-title function_">openSync</span>(<span class="hljs-string">'./out.log'</span>, <span class="hljs-string">'a'</span>); 10341cb0ef41Sopenharmony_ci 10351cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> subprocess = <span class="hljs-title function_">spawn</span>(<span class="hljs-string">'prg'</span>, [], { 10361cb0ef41Sopenharmony_ci <span class="hljs-attr">detached</span>: <span class="hljs-literal">true</span>, 10371cb0ef41Sopenharmony_ci <span class="hljs-attr">stdio</span>: [ <span class="hljs-string">'ignore'</span>, out, err ], 10381cb0ef41Sopenharmony_ci}); 10391cb0ef41Sopenharmony_ci 10401cb0ef41Sopenharmony_cisubprocess.<span class="hljs-title function_">unref</span>();</code> <button class="copy-button">copy</button></pre> 10411cb0ef41Sopenharmony_ci<h5><code>options.stdio</code><span><a class="mark" href="#optionsstdio" id="optionsstdio">#</a></span><a aria-hidden="true" class="legacy" id="child_process_options_stdio"></a></h5> 10421cb0ef41Sopenharmony_ci<div class="api_metadata"> 10431cb0ef41Sopenharmony_ci<details class="changelog"><summary>History</summary> 10441cb0ef41Sopenharmony_ci<table> 10451cb0ef41Sopenharmony_ci<tbody><tr><th>Version</th><th>Changes</th></tr> 10461cb0ef41Sopenharmony_ci<tr><td>v15.6.0, v14.18.0</td> 10471cb0ef41Sopenharmony_ci<td><p>Added the <code>overlapped</code> stdio flag.</p></td></tr> 10481cb0ef41Sopenharmony_ci<tr><td>v3.3.1</td> 10491cb0ef41Sopenharmony_ci<td><p>The value <code>0</code> is now accepted as a file descriptor.</p></td></tr> 10501cb0ef41Sopenharmony_ci<tr><td>v0.7.10</td> 10511cb0ef41Sopenharmony_ci<td><p><span>Added in: v0.7.10</span></p></td></tr> 10521cb0ef41Sopenharmony_ci</tbody></table> 10531cb0ef41Sopenharmony_ci</details> 10541cb0ef41Sopenharmony_ci</div> 10551cb0ef41Sopenharmony_ci<p>The <code>options.stdio</code> option is used to configure the pipes that are established 10561cb0ef41Sopenharmony_cibetween the parent and child process. By default, the child's stdin, stdout, 10571cb0ef41Sopenharmony_ciand stderr are redirected to corresponding <a href="#subprocessstdin"><code>subprocess.stdin</code></a>, 10581cb0ef41Sopenharmony_ci<a href="#subprocessstdout"><code>subprocess.stdout</code></a>, and <a href="#subprocessstderr"><code>subprocess.stderr</code></a> streams on the 10591cb0ef41Sopenharmony_ci<a href="#class-childprocess"><code>ChildProcess</code></a> object. This is equivalent to setting the <code>options.stdio</code> 10601cb0ef41Sopenharmony_ciequal to <code>['pipe', 'pipe', 'pipe']</code>.</p> 10611cb0ef41Sopenharmony_ci<p>For convenience, <code>options.stdio</code> may be one of the following strings:</p> 10621cb0ef41Sopenharmony_ci<ul> 10631cb0ef41Sopenharmony_ci<li><code>'pipe'</code>: equivalent to <code>['pipe', 'pipe', 'pipe']</code> (the default)</li> 10641cb0ef41Sopenharmony_ci<li><code>'overlapped'</code>: equivalent to <code>['overlapped', 'overlapped', 'overlapped']</code></li> 10651cb0ef41Sopenharmony_ci<li><code>'ignore'</code>: equivalent to <code>['ignore', 'ignore', 'ignore']</code></li> 10661cb0ef41Sopenharmony_ci<li><code>'inherit'</code>: equivalent to <code>['inherit', 'inherit', 'inherit']</code> or <code>[0, 1, 2]</code></li> 10671cb0ef41Sopenharmony_ci</ul> 10681cb0ef41Sopenharmony_ci<p>Otherwise, the value of <code>options.stdio</code> is an array where each index corresponds 10691cb0ef41Sopenharmony_cito an fd in the child. The fds 0, 1, and 2 correspond to stdin, stdout, 10701cb0ef41Sopenharmony_ciand stderr, respectively. Additional fds can be specified to create additional 10711cb0ef41Sopenharmony_cipipes between the parent and child. The value is one of the following:</p> 10721cb0ef41Sopenharmony_ci<ol> 10731cb0ef41Sopenharmony_ci<li> 10741cb0ef41Sopenharmony_ci<p><code>'pipe'</code>: Create a pipe between the child process and the parent process. 10751cb0ef41Sopenharmony_ciThe parent end of the pipe is exposed to the parent as a property on the 10761cb0ef41Sopenharmony_ci<code>child_process</code> object as <a href="#subprocessstdio"><code>subprocess.stdio[fd]</code></a>. Pipes 10771cb0ef41Sopenharmony_cicreated for fds 0, 1, and 2 are also available as <a href="#subprocessstdin"><code>subprocess.stdin</code></a>, 10781cb0ef41Sopenharmony_ci<a href="#subprocessstdout"><code>subprocess.stdout</code></a> and <a href="#subprocessstderr"><code>subprocess.stderr</code></a>, respectively. 10791cb0ef41Sopenharmony_ciThese are not actual Unix pipes and therefore the child process 10801cb0ef41Sopenharmony_cican not use them by their descriptor files, 10811cb0ef41Sopenharmony_cie.g. <code>/dev/fd/2</code> or <code>/dev/stdout</code>.</p> 10821cb0ef41Sopenharmony_ci</li> 10831cb0ef41Sopenharmony_ci<li> 10841cb0ef41Sopenharmony_ci<p><code>'overlapped'</code>: Same as <code>'pipe'</code> except that the <code>FILE_FLAG_OVERLAPPED</code> flag 10851cb0ef41Sopenharmony_ciis set on the handle. This is necessary for overlapped I/O on the child 10861cb0ef41Sopenharmony_ciprocess's stdio handles. See the 10871cb0ef41Sopenharmony_ci<a href="https://docs.microsoft.com/en-us/windows/win32/fileio/synchronous-and-asynchronous-i-o">docs</a> 10881cb0ef41Sopenharmony_cifor more details. This is exactly the same as <code>'pipe'</code> on non-Windows 10891cb0ef41Sopenharmony_cisystems.</p> 10901cb0ef41Sopenharmony_ci</li> 10911cb0ef41Sopenharmony_ci<li> 10921cb0ef41Sopenharmony_ci<p><code>'ipc'</code>: Create an IPC channel for passing messages/file descriptors 10931cb0ef41Sopenharmony_cibetween parent and child. A <a href="#class-childprocess"><code>ChildProcess</code></a> may have at most one IPC 10941cb0ef41Sopenharmony_cistdio file descriptor. Setting this option enables the 10951cb0ef41Sopenharmony_ci<a href="#subprocesssendmessage-sendhandle-options-callback"><code>subprocess.send()</code></a> method. If the child is a Node.js process, the 10961cb0ef41Sopenharmony_cipresence of an IPC channel will enable <a href="process.html#processsendmessage-sendhandle-options-callback"><code>process.send()</code></a> and 10971cb0ef41Sopenharmony_ci<a href="process.html#processdisconnect"><code>process.disconnect()</code></a> methods, as well as <a href="process.html#event-disconnect"><code>'disconnect'</code></a> and 10981cb0ef41Sopenharmony_ci<a href="process.html#event-message"><code>'message'</code></a> events within the child.</p> 10991cb0ef41Sopenharmony_ci<p>Accessing the IPC channel fd in any way other than <a href="process.html#processsendmessage-sendhandle-options-callback"><code>process.send()</code></a> 11001cb0ef41Sopenharmony_cior using the IPC channel with a child process that is not a Node.js instance 11011cb0ef41Sopenharmony_ciis not supported.</p> 11021cb0ef41Sopenharmony_ci</li> 11031cb0ef41Sopenharmony_ci<li> 11041cb0ef41Sopenharmony_ci<p><code>'ignore'</code>: Instructs Node.js to ignore the fd in the child. While Node.js 11051cb0ef41Sopenharmony_ciwill always open fds 0, 1, and 2 for the processes it spawns, setting the fd 11061cb0ef41Sopenharmony_cito <code>'ignore'</code> will cause Node.js to open <code>/dev/null</code> and attach it to the 11071cb0ef41Sopenharmony_cichild's fd.</p> 11081cb0ef41Sopenharmony_ci</li> 11091cb0ef41Sopenharmony_ci<li> 11101cb0ef41Sopenharmony_ci<p><code>'inherit'</code>: Pass through the corresponding stdio stream to/from the 11111cb0ef41Sopenharmony_ciparent process. In the first three positions, this is equivalent to 11121cb0ef41Sopenharmony_ci<code>process.stdin</code>, <code>process.stdout</code>, and <code>process.stderr</code>, respectively. In 11131cb0ef41Sopenharmony_ciany other position, equivalent to <code>'ignore'</code>.</p> 11141cb0ef41Sopenharmony_ci</li> 11151cb0ef41Sopenharmony_ci<li> 11161cb0ef41Sopenharmony_ci<p><a href="stream.html#stream" class="type"><Stream></a> object: Share a readable or writable stream that refers to a tty, 11171cb0ef41Sopenharmony_cifile, socket, or a pipe with the child process. The stream's underlying 11181cb0ef41Sopenharmony_cifile descriptor is duplicated in the child process to the fd that 11191cb0ef41Sopenharmony_cicorresponds to the index in the <code>stdio</code> array. The stream must have an 11201cb0ef41Sopenharmony_ciunderlying descriptor (file streams do not until the <code>'open'</code> event has 11211cb0ef41Sopenharmony_cioccurred).</p> 11221cb0ef41Sopenharmony_ci</li> 11231cb0ef41Sopenharmony_ci<li> 11241cb0ef41Sopenharmony_ci<p>Positive integer: The integer value is interpreted as a file descriptor 11251cb0ef41Sopenharmony_cithat is open in the parent process. It is shared with the child 11261cb0ef41Sopenharmony_ciprocess, similar to how <a href="stream.html#stream" class="type"><Stream></a> objects can be shared. Passing sockets 11271cb0ef41Sopenharmony_ciis not supported on Windows.</p> 11281cb0ef41Sopenharmony_ci</li> 11291cb0ef41Sopenharmony_ci<li> 11301cb0ef41Sopenharmony_ci<p><code>null</code>, <code>undefined</code>: Use default value. For stdio fds 0, 1, and 2 (in other 11311cb0ef41Sopenharmony_ciwords, stdin, stdout, and stderr) a pipe is created. For fd 3 and up, the 11321cb0ef41Sopenharmony_cidefault is <code>'ignore'</code>.</p> 11331cb0ef41Sopenharmony_ci</li> 11341cb0ef41Sopenharmony_ci</ol> 11351cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 11361cb0ef41Sopenharmony_ci 11371cb0ef41Sopenharmony_ci<span class="hljs-comment">// Child will use parent's stdios.</span> 11381cb0ef41Sopenharmony_ci<span class="hljs-title function_">spawn</span>(<span class="hljs-string">'prg'</span>, [], { <span class="hljs-attr">stdio</span>: <span class="hljs-string">'inherit'</span> }); 11391cb0ef41Sopenharmony_ci 11401cb0ef41Sopenharmony_ci<span class="hljs-comment">// Spawn child sharing only stderr.</span> 11411cb0ef41Sopenharmony_ci<span class="hljs-title function_">spawn</span>(<span class="hljs-string">'prg'</span>, [], { <span class="hljs-attr">stdio</span>: [<span class="hljs-string">'pipe'</span>, <span class="hljs-string">'pipe'</span>, process.<span class="hljs-property">stderr</span>] }); 11421cb0ef41Sopenharmony_ci 11431cb0ef41Sopenharmony_ci<span class="hljs-comment">// Open an extra fd=4, to interact with programs presenting a</span> 11441cb0ef41Sopenharmony_ci<span class="hljs-comment">// startd-style interface.</span> 11451cb0ef41Sopenharmony_ci<span class="hljs-title function_">spawn</span>(<span class="hljs-string">'prg'</span>, [], { <span class="hljs-attr">stdio</span>: [<span class="hljs-string">'pipe'</span>, <span class="hljs-literal">null</span>, <span class="hljs-literal">null</span>, <span class="hljs-literal">null</span>, <span class="hljs-string">'pipe'</span>] });</code> <button class="copy-button">copy</button></pre> 11461cb0ef41Sopenharmony_ci<p><em>It is worth noting that when an IPC channel is established between the 11471cb0ef41Sopenharmony_ciparent and child processes, and the child is a Node.js process, the child 11481cb0ef41Sopenharmony_ciis launched with the IPC channel unreferenced (using <code>unref()</code>) until the 11491cb0ef41Sopenharmony_cichild registers an event handler for the <a href="process.html#event-disconnect"><code>'disconnect'</code></a> event 11501cb0ef41Sopenharmony_cior the <a href="process.html#event-message"><code>'message'</code></a> event. This allows the child to exit 11511cb0ef41Sopenharmony_cinormally without the process being held open by the open IPC channel.</em></p> 11521cb0ef41Sopenharmony_ci<p>On Unix-like operating systems, the <a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a> method 11531cb0ef41Sopenharmony_ciperforms memory operations synchronously before decoupling the event loop 11541cb0ef41Sopenharmony_cifrom the child. Applications with a large memory footprint may find frequent 11551cb0ef41Sopenharmony_ci<a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a> calls to be a bottleneck. For more information, 11561cb0ef41Sopenharmony_cisee <a href="https://bugs.chromium.org/p/v8/issues/detail?id=7381">V8 issue 7381</a>.</p> 11571cb0ef41Sopenharmony_ci<p>See also: <a href="#child_processexeccommand-options-callback"><code>child_process.exec()</code></a> and <a href="#child_processforkmodulepath-args-options"><code>child_process.fork()</code></a>.</p> 11581cb0ef41Sopenharmony_ci</section><section><h3>Synchronous process creation<span><a class="mark" href="#synchronous-process-creation" id="synchronous-process-creation">#</a></span><a aria-hidden="true" class="legacy" id="child_process_synchronous_process_creation"></a></h3> 11591cb0ef41Sopenharmony_ci<p>The <a href="#child_processspawnsynccommand-args-options"><code>child_process.spawnSync()</code></a>, <a href="#child_processexecsynccommand-options"><code>child_process.execSync()</code></a>, and 11601cb0ef41Sopenharmony_ci<a href="#child_processexecfilesyncfile-args-options"><code>child_process.execFileSync()</code></a> methods are synchronous and will block the 11611cb0ef41Sopenharmony_ciNode.js event loop, pausing execution of any additional code until the spawned 11621cb0ef41Sopenharmony_ciprocess exits.</p> 11631cb0ef41Sopenharmony_ci<p>Blocking calls like these are mostly useful for simplifying general-purpose 11641cb0ef41Sopenharmony_ciscripting tasks and for simplifying the loading/processing of application 11651cb0ef41Sopenharmony_ciconfiguration at startup.</p> 11661cb0ef41Sopenharmony_ci<h4><code>child_process.execFileSync(file[, args][, options])</code><span><a class="mark" href="#child_processexecfilesyncfile-args-options" id="child_processexecfilesyncfile-args-options">#</a></span><a aria-hidden="true" class="legacy" id="child_process_child_process_execfilesync_file_args_options"></a></h4> 11671cb0ef41Sopenharmony_ci<div class="api_metadata"> 11681cb0ef41Sopenharmony_ci<details class="changelog"><summary>History</summary> 11691cb0ef41Sopenharmony_ci<table> 11701cb0ef41Sopenharmony_ci<tbody><tr><th>Version</th><th>Changes</th></tr> 11711cb0ef41Sopenharmony_ci<tr><td>v16.4.0, v14.18.0</td> 11721cb0ef41Sopenharmony_ci<td><p>The <code>cwd</code> option can be a WHATWG <code>URL</code> object using <code>file:</code> protocol.</p></td></tr> 11731cb0ef41Sopenharmony_ci<tr><td>v10.10.0</td> 11741cb0ef41Sopenharmony_ci<td><p>The <code>input</code> option can now be any <code>TypedArray</code> or a <code>DataView</code>.</p></td></tr> 11751cb0ef41Sopenharmony_ci<tr><td>v8.8.0</td> 11761cb0ef41Sopenharmony_ci<td><p>The <code>windowsHide</code> option is supported now.</p></td></tr> 11771cb0ef41Sopenharmony_ci<tr><td>v8.0.0</td> 11781cb0ef41Sopenharmony_ci<td><p>The <code>input</code> option can now be a <code>Uint8Array</code>.</p></td></tr> 11791cb0ef41Sopenharmony_ci<tr><td>v6.2.1, v4.5.0</td> 11801cb0ef41Sopenharmony_ci<td><p>The <code>encoding</code> option can now explicitly be set to <code>buffer</code>.</p></td></tr> 11811cb0ef41Sopenharmony_ci<tr><td>v0.11.12</td> 11821cb0ef41Sopenharmony_ci<td><p><span>Added in: v0.11.12</span></p></td></tr> 11831cb0ef41Sopenharmony_ci</tbody></table> 11841cb0ef41Sopenharmony_ci</details> 11851cb0ef41Sopenharmony_ci</div> 11861cb0ef41Sopenharmony_ci<ul> 11871cb0ef41Sopenharmony_ci<li><code>file</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The name or path of the executable file to run.</li> 11881cb0ef41Sopenharmony_ci<li><code>args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> List of string arguments.</li> 11891cb0ef41Sopenharmony_ci<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 11901cb0ef41Sopenharmony_ci<ul> 11911cb0ef41Sopenharmony_ci<li><code>cwd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="url.html#the-whatwg-url-api" class="type"><URL></a> Current working directory of the child process.</li> 11921cb0ef41Sopenharmony_ci<li><code>input</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> The value which will be passed 11931cb0ef41Sopenharmony_cias stdin to the spawned process. Supplying this value will override 11941cb0ef41Sopenharmony_ci<code>stdio[0]</code>.</li> 11951cb0ef41Sopenharmony_ci<li><code>stdio</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" class="type"><Array></a> Child's stdio configuration. <code>stderr</code> by default will 11961cb0ef41Sopenharmony_cibe output to the parent process' stderr unless <code>stdio</code> is specified. 11971cb0ef41Sopenharmony_ci<strong>Default:</strong> <code>'pipe'</code>.</li> 11981cb0ef41Sopenharmony_ci<li><code>env</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Environment key-value pairs. <strong>Default:</strong> <code>process.env</code>.</li> 11991cb0ef41Sopenharmony_ci<li><code>uid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the user identity of the process (see <a href="http://man7.org/linux/man-pages/man2/setuid.2.html"><code>setuid(2)</code></a>).</li> 12001cb0ef41Sopenharmony_ci<li><code>gid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the group identity of the process (see <a href="http://man7.org/linux/man-pages/man2/setgid.2.html"><code>setgid(2)</code></a>).</li> 12011cb0ef41Sopenharmony_ci<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> In milliseconds the maximum amount of time the process 12021cb0ef41Sopenharmony_ciis allowed to run. <strong>Default:</strong> <code>undefined</code>.</li> 12031cb0ef41Sopenharmony_ci<li><code>killSignal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The signal value to be used when the spawned 12041cb0ef41Sopenharmony_ciprocess will be killed. <strong>Default:</strong> <code>'SIGTERM'</code>.</li> 12051cb0ef41Sopenharmony_ci<li><code>maxBuffer</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Largest amount of data in bytes allowed on stdout or 12061cb0ef41Sopenharmony_cistderr. If exceeded, the child process is terminated. See caveat at 12071cb0ef41Sopenharmony_ci<a href="#maxbuffer-and-unicode"><code>maxBuffer</code> and Unicode</a>. <strong>Default:</strong> <code>1024 * 1024</code>.</li> 12081cb0ef41Sopenharmony_ci<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The encoding used for all stdio inputs and outputs. 12091cb0ef41Sopenharmony_ci<strong>Default:</strong> <code>'buffer'</code>.</li> 12101cb0ef41Sopenharmony_ci<li><code>windowsHide</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Hide the subprocess console window that would 12111cb0ef41Sopenharmony_cinormally be created on Windows systems. <strong>Default:</strong> <code>false</code>.</li> 12121cb0ef41Sopenharmony_ci<li><code>shell</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If <code>true</code>, runs <code>command</code> inside of a shell. Uses 12131cb0ef41Sopenharmony_ci<code>'/bin/sh'</code> on Unix, and <code>process.env.ComSpec</code> on Windows. A different 12141cb0ef41Sopenharmony_cishell can be specified as a string. See <a href="#shell-requirements">Shell requirements</a> and 12151cb0ef41Sopenharmony_ci<a href="#default-windows-shell">Default Windows shell</a>. <strong>Default:</strong> <code>false</code> (no shell).</li> 12161cb0ef41Sopenharmony_ci</ul> 12171cb0ef41Sopenharmony_ci</li> 12181cb0ef41Sopenharmony_ci<li>Returns: <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The stdout from the command.</li> 12191cb0ef41Sopenharmony_ci</ul> 12201cb0ef41Sopenharmony_ci<p>The <code>child_process.execFileSync()</code> method is generally identical to 12211cb0ef41Sopenharmony_ci<a href="#child_processexecfilefile-args-options-callback"><code>child_process.execFile()</code></a> with the exception that the method will not 12221cb0ef41Sopenharmony_cireturn until the child process has fully closed. When a timeout has been 12231cb0ef41Sopenharmony_ciencountered and <code>killSignal</code> is sent, the method won't return until the process 12241cb0ef41Sopenharmony_cihas completely exited.</p> 12251cb0ef41Sopenharmony_ci<p>If the child process intercepts and handles the <code>SIGTERM</code> signal and 12261cb0ef41Sopenharmony_cidoes not exit, the parent process will still wait until the child process has 12271cb0ef41Sopenharmony_ciexited.</p> 12281cb0ef41Sopenharmony_ci<p>If the process times out or has a non-zero exit code, this method will throw an 12291cb0ef41Sopenharmony_ci<a href="errors.html#class-error"><code>Error</code></a> that will include the full result of the underlying 12301cb0ef41Sopenharmony_ci<a href="#child_processspawnsynccommand-args-options"><code>child_process.spawnSync()</code></a>.</p> 12311cb0ef41Sopenharmony_ci<p><strong>If the <code>shell</code> option is enabled, do not pass unsanitized user input to this 12321cb0ef41Sopenharmony_cifunction. Any input containing shell metacharacters may be used to trigger 12331cb0ef41Sopenharmony_ciarbitrary command execution.</strong></p> 12341cb0ef41Sopenharmony_ci<h4><code>child_process.execSync(command[, options])</code><span><a class="mark" href="#child_processexecsynccommand-options" id="child_processexecsynccommand-options">#</a></span><a aria-hidden="true" class="legacy" id="child_process_child_process_execsync_command_options"></a></h4> 12351cb0ef41Sopenharmony_ci<div class="api_metadata"> 12361cb0ef41Sopenharmony_ci<details class="changelog"><summary>History</summary> 12371cb0ef41Sopenharmony_ci<table> 12381cb0ef41Sopenharmony_ci<tbody><tr><th>Version</th><th>Changes</th></tr> 12391cb0ef41Sopenharmony_ci<tr><td>v16.4.0, v14.18.0</td> 12401cb0ef41Sopenharmony_ci<td><p>The <code>cwd</code> option can be a WHATWG <code>URL</code> object using <code>file:</code> protocol.</p></td></tr> 12411cb0ef41Sopenharmony_ci<tr><td>v10.10.0</td> 12421cb0ef41Sopenharmony_ci<td><p>The <code>input</code> option can now be any <code>TypedArray</code> or a <code>DataView</code>.</p></td></tr> 12431cb0ef41Sopenharmony_ci<tr><td>v8.8.0</td> 12441cb0ef41Sopenharmony_ci<td><p>The <code>windowsHide</code> option is supported now.</p></td></tr> 12451cb0ef41Sopenharmony_ci<tr><td>v8.0.0</td> 12461cb0ef41Sopenharmony_ci<td><p>The <code>input</code> option can now be a <code>Uint8Array</code>.</p></td></tr> 12471cb0ef41Sopenharmony_ci<tr><td>v0.11.12</td> 12481cb0ef41Sopenharmony_ci<td><p><span>Added in: v0.11.12</span></p></td></tr> 12491cb0ef41Sopenharmony_ci</tbody></table> 12501cb0ef41Sopenharmony_ci</details> 12511cb0ef41Sopenharmony_ci</div> 12521cb0ef41Sopenharmony_ci<ul> 12531cb0ef41Sopenharmony_ci<li><code>command</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The command to run.</li> 12541cb0ef41Sopenharmony_ci<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 12551cb0ef41Sopenharmony_ci<ul> 12561cb0ef41Sopenharmony_ci<li><code>cwd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="url.html#the-whatwg-url-api" class="type"><URL></a> Current working directory of the child process.</li> 12571cb0ef41Sopenharmony_ci<li><code>input</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> The value which will be passed 12581cb0ef41Sopenharmony_cias stdin to the spawned process. Supplying this value will override 12591cb0ef41Sopenharmony_ci<code>stdio[0]</code>.</li> 12601cb0ef41Sopenharmony_ci<li><code>stdio</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" class="type"><Array></a> Child's stdio configuration. <code>stderr</code> by default will 12611cb0ef41Sopenharmony_cibe output to the parent process' stderr unless <code>stdio</code> is specified. 12621cb0ef41Sopenharmony_ci<strong>Default:</strong> <code>'pipe'</code>.</li> 12631cb0ef41Sopenharmony_ci<li><code>env</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Environment key-value pairs. <strong>Default:</strong> <code>process.env</code>.</li> 12641cb0ef41Sopenharmony_ci<li><code>shell</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Shell to execute the command with. See 12651cb0ef41Sopenharmony_ci<a href="#shell-requirements">Shell requirements</a> and <a href="#default-windows-shell">Default Windows shell</a>. <strong>Default:</strong> 12661cb0ef41Sopenharmony_ci<code>'/bin/sh'</code> on Unix, <code>process.env.ComSpec</code> on Windows.</li> 12671cb0ef41Sopenharmony_ci<li><code>uid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the user identity of the process. (See <a href="http://man7.org/linux/man-pages/man2/setuid.2.html"><code>setuid(2)</code></a>).</li> 12681cb0ef41Sopenharmony_ci<li><code>gid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the group identity of the process. (See <a href="http://man7.org/linux/man-pages/man2/setgid.2.html"><code>setgid(2)</code></a>).</li> 12691cb0ef41Sopenharmony_ci<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> In milliseconds the maximum amount of time the process 12701cb0ef41Sopenharmony_ciis allowed to run. <strong>Default:</strong> <code>undefined</code>.</li> 12711cb0ef41Sopenharmony_ci<li><code>killSignal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The signal value to be used when the spawned 12721cb0ef41Sopenharmony_ciprocess will be killed. <strong>Default:</strong> <code>'SIGTERM'</code>.</li> 12731cb0ef41Sopenharmony_ci<li><code>maxBuffer</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Largest amount of data in bytes allowed on stdout or 12741cb0ef41Sopenharmony_cistderr. If exceeded, the child process is terminated and any output is 12751cb0ef41Sopenharmony_citruncated. See caveat at <a href="#maxbuffer-and-unicode"><code>maxBuffer</code> and Unicode</a>. 12761cb0ef41Sopenharmony_ci<strong>Default:</strong> <code>1024 * 1024</code>.</li> 12771cb0ef41Sopenharmony_ci<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The encoding used for all stdio inputs and outputs. 12781cb0ef41Sopenharmony_ci<strong>Default:</strong> <code>'buffer'</code>.</li> 12791cb0ef41Sopenharmony_ci<li><code>windowsHide</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Hide the subprocess console window that would 12801cb0ef41Sopenharmony_cinormally be created on Windows systems. <strong>Default:</strong> <code>false</code>.</li> 12811cb0ef41Sopenharmony_ci</ul> 12821cb0ef41Sopenharmony_ci</li> 12831cb0ef41Sopenharmony_ci<li>Returns: <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The stdout from the command.</li> 12841cb0ef41Sopenharmony_ci</ul> 12851cb0ef41Sopenharmony_ci<p>The <code>child_process.execSync()</code> method is generally identical to 12861cb0ef41Sopenharmony_ci<a href="#child_processexeccommand-options-callback"><code>child_process.exec()</code></a> with the exception that the method will not return 12871cb0ef41Sopenharmony_ciuntil the child process has fully closed. When a timeout has been encountered 12881cb0ef41Sopenharmony_ciand <code>killSignal</code> is sent, the method won't return until the process has 12891cb0ef41Sopenharmony_cicompletely exited. If the child process intercepts and handles the <code>SIGTERM</code> 12901cb0ef41Sopenharmony_cisignal and doesn't exit, the parent process will wait until the child process 12911cb0ef41Sopenharmony_cihas exited.</p> 12921cb0ef41Sopenharmony_ci<p>If the process times out or has a non-zero exit code, this method will throw. 12931cb0ef41Sopenharmony_ciThe <a href="errors.html#class-error"><code>Error</code></a> object will contain the entire result from 12941cb0ef41Sopenharmony_ci<a href="#child_processspawnsynccommand-args-options"><code>child_process.spawnSync()</code></a>.</p> 12951cb0ef41Sopenharmony_ci<p><strong>Never pass unsanitized user input to this function. Any input containing shell 12961cb0ef41Sopenharmony_cimetacharacters may be used to trigger arbitrary command execution.</strong></p> 12971cb0ef41Sopenharmony_ci<h4><code>child_process.spawnSync(command[, args][, options])</code><span><a class="mark" href="#child_processspawnsynccommand-args-options" id="child_processspawnsynccommand-args-options">#</a></span><a aria-hidden="true" class="legacy" id="child_process_child_process_spawnsync_command_args_options"></a></h4> 12981cb0ef41Sopenharmony_ci<div class="api_metadata"> 12991cb0ef41Sopenharmony_ci<details class="changelog"><summary>History</summary> 13001cb0ef41Sopenharmony_ci<table> 13011cb0ef41Sopenharmony_ci<tbody><tr><th>Version</th><th>Changes</th></tr> 13021cb0ef41Sopenharmony_ci<tr><td>v16.4.0, v14.18.0</td> 13031cb0ef41Sopenharmony_ci<td><p>The <code>cwd</code> option can be a WHATWG <code>URL</code> object using <code>file:</code> protocol.</p></td></tr> 13041cb0ef41Sopenharmony_ci<tr><td>v10.10.0</td> 13051cb0ef41Sopenharmony_ci<td><p>The <code>input</code> option can now be any <code>TypedArray</code> or a <code>DataView</code>.</p></td></tr> 13061cb0ef41Sopenharmony_ci<tr><td>v8.8.0</td> 13071cb0ef41Sopenharmony_ci<td><p>The <code>windowsHide</code> option is supported now.</p></td></tr> 13081cb0ef41Sopenharmony_ci<tr><td>v8.0.0</td> 13091cb0ef41Sopenharmony_ci<td><p>The <code>input</code> option can now be a <code>Uint8Array</code>.</p></td></tr> 13101cb0ef41Sopenharmony_ci<tr><td>v5.7.0</td> 13111cb0ef41Sopenharmony_ci<td><p>The <code>shell</code> option is supported now.</p></td></tr> 13121cb0ef41Sopenharmony_ci<tr><td>v6.2.1, v4.5.0</td> 13131cb0ef41Sopenharmony_ci<td><p>The <code>encoding</code> option can now explicitly be set to <code>buffer</code>.</p></td></tr> 13141cb0ef41Sopenharmony_ci<tr><td>v0.11.12</td> 13151cb0ef41Sopenharmony_ci<td><p><span>Added in: v0.11.12</span></p></td></tr> 13161cb0ef41Sopenharmony_ci</tbody></table> 13171cb0ef41Sopenharmony_ci</details> 13181cb0ef41Sopenharmony_ci</div> 13191cb0ef41Sopenharmony_ci<ul> 13201cb0ef41Sopenharmony_ci<li><code>command</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The command to run.</li> 13211cb0ef41Sopenharmony_ci<li><code>args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> List of string arguments.</li> 13221cb0ef41Sopenharmony_ci<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 13231cb0ef41Sopenharmony_ci<ul> 13241cb0ef41Sopenharmony_ci<li><code>cwd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="url.html#the-whatwg-url-api" class="type"><URL></a> Current working directory of the child process.</li> 13251cb0ef41Sopenharmony_ci<li><code>input</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> The value which will be passed 13261cb0ef41Sopenharmony_cias stdin to the spawned process. Supplying this value will override 13271cb0ef41Sopenharmony_ci<code>stdio[0]</code>.</li> 13281cb0ef41Sopenharmony_ci<li><code>argv0</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Explicitly set the value of <code>argv[0]</code> sent to the child 13291cb0ef41Sopenharmony_ciprocess. This will be set to <code>command</code> if not specified.</li> 13301cb0ef41Sopenharmony_ci<li><code>stdio</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" class="type"><Array></a> Child's stdio configuration.</li> 13311cb0ef41Sopenharmony_ci<li><code>env</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Environment key-value pairs. <strong>Default:</strong> <code>process.env</code>.</li> 13321cb0ef41Sopenharmony_ci<li><code>uid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the user identity of the process (see <a href="http://man7.org/linux/man-pages/man2/setuid.2.html"><code>setuid(2)</code></a>).</li> 13331cb0ef41Sopenharmony_ci<li><code>gid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the group identity of the process (see <a href="http://man7.org/linux/man-pages/man2/setgid.2.html"><code>setgid(2)</code></a>).</li> 13341cb0ef41Sopenharmony_ci<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> In milliseconds the maximum amount of time the process 13351cb0ef41Sopenharmony_ciis allowed to run. <strong>Default:</strong> <code>undefined</code>.</li> 13361cb0ef41Sopenharmony_ci<li><code>killSignal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The signal value to be used when the spawned 13371cb0ef41Sopenharmony_ciprocess will be killed. <strong>Default:</strong> <code>'SIGTERM'</code>.</li> 13381cb0ef41Sopenharmony_ci<li><code>maxBuffer</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Largest amount of data in bytes allowed on stdout or 13391cb0ef41Sopenharmony_cistderr. If exceeded, the child process is terminated and any output is 13401cb0ef41Sopenharmony_citruncated. See caveat at <a href="#maxbuffer-and-unicode"><code>maxBuffer</code> and Unicode</a>. 13411cb0ef41Sopenharmony_ci<strong>Default:</strong> <code>1024 * 1024</code>.</li> 13421cb0ef41Sopenharmony_ci<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The encoding used for all stdio inputs and outputs. 13431cb0ef41Sopenharmony_ci<strong>Default:</strong> <code>'buffer'</code>.</li> 13441cb0ef41Sopenharmony_ci<li><code>shell</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If <code>true</code>, runs <code>command</code> inside of a shell. Uses 13451cb0ef41Sopenharmony_ci<code>'/bin/sh'</code> on Unix, and <code>process.env.ComSpec</code> on Windows. A different 13461cb0ef41Sopenharmony_cishell can be specified as a string. See <a href="#shell-requirements">Shell requirements</a> and 13471cb0ef41Sopenharmony_ci<a href="#default-windows-shell">Default Windows shell</a>. <strong>Default:</strong> <code>false</code> (no shell).</li> 13481cb0ef41Sopenharmony_ci<li><code>windowsVerbatimArguments</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> No quoting or escaping of arguments is 13491cb0ef41Sopenharmony_cidone on Windows. Ignored on Unix. This is set to <code>true</code> automatically 13501cb0ef41Sopenharmony_ciwhen <code>shell</code> is specified and is CMD. <strong>Default:</strong> <code>false</code>.</li> 13511cb0ef41Sopenharmony_ci<li><code>windowsHide</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Hide the subprocess console window that would 13521cb0ef41Sopenharmony_cinormally be created on Windows systems. <strong>Default:</strong> <code>false</code>.</li> 13531cb0ef41Sopenharmony_ci</ul> 13541cb0ef41Sopenharmony_ci</li> 13551cb0ef41Sopenharmony_ci<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 13561cb0ef41Sopenharmony_ci<ul> 13571cb0ef41Sopenharmony_ci<li><code>pid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Pid of the child process.</li> 13581cb0ef41Sopenharmony_ci<li><code>output</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" class="type"><Array></a> Array of results from stdio output.</li> 13591cb0ef41Sopenharmony_ci<li><code>stdout</code> <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The contents of <code>output[1]</code>.</li> 13601cb0ef41Sopenharmony_ci<li><code>stderr</code> <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The contents of <code>output[2]</code>.</li> 13611cb0ef41Sopenharmony_ci<li><code>status</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Null_type" class="type"><null></a> The exit code of the subprocess, or <code>null</code> if the 13621cb0ef41Sopenharmony_cisubprocess terminated due to a signal.</li> 13631cb0ef41Sopenharmony_ci<li><code>signal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Null_type" class="type"><null></a> The signal used to kill the subprocess, or <code>null</code> if 13641cb0ef41Sopenharmony_cithe subprocess did not terminate due to a signal.</li> 13651cb0ef41Sopenharmony_ci<li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a> The error object if the child process failed or timed out.</li> 13661cb0ef41Sopenharmony_ci</ul> 13671cb0ef41Sopenharmony_ci</li> 13681cb0ef41Sopenharmony_ci</ul> 13691cb0ef41Sopenharmony_ci<p>The <code>child_process.spawnSync()</code> method is generally identical to 13701cb0ef41Sopenharmony_ci<a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a> with the exception that the function will not return 13711cb0ef41Sopenharmony_ciuntil the child process has fully closed. When a timeout has been encountered 13721cb0ef41Sopenharmony_ciand <code>killSignal</code> is sent, the method won't return until the process has 13731cb0ef41Sopenharmony_cicompletely exited. If the process intercepts and handles the <code>SIGTERM</code> signal 13741cb0ef41Sopenharmony_ciand doesn't exit, the parent process will wait until the child process has 13751cb0ef41Sopenharmony_ciexited.</p> 13761cb0ef41Sopenharmony_ci<p><strong>If the <code>shell</code> option is enabled, do not pass unsanitized user input to this 13771cb0ef41Sopenharmony_cifunction. Any input containing shell metacharacters may be used to trigger 13781cb0ef41Sopenharmony_ciarbitrary command execution.</strong></p> 13791cb0ef41Sopenharmony_ci</section><section><h3>Class: <code>ChildProcess</code><span><a class="mark" href="#class-childprocess" id="class-childprocess">#</a></span><a aria-hidden="true" class="legacy" id="child_process_class_childprocess"></a></h3> 13801cb0ef41Sopenharmony_ci<div class="api_metadata"> 13811cb0ef41Sopenharmony_ci<span>Added in: v2.2.0</span> 13821cb0ef41Sopenharmony_ci</div> 13831cb0ef41Sopenharmony_ci<ul> 13841cb0ef41Sopenharmony_ci<li>Extends: <a href="events.html#class-eventemitter" class="type"><EventEmitter></a></li> 13851cb0ef41Sopenharmony_ci</ul> 13861cb0ef41Sopenharmony_ci<p>Instances of the <code>ChildProcess</code> represent spawned child processes.</p> 13871cb0ef41Sopenharmony_ci<p>Instances of <code>ChildProcess</code> are not intended to be created directly. Rather, 13881cb0ef41Sopenharmony_ciuse the <a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a>, <a href="#child_processexeccommand-options-callback"><code>child_process.exec()</code></a>, 13891cb0ef41Sopenharmony_ci<a href="#child_processexecfilefile-args-options-callback"><code>child_process.execFile()</code></a>, or <a href="#child_processforkmodulepath-args-options"><code>child_process.fork()</code></a> methods to create 13901cb0ef41Sopenharmony_ciinstances of <code>ChildProcess</code>.</p> 13911cb0ef41Sopenharmony_ci<h4>Event: <code>'close'</code><span><a class="mark" href="#event-close" id="event-close">#</a></span><a aria-hidden="true" class="legacy" id="child_process_event_close"></a></h4> 13921cb0ef41Sopenharmony_ci<div class="api_metadata"> 13931cb0ef41Sopenharmony_ci<span>Added in: v0.7.7</span> 13941cb0ef41Sopenharmony_ci</div> 13951cb0ef41Sopenharmony_ci<ul> 13961cb0ef41Sopenharmony_ci<li><code>code</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The exit code if the child exited on its own.</li> 13971cb0ef41Sopenharmony_ci<li><code>signal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The signal by which the child process was terminated.</li> 13981cb0ef41Sopenharmony_ci</ul> 13991cb0ef41Sopenharmony_ci<p>The <code>'close'</code> event is emitted after a process has ended <em>and</em> the stdio 14001cb0ef41Sopenharmony_cistreams of a child process have been closed. This is distinct from the 14011cb0ef41Sopenharmony_ci<a href="#event-exit"><code>'exit'</code></a> event, since multiple processes might share the same stdio 14021cb0ef41Sopenharmony_cistreams. The <code>'close'</code> event will always emit after <a href="#event-exit"><code>'exit'</code></a> was 14031cb0ef41Sopenharmony_cialready emitted, or <a href="#event-error"><code>'error'</code></a> if the child failed to spawn.</p> 14041cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 14051cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> ls = <span class="hljs-title function_">spawn</span>(<span class="hljs-string">'ls'</span>, [<span class="hljs-string">'-lh'</span>, <span class="hljs-string">'/usr'</span>]); 14061cb0ef41Sopenharmony_ci 14071cb0ef41Sopenharmony_cils.<span class="hljs-property">stdout</span>.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 14081cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`stdout: <span class="hljs-subst">${data}</span>`</span>); 14091cb0ef41Sopenharmony_ci}); 14101cb0ef41Sopenharmony_ci 14111cb0ef41Sopenharmony_cils.<span class="hljs-title function_">on</span>(<span class="hljs-string">'close'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 14121cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`child process close all stdio with code <span class="hljs-subst">${code}</span>`</span>); 14131cb0ef41Sopenharmony_ci}); 14141cb0ef41Sopenharmony_ci 14151cb0ef41Sopenharmony_cils.<span class="hljs-title function_">on</span>(<span class="hljs-string">'exit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 14161cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`child process exited with code <span class="hljs-subst">${code}</span>`</span>); 14171cb0ef41Sopenharmony_ci});</code> <button class="copy-button">copy</button></pre> 14181cb0ef41Sopenharmony_ci<h4>Event: <code>'disconnect'</code><span><a class="mark" href="#event-disconnect" id="event-disconnect">#</a></span><a aria-hidden="true" class="legacy" id="child_process_event_disconnect"></a></h4> 14191cb0ef41Sopenharmony_ci<div class="api_metadata"> 14201cb0ef41Sopenharmony_ci<span>Added in: v0.7.2</span> 14211cb0ef41Sopenharmony_ci</div> 14221cb0ef41Sopenharmony_ci<p>The <code>'disconnect'</code> event is emitted after calling the 14231cb0ef41Sopenharmony_ci<a href="#subprocessdisconnect"><code>subprocess.disconnect()</code></a> method in parent process or 14241cb0ef41Sopenharmony_ci<a href="process.html#processdisconnect"><code>process.disconnect()</code></a> in child process. After disconnecting it is no longer 14251cb0ef41Sopenharmony_cipossible to send or receive messages, and the <a href="#subprocessconnected"><code>subprocess.connected</code></a> 14261cb0ef41Sopenharmony_ciproperty is <code>false</code>.</p> 14271cb0ef41Sopenharmony_ci<h4>Event: <code>'error'</code><span><a class="mark" href="#event-error" id="event-error">#</a></span><a aria-hidden="true" class="legacy" id="child_process_event_error"></a></h4> 14281cb0ef41Sopenharmony_ci<ul> 14291cb0ef41Sopenharmony_ci<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a> The error.</li> 14301cb0ef41Sopenharmony_ci</ul> 14311cb0ef41Sopenharmony_ci<p>The <code>'error'</code> event is emitted whenever:</p> 14321cb0ef41Sopenharmony_ci<ul> 14331cb0ef41Sopenharmony_ci<li>The process could not be spawned.</li> 14341cb0ef41Sopenharmony_ci<li>The process could not be killed.</li> 14351cb0ef41Sopenharmony_ci<li>Sending a message to the child process failed.</li> 14361cb0ef41Sopenharmony_ci<li>The child process was aborted via the <code>signal</code> option.</li> 14371cb0ef41Sopenharmony_ci</ul> 14381cb0ef41Sopenharmony_ci<p>The <code>'exit'</code> event may or may not fire after an error has occurred. When 14391cb0ef41Sopenharmony_cilistening to both the <code>'exit'</code> and <code>'error'</code> events, guard 14401cb0ef41Sopenharmony_ciagainst accidentally invoking handler functions multiple times.</p> 14411cb0ef41Sopenharmony_ci<p>See also <a href="#subprocesskillsignal"><code>subprocess.kill()</code></a> and <a href="#subprocesssendmessage-sendhandle-options-callback"><code>subprocess.send()</code></a>.</p> 14421cb0ef41Sopenharmony_ci<h4>Event: <code>'exit'</code><span><a class="mark" href="#event-exit" id="event-exit">#</a></span><a aria-hidden="true" class="legacy" id="child_process_event_exit"></a></h4> 14431cb0ef41Sopenharmony_ci<div class="api_metadata"> 14441cb0ef41Sopenharmony_ci<span>Added in: v0.1.90</span> 14451cb0ef41Sopenharmony_ci</div> 14461cb0ef41Sopenharmony_ci<ul> 14471cb0ef41Sopenharmony_ci<li><code>code</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The exit code if the child exited on its own.</li> 14481cb0ef41Sopenharmony_ci<li><code>signal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The signal by which the child process was terminated.</li> 14491cb0ef41Sopenharmony_ci</ul> 14501cb0ef41Sopenharmony_ci<p>The <code>'exit'</code> event is emitted after the child process ends. If the process 14511cb0ef41Sopenharmony_ciexited, <code>code</code> is the final exit code of the process, otherwise <code>null</code>. If the 14521cb0ef41Sopenharmony_ciprocess terminated due to receipt of a signal, <code>signal</code> is the string name of 14531cb0ef41Sopenharmony_cithe signal, otherwise <code>null</code>. One of the two will always be non-<code>null</code>.</p> 14541cb0ef41Sopenharmony_ci<p>When the <code>'exit'</code> event is triggered, child process stdio streams might still be 14551cb0ef41Sopenharmony_ciopen.</p> 14561cb0ef41Sopenharmony_ci<p>Node.js establishes signal handlers for <code>SIGINT</code> and <code>SIGTERM</code> and Node.js 14571cb0ef41Sopenharmony_ciprocesses will not terminate immediately due to receipt of those signals. 14581cb0ef41Sopenharmony_ciRather, Node.js will perform a sequence of cleanup actions and then will 14591cb0ef41Sopenharmony_cire-raise the handled signal.</p> 14601cb0ef41Sopenharmony_ci<p>See <a href="http://man7.org/linux/man-pages/man2/waitpid.2.html"><code>waitpid(2)</code></a>.</p> 14611cb0ef41Sopenharmony_ci<h4>Event: <code>'message'</code><span><a class="mark" href="#event-message" id="event-message">#</a></span><a aria-hidden="true" class="legacy" id="child_process_event_message"></a></h4> 14621cb0ef41Sopenharmony_ci<div class="api_metadata"> 14631cb0ef41Sopenharmony_ci<span>Added in: v0.5.9</span> 14641cb0ef41Sopenharmony_ci</div> 14651cb0ef41Sopenharmony_ci<ul> 14661cb0ef41Sopenharmony_ci<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> A parsed JSON object or primitive value.</li> 14671cb0ef41Sopenharmony_ci<li><code>sendHandle</code> <a href="net.html#serverlistenhandle-backlog-callback" class="type"><Handle></a> A <a href="net.html#class-netsocket"><code>net.Socket</code></a> or <a href="net.html#class-netserver"><code>net.Server</code></a> object, or 14681cb0ef41Sopenharmony_ciundefined.</li> 14691cb0ef41Sopenharmony_ci</ul> 14701cb0ef41Sopenharmony_ci<p>The <code>'message'</code> event is triggered when a child process uses 14711cb0ef41Sopenharmony_ci<a href="process.html#processsendmessage-sendhandle-options-callback"><code>process.send()</code></a> to send messages.</p> 14721cb0ef41Sopenharmony_ci<p>The message goes through serialization and parsing. The resulting 14731cb0ef41Sopenharmony_cimessage might not be the same as what is originally sent.</p> 14741cb0ef41Sopenharmony_ci<p>If the <code>serialization</code> option was set to <code>'advanced'</code> used when spawning the 14751cb0ef41Sopenharmony_cichild process, the <code>message</code> argument can contain data that JSON is not able 14761cb0ef41Sopenharmony_cito represent. 14771cb0ef41Sopenharmony_ciSee <a href="#advanced-serialization">Advanced serialization</a> for more details.</p> 14781cb0ef41Sopenharmony_ci<h4>Event: <code>'spawn'</code><span><a class="mark" href="#event-spawn" id="event-spawn">#</a></span><a aria-hidden="true" class="legacy" id="child_process_event_spawn"></a></h4> 14791cb0ef41Sopenharmony_ci<div class="api_metadata"> 14801cb0ef41Sopenharmony_ci<span>Added in: v15.1.0, v14.17.0</span> 14811cb0ef41Sopenharmony_ci</div> 14821cb0ef41Sopenharmony_ci<p>The <code>'spawn'</code> event is emitted once the child process has spawned successfully. 14831cb0ef41Sopenharmony_ciIf the child process does not spawn successfully, the <code>'spawn'</code> event is not 14841cb0ef41Sopenharmony_ciemitted and the <code>'error'</code> event is emitted instead.</p> 14851cb0ef41Sopenharmony_ci<p>If emitted, the <code>'spawn'</code> event comes before all other events and before any 14861cb0ef41Sopenharmony_cidata is received via <code>stdout</code> or <code>stderr</code>.</p> 14871cb0ef41Sopenharmony_ci<p>The <code>'spawn'</code> event will fire regardless of whether an error occurs <strong>within</strong> 14881cb0ef41Sopenharmony_cithe spawned process. For example, if <code>bash some-command</code> spawns successfully, 14891cb0ef41Sopenharmony_cithe <code>'spawn'</code> event will fire, though <code>bash</code> may fail to spawn <code>some-command</code>. 14901cb0ef41Sopenharmony_ciThis caveat also applies when using <code>{ shell: true }</code>.</p> 14911cb0ef41Sopenharmony_ci<h4><code>subprocess.channel</code><span><a class="mark" href="#subprocesschannel" id="subprocesschannel">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_channel"></a></h4> 14921cb0ef41Sopenharmony_ci<div class="api_metadata"> 14931cb0ef41Sopenharmony_ci<details class="changelog"><summary>History</summary> 14941cb0ef41Sopenharmony_ci<table> 14951cb0ef41Sopenharmony_ci<tbody><tr><th>Version</th><th>Changes</th></tr> 14961cb0ef41Sopenharmony_ci<tr><td>v14.0.0</td> 14971cb0ef41Sopenharmony_ci<td><p>The object no longer accidentally exposes native C++ bindings.</p></td></tr> 14981cb0ef41Sopenharmony_ci<tr><td>v7.1.0</td> 14991cb0ef41Sopenharmony_ci<td><p><span>Added in: v7.1.0</span></p></td></tr> 15001cb0ef41Sopenharmony_ci</tbody></table> 15011cb0ef41Sopenharmony_ci</details> 15021cb0ef41Sopenharmony_ci</div> 15031cb0ef41Sopenharmony_ci<ul> 15041cb0ef41Sopenharmony_ci<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> A pipe representing the IPC channel to the child process.</li> 15051cb0ef41Sopenharmony_ci</ul> 15061cb0ef41Sopenharmony_ci<p>The <code>subprocess.channel</code> property is a reference to the child's IPC channel. If 15071cb0ef41Sopenharmony_cino IPC channel exists, this property is <code>undefined</code>.</p> 15081cb0ef41Sopenharmony_ci<h5><code>subprocess.channel.ref()</code><span><a class="mark" href="#subprocesschannelref" id="subprocesschannelref">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_channel_ref"></a></h5> 15091cb0ef41Sopenharmony_ci<div class="api_metadata"> 15101cb0ef41Sopenharmony_ci<span>Added in: v7.1.0</span> 15111cb0ef41Sopenharmony_ci</div> 15121cb0ef41Sopenharmony_ci<p>This method makes the IPC channel keep the event loop of the parent process 15131cb0ef41Sopenharmony_cirunning if <code>.unref()</code> has been called before.</p> 15141cb0ef41Sopenharmony_ci<h5><code>subprocess.channel.unref()</code><span><a class="mark" href="#subprocesschannelunref" id="subprocesschannelunref">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_channel_unref"></a></h5> 15151cb0ef41Sopenharmony_ci<div class="api_metadata"> 15161cb0ef41Sopenharmony_ci<span>Added in: v7.1.0</span> 15171cb0ef41Sopenharmony_ci</div> 15181cb0ef41Sopenharmony_ci<p>This method makes the IPC channel not keep the event loop of the parent process 15191cb0ef41Sopenharmony_cirunning, and lets it finish even while the channel is open.</p> 15201cb0ef41Sopenharmony_ci<h4><code>subprocess.connected</code><span><a class="mark" href="#subprocessconnected" id="subprocessconnected">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_connected"></a></h4> 15211cb0ef41Sopenharmony_ci<div class="api_metadata"> 15221cb0ef41Sopenharmony_ci<span>Added in: v0.7.2</span> 15231cb0ef41Sopenharmony_ci</div> 15241cb0ef41Sopenharmony_ci<ul> 15251cb0ef41Sopenharmony_ci<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Set to <code>false</code> after <code>subprocess.disconnect()</code> is called.</li> 15261cb0ef41Sopenharmony_ci</ul> 15271cb0ef41Sopenharmony_ci<p>The <code>subprocess.connected</code> property indicates whether it is still possible to 15281cb0ef41Sopenharmony_cisend and receive messages from a child process. When <code>subprocess.connected</code> is 15291cb0ef41Sopenharmony_ci<code>false</code>, it is no longer possible to send or receive messages.</p> 15301cb0ef41Sopenharmony_ci<h4><code>subprocess.disconnect()</code><span><a class="mark" href="#subprocessdisconnect" id="subprocessdisconnect">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_disconnect"></a></h4> 15311cb0ef41Sopenharmony_ci<div class="api_metadata"> 15321cb0ef41Sopenharmony_ci<span>Added in: v0.7.2</span> 15331cb0ef41Sopenharmony_ci</div> 15341cb0ef41Sopenharmony_ci<p>Closes the IPC channel between parent and child, allowing the child to exit 15351cb0ef41Sopenharmony_cigracefully once there are no other connections keeping it alive. After calling 15361cb0ef41Sopenharmony_cithis method the <code>subprocess.connected</code> and <code>process.connected</code> properties in 15371cb0ef41Sopenharmony_ciboth the parent and child (respectively) will be set to <code>false</code>, and it will be 15381cb0ef41Sopenharmony_cino longer possible to pass messages between the processes.</p> 15391cb0ef41Sopenharmony_ci<p>The <code>'disconnect'</code> event will be emitted when there are no messages in the 15401cb0ef41Sopenharmony_ciprocess of being received. This will most often be triggered immediately after 15411cb0ef41Sopenharmony_cicalling <code>subprocess.disconnect()</code>.</p> 15421cb0ef41Sopenharmony_ci<p>When the child process is a Node.js instance (e.g. spawned using 15431cb0ef41Sopenharmony_ci<a href="#child_processforkmodulepath-args-options"><code>child_process.fork()</code></a>), the <code>process.disconnect()</code> method can be invoked 15441cb0ef41Sopenharmony_ciwithin the child process to close the IPC channel as well.</p> 15451cb0ef41Sopenharmony_ci<h4><code>subprocess.exitCode</code><span><a class="mark" href="#subprocessexitcode" id="subprocessexitcode">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_exitcode"></a></h4> 15461cb0ef41Sopenharmony_ci<ul> 15471cb0ef41Sopenharmony_ci<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 15481cb0ef41Sopenharmony_ci</ul> 15491cb0ef41Sopenharmony_ci<p>The <code>subprocess.exitCode</code> property indicates the exit code of the child process. 15501cb0ef41Sopenharmony_ciIf the child process is still running, the field will be <code>null</code>.</p> 15511cb0ef41Sopenharmony_ci<h4><code>subprocess.kill([signal])</code><span><a class="mark" href="#subprocesskillsignal" id="subprocesskillsignal">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_kill_signal"></a></h4> 15521cb0ef41Sopenharmony_ci<div class="api_metadata"> 15531cb0ef41Sopenharmony_ci<span>Added in: v0.1.90</span> 15541cb0ef41Sopenharmony_ci</div> 15551cb0ef41Sopenharmony_ci<ul> 15561cb0ef41Sopenharmony_ci<li><code>signal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 15571cb0ef41Sopenharmony_ci<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 15581cb0ef41Sopenharmony_ci</ul> 15591cb0ef41Sopenharmony_ci<p>The <code>subprocess.kill()</code> method sends a signal to the child process. If no 15601cb0ef41Sopenharmony_ciargument is given, the process will be sent the <code>'SIGTERM'</code> signal. See 15611cb0ef41Sopenharmony_ci<a href="http://man7.org/linux/man-pages/man7/signal.7.html"><code>signal(7)</code></a> for a list of available signals. This function returns <code>true</code> if 15621cb0ef41Sopenharmony_ci<a href="http://man7.org/linux/man-pages/man2/kill.2.html"><code>kill(2)</code></a> succeeds, and <code>false</code> otherwise.</p> 15631cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 15641cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> grep = <span class="hljs-title function_">spawn</span>(<span class="hljs-string">'grep'</span>, [<span class="hljs-string">'ssh'</span>]); 15651cb0ef41Sopenharmony_ci 15661cb0ef41Sopenharmony_cigrep.<span class="hljs-title function_">on</span>(<span class="hljs-string">'close'</span>, <span class="hljs-function">(<span class="hljs-params">code, signal</span>) =></span> { 15671cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>( 15681cb0ef41Sopenharmony_ci <span class="hljs-string">`child process terminated due to receipt of signal <span class="hljs-subst">${signal}</span>`</span>); 15691cb0ef41Sopenharmony_ci}); 15701cb0ef41Sopenharmony_ci 15711cb0ef41Sopenharmony_ci<span class="hljs-comment">// Send SIGHUP to process.</span> 15721cb0ef41Sopenharmony_cigrep.<span class="hljs-title function_">kill</span>(<span class="hljs-string">'SIGHUP'</span>);</code> <button class="copy-button">copy</button></pre> 15731cb0ef41Sopenharmony_ci<p>The <a href="#class-childprocess"><code>ChildProcess</code></a> object may emit an <a href="#event-error"><code>'error'</code></a> event if the signal 15741cb0ef41Sopenharmony_cicannot be delivered. Sending a signal to a child process that has already exited 15751cb0ef41Sopenharmony_ciis not an error but may have unforeseen consequences. Specifically, if the 15761cb0ef41Sopenharmony_ciprocess identifier (PID) has been reassigned to another process, the signal will 15771cb0ef41Sopenharmony_cibe delivered to that process instead which can have unexpected results.</p> 15781cb0ef41Sopenharmony_ci<p>While the function is called <code>kill</code>, the signal delivered to the child process 15791cb0ef41Sopenharmony_cimay not actually terminate the process.</p> 15801cb0ef41Sopenharmony_ci<p>See <a href="http://man7.org/linux/man-pages/man2/kill.2.html"><code>kill(2)</code></a> for reference.</p> 15811cb0ef41Sopenharmony_ci<p>On Windows, where POSIX signals do not exist, the <code>signal</code> argument will be 15821cb0ef41Sopenharmony_ciignored, and the process will be killed forcefully and abruptly (similar to 15831cb0ef41Sopenharmony_ci<code>'SIGKILL'</code>). 15841cb0ef41Sopenharmony_ciSee <a href="process.html#signal-events">Signal Events</a> for more details.</p> 15851cb0ef41Sopenharmony_ci<p>On Linux, child processes of child processes will not be terminated 15861cb0ef41Sopenharmony_ciwhen attempting to kill their parent. This is likely to happen when running a 15871cb0ef41Sopenharmony_cinew process in a shell or with the use of the <code>shell</code> option of <code>ChildProcess</code>:</p> 15881cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-meta">'use strict'</span>; 15891cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> { spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 15901cb0ef41Sopenharmony_ci 15911cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> subprocess = <span class="hljs-title function_">spawn</span>( 15921cb0ef41Sopenharmony_ci <span class="hljs-string">'sh'</span>, 15931cb0ef41Sopenharmony_ci [ 15941cb0ef41Sopenharmony_ci <span class="hljs-string">'-c'</span>, 15951cb0ef41Sopenharmony_ci <span class="hljs-string">`node -e "setInterval(() => { 15961cb0ef41Sopenharmony_ci console.log(process.pid, 'is alive') 15971cb0ef41Sopenharmony_ci }, 500);"`</span>, 15981cb0ef41Sopenharmony_ci ], { 15991cb0ef41Sopenharmony_ci <span class="hljs-attr">stdio</span>: [<span class="hljs-string">'inherit'</span>, <span class="hljs-string">'inherit'</span>, <span class="hljs-string">'inherit'</span>], 16001cb0ef41Sopenharmony_ci }, 16011cb0ef41Sopenharmony_ci); 16021cb0ef41Sopenharmony_ci 16031cb0ef41Sopenharmony_ci<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 16041cb0ef41Sopenharmony_ci subprocess.<span class="hljs-title function_">kill</span>(); <span class="hljs-comment">// Does not terminate the Node.js process in the shell.</span> 16051cb0ef41Sopenharmony_ci}, <span class="hljs-number">2000</span>);</code> <button class="copy-button">copy</button></pre> 16061cb0ef41Sopenharmony_ci<h4><code>subprocess[Symbol.dispose]()</code><span><a class="mark" href="#subprocesssymboldispose" id="subprocesssymboldispose">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_symbol_dispose"></a></h4> 16071cb0ef41Sopenharmony_ci<div class="api_metadata"> 16081cb0ef41Sopenharmony_ci<span>Added in: v18.18.0</span> 16091cb0ef41Sopenharmony_ci</div> 16101cb0ef41Sopenharmony_ci<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 16111cb0ef41Sopenharmony_ci<p>Calls <a href="#subprocesskillsignal"><code>subprocess.kill()</code></a> with <code>'SIGTERM'</code>.</p> 16121cb0ef41Sopenharmony_ci<h4><code>subprocess.killed</code><span><a class="mark" href="#subprocesskilled" id="subprocesskilled">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_killed"></a></h4> 16131cb0ef41Sopenharmony_ci<div class="api_metadata"> 16141cb0ef41Sopenharmony_ci<span>Added in: v0.5.10</span> 16151cb0ef41Sopenharmony_ci</div> 16161cb0ef41Sopenharmony_ci<ul> 16171cb0ef41Sopenharmony_ci<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Set to <code>true</code> after <code>subprocess.kill()</code> is used to successfully 16181cb0ef41Sopenharmony_cisend a signal to the child process.</li> 16191cb0ef41Sopenharmony_ci</ul> 16201cb0ef41Sopenharmony_ci<p>The <code>subprocess.killed</code> property indicates whether the child process 16211cb0ef41Sopenharmony_cisuccessfully received a signal from <code>subprocess.kill()</code>. The <code>killed</code> property 16221cb0ef41Sopenharmony_cidoes not indicate that the child process has been terminated.</p> 16231cb0ef41Sopenharmony_ci<h4><code>subprocess.pid</code><span><a class="mark" href="#subprocesspid" id="subprocesspid">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_pid"></a></h4> 16241cb0ef41Sopenharmony_ci<div class="api_metadata"> 16251cb0ef41Sopenharmony_ci<span>Added in: v0.1.90</span> 16261cb0ef41Sopenharmony_ci</div> 16271cb0ef41Sopenharmony_ci<ul> 16281cb0ef41Sopenharmony_ci<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Undefined_type" class="type"><undefined></a></li> 16291cb0ef41Sopenharmony_ci</ul> 16301cb0ef41Sopenharmony_ci<p>Returns the process identifier (PID) of the child process. If the child process 16311cb0ef41Sopenharmony_cifails to spawn due to errors, then the value is <code>undefined</code> and <code>error</code> is 16321cb0ef41Sopenharmony_ciemitted.</p> 16331cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 16341cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> grep = <span class="hljs-title function_">spawn</span>(<span class="hljs-string">'grep'</span>, [<span class="hljs-string">'ssh'</span>]); 16351cb0ef41Sopenharmony_ci 16361cb0ef41Sopenharmony_ci<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Spawned child pid: <span class="hljs-subst">${grep.pid}</span>`</span>); 16371cb0ef41Sopenharmony_cigrep.<span class="hljs-property">stdin</span>.<span class="hljs-title function_">end</span>();</code> <button class="copy-button">copy</button></pre> 16381cb0ef41Sopenharmony_ci<h4><code>subprocess.ref()</code><span><a class="mark" href="#subprocessref" id="subprocessref">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_ref"></a></h4> 16391cb0ef41Sopenharmony_ci<div class="api_metadata"> 16401cb0ef41Sopenharmony_ci<span>Added in: v0.7.10</span> 16411cb0ef41Sopenharmony_ci</div> 16421cb0ef41Sopenharmony_ci<p>Calling <code>subprocess.ref()</code> after making a call to <code>subprocess.unref()</code> will 16431cb0ef41Sopenharmony_cirestore the removed reference count for the child process, forcing the parent 16441cb0ef41Sopenharmony_cito wait for the child to exit before exiting itself.</p> 16451cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 16461cb0ef41Sopenharmony_ci 16471cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> subprocess = <span class="hljs-title function_">spawn</span>(process.<span class="hljs-property">argv</span>[<span class="hljs-number">0</span>], [<span class="hljs-string">'child_program.js'</span>], { 16481cb0ef41Sopenharmony_ci <span class="hljs-attr">detached</span>: <span class="hljs-literal">true</span>, 16491cb0ef41Sopenharmony_ci <span class="hljs-attr">stdio</span>: <span class="hljs-string">'ignore'</span>, 16501cb0ef41Sopenharmony_ci}); 16511cb0ef41Sopenharmony_ci 16521cb0ef41Sopenharmony_cisubprocess.<span class="hljs-title function_">unref</span>(); 16531cb0ef41Sopenharmony_cisubprocess.<span class="hljs-title function_">ref</span>();</code> <button class="copy-button">copy</button></pre> 16541cb0ef41Sopenharmony_ci<h4><code>subprocess.send(message[, sendHandle[, options]][, callback])</code><span><a class="mark" href="#subprocesssendmessage-sendhandle-options-callback" id="subprocesssendmessage-sendhandle-options-callback">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_send_message_sendhandle_options_callback"></a></h4> 16551cb0ef41Sopenharmony_ci<div class="api_metadata"> 16561cb0ef41Sopenharmony_ci<details class="changelog"><summary>History</summary> 16571cb0ef41Sopenharmony_ci<table> 16581cb0ef41Sopenharmony_ci<tbody><tr><th>Version</th><th>Changes</th></tr> 16591cb0ef41Sopenharmony_ci<tr><td>v5.8.0</td> 16601cb0ef41Sopenharmony_ci<td><p>The <code>options</code> parameter, and the <code>keepOpen</code> option in particular, is supported now.</p></td></tr> 16611cb0ef41Sopenharmony_ci<tr><td>v5.0.0</td> 16621cb0ef41Sopenharmony_ci<td><p>This method returns a boolean for flow control now.</p></td></tr> 16631cb0ef41Sopenharmony_ci<tr><td>v4.0.0</td> 16641cb0ef41Sopenharmony_ci<td><p>The <code>callback</code> parameter is supported now.</p></td></tr> 16651cb0ef41Sopenharmony_ci<tr><td>v0.5.9</td> 16661cb0ef41Sopenharmony_ci<td><p><span>Added in: v0.5.9</span></p></td></tr> 16671cb0ef41Sopenharmony_ci</tbody></table> 16681cb0ef41Sopenharmony_ci</details> 16691cb0ef41Sopenharmony_ci</div> 16701cb0ef41Sopenharmony_ci<ul> 16711cb0ef41Sopenharmony_ci<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 16721cb0ef41Sopenharmony_ci<li><code>sendHandle</code> <a href="net.html#serverlistenhandle-backlog-callback" class="type"><Handle></a></li> 16731cb0ef41Sopenharmony_ci<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> The <code>options</code> argument, if present, is an object used to 16741cb0ef41Sopenharmony_ciparameterize the sending of certain types of handles. <code>options</code> supports 16751cb0ef41Sopenharmony_cithe following properties: 16761cb0ef41Sopenharmony_ci<ul> 16771cb0ef41Sopenharmony_ci<li><code>keepOpen</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> A value that can be used when passing instances of 16781cb0ef41Sopenharmony_ci<code>net.Socket</code>. When <code>true</code>, the socket is kept open in the sending process. 16791cb0ef41Sopenharmony_ci<strong>Default:</strong> <code>false</code>.</li> 16801cb0ef41Sopenharmony_ci</ul> 16811cb0ef41Sopenharmony_ci</li> 16821cb0ef41Sopenharmony_ci<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 16831cb0ef41Sopenharmony_ci<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 16841cb0ef41Sopenharmony_ci</ul> 16851cb0ef41Sopenharmony_ci<p>When an IPC channel has been established between the parent and child ( 16861cb0ef41Sopenharmony_cii.e. when using <a href="#child_processforkmodulepath-args-options"><code>child_process.fork()</code></a>), the <code>subprocess.send()</code> method can 16871cb0ef41Sopenharmony_cibe used to send messages to the child process. When the child process is a 16881cb0ef41Sopenharmony_ciNode.js instance, these messages can be received via the <a href="process.html#event-message"><code>'message'</code></a> event.</p> 16891cb0ef41Sopenharmony_ci<p>The message goes through serialization and parsing. The resulting 16901cb0ef41Sopenharmony_cimessage might not be the same as what is originally sent.</p> 16911cb0ef41Sopenharmony_ci<p>For example, in the parent script:</p> 16921cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> cp = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 16931cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> n = cp.<span class="hljs-title function_">fork</span>(<span class="hljs-string">`<span class="hljs-subst">${__dirname}</span>/sub.js`</span>); 16941cb0ef41Sopenharmony_ci 16951cb0ef41Sopenharmony_cin.<span class="hljs-title function_">on</span>(<span class="hljs-string">'message'</span>, <span class="hljs-function">(<span class="hljs-params">m</span>) =></span> { 16961cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'PARENT got message:'</span>, m); 16971cb0ef41Sopenharmony_ci}); 16981cb0ef41Sopenharmony_ci 16991cb0ef41Sopenharmony_ci<span class="hljs-comment">// Causes the child to print: CHILD got message: { hello: 'world' }</span> 17001cb0ef41Sopenharmony_cin.<span class="hljs-title function_">send</span>({ <span class="hljs-attr">hello</span>: <span class="hljs-string">'world'</span> });</code> <button class="copy-button">copy</button></pre> 17011cb0ef41Sopenharmony_ci<p>And then the child script, <code>'sub.js'</code> might look like this:</p> 17021cb0ef41Sopenharmony_ci<pre><code class="language-js">process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'message'</span>, <span class="hljs-function">(<span class="hljs-params">m</span>) =></span> { 17031cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'CHILD got message:'</span>, m); 17041cb0ef41Sopenharmony_ci}); 17051cb0ef41Sopenharmony_ci 17061cb0ef41Sopenharmony_ci<span class="hljs-comment">// Causes the parent to print: PARENT got message: { foo: 'bar', baz: null }</span> 17071cb0ef41Sopenharmony_ciprocess.<span class="hljs-title function_">send</span>({ <span class="hljs-attr">foo</span>: <span class="hljs-string">'bar'</span>, <span class="hljs-attr">baz</span>: <span class="hljs-title class_">NaN</span> });</code> <button class="copy-button">copy</button></pre> 17081cb0ef41Sopenharmony_ci<p>Child Node.js processes will have a <a href="process.html#processsendmessage-sendhandle-options-callback"><code>process.send()</code></a> method of their own 17091cb0ef41Sopenharmony_cithat allows the child to send messages back to the parent.</p> 17101cb0ef41Sopenharmony_ci<p>There is a special case when sending a <code>{cmd: 'NODE_foo'}</code> message. Messages 17111cb0ef41Sopenharmony_cicontaining a <code>NODE_</code> prefix in the <code>cmd</code> property are reserved for use within 17121cb0ef41Sopenharmony_ciNode.js core and will not be emitted in the child's <a href="process.html#event-message"><code>'message'</code></a> 17131cb0ef41Sopenharmony_cievent. Rather, such messages are emitted using the 17141cb0ef41Sopenharmony_ci<code>'internalMessage'</code> event and are consumed internally by Node.js. 17151cb0ef41Sopenharmony_ciApplications should avoid using such messages or listening for 17161cb0ef41Sopenharmony_ci<code>'internalMessage'</code> events as it is subject to change without notice.</p> 17171cb0ef41Sopenharmony_ci<p>The optional <code>sendHandle</code> argument that may be passed to <code>subprocess.send()</code> is 17181cb0ef41Sopenharmony_cifor passing a TCP server or socket object to the child process. The child will 17191cb0ef41Sopenharmony_cireceive the object as the second argument passed to the callback function 17201cb0ef41Sopenharmony_ciregistered on the <a href="process.html#event-message"><code>'message'</code></a> event. Any data that is received 17211cb0ef41Sopenharmony_ciand buffered in the socket will not be sent to the child.</p> 17221cb0ef41Sopenharmony_ci<p>The optional <code>callback</code> is a function that is invoked after the message is 17231cb0ef41Sopenharmony_cisent but before the child may have received it. The function is called with a 17241cb0ef41Sopenharmony_cisingle argument: <code>null</code> on success, or an <a href="errors.html#class-error"><code>Error</code></a> object on failure.</p> 17251cb0ef41Sopenharmony_ci<p>If no <code>callback</code> function is provided and the message cannot be sent, an 17261cb0ef41Sopenharmony_ci<code>'error'</code> event will be emitted by the <a href="#class-childprocess"><code>ChildProcess</code></a> object. This can 17271cb0ef41Sopenharmony_cihappen, for instance, when the child process has already exited.</p> 17281cb0ef41Sopenharmony_ci<p><code>subprocess.send()</code> will return <code>false</code> if the channel has closed or when the 17291cb0ef41Sopenharmony_cibacklog of unsent messages exceeds a threshold that makes it unwise to send 17301cb0ef41Sopenharmony_cimore. Otherwise, the method returns <code>true</code>. The <code>callback</code> function can be 17311cb0ef41Sopenharmony_ciused to implement flow control.</p> 17321cb0ef41Sopenharmony_ci<h5>Example: sending a server object<span><a class="mark" href="#example-sending-a-server-object" id="example-sending-a-server-object">#</a></span><a aria-hidden="true" class="legacy" id="child_process_example_sending_a_server_object"></a></h5> 17331cb0ef41Sopenharmony_ci<p>The <code>sendHandle</code> argument can be used, for instance, to pass the handle of 17341cb0ef41Sopenharmony_cia TCP server object to the child process as illustrated in the example below:</p> 17351cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> subprocess = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>).<span class="hljs-title function_">fork</span>(<span class="hljs-string">'subprocess.js'</span>); 17361cb0ef41Sopenharmony_ci 17371cb0ef41Sopenharmony_ci<span class="hljs-comment">// Open up the server object and send the handle.</span> 17381cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> server = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:net'</span>).<span class="hljs-title function_">createServer</span>(); 17391cb0ef41Sopenharmony_ciserver.<span class="hljs-title function_">on</span>(<span class="hljs-string">'connection'</span>, <span class="hljs-function">(<span class="hljs-params">socket</span>) =></span> { 17401cb0ef41Sopenharmony_ci socket.<span class="hljs-title function_">end</span>(<span class="hljs-string">'handled by parent'</span>); 17411cb0ef41Sopenharmony_ci}); 17421cb0ef41Sopenharmony_ciserver.<span class="hljs-title function_">listen</span>(<span class="hljs-number">1337</span>, <span class="hljs-function">() =></span> { 17431cb0ef41Sopenharmony_ci subprocess.<span class="hljs-title function_">send</span>(<span class="hljs-string">'server'</span>, server); 17441cb0ef41Sopenharmony_ci});</code> <button class="copy-button">copy</button></pre> 17451cb0ef41Sopenharmony_ci<p>The child would then receive the server object as:</p> 17461cb0ef41Sopenharmony_ci<pre><code class="language-js">process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'message'</span>, <span class="hljs-function">(<span class="hljs-params">m, server</span>) =></span> { 17471cb0ef41Sopenharmony_ci <span class="hljs-keyword">if</span> (m === <span class="hljs-string">'server'</span>) { 17481cb0ef41Sopenharmony_ci server.<span class="hljs-title function_">on</span>(<span class="hljs-string">'connection'</span>, <span class="hljs-function">(<span class="hljs-params">socket</span>) =></span> { 17491cb0ef41Sopenharmony_ci socket.<span class="hljs-title function_">end</span>(<span class="hljs-string">'handled by child'</span>); 17501cb0ef41Sopenharmony_ci }); 17511cb0ef41Sopenharmony_ci } 17521cb0ef41Sopenharmony_ci});</code> <button class="copy-button">copy</button></pre> 17531cb0ef41Sopenharmony_ci<p>Once the server is now shared between the parent and child, some connections 17541cb0ef41Sopenharmony_cican be handled by the parent and some by the child.</p> 17551cb0ef41Sopenharmony_ci<p>While the example above uses a server created using the <code>node:net</code> module, 17561cb0ef41Sopenharmony_ci<code>node:dgram</code> module servers use exactly the same workflow with the exceptions of 17571cb0ef41Sopenharmony_cilistening on a <code>'message'</code> event instead of <code>'connection'</code> and using 17581cb0ef41Sopenharmony_ci<code>server.bind()</code> instead of <code>server.listen()</code>. This is, however, only 17591cb0ef41Sopenharmony_cisupported on Unix platforms.</p> 17601cb0ef41Sopenharmony_ci<h5>Example: sending a socket object<span><a class="mark" href="#example-sending-a-socket-object" id="example-sending-a-socket-object">#</a></span><a aria-hidden="true" class="legacy" id="child_process_example_sending_a_socket_object"></a></h5> 17611cb0ef41Sopenharmony_ci<p>Similarly, the <code>sendHandler</code> argument can be used to pass the handle of a 17621cb0ef41Sopenharmony_cisocket to the child process. The example below spawns two children that each 17631cb0ef41Sopenharmony_cihandle connections with "normal" or "special" priority:</p> 17641cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { fork } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 17651cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> normal = <span class="hljs-title function_">fork</span>(<span class="hljs-string">'subprocess.js'</span>, [<span class="hljs-string">'normal'</span>]); 17661cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> special = <span class="hljs-title function_">fork</span>(<span class="hljs-string">'subprocess.js'</span>, [<span class="hljs-string">'special'</span>]); 17671cb0ef41Sopenharmony_ci 17681cb0ef41Sopenharmony_ci<span class="hljs-comment">// Open up the server and send sockets to child. Use pauseOnConnect to prevent</span> 17691cb0ef41Sopenharmony_ci<span class="hljs-comment">// the sockets from being read before they are sent to the child process.</span> 17701cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> server = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:net'</span>).<span class="hljs-title function_">createServer</span>({ <span class="hljs-attr">pauseOnConnect</span>: <span class="hljs-literal">true</span> }); 17711cb0ef41Sopenharmony_ciserver.<span class="hljs-title function_">on</span>(<span class="hljs-string">'connection'</span>, <span class="hljs-function">(<span class="hljs-params">socket</span>) =></span> { 17721cb0ef41Sopenharmony_ci 17731cb0ef41Sopenharmony_ci <span class="hljs-comment">// If this is special priority...</span> 17741cb0ef41Sopenharmony_ci <span class="hljs-keyword">if</span> (socket.<span class="hljs-property">remoteAddress</span> === <span class="hljs-string">'74.125.127.100'</span>) { 17751cb0ef41Sopenharmony_ci special.<span class="hljs-title function_">send</span>(<span class="hljs-string">'socket'</span>, socket); 17761cb0ef41Sopenharmony_ci <span class="hljs-keyword">return</span>; 17771cb0ef41Sopenharmony_ci } 17781cb0ef41Sopenharmony_ci <span class="hljs-comment">// This is normal priority.</span> 17791cb0ef41Sopenharmony_ci normal.<span class="hljs-title function_">send</span>(<span class="hljs-string">'socket'</span>, socket); 17801cb0ef41Sopenharmony_ci}); 17811cb0ef41Sopenharmony_ciserver.<span class="hljs-title function_">listen</span>(<span class="hljs-number">1337</span>);</code> <button class="copy-button">copy</button></pre> 17821cb0ef41Sopenharmony_ci<p>The <code>subprocess.js</code> would receive the socket handle as the second argument 17831cb0ef41Sopenharmony_cipassed to the event callback function:</p> 17841cb0ef41Sopenharmony_ci<pre><code class="language-js">process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'message'</span>, <span class="hljs-function">(<span class="hljs-params">m, socket</span>) =></span> { 17851cb0ef41Sopenharmony_ci <span class="hljs-keyword">if</span> (m === <span class="hljs-string">'socket'</span>) { 17861cb0ef41Sopenharmony_ci <span class="hljs-keyword">if</span> (socket) { 17871cb0ef41Sopenharmony_ci <span class="hljs-comment">// Check that the client socket exists.</span> 17881cb0ef41Sopenharmony_ci <span class="hljs-comment">// It is possible for the socket to be closed between the time it is</span> 17891cb0ef41Sopenharmony_ci <span class="hljs-comment">// sent and the time it is received in the child process.</span> 17901cb0ef41Sopenharmony_ci socket.<span class="hljs-title function_">end</span>(<span class="hljs-string">`Request handled with <span class="hljs-subst">${process.argv[<span class="hljs-number">2</span>]}</span> priority`</span>); 17911cb0ef41Sopenharmony_ci } 17921cb0ef41Sopenharmony_ci } 17931cb0ef41Sopenharmony_ci});</code> <button class="copy-button">copy</button></pre> 17941cb0ef41Sopenharmony_ci<p>Do not use <code>.maxConnections</code> on a socket that has been passed to a subprocess. 17951cb0ef41Sopenharmony_ciThe parent cannot track when the socket is destroyed.</p> 17961cb0ef41Sopenharmony_ci<p>Any <code>'message'</code> handlers in the subprocess should verify that <code>socket</code> exists, 17971cb0ef41Sopenharmony_cias the connection may have been closed during the time it takes to send the 17981cb0ef41Sopenharmony_ciconnection to the child.</p> 17991cb0ef41Sopenharmony_ci<h4><code>subprocess.signalCode</code><span><a class="mark" href="#subprocesssignalcode" id="subprocesssignalcode">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_signalcode"></a></h4> 18001cb0ef41Sopenharmony_ci<ul> 18011cb0ef41Sopenharmony_ci<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Null_type" class="type"><null></a></li> 18021cb0ef41Sopenharmony_ci</ul> 18031cb0ef41Sopenharmony_ci<p>The <code>subprocess.signalCode</code> property indicates the signal received by 18041cb0ef41Sopenharmony_cithe child process if any, else <code>null</code>.</p> 18051cb0ef41Sopenharmony_ci<h4><code>subprocess.spawnargs</code><span><a class="mark" href="#subprocessspawnargs" id="subprocessspawnargs">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_spawnargs"></a></h4> 18061cb0ef41Sopenharmony_ci<ul> 18071cb0ef41Sopenharmony_ci<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" class="type"><Array></a></li> 18081cb0ef41Sopenharmony_ci</ul> 18091cb0ef41Sopenharmony_ci<p>The <code>subprocess.spawnargs</code> property represents the full list of command-line 18101cb0ef41Sopenharmony_ciarguments the child process was launched with.</p> 18111cb0ef41Sopenharmony_ci<h4><code>subprocess.spawnfile</code><span><a class="mark" href="#subprocessspawnfile" id="subprocessspawnfile">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_spawnfile"></a></h4> 18121cb0ef41Sopenharmony_ci<ul> 18131cb0ef41Sopenharmony_ci<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 18141cb0ef41Sopenharmony_ci</ul> 18151cb0ef41Sopenharmony_ci<p>The <code>subprocess.spawnfile</code> property indicates the executable file name of 18161cb0ef41Sopenharmony_cithe child process that is launched.</p> 18171cb0ef41Sopenharmony_ci<p>For <a href="#child_processforkmodulepath-args-options"><code>child_process.fork()</code></a>, its value will be equal to 18181cb0ef41Sopenharmony_ci<a href="process.html#processexecpath"><code>process.execPath</code></a>. 18191cb0ef41Sopenharmony_ciFor <a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a>, its value will be the name of 18201cb0ef41Sopenharmony_cithe executable file. 18211cb0ef41Sopenharmony_ciFor <a href="#child_processexeccommand-options-callback"><code>child_process.exec()</code></a>, its value will be the name of the shell 18221cb0ef41Sopenharmony_ciin which the child process is launched.</p> 18231cb0ef41Sopenharmony_ci<h4><code>subprocess.stderr</code><span><a class="mark" href="#subprocessstderr" id="subprocessstderr">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_stderr"></a></h4> 18241cb0ef41Sopenharmony_ci<div class="api_metadata"> 18251cb0ef41Sopenharmony_ci<span>Added in: v0.1.90</span> 18261cb0ef41Sopenharmony_ci</div> 18271cb0ef41Sopenharmony_ci<ul> 18281cb0ef41Sopenharmony_ci<li><a href="stream.html#class-streamreadable" class="type"><stream.Readable></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Null_type" class="type"><null></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Undefined_type" class="type"><undefined></a></li> 18291cb0ef41Sopenharmony_ci</ul> 18301cb0ef41Sopenharmony_ci<p>A <code>Readable Stream</code> that represents the child process's <code>stderr</code>.</p> 18311cb0ef41Sopenharmony_ci<p>If the child was spawned with <code>stdio[2]</code> set to anything other than <code>'pipe'</code>, 18321cb0ef41Sopenharmony_cithen this will be <code>null</code>.</p> 18331cb0ef41Sopenharmony_ci<p><code>subprocess.stderr</code> is an alias for <code>subprocess.stdio[2]</code>. Both properties will 18341cb0ef41Sopenharmony_cirefer to the same value.</p> 18351cb0ef41Sopenharmony_ci<p>The <code>subprocess.stderr</code> property can be <code>null</code> or <code>undefined</code> 18361cb0ef41Sopenharmony_ciif the child process could not be successfully spawned.</p> 18371cb0ef41Sopenharmony_ci<h4><code>subprocess.stdin</code><span><a class="mark" href="#subprocessstdin" id="subprocessstdin">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_stdin"></a></h4> 18381cb0ef41Sopenharmony_ci<div class="api_metadata"> 18391cb0ef41Sopenharmony_ci<span>Added in: v0.1.90</span> 18401cb0ef41Sopenharmony_ci</div> 18411cb0ef41Sopenharmony_ci<ul> 18421cb0ef41Sopenharmony_ci<li><a href="stream.html#class-streamwritable" class="type"><stream.Writable></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Null_type" class="type"><null></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Undefined_type" class="type"><undefined></a></li> 18431cb0ef41Sopenharmony_ci</ul> 18441cb0ef41Sopenharmony_ci<p>A <code>Writable Stream</code> that represents the child process's <code>stdin</code>.</p> 18451cb0ef41Sopenharmony_ci<p>If a child process waits to read all of its input, the child will not continue 18461cb0ef41Sopenharmony_ciuntil this stream has been closed via <code>end()</code>.</p> 18471cb0ef41Sopenharmony_ci<p>If the child was spawned with <code>stdio[0]</code> set to anything other than <code>'pipe'</code>, 18481cb0ef41Sopenharmony_cithen this will be <code>null</code>.</p> 18491cb0ef41Sopenharmony_ci<p><code>subprocess.stdin</code> is an alias for <code>subprocess.stdio[0]</code>. Both properties will 18501cb0ef41Sopenharmony_cirefer to the same value.</p> 18511cb0ef41Sopenharmony_ci<p>The <code>subprocess.stdin</code> property can be <code>null</code> or <code>undefined</code> 18521cb0ef41Sopenharmony_ciif the child process could not be successfully spawned.</p> 18531cb0ef41Sopenharmony_ci<h4><code>subprocess.stdio</code><span><a class="mark" href="#subprocessstdio" id="subprocessstdio">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_stdio"></a></h4> 18541cb0ef41Sopenharmony_ci<div class="api_metadata"> 18551cb0ef41Sopenharmony_ci<span>Added in: v0.7.10</span> 18561cb0ef41Sopenharmony_ci</div> 18571cb0ef41Sopenharmony_ci<ul> 18581cb0ef41Sopenharmony_ci<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" class="type"><Array></a></li> 18591cb0ef41Sopenharmony_ci</ul> 18601cb0ef41Sopenharmony_ci<p>A sparse array of pipes to the child process, corresponding with positions in 18611cb0ef41Sopenharmony_cithe <a href="#optionsstdio"><code>stdio</code></a> option passed to <a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a> that have been set 18621cb0ef41Sopenharmony_cito the value <code>'pipe'</code>. <code>subprocess.stdio[0]</code>, <code>subprocess.stdio[1]</code>, and 18631cb0ef41Sopenharmony_ci<code>subprocess.stdio[2]</code> are also available as <code>subprocess.stdin</code>, 18641cb0ef41Sopenharmony_ci<code>subprocess.stdout</code>, and <code>subprocess.stderr</code>, respectively.</p> 18651cb0ef41Sopenharmony_ci<p>In the following example, only the child's fd <code>1</code> (stdout) is configured as a 18661cb0ef41Sopenharmony_cipipe, so only the parent's <code>subprocess.stdio[1]</code> is a stream, all other values 18671cb0ef41Sopenharmony_ciin the array are <code>null</code>.</p> 18681cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert'</span>); 18691cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> fs = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:fs'</span>); 18701cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> child_process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 18711cb0ef41Sopenharmony_ci 18721cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> subprocess = child_process.<span class="hljs-title function_">spawn</span>(<span class="hljs-string">'ls'</span>, { 18731cb0ef41Sopenharmony_ci <span class="hljs-attr">stdio</span>: [ 18741cb0ef41Sopenharmony_ci <span class="hljs-number">0</span>, <span class="hljs-comment">// Use parent's stdin for child.</span> 18751cb0ef41Sopenharmony_ci <span class="hljs-string">'pipe'</span>, <span class="hljs-comment">// Pipe child's stdout to parent.</span> 18761cb0ef41Sopenharmony_ci fs.<span class="hljs-title function_">openSync</span>(<span class="hljs-string">'err.out'</span>, <span class="hljs-string">'w'</span>), <span class="hljs-comment">// Direct child's stderr to a file.</span> 18771cb0ef41Sopenharmony_ci ], 18781cb0ef41Sopenharmony_ci}); 18791cb0ef41Sopenharmony_ci 18801cb0ef41Sopenharmony_ciassert.<span class="hljs-title function_">strictEqual</span>(subprocess.<span class="hljs-property">stdio</span>[<span class="hljs-number">0</span>], <span class="hljs-literal">null</span>); 18811cb0ef41Sopenharmony_ciassert.<span class="hljs-title function_">strictEqual</span>(subprocess.<span class="hljs-property">stdio</span>[<span class="hljs-number">0</span>], subprocess.<span class="hljs-property">stdin</span>); 18821cb0ef41Sopenharmony_ci 18831cb0ef41Sopenharmony_ci<span class="hljs-title function_">assert</span>(subprocess.<span class="hljs-property">stdout</span>); 18841cb0ef41Sopenharmony_ciassert.<span class="hljs-title function_">strictEqual</span>(subprocess.<span class="hljs-property">stdio</span>[<span class="hljs-number">1</span>], subprocess.<span class="hljs-property">stdout</span>); 18851cb0ef41Sopenharmony_ci 18861cb0ef41Sopenharmony_ciassert.<span class="hljs-title function_">strictEqual</span>(subprocess.<span class="hljs-property">stdio</span>[<span class="hljs-number">2</span>], <span class="hljs-literal">null</span>); 18871cb0ef41Sopenharmony_ciassert.<span class="hljs-title function_">strictEqual</span>(subprocess.<span class="hljs-property">stdio</span>[<span class="hljs-number">2</span>], subprocess.<span class="hljs-property">stderr</span>);</code> <button class="copy-button">copy</button></pre> 18881cb0ef41Sopenharmony_ci<p>The <code>subprocess.stdio</code> property can be <code>undefined</code> if the child process could 18891cb0ef41Sopenharmony_cinot be successfully spawned.</p> 18901cb0ef41Sopenharmony_ci<h4><code>subprocess.stdout</code><span><a class="mark" href="#subprocessstdout" id="subprocessstdout">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_stdout"></a></h4> 18911cb0ef41Sopenharmony_ci<div class="api_metadata"> 18921cb0ef41Sopenharmony_ci<span>Added in: v0.1.90</span> 18931cb0ef41Sopenharmony_ci</div> 18941cb0ef41Sopenharmony_ci<ul> 18951cb0ef41Sopenharmony_ci<li><a href="stream.html#class-streamreadable" class="type"><stream.Readable></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Null_type" class="type"><null></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Undefined_type" class="type"><undefined></a></li> 18961cb0ef41Sopenharmony_ci</ul> 18971cb0ef41Sopenharmony_ci<p>A <code>Readable Stream</code> that represents the child process's <code>stdout</code>.</p> 18981cb0ef41Sopenharmony_ci<p>If the child was spawned with <code>stdio[1]</code> set to anything other than <code>'pipe'</code>, 18991cb0ef41Sopenharmony_cithen this will be <code>null</code>.</p> 19001cb0ef41Sopenharmony_ci<p><code>subprocess.stdout</code> is an alias for <code>subprocess.stdio[1]</code>. Both properties will 19011cb0ef41Sopenharmony_cirefer to the same value.</p> 19021cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 19031cb0ef41Sopenharmony_ci 19041cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> subprocess = <span class="hljs-title function_">spawn</span>(<span class="hljs-string">'ls'</span>); 19051cb0ef41Sopenharmony_ci 19061cb0ef41Sopenharmony_cisubprocess.<span class="hljs-property">stdout</span>.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 19071cb0ef41Sopenharmony_ci <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Received chunk <span class="hljs-subst">${data}</span>`</span>); 19081cb0ef41Sopenharmony_ci});</code> <button class="copy-button">copy</button></pre> 19091cb0ef41Sopenharmony_ci<p>The <code>subprocess.stdout</code> property can be <code>null</code> or <code>undefined</code> 19101cb0ef41Sopenharmony_ciif the child process could not be successfully spawned.</p> 19111cb0ef41Sopenharmony_ci<h4><code>subprocess.unref()</code><span><a class="mark" href="#subprocessunref" id="subprocessunref">#</a></span><a aria-hidden="true" class="legacy" id="child_process_subprocess_unref"></a></h4> 19121cb0ef41Sopenharmony_ci<div class="api_metadata"> 19131cb0ef41Sopenharmony_ci<span>Added in: v0.7.10</span> 19141cb0ef41Sopenharmony_ci</div> 19151cb0ef41Sopenharmony_ci<p>By default, the parent will wait for the detached child to exit. To prevent the 19161cb0ef41Sopenharmony_ciparent from waiting for a given <code>subprocess</code> to exit, use the 19171cb0ef41Sopenharmony_ci<code>subprocess.unref()</code> method. Doing so will cause the parent's event loop to not 19181cb0ef41Sopenharmony_ciinclude the child in its reference count, allowing the parent to exit 19191cb0ef41Sopenharmony_ciindependently of the child, unless there is an established IPC channel between 19201cb0ef41Sopenharmony_cithe child and the parent.</p> 19211cb0ef41Sopenharmony_ci<pre><code class="language-js"><span class="hljs-keyword">const</span> { spawn } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 19221cb0ef41Sopenharmony_ci 19231cb0ef41Sopenharmony_ci<span class="hljs-keyword">const</span> subprocess = <span class="hljs-title function_">spawn</span>(process.<span class="hljs-property">argv</span>[<span class="hljs-number">0</span>], [<span class="hljs-string">'child_program.js'</span>], { 19241cb0ef41Sopenharmony_ci <span class="hljs-attr">detached</span>: <span class="hljs-literal">true</span>, 19251cb0ef41Sopenharmony_ci <span class="hljs-attr">stdio</span>: <span class="hljs-string">'ignore'</span>, 19261cb0ef41Sopenharmony_ci}); 19271cb0ef41Sopenharmony_ci 19281cb0ef41Sopenharmony_cisubprocess.<span class="hljs-title function_">unref</span>();</code> <button class="copy-button">copy</button></pre> 19291cb0ef41Sopenharmony_ci</section><section><h3><code>maxBuffer</code> and Unicode<span><a class="mark" href="#maxbuffer-and-unicode" id="maxbuffer-and-unicode">#</a></span><a aria-hidden="true" class="legacy" id="child_process_maxbuffer_and_unicode"></a></h3> 19301cb0ef41Sopenharmony_ci<p>The <code>maxBuffer</code> option specifies the largest number of bytes allowed on <code>stdout</code> 19311cb0ef41Sopenharmony_cior <code>stderr</code>. If this value is exceeded, then the child process is terminated. 19321cb0ef41Sopenharmony_ciThis impacts output that includes multibyte character encodings such as UTF-8 or 19331cb0ef41Sopenharmony_ciUTF-16. For instance, <code>console.log('中文测试')</code> will send 13 UTF-8 encoded bytes 19341cb0ef41Sopenharmony_cito <code>stdout</code> although there are only 4 characters.</p> 19351cb0ef41Sopenharmony_ci</section><section><h3>Shell requirements<span><a class="mark" href="#shell-requirements" id="shell-requirements">#</a></span><a aria-hidden="true" class="legacy" id="child_process_shell_requirements"></a></h3> 19361cb0ef41Sopenharmony_ci<p>The shell should understand the <code>-c</code> switch. If the shell is <code>'cmd.exe'</code>, it 19371cb0ef41Sopenharmony_cishould understand the <code>/d /s /c</code> switches and command-line parsing should be 19381cb0ef41Sopenharmony_cicompatible.</p> 19391cb0ef41Sopenharmony_ci</section><section><h3>Default Windows shell<span><a class="mark" href="#default-windows-shell" id="default-windows-shell">#</a></span><a aria-hidden="true" class="legacy" id="child_process_default_windows_shell"></a></h3> 19401cb0ef41Sopenharmony_ci<p>Although Microsoft specifies <code>%COMSPEC%</code> must contain the path to 19411cb0ef41Sopenharmony_ci<code>'cmd.exe'</code> in the root environment, child processes are not always subject to 19421cb0ef41Sopenharmony_cithe same requirement. Thus, in <code>child_process</code> functions where a shell can be 19431cb0ef41Sopenharmony_cispawned, <code>'cmd.exe'</code> is used as a fallback if <code>process.env.ComSpec</code> is 19441cb0ef41Sopenharmony_ciunavailable.</p> 19451cb0ef41Sopenharmony_ci</section><section><h3>Advanced serialization<span><a class="mark" href="#advanced-serialization" id="advanced-serialization">#</a></span><a aria-hidden="true" class="legacy" id="child_process_advanced_serialization"></a></h3> 19461cb0ef41Sopenharmony_ci<div class="api_metadata"> 19471cb0ef41Sopenharmony_ci<span>Added in: v13.2.0, v12.16.0</span> 19481cb0ef41Sopenharmony_ci</div> 19491cb0ef41Sopenharmony_ci<p>Child processes support a serialization mechanism for IPC that is based on the 19501cb0ef41Sopenharmony_ci<a href="v8.html#serialization-api">serialization API of the <code>node:v8</code> module</a>, based on the 19511cb0ef41Sopenharmony_ci<a href="https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm">HTML structured clone algorithm</a>. This is generally more powerful and 19521cb0ef41Sopenharmony_cisupports more built-in JavaScript object types, such as <code>BigInt</code>, <code>Map</code> 19531cb0ef41Sopenharmony_ciand <code>Set</code>, <code>ArrayBuffer</code> and <code>TypedArray</code>, <code>Buffer</code>, <code>Error</code>, <code>RegExp</code> etc.</p> 19541cb0ef41Sopenharmony_ci<p>However, this format is not a full superset of JSON, and e.g. properties set on 19551cb0ef41Sopenharmony_ciobjects of such built-in types will not be passed on through the serialization 19561cb0ef41Sopenharmony_cistep. Additionally, performance may not be equivalent to that of JSON, depending 19571cb0ef41Sopenharmony_cion the structure of the passed data. 19581cb0ef41Sopenharmony_ciTherefore, this feature requires opting in by setting the 19591cb0ef41Sopenharmony_ci<code>serialization</code> option to <code>'advanced'</code> when calling <a href="#child_processspawncommand-args-options"><code>child_process.spawn()</code></a> 19601cb0ef41Sopenharmony_cior <a href="#child_processforkmodulepath-args-options"><code>child_process.fork()</code></a>.</p></section> 19611cb0ef41Sopenharmony_ci <!-- API END --> 19621cb0ef41Sopenharmony_ci </div> 19631cb0ef41Sopenharmony_ci </div> 19641cb0ef41Sopenharmony_ci </div> 19651cb0ef41Sopenharmony_ci</body> 19661cb0ef41Sopenharmony_ci</html> 1967