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id="gtoc"> 113 <ul> 114 <li class="pinned-header">Node.js v18.20.1</li> 115 116 <li class="picker-header"> 117 <a href="#"> 118 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 119 Table of contents 120 </a> 121 122 <div class="picker"><div class="toc"><ul> 123<li><a href="#process">Process</a> 124<ul> 125<li><a href="#process-events">Process events</a> 126<ul> 127<li><a href="#event-beforeexit">Event: <code>'beforeExit'</code></a></li> 128<li><a href="#event-disconnect">Event: <code>'disconnect'</code></a></li> 129<li><a href="#event-exit">Event: <code>'exit'</code></a></li> 130<li><a href="#event-message">Event: <code>'message'</code></a></li> 131<li><span class="stability_0"><a href="#event-multipleresolves">Event: <code>'multipleResolves'</code></a></span></li> 132<li><a href="#event-rejectionhandled">Event: <code>'rejectionHandled'</code></a></li> 133<li><a href="#event-uncaughtexception">Event: <code>'uncaughtException'</code></a> 134<ul> 135<li><a href="#warning-using-uncaughtexception-correctly">Warning: Using <code>'uncaughtException'</code> correctly</a></li> 136</ul> 137</li> 138<li><a href="#event-uncaughtexceptionmonitor">Event: <code>'uncaughtExceptionMonitor'</code></a></li> 139<li><a href="#event-unhandledrejection">Event: <code>'unhandledRejection'</code></a></li> 140<li><a href="#event-warning">Event: <code>'warning'</code></a></li> 141<li><a href="#event-worker">Event: <code>'worker'</code></a> 142<ul> 143<li><a href="#emitting-custom-warnings">Emitting custom warnings</a></li> 144<li><a href="#nodejs-warning-names">Node.js warning names</a></li> 145</ul> 146</li> 147<li><a href="#signal-events">Signal events</a></li> 148</ul> 149</li> 150<li><a href="#processabort"><code>process.abort()</code></a></li> 151<li><a href="#processallowednodeenvironmentflags"><code>process.allowedNodeEnvironmentFlags</code></a></li> 152<li><a href="#processarch"><code>process.arch</code></a></li> 153<li><a href="#processargv"><code>process.argv</code></a></li> 154<li><a href="#processargv0"><code>process.argv0</code></a></li> 155<li><a href="#processchannel"><code>process.channel</code></a> 156<ul> 157<li><a href="#processchannelref"><code>process.channel.ref()</code></a></li> 158<li><a href="#processchannelunref"><code>process.channel.unref()</code></a></li> 159</ul> 160</li> 161<li><a href="#processchdirdirectory"><code>process.chdir(directory)</code></a></li> 162<li><a href="#processconfig"><code>process.config</code></a></li> 163<li><a href="#processconnected"><code>process.connected</code></a></li> 164<li><span class="stability_1"><a href="#processconstrainedmemory"><code>process.constrainedMemory()</code></a></span></li> 165<li><a href="#processcpuusagepreviousvalue"><code>process.cpuUsage([previousValue])</code></a></li> 166<li><a href="#processcwd"><code>process.cwd()</code></a></li> 167<li><a href="#processdebugport"><code>process.debugPort</code></a></li> 168<li><a href="#processdisconnect"><code>process.disconnect()</code></a></li> 169<li><a href="#processdlopenmodule-filename-flags"><code>process.dlopen(module, filename[, flags])</code></a></li> 170<li><a href="#processemitwarningwarning-options"><code>process.emitWarning(warning[, options])</code></a></li> 171<li><a href="#processemitwarningwarning-type-code-ctor"><code>process.emitWarning(warning[, type[, code]][, ctor])</code></a> 172<ul> 173<li><a href="#avoiding-duplicate-warnings">Avoiding duplicate warnings</a></li> 174</ul> 175</li> 176<li><a href="#processenv"><code>process.env</code></a></li> 177<li><a href="#processexecargv"><code>process.execArgv</code></a></li> 178<li><a href="#processexecpath"><code>process.execPath</code></a></li> 179<li><a href="#processexitcode"><code>process.exit([code])</code></a></li> 180<li><a href="#processexitcode_1"><code>process.exitCode</code></a></li> 181<li><span class="stability_1"><a href="#processgetactiveresourcesinfo"><code>process.getActiveResourcesInfo()</code></a></span></li> 182<li><a href="#processgetegid"><code>process.getegid()</code></a></li> 183<li><a href="#processgeteuid"><code>process.geteuid()</code></a></li> 184<li><a href="#processgetgid"><code>process.getgid()</code></a></li> 185<li><a href="#processgetgroups"><code>process.getgroups()</code></a></li> 186<li><a href="#processgetuid"><code>process.getuid()</code></a></li> 187<li><a href="#processhasuncaughtexceptioncapturecallback"><code>process.hasUncaughtExceptionCaptureCallback()</code></a></li> 188<li><span class="stability_3"><a href="#processhrtimetime"><code>process.hrtime([time])</code></a></span></li> 189<li><a href="#processhrtimebigint"><code>process.hrtime.bigint()</code></a></li> 190<li><a href="#processinitgroupsuser-extragroup"><code>process.initgroups(user, extraGroup)</code></a></li> 191<li><a href="#processkillpid-signal"><code>process.kill(pid[, signal])</code></a></li> 192<li><span class="stability_0"><a href="#processmainmodule"><code>process.mainModule</code></a></span></li> 193<li><a href="#processmemoryusage"><code>process.memoryUsage()</code></a></li> 194<li><a href="#processmemoryusagerss"><code>process.memoryUsage.rss()</code></a></li> 195<li><a href="#processnexttickcallback-args"><code>process.nextTick(callback[, ...args])</code></a> 196<ul> 197<li><a href="#when-to-use-queuemicrotask-vs-processnexttick">When to use <code>queueMicrotask()</code> vs. <code>process.nextTick()</code></a></li> 198</ul> 199</li> 200<li><a href="#processnodeprecation"><code>process.noDeprecation</code></a></li> 201<li><a href="#processpid"><code>process.pid</code></a></li> 202<li><a href="#processplatform"><code>process.platform</code></a></li> 203<li><a href="#processppid"><code>process.ppid</code></a></li> 204<li><a href="#processrelease"><code>process.release</code></a></li> 205<li><a href="#processreport"><code>process.report</code></a> 206<ul> 207<li><a href="#processreportcompact"><code>process.report.compact</code></a></li> 208<li><a href="#processreportdirectory"><code>process.report.directory</code></a></li> 209<li><a href="#processreportfilename"><code>process.report.filename</code></a></li> 210<li><a href="#processreportgetreporterr"><code>process.report.getReport([err])</code></a></li> 211<li><a href="#processreportreportonfatalerror"><code>process.report.reportOnFatalError</code></a></li> 212<li><a href="#processreportreportonsignal"><code>process.report.reportOnSignal</code></a></li> 213<li><a href="#processreportreportonuncaughtexception"><code>process.report.reportOnUncaughtException</code></a></li> 214<li><a href="#processreportsignal"><code>process.report.signal</code></a></li> 215<li><a href="#processreportwritereportfilename-err"><code>process.report.writeReport([filename][, err])</code></a></li> 216</ul> 217</li> 218<li><a href="#processresourceusage"><code>process.resourceUsage()</code></a></li> 219<li><a href="#processsendmessage-sendhandle-options-callback"><code>process.send(message[, sendHandle[, options]][, callback])</code></a></li> 220<li><a href="#processsetegidid"><code>process.setegid(id)</code></a></li> 221<li><a href="#processseteuidid"><code>process.seteuid(id)</code></a></li> 222<li><a href="#processsetgidid"><code>process.setgid(id)</code></a></li> 223<li><a href="#processsetgroupsgroups"><code>process.setgroups(groups)</code></a></li> 224<li><a href="#processsetuidid"><code>process.setuid(id)</code></a></li> 225<li><span class="stability_1"><a href="#processsetsourcemapsenabledval"><code>process.setSourceMapsEnabled(val)</code></a></span></li> 226<li><a href="#processsetuncaughtexceptioncapturecallbackfn"><code>process.setUncaughtExceptionCaptureCallback(fn)</code></a></li> 227<li><span class="stability_1"><a href="#processsourcemapsenabled"><code>process.sourceMapsEnabled</code></a></span></li> 228<li><a href="#processstderr"><code>process.stderr</code></a> 229<ul> 230<li><a href="#processstderrfd"><code>process.stderr.fd</code></a></li> 231</ul> 232</li> 233<li><a href="#processstdin"><code>process.stdin</code></a> 234<ul> 235<li><a href="#processstdinfd"><code>process.stdin.fd</code></a></li> 236</ul> 237</li> 238<li><a href="#processstdout"><code>process.stdout</code></a> 239<ul> 240<li><a href="#processstdoutfd"><code>process.stdout.fd</code></a></li> 241<li><a href="#a-note-on-process-io">A note on process I/O</a></li> 242</ul> 243</li> 244<li><a href="#processthrowdeprecation"><code>process.throwDeprecation</code></a></li> 245<li><a href="#processtitle"><code>process.title</code></a></li> 246<li><a href="#processtracedeprecation"><code>process.traceDeprecation</code></a></li> 247<li><span class="stability_0"><a href="#processumask"><code>process.umask()</code></a></span></li> 248<li><a href="#processumaskmask"><code>process.umask(mask)</code></a></li> 249<li><a href="#processuptime"><code>process.uptime()</code></a></li> 250<li><a href="#processversion"><code>process.version</code></a></li> 251<li><a href="#processversions"><code>process.versions</code></a></li> 252<li><a href="#exit-codes">Exit codes</a></li> 253</ul> 254</li> 255</ul></div></div> 256 </li> 257 258 259 <li class="picker-header"> 260 <a href="#"> 261 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 262 Index 263 </a> 264 265 <div class="picker"><ul> 266<li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> 267<li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> 268 269 <li> 270 <a href="index.html">Index</a> 271 </li> 272 </ul> 273 274<hr class="line"> 275<ul> 276<li><a href="assert.html" class="nav-assert">Assertion testing</a></li> 277<li><a href="async_context.html" class="nav-async_context">Asynchronous context tracking</a></li> 278<li><a href="async_hooks.html" class="nav-async_hooks">Async hooks</a></li> 279<li><a href="buffer.html" 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class="nav-zlib">Zlib</a></li> 336</ul> 337<hr class="line"> 338<ul> 339<li><a href="https://github.com/nodejs/node" class="nav-https-github-com-nodejs-node">Code repository and issue tracker</a></li> 340</ul></div> 341 </li> 342 343 344 <li class="picker-header"> 345 <a href="#"> 346 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 347 Other versions 348 </a> 349 <div class="picker"><ol id="alt-docs"><li><a href="https://nodejs.org/docs/latest-v21.x/api/process.html">21.x</a></li> 350<li><a href="https://nodejs.org/docs/latest-v20.x/api/process.html">20.x <b>LTS</b></a></li> 351<li><a href="https://nodejs.org/docs/latest-v19.x/api/process.html">19.x</a></li> 352<li><a href="https://nodejs.org/docs/latest-v18.x/api/process.html">18.x <b>LTS</b></a></li> 353<li><a href="https://nodejs.org/docs/latest-v17.x/api/process.html">17.x</a></li> 354<li><a href="https://nodejs.org/docs/latest-v16.x/api/process.html">16.x</a></li> 355<li><a href="https://nodejs.org/docs/latest-v15.x/api/process.html">15.x</a></li> 356<li><a href="https://nodejs.org/docs/latest-v14.x/api/process.html">14.x</a></li> 357<li><a href="https://nodejs.org/docs/latest-v13.x/api/process.html">13.x</a></li> 358<li><a href="https://nodejs.org/docs/latest-v12.x/api/process.html">12.x</a></li> 359<li><a href="https://nodejs.org/docs/latest-v11.x/api/process.html">11.x</a></li> 360<li><a href="https://nodejs.org/docs/latest-v10.x/api/process.html">10.x</a></li> 361<li><a href="https://nodejs.org/docs/latest-v9.x/api/process.html">9.x</a></li> 362<li><a href="https://nodejs.org/docs/latest-v8.x/api/process.html">8.x</a></li> 363<li><a href="https://nodejs.org/docs/latest-v7.x/api/process.html">7.x</a></li> 364<li><a href="https://nodejs.org/docs/latest-v6.x/api/process.html">6.x</a></li> 365<li><a href="https://nodejs.org/docs/latest-v5.x/api/process.html">5.x</a></li> 366<li><a href="https://nodejs.org/docs/latest-v4.x/api/process.html">4.x</a></li> 367<li><a href="https://nodejs.org/docs/latest-v0.12.x/api/process.html">0.12.x</a></li> 368<li><a href="https://nodejs.org/docs/latest-v0.10.x/api/process.html">0.10.x</a></li></ol></div> 369 </li> 370 371 <li class="picker-header"> 372 <a href="#"> 373 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 374 Options 375 </a> 376 377 <div class="picker"> 378 <ul> 379 <li> 380 <a href="all.html">View on single page</a> 381 </li> 382 <li> 383 <a href="process.json">View as JSON</a> 384 </li> 385 <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/main/doc/api/process.md">Edit on GitHub</a></li> 386 </ul> 387 </div> 388 </li> 389 </ul> 390 </div> 391 <hr> 392 </header> 393 394 <details id="toc" open><summary>Table of contents</summary><ul> 395<li><a href="#process">Process</a> 396<ul> 397<li><a href="#process-events">Process events</a> 398<ul> 399<li><a href="#event-beforeexit">Event: <code>'beforeExit'</code></a></li> 400<li><a href="#event-disconnect">Event: <code>'disconnect'</code></a></li> 401<li><a href="#event-exit">Event: <code>'exit'</code></a></li> 402<li><a href="#event-message">Event: <code>'message'</code></a></li> 403<li><span class="stability_0"><a href="#event-multipleresolves">Event: <code>'multipleResolves'</code></a></span></li> 404<li><a href="#event-rejectionhandled">Event: <code>'rejectionHandled'</code></a></li> 405<li><a href="#event-uncaughtexception">Event: <code>'uncaughtException'</code></a> 406<ul> 407<li><a href="#warning-using-uncaughtexception-correctly">Warning: Using <code>'uncaughtException'</code> correctly</a></li> 408</ul> 409</li> 410<li><a href="#event-uncaughtexceptionmonitor">Event: <code>'uncaughtExceptionMonitor'</code></a></li> 411<li><a href="#event-unhandledrejection">Event: <code>'unhandledRejection'</code></a></li> 412<li><a href="#event-warning">Event: <code>'warning'</code></a></li> 413<li><a href="#event-worker">Event: <code>'worker'</code></a> 414<ul> 415<li><a href="#emitting-custom-warnings">Emitting custom warnings</a></li> 416<li><a href="#nodejs-warning-names">Node.js warning names</a></li> 417</ul> 418</li> 419<li><a href="#signal-events">Signal events</a></li> 420</ul> 421</li> 422<li><a href="#processabort"><code>process.abort()</code></a></li> 423<li><a href="#processallowednodeenvironmentflags"><code>process.allowedNodeEnvironmentFlags</code></a></li> 424<li><a href="#processarch"><code>process.arch</code></a></li> 425<li><a href="#processargv"><code>process.argv</code></a></li> 426<li><a href="#processargv0"><code>process.argv0</code></a></li> 427<li><a href="#processchannel"><code>process.channel</code></a> 428<ul> 429<li><a href="#processchannelref"><code>process.channel.ref()</code></a></li> 430<li><a href="#processchannelunref"><code>process.channel.unref()</code></a></li> 431</ul> 432</li> 433<li><a href="#processchdirdirectory"><code>process.chdir(directory)</code></a></li> 434<li><a href="#processconfig"><code>process.config</code></a></li> 435<li><a href="#processconnected"><code>process.connected</code></a></li> 436<li><span class="stability_1"><a href="#processconstrainedmemory"><code>process.constrainedMemory()</code></a></span></li> 437<li><a href="#processcpuusagepreviousvalue"><code>process.cpuUsage([previousValue])</code></a></li> 438<li><a href="#processcwd"><code>process.cwd()</code></a></li> 439<li><a href="#processdebugport"><code>process.debugPort</code></a></li> 440<li><a href="#processdisconnect"><code>process.disconnect()</code></a></li> 441<li><a href="#processdlopenmodule-filename-flags"><code>process.dlopen(module, filename[, flags])</code></a></li> 442<li><a href="#processemitwarningwarning-options"><code>process.emitWarning(warning[, options])</code></a></li> 443<li><a href="#processemitwarningwarning-type-code-ctor"><code>process.emitWarning(warning[, type[, code]][, ctor])</code></a> 444<ul> 445<li><a href="#avoiding-duplicate-warnings">Avoiding duplicate warnings</a></li> 446</ul> 447</li> 448<li><a href="#processenv"><code>process.env</code></a></li> 449<li><a href="#processexecargv"><code>process.execArgv</code></a></li> 450<li><a href="#processexecpath"><code>process.execPath</code></a></li> 451<li><a href="#processexitcode"><code>process.exit([code])</code></a></li> 452<li><a href="#processexitcode_1"><code>process.exitCode</code></a></li> 453<li><span class="stability_1"><a href="#processgetactiveresourcesinfo"><code>process.getActiveResourcesInfo()</code></a></span></li> 454<li><a href="#processgetegid"><code>process.getegid()</code></a></li> 455<li><a href="#processgeteuid"><code>process.geteuid()</code></a></li> 456<li><a href="#processgetgid"><code>process.getgid()</code></a></li> 457<li><a href="#processgetgroups"><code>process.getgroups()</code></a></li> 458<li><a href="#processgetuid"><code>process.getuid()</code></a></li> 459<li><a href="#processhasuncaughtexceptioncapturecallback"><code>process.hasUncaughtExceptionCaptureCallback()</code></a></li> 460<li><span class="stability_3"><a href="#processhrtimetime"><code>process.hrtime([time])</code></a></span></li> 461<li><a href="#processhrtimebigint"><code>process.hrtime.bigint()</code></a></li> 462<li><a href="#processinitgroupsuser-extragroup"><code>process.initgroups(user, extraGroup)</code></a></li> 463<li><a href="#processkillpid-signal"><code>process.kill(pid[, signal])</code></a></li> 464<li><span class="stability_0"><a href="#processmainmodule"><code>process.mainModule</code></a></span></li> 465<li><a href="#processmemoryusage"><code>process.memoryUsage()</code></a></li> 466<li><a href="#processmemoryusagerss"><code>process.memoryUsage.rss()</code></a></li> 467<li><a href="#processnexttickcallback-args"><code>process.nextTick(callback[, ...args])</code></a> 468<ul> 469<li><a href="#when-to-use-queuemicrotask-vs-processnexttick">When to use <code>queueMicrotask()</code> vs. <code>process.nextTick()</code></a></li> 470</ul> 471</li> 472<li><a href="#processnodeprecation"><code>process.noDeprecation</code></a></li> 473<li><a href="#processpid"><code>process.pid</code></a></li> 474<li><a href="#processplatform"><code>process.platform</code></a></li> 475<li><a href="#processppid"><code>process.ppid</code></a></li> 476<li><a href="#processrelease"><code>process.release</code></a></li> 477<li><a href="#processreport"><code>process.report</code></a> 478<ul> 479<li><a href="#processreportcompact"><code>process.report.compact</code></a></li> 480<li><a href="#processreportdirectory"><code>process.report.directory</code></a></li> 481<li><a href="#processreportfilename"><code>process.report.filename</code></a></li> 482<li><a href="#processreportgetreporterr"><code>process.report.getReport([err])</code></a></li> 483<li><a href="#processreportreportonfatalerror"><code>process.report.reportOnFatalError</code></a></li> 484<li><a href="#processreportreportonsignal"><code>process.report.reportOnSignal</code></a></li> 485<li><a href="#processreportreportonuncaughtexception"><code>process.report.reportOnUncaughtException</code></a></li> 486<li><a href="#processreportsignal"><code>process.report.signal</code></a></li> 487<li><a href="#processreportwritereportfilename-err"><code>process.report.writeReport([filename][, err])</code></a></li> 488</ul> 489</li> 490<li><a href="#processresourceusage"><code>process.resourceUsage()</code></a></li> 491<li><a href="#processsendmessage-sendhandle-options-callback"><code>process.send(message[, sendHandle[, options]][, callback])</code></a></li> 492<li><a href="#processsetegidid"><code>process.setegid(id)</code></a></li> 493<li><a href="#processseteuidid"><code>process.seteuid(id)</code></a></li> 494<li><a href="#processsetgidid"><code>process.setgid(id)</code></a></li> 495<li><a href="#processsetgroupsgroups"><code>process.setgroups(groups)</code></a></li> 496<li><a href="#processsetuidid"><code>process.setuid(id)</code></a></li> 497<li><span class="stability_1"><a href="#processsetsourcemapsenabledval"><code>process.setSourceMapsEnabled(val)</code></a></span></li> 498<li><a href="#processsetuncaughtexceptioncapturecallbackfn"><code>process.setUncaughtExceptionCaptureCallback(fn)</code></a></li> 499<li><span class="stability_1"><a href="#processsourcemapsenabled"><code>process.sourceMapsEnabled</code></a></span></li> 500<li><a href="#processstderr"><code>process.stderr</code></a> 501<ul> 502<li><a href="#processstderrfd"><code>process.stderr.fd</code></a></li> 503</ul> 504</li> 505<li><a href="#processstdin"><code>process.stdin</code></a> 506<ul> 507<li><a href="#processstdinfd"><code>process.stdin.fd</code></a></li> 508</ul> 509</li> 510<li><a href="#processstdout"><code>process.stdout</code></a> 511<ul> 512<li><a href="#processstdoutfd"><code>process.stdout.fd</code></a></li> 513<li><a href="#a-note-on-process-io">A note on process I/O</a></li> 514</ul> 515</li> 516<li><a href="#processthrowdeprecation"><code>process.throwDeprecation</code></a></li> 517<li><a href="#processtitle"><code>process.title</code></a></li> 518<li><a href="#processtracedeprecation"><code>process.traceDeprecation</code></a></li> 519<li><span class="stability_0"><a href="#processumask"><code>process.umask()</code></a></span></li> 520<li><a href="#processumaskmask"><code>process.umask(mask)</code></a></li> 521<li><a href="#processuptime"><code>process.uptime()</code></a></li> 522<li><a href="#processversion"><code>process.version</code></a></li> 523<li><a href="#processversions"><code>process.versions</code></a></li> 524<li><a href="#exit-codes">Exit codes</a></li> 525</ul> 526</li> 527</ul></details> 528 529 <div id="apicontent"> 530 <h2>Process<span><a class="mark" href="#process" id="process">#</a></span><a aria-hidden="true" class="legacy" id="process_process"></a></h2> 531 532 533<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v18.20.1/lib/process.js">lib/process.js</a></p> 534<p>The <code>process</code> object provides information about, and control over, the current 535Node.js process.</p> 536 537<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>;</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>);</code><button class="copy-button">copy</button></pre> 538<section><h3>Process events<span><a class="mark" href="#process-events" id="process-events">#</a></span><a aria-hidden="true" class="legacy" id="process_process_events"></a></h3> 539<p>The <code>process</code> object is an instance of <a href="events.html#class-eventemitter"><code>EventEmitter</code></a>.</p> 540<h4>Event: <code>'beforeExit'</code><span><a class="mark" href="#event-beforeexit" id="event-beforeexit">#</a></span><a aria-hidden="true" class="legacy" id="process_event_beforeexit"></a></h4> 541<div class="api_metadata"> 542<span>Added in: v0.11.12</span> 543</div> 544<p>The <code>'beforeExit'</code> event is emitted when Node.js empties its event loop and has 545no additional work to schedule. Normally, the Node.js process will exit when 546there is no work scheduled, but a listener registered on the <code>'beforeExit'</code> 547event can make asynchronous calls, and thereby cause the Node.js process to 548continue.</p> 549<p>The listener callback function is invoked with the value of 550<a href="#processexitcode_1"><code>process.exitCode</code></a> passed as the only argument.</p> 551<p>The <code>'beforeExit'</code> event is <em>not</em> emitted for conditions causing explicit 552termination, such as calling <a href="#processexitcode"><code>process.exit()</code></a> or uncaught exceptions.</p> 553<p>The <code>'beforeExit'</code> should <em>not</em> be used as an alternative to the <code>'exit'</code> event 554unless the intention is to schedule additional work.</p> 555 556<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 557 558process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'beforeExit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 559 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Process beforeExit event with code: '</span>, code); 560}); 561 562process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'exit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 563 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Process exit event with code: '</span>, code); 564}); 565 566<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'This message is displayed first.'</span>); 567 568<span class="hljs-comment">// Prints:</span> 569<span class="hljs-comment">// This message is displayed first.</span> 570<span class="hljs-comment">// Process beforeExit event with code: 0</span> 571<span class="hljs-comment">// Process exit event with code: 0</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 572 573process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'beforeExit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 574 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Process beforeExit event with code: '</span>, code); 575}); 576 577process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'exit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 578 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Process exit event with code: '</span>, code); 579}); 580 581<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'This message is displayed first.'</span>); 582 583<span class="hljs-comment">// Prints:</span> 584<span class="hljs-comment">// This message is displayed first.</span> 585<span class="hljs-comment">// Process beforeExit event with code: 0</span> 586<span class="hljs-comment">// Process exit event with code: 0</span></code><button class="copy-button">copy</button></pre> 587<h4>Event: <code>'disconnect'</code><span><a class="mark" href="#event-disconnect" id="event-disconnect">#</a></span><a aria-hidden="true" class="legacy" id="process_event_disconnect"></a></h4> 588<div class="api_metadata"> 589<span>Added in: v0.7.7</span> 590</div> 591<p>If the Node.js process is spawned with an IPC channel (see the <a href="child_process.html">Child Process</a> 592and <a href="cluster.html">Cluster</a> documentation), the <code>'disconnect'</code> event will be emitted when 593the IPC channel is closed.</p> 594<h4>Event: <code>'exit'</code><span><a class="mark" href="#event-exit" id="event-exit">#</a></span><a aria-hidden="true" class="legacy" id="process_event_exit"></a></h4> 595<div class="api_metadata"> 596<span>Added in: v0.1.7</span> 597</div> 598<ul> 599<li><code>code</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 600</ul> 601<p>The <code>'exit'</code> event is emitted when the Node.js process is about to exit as a 602result of either:</p> 603<ul> 604<li>The <code>process.exit()</code> method being called explicitly;</li> 605<li>The Node.js event loop no longer having any additional work to perform.</li> 606</ul> 607<p>There is no way to prevent the exiting of the event loop at this point, and once 608all <code>'exit'</code> listeners have finished running the Node.js process will terminate.</p> 609<p>The listener callback function is invoked with the exit code specified either 610by the <a href="#processexitcode_1"><code>process.exitCode</code></a> property, or the <code>exitCode</code> argument passed to the 611<a href="#processexitcode"><code>process.exit()</code></a> method.</p> 612 613<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 614 615process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'exit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 616 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`About to exit with code: <span class="hljs-subst">${code}</span>`</span>); 617});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 618 619process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'exit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 620 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`About to exit with code: <span class="hljs-subst">${code}</span>`</span>); 621});</code><button class="copy-button">copy</button></pre> 622<p>Listener functions <strong>must</strong> only perform <strong>synchronous</strong> operations. The Node.js 623process will exit immediately after calling the <code>'exit'</code> event listeners 624causing any additional work still queued in the event loop to be abandoned. 625In the following example, for instance, the timeout will never occur:</p> 626 627<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 628 629process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'exit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 630 <span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 631 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'This will not run'</span>); 632 }, <span class="hljs-number">0</span>); 633});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 634 635process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'exit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 636 <span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 637 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'This will not run'</span>); 638 }, <span class="hljs-number">0</span>); 639});</code><button class="copy-button">copy</button></pre> 640<h4>Event: <code>'message'</code><span><a class="mark" href="#event-message" id="event-message">#</a></span><a aria-hidden="true" class="legacy" id="process_event_message"></a></h4> 641<div class="api_metadata"> 642<span>Added in: v0.5.10</span> 643</div> 644<ul> 645<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> | <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#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> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Null_type" class="type"><null></a> a parsed JSON object 646or a serializable primitive value.</li> 647<li><code>sendHandle</code> <a href="net.html#class-netserver" class="type"><net.Server></a> | <a href="net.html#class-netsocket" class="type"><net.Socket></a> a <a href="net.html#class-netserver"><code>net.Server</code></a> or <a href="net.html#class-netsocket"><code>net.Socket</code></a> 648object, or undefined.</li> 649</ul> 650<p>If the Node.js process is spawned with an IPC channel (see the <a href="child_process.html">Child Process</a> 651and <a href="cluster.html">Cluster</a> documentation), the <code>'message'</code> event is emitted whenever a 652message sent by a parent process using <a href="child_process.html#subprocesssendmessage-sendhandle-options-callback"><code>childprocess.send()</code></a> is received by 653the child process.</p> 654<p>The message goes through serialization and parsing. The resulting message might 655not be the same as what is originally sent.</p> 656<p>If the <code>serialization</code> option was set to <code>advanced</code> used when spawning the 657process, the <code>message</code> argument can contain data that JSON is not able 658to represent. 659See <a href="child_process.html#advanced-serialization">Advanced serialization for <code>child_process</code></a> for more details.</p> 660<h4>Event: <code>'multipleResolves'</code><span><a class="mark" href="#event-multipleresolves" id="event-multipleresolves">#</a></span><a aria-hidden="true" class="legacy" id="process_event_multipleresolves"></a></h4> 661<div class="api_metadata"> 662<span>Added in: v10.12.0</span><span>Deprecated since: v17.6.0</span> 663</div> 664<p></p><div class="api_stability api_stability_0"><a href="documentation.html#stability-index">Stability: 0</a> - Deprecated</div><p></p> 665<ul> 666<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The resolution type. One of <code>'resolve'</code> or <code>'reject'</code>.</li> 667<li><code>promise</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> The promise that resolved or rejected more than once.</li> 668<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The value with which the promise was either resolved or 669rejected after the original resolve.</li> 670</ul> 671<p>The <code>'multipleResolves'</code> event is emitted whenever a <code>Promise</code> has been either:</p> 672<ul> 673<li>Resolved more than once.</li> 674<li>Rejected more than once.</li> 675<li>Rejected after resolve.</li> 676<li>Resolved after reject.</li> 677</ul> 678<p>This is useful for tracking potential errors in an application while using the 679<code>Promise</code> constructor, as multiple resolutions are silently swallowed. However, 680the occurrence of this event does not necessarily indicate an error. For 681example, <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/race"><code>Promise.race()</code></a> can trigger a <code>'multipleResolves'</code> event.</p> 682<p>Because of the unreliability of the event in cases like the 683<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/race"><code>Promise.race()</code></a> example above it has been deprecated.</p> 684 685<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 686 687process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'multipleResolves'</span>, <span class="hljs-function">(<span class="hljs-params">type, promise, reason</span>) =></span> { 688 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(type, promise, reason); 689 <span class="hljs-title function_">setImmediate</span>(<span class="hljs-function">() =></span> process.<span class="hljs-title function_">exit</span>(<span class="hljs-number">1</span>)); 690}); 691 692<span class="hljs-keyword">async</span> <span class="hljs-keyword">function</span> <span class="hljs-title function_">main</span>(<span class="hljs-params"></span>) { 693 <span class="hljs-keyword">try</span> { 694 <span class="hljs-keyword">return</span> <span class="hljs-keyword">await</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Promise</span>(<span class="hljs-function">(<span class="hljs-params">resolve, reject</span>) =></span> { 695 <span class="hljs-title function_">resolve</span>(<span class="hljs-string">'First call'</span>); 696 <span class="hljs-title function_">resolve</span>(<span class="hljs-string">'Swallowed resolve'</span>); 697 <span class="hljs-title function_">reject</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Swallowed reject'</span>)); 698 }); 699 } <span class="hljs-keyword">catch</span> { 700 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Failed'</span>); 701 } 702} 703 704<span class="hljs-title function_">main</span>().<span class="hljs-title function_">then</span>(<span class="hljs-variable language_">console</span>.<span class="hljs-property">log</span>); 705<span class="hljs-comment">// resolve: Promise { 'First call' } 'Swallowed resolve'</span> 706<span class="hljs-comment">// reject: Promise { 'First call' } Error: Swallowed reject</span> 707<span class="hljs-comment">// at Promise (*)</span> 708<span class="hljs-comment">// at new Promise (<anonymous>)</span> 709<span class="hljs-comment">// at main (*)</span> 710<span class="hljs-comment">// First call</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 711 712process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'multipleResolves'</span>, <span class="hljs-function">(<span class="hljs-params">type, promise, reason</span>) =></span> { 713 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(type, promise, reason); 714 <span class="hljs-title function_">setImmediate</span>(<span class="hljs-function">() =></span> process.<span class="hljs-title function_">exit</span>(<span class="hljs-number">1</span>)); 715}); 716 717<span class="hljs-keyword">async</span> <span class="hljs-keyword">function</span> <span class="hljs-title function_">main</span>(<span class="hljs-params"></span>) { 718 <span class="hljs-keyword">try</span> { 719 <span class="hljs-keyword">return</span> <span class="hljs-keyword">await</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Promise</span>(<span class="hljs-function">(<span class="hljs-params">resolve, reject</span>) =></span> { 720 <span class="hljs-title function_">resolve</span>(<span class="hljs-string">'First call'</span>); 721 <span class="hljs-title function_">resolve</span>(<span class="hljs-string">'Swallowed resolve'</span>); 722 <span class="hljs-title function_">reject</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Swallowed reject'</span>)); 723 }); 724 } <span class="hljs-keyword">catch</span> { 725 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Failed'</span>); 726 } 727} 728 729<span class="hljs-title function_">main</span>().<span class="hljs-title function_">then</span>(<span class="hljs-variable language_">console</span>.<span class="hljs-property">log</span>); 730<span class="hljs-comment">// resolve: Promise { 'First call' } 'Swallowed resolve'</span> 731<span class="hljs-comment">// reject: Promise { 'First call' } Error: Swallowed reject</span> 732<span class="hljs-comment">// at Promise (*)</span> 733<span class="hljs-comment">// at new Promise (<anonymous>)</span> 734<span class="hljs-comment">// at main (*)</span> 735<span class="hljs-comment">// First call</span></code><button class="copy-button">copy</button></pre> 736<h4>Event: <code>'rejectionHandled'</code><span><a class="mark" href="#event-rejectionhandled" id="event-rejectionhandled">#</a></span><a aria-hidden="true" class="legacy" id="process_event_rejectionhandled"></a></h4> 737<div class="api_metadata"> 738<span>Added in: v1.4.1</span> 739</div> 740<ul> 741<li><code>promise</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> The late handled promise.</li> 742</ul> 743<p>The <code>'rejectionHandled'</code> event is emitted whenever a <code>Promise</code> has been rejected 744and an error handler was attached to it (using <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/catch"><code>promise.catch()</code></a>, for 745example) later than one turn of the Node.js event loop.</p> 746<p>The <code>Promise</code> object would have previously been emitted in an 747<code>'unhandledRejection'</code> event, but during the course of processing gained a 748rejection handler.</p> 749<p>There is no notion of a top level for a <code>Promise</code> chain at which rejections can 750always be handled. Being inherently asynchronous in nature, a <code>Promise</code> 751rejection can be handled at a future point in time, possibly much later than 752the event loop turn it takes for the <code>'unhandledRejection'</code> event to be emitted.</p> 753<p>Another way of stating this is that, unlike in synchronous code where there is 754an ever-growing list of unhandled exceptions, with Promises there can be a 755growing-and-shrinking list of unhandled rejections.</p> 756<p>In synchronous code, the <code>'uncaughtException'</code> event is emitted when the list of 757unhandled exceptions grows.</p> 758<p>In asynchronous code, the <code>'unhandledRejection'</code> event is emitted when the list 759of unhandled rejections grows, and the <code>'rejectionHandled'</code> event is emitted 760when the list of unhandled rejections shrinks.</p> 761 762<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 763 764<span class="hljs-keyword">const</span> unhandledRejections = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Map</span>(); 765process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'unhandledRejection'</span>, <span class="hljs-function">(<span class="hljs-params">reason, promise</span>) =></span> { 766 unhandledRejections.<span class="hljs-title function_">set</span>(promise, reason); 767}); 768process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'rejectionHandled'</span>, <span class="hljs-function">(<span class="hljs-params">promise</span>) =></span> { 769 unhandledRejections.<span class="hljs-title function_">delete</span>(promise); 770});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 771 772<span class="hljs-keyword">const</span> unhandledRejections = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Map</span>(); 773process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'unhandledRejection'</span>, <span class="hljs-function">(<span class="hljs-params">reason, promise</span>) =></span> { 774 unhandledRejections.<span class="hljs-title function_">set</span>(promise, reason); 775}); 776process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'rejectionHandled'</span>, <span class="hljs-function">(<span class="hljs-params">promise</span>) =></span> { 777 unhandledRejections.<span class="hljs-title function_">delete</span>(promise); 778});</code><button class="copy-button">copy</button></pre> 779<p>In this example, the <code>unhandledRejections</code> <code>Map</code> will grow and shrink over time, 780reflecting rejections that start unhandled and then become handled. It is 781possible to record such errors in an error log, either periodically (which is 782likely best for long-running application) or upon process exit (which is likely 783most convenient for scripts).</p> 784<h4>Event: <code>'uncaughtException'</code><span><a class="mark" href="#event-uncaughtexception" id="event-uncaughtexception">#</a></span><a aria-hidden="true" class="legacy" id="process_event_uncaughtexception"></a></h4> 785<div class="api_metadata"> 786<details class="changelog"><summary>History</summary> 787<table> 788<tbody><tr><th>Version</th><th>Changes</th></tr> 789<tr><td>v12.0.0, v10.17.0</td> 790<td><p>Added the <code>origin</code> argument.</p></td></tr> 791<tr><td>v0.1.18</td> 792<td><p><span>Added in: v0.1.18</span></p></td></tr> 793</tbody></table> 794</details> 795</div> 796<ul> 797<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a> The uncaught exception.</li> 798<li><code>origin</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Indicates if the exception originates from an unhandled 799rejection or from a synchronous error. Can either be <code>'uncaughtException'</code> or 800<code>'unhandledRejection'</code>. The latter is used when an exception happens in a 801<code>Promise</code> based async context (or if a <code>Promise</code> is rejected) and 802<a href="cli.html#--unhandled-rejectionsmode"><code>--unhandled-rejections</code></a> flag set to <code>strict</code> or <code>throw</code> (which is the 803default) and the rejection is not handled, or when a rejection happens during 804the command line entry point's ES module static loading phase.</li> 805</ul> 806<p>The <code>'uncaughtException'</code> event is emitted when an uncaught JavaScript 807exception bubbles all the way back to the event loop. By default, Node.js 808handles such exceptions by printing the stack trace to <code>stderr</code> and exiting 809with code 1, overriding any previously set <a href="#processexitcode_1"><code>process.exitCode</code></a>. 810Adding a handler for the <code>'uncaughtException'</code> event overrides this default 811behavior. Alternatively, change the <a href="#processexitcode_1"><code>process.exitCode</code></a> in the 812<code>'uncaughtException'</code> handler which will result in the process exiting with the 813provided exit code. Otherwise, in the presence of such handler the process will 814exit with 0.</p> 815 816<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 817 818process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'uncaughtException'</span>, <span class="hljs-function">(<span class="hljs-params">err, origin</span>) =></span> { 819 fs.<span class="hljs-title function_">writeSync</span>( 820 process.<span class="hljs-property">stderr</span>.<span class="hljs-property">fd</span>, 821 <span class="hljs-string">`Caught exception: <span class="hljs-subst">${err}</span>\n`</span> + 822 <span class="hljs-string">`Exception origin: <span class="hljs-subst">${origin}</span>`</span>, 823 ); 824}); 825 826<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 827 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'This will still run.'</span>); 828}, <span class="hljs-number">500</span>); 829 830<span class="hljs-comment">// Intentionally cause an exception, but don't catch it.</span> 831<span class="hljs-title function_">nonexistentFunc</span>(); 832<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'This will not run.'</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 833 834process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'uncaughtException'</span>, <span class="hljs-function">(<span class="hljs-params">err, origin</span>) =></span> { 835 fs.<span class="hljs-title function_">writeSync</span>( 836 process.<span class="hljs-property">stderr</span>.<span class="hljs-property">fd</span>, 837 <span class="hljs-string">`Caught exception: <span class="hljs-subst">${err}</span>\n`</span> + 838 <span class="hljs-string">`Exception origin: <span class="hljs-subst">${origin}</span>`</span>, 839 ); 840}); 841 842<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 843 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'This will still run.'</span>); 844}, <span class="hljs-number">500</span>); 845 846<span class="hljs-comment">// Intentionally cause an exception, but don't catch it.</span> 847<span class="hljs-title function_">nonexistentFunc</span>(); 848<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'This will not run.'</span>);</code><button class="copy-button">copy</button></pre> 849<p>It is possible to monitor <code>'uncaughtException'</code> events without overriding the 850default behavior to exit the process by installing a 851<code>'uncaughtExceptionMonitor'</code> listener.</p> 852<h5>Warning: Using <code>'uncaughtException'</code> correctly<span><a class="mark" href="#warning-using-uncaughtexception-correctly" id="warning-using-uncaughtexception-correctly">#</a></span><a aria-hidden="true" class="legacy" id="process_warning_using_uncaughtexception_correctly"></a></h5> 853<p><code>'uncaughtException'</code> is a crude mechanism for exception handling 854intended to be used only as a last resort. The event <em>should not</em> be used as 855an equivalent to <code>On Error Resume Next</code>. Unhandled exceptions inherently mean 856that an application is in an undefined state. Attempting to resume application 857code without properly recovering from the exception can cause additional 858unforeseen and unpredictable issues.</p> 859<p>Exceptions thrown from within the event handler will not be caught. Instead the 860process will exit with a non-zero exit code and the stack trace will be printed. 861This is to avoid infinite recursion.</p> 862<p>Attempting to resume normally after an uncaught exception can be similar to 863pulling out the power cord when upgrading a computer. Nine out of ten 864times, nothing happens. But the tenth time, the system becomes corrupted.</p> 865<p>The correct use of <code>'uncaughtException'</code> is to perform synchronous cleanup 866of allocated resources (e.g. file descriptors, handles, etc) before shutting 867down the process. <strong>It is not safe to resume normal operation after 868<code>'uncaughtException'</code>.</strong></p> 869<p>To restart a crashed application in a more reliable way, whether 870<code>'uncaughtException'</code> is emitted or not, an external monitor should be employed 871in a separate process to detect application failures and recover or restart as 872needed.</p> 873<h4>Event: <code>'uncaughtExceptionMonitor'</code><span><a class="mark" href="#event-uncaughtexceptionmonitor" id="event-uncaughtexceptionmonitor">#</a></span><a aria-hidden="true" class="legacy" id="process_event_uncaughtexceptionmonitor"></a></h4> 874<div class="api_metadata"> 875<span>Added in: v13.7.0, v12.17.0</span> 876</div> 877<ul> 878<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a> The uncaught exception.</li> 879<li><code>origin</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Indicates if the exception originates from an unhandled 880rejection or from synchronous errors. Can either be <code>'uncaughtException'</code> or 881<code>'unhandledRejection'</code>. The latter is used when an exception happens in a 882<code>Promise</code> based async context (or if a <code>Promise</code> is rejected) and 883<a href="cli.html#--unhandled-rejectionsmode"><code>--unhandled-rejections</code></a> flag set to <code>strict</code> or <code>throw</code> (which is the 884default) and the rejection is not handled, or when a rejection happens during 885the command line entry point's ES module static loading phase.</li> 886</ul> 887<p>The <code>'uncaughtExceptionMonitor'</code> event is emitted before an 888<code>'uncaughtException'</code> event is emitted or a hook installed via 889<a href="#processsetuncaughtexceptioncapturecallbackfn"><code>process.setUncaughtExceptionCaptureCallback()</code></a> is called.</p> 890<p>Installing an <code>'uncaughtExceptionMonitor'</code> listener does not change the behavior 891once an <code>'uncaughtException'</code> event is emitted. The process will 892still crash if no <code>'uncaughtException'</code> listener is installed.</p> 893 894<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 895 896process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'uncaughtExceptionMonitor'</span>, <span class="hljs-function">(<span class="hljs-params">err, origin</span>) =></span> { 897 <span class="hljs-title class_">MyMonitoringTool</span>.<span class="hljs-title function_">logSync</span>(err, origin); 898}); 899 900<span class="hljs-comment">// Intentionally cause an exception, but don't catch it.</span> 901<span class="hljs-title function_">nonexistentFunc</span>(); 902<span class="hljs-comment">// Still crashes Node.js</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 903 904process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'uncaughtExceptionMonitor'</span>, <span class="hljs-function">(<span class="hljs-params">err, origin</span>) =></span> { 905 <span class="hljs-title class_">MyMonitoringTool</span>.<span class="hljs-title function_">logSync</span>(err, origin); 906}); 907 908<span class="hljs-comment">// Intentionally cause an exception, but don't catch it.</span> 909<span class="hljs-title function_">nonexistentFunc</span>(); 910<span class="hljs-comment">// Still crashes Node.js</span></code><button class="copy-button">copy</button></pre> 911<h4>Event: <code>'unhandledRejection'</code><span><a class="mark" href="#event-unhandledrejection" id="event-unhandledrejection">#</a></span><a aria-hidden="true" class="legacy" id="process_event_unhandledrejection"></a></h4> 912<div class="api_metadata"> 913<details class="changelog"><summary>History</summary> 914<table> 915<tbody><tr><th>Version</th><th>Changes</th></tr> 916<tr><td>v7.0.0</td> 917<td><p>Not handling <code>Promise</code> rejections is deprecated.</p></td></tr> 918<tr><td>v6.6.0</td> 919<td><p>Unhandled <code>Promise</code> rejections will now emit a process warning.</p></td></tr> 920<tr><td>v1.4.1</td> 921<td><p><span>Added in: v1.4.1</span></p></td></tr> 922</tbody></table> 923</details> 924</div> 925<ul> 926<li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The object with which the promise was rejected 927(typically an <a href="errors.html#class-error"><code>Error</code></a> object).</li> 928<li><code>promise</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> The rejected promise.</li> 929</ul> 930<p>The <code>'unhandledRejection'</code> event is emitted whenever a <code>Promise</code> is rejected and 931no error handler is attached to the promise within a turn of the event loop. 932When programming with Promises, exceptions are encapsulated as "rejected 933promises". Rejections can be caught and handled using <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/catch"><code>promise.catch()</code></a> and 934are propagated through a <code>Promise</code> chain. The <code>'unhandledRejection'</code> event is 935useful for detecting and keeping track of promises that were rejected whose 936rejections have not yet been handled.</p> 937 938<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 939 940process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'unhandledRejection'</span>, <span class="hljs-function">(<span class="hljs-params">reason, promise</span>) =></span> { 941 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Unhandled Rejection at:'</span>, promise, <span class="hljs-string">'reason:'</span>, reason); 942 <span class="hljs-comment">// Application specific logging, throwing an error, or other logic here</span> 943}); 944 945somePromise.<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">res</span>) =></span> { 946 <span class="hljs-keyword">return</span> <span class="hljs-title function_">reportToUser</span>(<span class="hljs-title class_">JSON</span>.<span class="hljs-title function_">pasre</span>(res)); <span class="hljs-comment">// Note the typo (`pasre`)</span> 947}); <span class="hljs-comment">// No `.catch()` or `.then()`</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 948 949process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'unhandledRejection'</span>, <span class="hljs-function">(<span class="hljs-params">reason, promise</span>) =></span> { 950 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Unhandled Rejection at:'</span>, promise, <span class="hljs-string">'reason:'</span>, reason); 951 <span class="hljs-comment">// Application specific logging, throwing an error, or other logic here</span> 952}); 953 954somePromise.<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">res</span>) =></span> { 955 <span class="hljs-keyword">return</span> <span class="hljs-title function_">reportToUser</span>(<span class="hljs-title class_">JSON</span>.<span class="hljs-title function_">pasre</span>(res)); <span class="hljs-comment">// Note the typo (`pasre`)</span> 956}); <span class="hljs-comment">// No `.catch()` or `.then()`</span></code><button class="copy-button">copy</button></pre> 957<p>The following will also trigger the <code>'unhandledRejection'</code> event to be 958emitted:</p> 959 960<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 961 962<span class="hljs-keyword">function</span> <span class="hljs-title function_">SomeResource</span>(<span class="hljs-params"></span>) { 963 <span class="hljs-comment">// Initially set the loaded status to a rejected promise</span> 964 <span class="hljs-variable language_">this</span>.<span class="hljs-property">loaded</span> = <span class="hljs-title class_">Promise</span>.<span class="hljs-title function_">reject</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Resource not yet loaded!'</span>)); 965} 966 967<span class="hljs-keyword">const</span> resource = <span class="hljs-keyword">new</span> <span class="hljs-title class_">SomeResource</span>(); 968<span class="hljs-comment">// no .catch or .then on resource.loaded for at least a turn</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 969 970<span class="hljs-keyword">function</span> <span class="hljs-title function_">SomeResource</span>(<span class="hljs-params"></span>) { 971 <span class="hljs-comment">// Initially set the loaded status to a rejected promise</span> 972 <span class="hljs-variable language_">this</span>.<span class="hljs-property">loaded</span> = <span class="hljs-title class_">Promise</span>.<span class="hljs-title function_">reject</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Resource not yet loaded!'</span>)); 973} 974 975<span class="hljs-keyword">const</span> resource = <span class="hljs-keyword">new</span> <span class="hljs-title class_">SomeResource</span>(); 976<span class="hljs-comment">// no .catch or .then on resource.loaded for at least a turn</span></code><button class="copy-button">copy</button></pre> 977<p>In this example case, it is possible to track the rejection as a developer error 978as would typically be the case for other <code>'unhandledRejection'</code> events. To 979address such failures, a non-operational 980<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/catch"><code>.catch(() => { })</code></a> handler may be attached to 981<code>resource.loaded</code>, which would prevent the <code>'unhandledRejection'</code> event from 982being emitted.</p> 983<h4>Event: <code>'warning'</code><span><a class="mark" href="#event-warning" id="event-warning">#</a></span><a aria-hidden="true" class="legacy" id="process_event_warning"></a></h4> 984<div class="api_metadata"> 985<span>Added in: v6.0.0</span> 986</div> 987<ul> 988<li><code>warning</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a> Key properties of the warning are: 989<ul> 990<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The name of the warning. <strong>Default:</strong> <code>'Warning'</code>.</li> 991<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A system-provided description of the warning.</li> 992<li><code>stack</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A stack trace to the location in the code where the warning 993was issued.</li> 994</ul> 995</li> 996</ul> 997<p>The <code>'warning'</code> event is emitted whenever Node.js emits a process warning.</p> 998<p>A process warning is similar to an error in that it describes exceptional 999conditions that are being brought to the user's attention. However, warnings 1000are not part of the normal Node.js and JavaScript error handling flow. 1001Node.js can emit warnings whenever it detects bad coding practices that could 1002lead to sub-optimal application performance, bugs, or security vulnerabilities.</p> 1003 1004<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1005 1006process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'warning'</span>, <span class="hljs-function">(<span class="hljs-params">warning</span>) =></span> { 1007 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">name</span>); <span class="hljs-comment">// Print the warning name</span> 1008 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">message</span>); <span class="hljs-comment">// Print the warning message</span> 1009 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">stack</span>); <span class="hljs-comment">// Print the stack trace</span> 1010});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1011 1012process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'warning'</span>, <span class="hljs-function">(<span class="hljs-params">warning</span>) =></span> { 1013 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">name</span>); <span class="hljs-comment">// Print the warning name</span> 1014 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">message</span>); <span class="hljs-comment">// Print the warning message</span> 1015 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">stack</span>); <span class="hljs-comment">// Print the stack trace</span> 1016});</code><button class="copy-button">copy</button></pre> 1017<p>By default, Node.js will print process warnings to <code>stderr</code>. The <code>--no-warnings</code> 1018command-line option can be used to suppress the default console output but the 1019<code>'warning'</code> event will still be emitted by the <code>process</code> object.</p> 1020<p>The following example illustrates the warning that is printed to <code>stderr</code> when 1021too many listeners have been added to an event:</p> 1022<pre><code class="language-console"><span class="hljs-meta prompt_">$ </span><span class="language-bash">node</span> 1023<span class="hljs-meta prompt_">> </span><span class="language-bash">events.defaultMaxListeners = 1;</span> 1024<span class="hljs-meta prompt_">> </span><span class="language-bash">process.on(<span class="hljs-string">'foo'</span>, () => {});</span> 1025<span class="hljs-meta prompt_">> </span><span class="language-bash">process.on(<span class="hljs-string">'foo'</span>, () => {});</span> 1026<span class="hljs-meta prompt_">> </span><span class="language-bash">(node:38638) MaxListenersExceededWarning: Possible EventEmitter memory leak</span> 1027detected. 2 foo listeners added. Use emitter.setMaxListeners() to increase limit</code> <button class="copy-button">copy</button></pre> 1028<p>In contrast, the following example turns off the default warning output and 1029adds a custom handler to the <code>'warning'</code> event:</p> 1030<pre><code class="language-console"><span class="hljs-meta prompt_">$ </span><span class="language-bash">node --no-warnings</span> 1031<span class="hljs-meta prompt_">> </span><span class="language-bash">const p = process.on(<span class="hljs-string">'warning'</span>, (warning) => console.warn(<span class="hljs-string">'Do not do that!'</span>));</span> 1032<span class="hljs-meta prompt_">> </span><span class="language-bash">events.defaultMaxListeners = 1;</span> 1033<span class="hljs-meta prompt_">> </span><span class="language-bash">process.on(<span class="hljs-string">'foo'</span>, () => {});</span> 1034<span class="hljs-meta prompt_">> </span><span class="language-bash">process.on(<span class="hljs-string">'foo'</span>, () => {});</span> 1035<span class="hljs-meta prompt_">> </span><span class="language-bash">Do not <span class="hljs-keyword">do</span> that!</span></code> <button class="copy-button">copy</button></pre> 1036<p>The <code>--trace-warnings</code> command-line option can be used to have the default 1037console output for warnings include the full stack trace of the warning.</p> 1038<p>Launching Node.js using the <code>--throw-deprecation</code> command-line flag will 1039cause custom deprecation warnings to be thrown as exceptions.</p> 1040<p>Using the <code>--trace-deprecation</code> command-line flag will cause the custom 1041deprecation to be printed to <code>stderr</code> along with the stack trace.</p> 1042<p>Using the <code>--no-deprecation</code> command-line flag will suppress all reporting 1043of the custom deprecation.</p> 1044<p>The <code>*-deprecation</code> command-line flags only affect warnings that use the name 1045<code>'DeprecationWarning'</code>.</p> 1046<h4>Event: <code>'worker'</code><span><a class="mark" href="#event-worker" id="event-worker">#</a></span><a aria-hidden="true" class="legacy" id="process_event_worker"></a></h4> 1047<div class="api_metadata"> 1048<span>Added in: v16.2.0, v14.18.0</span> 1049</div> 1050<ul> 1051<li><code>worker</code> <a href="worker_threads.html#class-worker" class="type"><Worker></a> The <a href="worker_threads.html#class-worker" class="type"><Worker></a> that was created.</li> 1052</ul> 1053<p>The <code>'worker'</code> event is emitted after a new <a href="worker_threads.html#class-worker" class="type"><Worker></a> thread has been created.</p> 1054<h5>Emitting custom warnings<span><a class="mark" href="#emitting-custom-warnings" id="emitting-custom-warnings">#</a></span><a aria-hidden="true" class="legacy" id="process_emitting_custom_warnings"></a></h5> 1055<p>See the <a href="#processemitwarningwarning-type-code-ctor"><code>process.emitWarning()</code></a> method for issuing 1056custom or application-specific warnings.</p> 1057<h5>Node.js warning names<span><a class="mark" href="#nodejs-warning-names" id="nodejs-warning-names">#</a></span><a aria-hidden="true" class="legacy" id="process_node_js_warning_names"></a></h5> 1058<p>There are no strict guidelines for warning types (as identified by the <code>name</code> 1059property) emitted by Node.js. New types of warnings can be added at any time. 1060A few of the warning types that are most common include:</p> 1061<ul> 1062<li><code>'DeprecationWarning'</code> - Indicates use of a deprecated Node.js API or feature. 1063Such warnings must include a <code>'code'</code> property identifying the 1064<a href="deprecations.html">deprecation code</a>.</li> 1065<li><code>'ExperimentalWarning'</code> - Indicates use of an experimental Node.js API or 1066feature. Such features must be used with caution as they may change at any 1067time and are not subject to the same strict semantic-versioning and long-term 1068support policies as supported features.</li> 1069<li><code>'MaxListenersExceededWarning'</code> - Indicates that too many listeners for a 1070given event have been registered on either an <code>EventEmitter</code> or <code>EventTarget</code>. 1071This is often an indication of a memory leak.</li> 1072<li><code>'TimeoutOverflowWarning'</code> - Indicates that a numeric value that cannot fit 1073within a 32-bit signed integer has been provided to either the <code>setTimeout()</code> 1074or <code>setInterval()</code> functions.</li> 1075<li><code>'UnsupportedWarning'</code> - Indicates use of an unsupported option or feature 1076that will be ignored rather than treated as an error. One example is use of 1077the HTTP response status message when using the HTTP/2 compatibility API.</li> 1078</ul> 1079<h4>Signal events<span><a class="mark" href="#signal-events" id="signal-events">#</a></span><a aria-hidden="true" class="legacy" id="process_signal_events"></a></h4> 1080 1081 1082<p>Signal events will be emitted when the Node.js process receives a signal. Please 1083refer to <a href="http://man7.org/linux/man-pages/man7/signal.7.html"><code>signal(7)</code></a> for a listing of standard POSIX signal names such as 1084<code>'SIGINT'</code>, <code>'SIGHUP'</code>, etc.</p> 1085<p>Signals are not available on <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 1086<p>The signal handler will receive the signal's name (<code>'SIGINT'</code>, 1087<code>'SIGTERM'</code>, etc.) as the first argument.</p> 1088<p>The name of each event will be the uppercase common name for the signal (e.g. 1089<code>'SIGINT'</code> for <code>SIGINT</code> signals).</p> 1090 1091<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1092 1093<span class="hljs-comment">// Begin reading from stdin so the process does not exit.</span> 1094process.<span class="hljs-property">stdin</span>.<span class="hljs-title function_">resume</span>(); 1095 1096process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'SIGINT'</span>, <span class="hljs-function">() =></span> { 1097 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Received SIGINT. Press Control-D to exit.'</span>); 1098}); 1099 1100<span class="hljs-comment">// Using a single function to handle multiple signals</span> 1101<span class="hljs-keyword">function</span> <span class="hljs-title function_">handle</span>(<span class="hljs-params">signal</span>) { 1102 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Received <span class="hljs-subst">${signal}</span>`</span>); 1103} 1104 1105process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'SIGINT'</span>, handle); 1106process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'SIGTERM'</span>, handle);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1107 1108<span class="hljs-comment">// Begin reading from stdin so the process does not exit.</span> 1109process.<span class="hljs-property">stdin</span>.<span class="hljs-title function_">resume</span>(); 1110 1111process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'SIGINT'</span>, <span class="hljs-function">() =></span> { 1112 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Received SIGINT. Press Control-D to exit.'</span>); 1113}); 1114 1115<span class="hljs-comment">// Using a single function to handle multiple signals</span> 1116<span class="hljs-keyword">function</span> <span class="hljs-title function_">handle</span>(<span class="hljs-params">signal</span>) { 1117 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Received <span class="hljs-subst">${signal}</span>`</span>); 1118} 1119 1120process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'SIGINT'</span>, handle); 1121process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'SIGTERM'</span>, handle);</code><button class="copy-button">copy</button></pre> 1122<ul> 1123<li><code>'SIGUSR1'</code> is reserved by Node.js to start the <a href="debugger.html">debugger</a>. It's possible to 1124install a listener but doing so might interfere with the debugger.</li> 1125<li><code>'SIGTERM'</code> and <code>'SIGINT'</code> have default handlers on non-Windows platforms that 1126reset the terminal mode before exiting with code <code>128 + signal number</code>. If one 1127of these signals has a listener installed, its default behavior will be 1128removed (Node.js will no longer exit).</li> 1129<li><code>'SIGPIPE'</code> is ignored by default. It can have a listener installed.</li> 1130<li><code>'SIGHUP'</code> is generated on Windows when the console window is closed, and on 1131other platforms under various similar conditions. See <a href="http://man7.org/linux/man-pages/man7/signal.7.html"><code>signal(7)</code></a>. It can have a 1132listener installed, however Node.js will be unconditionally terminated by 1133Windows about 10 seconds later. On non-Windows platforms, the default 1134behavior of <code>SIGHUP</code> is to terminate Node.js, but once a listener has been 1135installed its default behavior will be removed.</li> 1136<li><code>'SIGTERM'</code> is not supported on Windows, it can be listened on.</li> 1137<li><code>'SIGINT'</code> from the terminal is supported on all platforms, and can usually be 1138generated with <kbd>Ctrl</kbd>+<kbd>C</kbd> (though this may be configurable). 1139It is not generated when <a href="tty.html#readstreamsetrawmodemode">terminal raw mode</a> is enabled 1140and <kbd>Ctrl</kbd>+<kbd>C</kbd> is used.</li> 1141<li><code>'SIGBREAK'</code> is delivered on Windows when <kbd>Ctrl</kbd>+<kbd>Break</kbd> is 1142pressed. On non-Windows platforms, it can be listened on, but there is no way 1143to send or generate it.</li> 1144<li><code>'SIGWINCH'</code> is delivered when the console has been resized. On Windows, this 1145will only happen on write to the console when the cursor is being moved, or 1146when a readable tty is used in raw mode.</li> 1147<li><code>'SIGKILL'</code> cannot have a listener installed, it will unconditionally 1148terminate Node.js on all platforms.</li> 1149<li><code>'SIGSTOP'</code> cannot have a listener installed.</li> 1150<li><code>'SIGBUS'</code>, <code>'SIGFPE'</code>, <code>'SIGSEGV'</code>, and <code>'SIGILL'</code>, when not raised 1151artificially using <a href="http://man7.org/linux/man-pages/man2/kill.2.html"><code>kill(2)</code></a>, inherently leave the process in a state from 1152which it is not safe to call JS listeners. Doing so might cause the process 1153to stop responding.</li> 1154<li><code>0</code> can be sent to test for the existence of a process, it has no effect if 1155the process exists, but will throw an error if the process does not exist.</li> 1156</ul> 1157<p>Windows does not support signals so has no equivalent to termination by signal, 1158but Node.js offers some emulation with <a href="#processkillpid-signal"><code>process.kill()</code></a>, and 1159<a href="child_process.html#subprocesskillsignal"><code>subprocess.kill()</code></a>:</p> 1160<ul> 1161<li>Sending <code>SIGINT</code>, <code>SIGTERM</code>, and <code>SIGKILL</code> will cause the unconditional 1162termination of the target process, and afterwards, subprocess will report that 1163the process was terminated by signal.</li> 1164<li>Sending signal <code>0</code> can be used as a platform independent way to test for the 1165existence of a process.</li> 1166</ul> 1167</section><section><h3><code>process.abort()</code><span><a class="mark" href="#processabort" id="processabort">#</a></span><a aria-hidden="true" class="legacy" id="process_process_abort"></a></h3> 1168<div class="api_metadata"> 1169<span>Added in: v0.7.0</span> 1170</div> 1171<p>The <code>process.abort()</code> method causes the Node.js process to exit immediately and 1172generate a core file.</p> 1173<p>This feature is not available in <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 1174</section><section><h3><code>process.allowedNodeEnvironmentFlags</code><span><a class="mark" href="#processallowednodeenvironmentflags" id="processallowednodeenvironmentflags">#</a></span><a aria-hidden="true" class="legacy" id="process_process_allowednodeenvironmentflags"></a></h3> 1175<div class="api_metadata"> 1176<span>Added in: v10.10.0</span> 1177</div> 1178<ul> 1179<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set" class="type"><Set></a></li> 1180</ul> 1181<p>The <code>process.allowedNodeEnvironmentFlags</code> property is a special, 1182read-only <code>Set</code> of flags allowable within the <a href="cli.html#node_optionsoptions"><code>NODE_OPTIONS</code></a> 1183environment variable.</p> 1184<p><code>process.allowedNodeEnvironmentFlags</code> extends <code>Set</code>, but overrides 1185<code>Set.prototype.has</code> to recognize several different possible flag 1186representations. <code>process.allowedNodeEnvironmentFlags.has()</code> will 1187return <code>true</code> in the following cases:</p> 1188<ul> 1189<li>Flags may omit leading single (<code>-</code>) or double (<code>--</code>) dashes; e.g., 1190<code>inspect-brk</code> for <code>--inspect-brk</code>, or <code>r</code> for <code>-r</code>.</li> 1191<li>Flags passed through to V8 (as listed in <code>--v8-options</code>) may replace 1192one or more <em>non-leading</em> dashes for an underscore, or vice-versa; 1193e.g., <code>--perf_basic_prof</code>, <code>--perf-basic-prof</code>, <code>--perf_basic-prof</code>, 1194etc.</li> 1195<li>Flags may contain one or more equals (<code>=</code>) characters; all 1196characters after and including the first equals will be ignored; 1197e.g., <code>--stack-trace-limit=100</code>.</li> 1198<li>Flags <em>must</em> be allowable within <a href="cli.html#node_optionsoptions"><code>NODE_OPTIONS</code></a>.</li> 1199</ul> 1200<p>When iterating over <code>process.allowedNodeEnvironmentFlags</code>, flags will 1201appear only <em>once</em>; each will begin with one or more dashes. Flags 1202passed through to V8 will contain underscores instead of non-leading 1203dashes:</p> 1204 1205<pre class="with-64-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { allowedNodeEnvironmentFlags } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1206 1207allowedNodeEnvironmentFlags.<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">flag</span>) =></span> { 1208 <span class="hljs-comment">// -r</span> 1209 <span class="hljs-comment">// --inspect-brk</span> 1210 <span class="hljs-comment">// --abort_on_uncaught_exception</span> 1211 <span class="hljs-comment">// ...</span> 1212});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { allowedNodeEnvironmentFlags } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1213 1214allowedNodeEnvironmentFlags.<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">flag</span>) =></span> { 1215 <span class="hljs-comment">// -r</span> 1216 <span class="hljs-comment">// --inspect-brk</span> 1217 <span class="hljs-comment">// --abort_on_uncaught_exception</span> 1218 <span class="hljs-comment">// ...</span> 1219});</code><button class="copy-button">copy</button></pre> 1220<p>The methods <code>add()</code>, <code>clear()</code>, and <code>delete()</code> of 1221<code>process.allowedNodeEnvironmentFlags</code> do nothing, and will fail 1222silently.</p> 1223<p>If Node.js was compiled <em>without</em> <a href="cli.html#node_optionsoptions"><code>NODE_OPTIONS</code></a> support (shown in 1224<a href="#processconfig"><code>process.config</code></a>), <code>process.allowedNodeEnvironmentFlags</code> will 1225contain what <em>would have</em> been allowable.</p> 1226</section><section><h3><code>process.arch</code><span><a class="mark" href="#processarch" id="processarch">#</a></span><a aria-hidden="true" class="legacy" id="process_process_arch"></a></h3> 1227<div class="api_metadata"> 1228<span>Added in: v0.5.0</span> 1229</div> 1230<ul> 1231<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1232</ul> 1233<p>The operating system CPU architecture for which the Node.js binary was compiled. 1234Possible values are: <code>'arm'</code>, <code>'arm64'</code>, <code>'ia32'</code>, <code>'mips'</code>,<code>'mipsel'</code>, <code>'ppc'</code>, 1235<code>'ppc64'</code>, <code>'s390'</code>, <code>'s390x'</code>, and <code>'x64'</code>.</p> 1236 1237<pre class="with-41-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { arch } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1238 1239<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`This processor architecture is <span class="hljs-subst">${arch}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { arch } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1240 1241<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`This processor architecture is <span class="hljs-subst">${arch}</span>`</span>);</code><button class="copy-button">copy</button></pre> 1242</section><section><h3><code>process.argv</code><span><a class="mark" href="#processargv" id="processargv">#</a></span><a aria-hidden="true" class="legacy" id="process_process_argv"></a></h3> 1243<div class="api_metadata"> 1244<span>Added in: v0.1.27</span> 1245</div> 1246<ul> 1247<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 1248</ul> 1249<p>The <code>process.argv</code> property returns an array containing the command-line 1250arguments passed when the Node.js process was launched. The first element will 1251be <a href="#processexecpath"><code>process.execPath</code></a>. See <code>process.argv0</code> if access to the original value 1252of <code>argv[0]</code> is needed. The second element will be the path to the JavaScript 1253file being executed. The remaining elements will be any additional command-line 1254arguments.</p> 1255<p>For example, assuming the following script for <code>process-args.js</code>:</p> 1256 1257<pre class="with-41-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { argv } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1258 1259<span class="hljs-comment">// print process.argv</span> 1260argv.<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">val, index</span>) =></span> { 1261 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`<span class="hljs-subst">${index}</span>: <span class="hljs-subst">${val}</span>`</span>); 1262});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { argv } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1263 1264<span class="hljs-comment">// print process.argv</span> 1265argv.<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">val, index</span>) =></span> { 1266 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`<span class="hljs-subst">${index}</span>: <span class="hljs-subst">${val}</span>`</span>); 1267});</code><button class="copy-button">copy</button></pre> 1268<p>Launching the Node.js process as:</p> 1269<pre><code class="language-console"><span class="hljs-meta prompt_">$ </span><span class="language-bash">node process-args.js one two=three four</span></code> <button class="copy-button">copy</button></pre> 1270<p>Would generate the output:</p> 1271<pre><code class="language-text">0: /usr/local/bin/node 12721: /Users/mjr/work/node/process-args.js 12732: one 12743: two=three 12754: four</code> <button class="copy-button">copy</button></pre> 1276</section><section><h3><code>process.argv0</code><span><a class="mark" href="#processargv0" id="processargv0">#</a></span><a aria-hidden="true" class="legacy" id="process_process_argv0"></a></h3> 1277<div class="api_metadata"> 1278<span>Added in: v6.4.0</span> 1279</div> 1280<ul> 1281<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1282</ul> 1283<p>The <code>process.argv0</code> property stores a read-only copy of the original value of 1284<code>argv[0]</code> passed when Node.js starts.</p> 1285<pre><code class="language-console"><span class="hljs-meta prompt_">$ </span><span class="language-bash">bash -c <span class="hljs-string">'exec -a customArgv0 ./node'</span></span> 1286<span class="hljs-meta prompt_">> </span><span class="language-bash">process.argv[0]</span> 1287'/Volumes/code/external/node/out/Release/node' 1288<span class="hljs-meta prompt_">> </span><span class="language-bash">process.argv0</span> 1289'customArgv0'</code> <button class="copy-button">copy</button></pre> 1290</section><section><h3><code>process.channel</code><span><a class="mark" href="#processchannel" id="processchannel">#</a></span><a aria-hidden="true" class="legacy" id="process_process_channel"></a></h3> 1291<div class="api_metadata"> 1292<details class="changelog"><summary>History</summary> 1293<table> 1294<tbody><tr><th>Version</th><th>Changes</th></tr> 1295<tr><td>v14.0.0</td> 1296<td><p>The object no longer accidentally exposes native C++ bindings.</p></td></tr> 1297<tr><td>v7.1.0</td> 1298<td><p><span>Added in: v7.1.0</span></p></td></tr> 1299</tbody></table> 1300</details> 1301</div> 1302<ul> 1303<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 1304</ul> 1305<p>If the Node.js process was spawned with an IPC channel (see the 1306<a href="child_process.html">Child Process</a> documentation), the <code>process.channel</code> 1307property is a reference to the IPC channel. If no IPC channel exists, this 1308property is <code>undefined</code>.</p> 1309<h4><code>process.channel.ref()</code><span><a class="mark" href="#processchannelref" id="processchannelref">#</a></span><a aria-hidden="true" class="legacy" id="process_process_channel_ref"></a></h4> 1310<div class="api_metadata"> 1311<span>Added in: v7.1.0</span> 1312</div> 1313<p>This method makes the IPC channel keep the event loop of the process 1314running if <code>.unref()</code> has been called before.</p> 1315<p>Typically, this is managed through the number of <code>'disconnect'</code> and <code>'message'</code> 1316listeners on the <code>process</code> object. However, this method can be used to 1317explicitly request a specific behavior.</p> 1318<h4><code>process.channel.unref()</code><span><a class="mark" href="#processchannelunref" id="processchannelunref">#</a></span><a aria-hidden="true" class="legacy" id="process_process_channel_unref"></a></h4> 1319<div class="api_metadata"> 1320<span>Added in: v7.1.0</span> 1321</div> 1322<p>This method makes the IPC channel not keep the event loop of the process 1323running, and lets it finish even while the channel is open.</p> 1324<p>Typically, this is managed through the number of <code>'disconnect'</code> and <code>'message'</code> 1325listeners on the <code>process</code> object. However, this method can be used to 1326explicitly request a specific behavior.</p> 1327</section><section><h3><code>process.chdir(directory)</code><span><a class="mark" href="#processchdirdirectory" id="processchdirdirectory">#</a></span><a aria-hidden="true" class="legacy" id="process_process_chdir_directory"></a></h3> 1328<div class="api_metadata"> 1329<span>Added in: v0.1.17</span> 1330</div> 1331<ul> 1332<li><code>directory</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1333</ul> 1334<p>The <code>process.chdir()</code> method changes the current working directory of the 1335Node.js process or throws an exception if doing so fails (for instance, if 1336the specified <code>directory</code> does not exist).</p> 1337 1338<pre class="with-47-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { chdir, cwd } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1339 1340<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Starting directory: <span class="hljs-subst">${cwd()}</span>`</span>); 1341<span class="hljs-keyword">try</span> { 1342 <span class="hljs-title function_">chdir</span>(<span class="hljs-string">'/tmp'</span>); 1343 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New directory: <span class="hljs-subst">${cwd()}</span>`</span>); 1344} <span class="hljs-keyword">catch</span> (err) { 1345 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`chdir: <span class="hljs-subst">${err}</span>`</span>); 1346}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { chdir, cwd } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1347 1348<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Starting directory: <span class="hljs-subst">${cwd()}</span>`</span>); 1349<span class="hljs-keyword">try</span> { 1350 <span class="hljs-title function_">chdir</span>(<span class="hljs-string">'/tmp'</span>); 1351 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New directory: <span class="hljs-subst">${cwd()}</span>`</span>); 1352} <span class="hljs-keyword">catch</span> (err) { 1353 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`chdir: <span class="hljs-subst">${err}</span>`</span>); 1354}</code><button class="copy-button">copy</button></pre> 1355<p>This feature is not available in <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 1356</section><section><h3><code>process.config</code><span><a class="mark" href="#processconfig" id="processconfig">#</a></span><a aria-hidden="true" class="legacy" id="process_process_config"></a></h3> 1357<div class="api_metadata"> 1358<details class="changelog"><summary>History</summary> 1359<table> 1360<tbody><tr><th>Version</th><th>Changes</th></tr> 1361<tr><td>v16.0.0</td> 1362<td><p>Modifying process.config has been deprecated.</p></td></tr> 1363<tr><td>v0.7.7</td> 1364<td><p><span>Added in: v0.7.7</span></p></td></tr> 1365</tbody></table> 1366</details> 1367</div> 1368<ul> 1369<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 1370</ul> 1371<p>The <code>process.config</code> property returns an <code>Object</code> containing the JavaScript 1372representation of the configure options used to compile the current Node.js 1373executable. This is the same as the <code>config.gypi</code> file that was produced when 1374running the <code>./configure</code> script.</p> 1375<p>An example of the possible output looks like:</p> 1376<!-- eslint-skip --> 1377<pre><code class="language-js">{ 1378 <span class="hljs-attr">target_defaults</span>: 1379 { <span class="hljs-attr">cflags</span>: [], 1380 <span class="hljs-attr">default_configuration</span>: <span class="hljs-string">'Release'</span>, 1381 <span class="hljs-attr">defines</span>: [], 1382 <span class="hljs-attr">include_dirs</span>: [], 1383 <span class="hljs-attr">libraries</span>: [] }, 1384 <span class="hljs-attr">variables</span>: 1385 { 1386 <span class="hljs-attr">host_arch</span>: <span class="hljs-string">'x64'</span>, 1387 <span class="hljs-attr">napi_build_version</span>: <span class="hljs-number">5</span>, 1388 <span class="hljs-attr">node_install_npm</span>: <span class="hljs-string">'true'</span>, 1389 <span class="hljs-attr">node_prefix</span>: <span class="hljs-string">''</span>, 1390 <span class="hljs-attr">node_shared_cares</span>: <span class="hljs-string">'false'</span>, 1391 <span class="hljs-attr">node_shared_http_parser</span>: <span class="hljs-string">'false'</span>, 1392 <span class="hljs-attr">node_shared_libuv</span>: <span class="hljs-string">'false'</span>, 1393 <span class="hljs-attr">node_shared_zlib</span>: <span class="hljs-string">'false'</span>, 1394 <span class="hljs-attr">node_use_dtrace</span>: <span class="hljs-string">'false'</span>, 1395 <span class="hljs-attr">node_use_openssl</span>: <span class="hljs-string">'true'</span>, 1396 <span class="hljs-attr">node_shared_openssl</span>: <span class="hljs-string">'false'</span>, 1397 <span class="hljs-attr">strict_aliasing</span>: <span class="hljs-string">'true'</span>, 1398 <span class="hljs-attr">target_arch</span>: <span class="hljs-string">'x64'</span>, 1399 <span class="hljs-attr">v8_use_snapshot</span>: <span class="hljs-number">1</span> 1400 } 1401}</code> <button class="copy-button">copy</button></pre> 1402<p>The <code>process.config</code> property is <strong>not</strong> read-only and there are existing 1403modules in the ecosystem that are known to extend, modify, or entirely replace 1404the value of <code>process.config</code>.</p> 1405<p>Modifying the <code>process.config</code> property, or any child-property of the 1406<code>process.config</code> object has been deprecated. The <code>process.config</code> will be made 1407read-only in a future release.</p> 1408</section><section><h3><code>process.connected</code><span><a class="mark" href="#processconnected" id="processconnected">#</a></span><a aria-hidden="true" class="legacy" id="process_process_connected"></a></h3> 1409<div class="api_metadata"> 1410<span>Added in: v0.7.2</span> 1411</div> 1412<ul> 1413<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1414</ul> 1415<p>If the Node.js process is spawned with an IPC channel (see the <a href="child_process.html">Child Process</a> 1416and <a href="cluster.html">Cluster</a> documentation), the <code>process.connected</code> property will return 1417<code>true</code> so long as the IPC channel is connected and will return <code>false</code> after 1418<code>process.disconnect()</code> is called.</p> 1419<p>Once <code>process.connected</code> is <code>false</code>, it is no longer possible to send messages 1420over the IPC channel using <code>process.send()</code>.</p> 1421</section><section><h3><code>process.constrainedMemory()</code><span><a class="mark" href="#processconstrainedmemory" id="processconstrainedmemory">#</a></span><a aria-hidden="true" class="legacy" id="process_process_constrainedmemory"></a></h3> 1422<div class="api_metadata"> 1423<span>Added in: v18.15.0</span> 1424</div> 1425<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 1426<ul> 1427<li><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#Undefined_type" class="type"><undefined></a></li> 1428</ul> 1429<p>Gets the amount of memory available to the process (in bytes) based on 1430limits imposed by the OS. If there is no such constraint, or the constraint 1431is unknown, <code>undefined</code> is returned.</p> 1432<p>See <a href="https://docs.libuv.org/en/v1.x/misc.html#c.uv_get_constrained_memory"><code>uv_get_constrained_memory</code></a> for more 1433information.</p> 1434</section><section><h3><code>process.cpuUsage([previousValue])</code><span><a class="mark" href="#processcpuusagepreviousvalue" id="processcpuusagepreviousvalue">#</a></span><a aria-hidden="true" class="legacy" id="process_process_cpuusage_previousvalue"></a></h3> 1435<div class="api_metadata"> 1436<span>Added in: v6.1.0</span> 1437</div> 1438<ul> 1439<li><code>previousValue</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> A previous return value from calling 1440<code>process.cpuUsage()</code></li> 1441<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1442<ul> 1443<li><code>user</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 1444<li><code>system</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 1445</ul> 1446</li> 1447</ul> 1448<p>The <code>process.cpuUsage()</code> method returns the user and system CPU time usage of 1449the current process, in an object with properties <code>user</code> and <code>system</code>, whose 1450values are microsecond values (millionth of a second). These values measure time 1451spent in user and system code respectively, and may end up being greater than 1452actual elapsed time if multiple CPU cores are performing work for this process.</p> 1453<p>The result of a previous call to <code>process.cpuUsage()</code> can be passed as the 1454argument to the function, to get a diff reading.</p> 1455 1456<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { cpuUsage } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1457 1458<span class="hljs-keyword">const</span> startUsage = <span class="hljs-title function_">cpuUsage</span>(); 1459<span class="hljs-comment">// { user: 38579, system: 6986 }</span> 1460 1461<span class="hljs-comment">// spin the CPU for 500 milliseconds</span> 1462<span class="hljs-keyword">const</span> now = <span class="hljs-title class_">Date</span>.<span class="hljs-title function_">now</span>(); 1463<span class="hljs-keyword">while</span> (<span class="hljs-title class_">Date</span>.<span class="hljs-title function_">now</span>() - now < <span class="hljs-number">500</span>); 1464 1465<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">cpuUsage</span>(startUsage)); 1466<span class="hljs-comment">// { user: 514883, system: 11226 }</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { cpuUsage } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1467 1468<span class="hljs-keyword">const</span> startUsage = <span class="hljs-title function_">cpuUsage</span>(); 1469<span class="hljs-comment">// { user: 38579, system: 6986 }</span> 1470 1471<span class="hljs-comment">// spin the CPU for 500 milliseconds</span> 1472<span class="hljs-keyword">const</span> now = <span class="hljs-title class_">Date</span>.<span class="hljs-title function_">now</span>(); 1473<span class="hljs-keyword">while</span> (<span class="hljs-title class_">Date</span>.<span class="hljs-title function_">now</span>() - now < <span class="hljs-number">500</span>); 1474 1475<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">cpuUsage</span>(startUsage)); 1476<span class="hljs-comment">// { user: 514883, system: 11226 }</span></code><button class="copy-button">copy</button></pre> 1477</section><section><h3><code>process.cwd()</code><span><a class="mark" href="#processcwd" id="processcwd">#</a></span><a aria-hidden="true" class="legacy" id="process_process_cwd"></a></h3> 1478<div class="api_metadata"> 1479<span>Added in: v0.1.8</span> 1480</div> 1481<ul> 1482<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1483</ul> 1484<p>The <code>process.cwd()</code> method returns the current working directory of the Node.js 1485process.</p> 1486 1487<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { cwd } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1488 1489<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current directory: <span class="hljs-subst">${cwd()}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { cwd } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1490 1491<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current directory: <span class="hljs-subst">${cwd()}</span>`</span>);</code><button class="copy-button">copy</button></pre> 1492</section><section><h3><code>process.debugPort</code><span><a class="mark" href="#processdebugport" id="processdebugport">#</a></span><a aria-hidden="true" class="legacy" id="process_process_debugport"></a></h3> 1493<div class="api_metadata"> 1494<span>Added in: v0.7.2</span> 1495</div> 1496<ul> 1497<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1498</ul> 1499<p>The port used by the Node.js debugger when enabled.</p> 1500 1501<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1502 1503process.<span class="hljs-property">debugPort</span> = <span class="hljs-number">5858</span>;</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1504 1505process.<span class="hljs-property">debugPort</span> = <span class="hljs-number">5858</span>;</code><button class="copy-button">copy</button></pre> 1506</section><section><h3><code>process.disconnect()</code><span><a class="mark" href="#processdisconnect" id="processdisconnect">#</a></span><a aria-hidden="true" class="legacy" id="process_process_disconnect"></a></h3> 1507<div class="api_metadata"> 1508<span>Added in: v0.7.2</span> 1509</div> 1510<p>If the Node.js process is spawned with an IPC channel (see the <a href="child_process.html">Child Process</a> 1511and <a href="cluster.html">Cluster</a> documentation), the <code>process.disconnect()</code> method will close the 1512IPC channel to the parent process, allowing the child process to exit gracefully 1513once there are no other connections keeping it alive.</p> 1514<p>The effect of calling <code>process.disconnect()</code> is the same as calling 1515<a href="child_process.html#subprocessdisconnect"><code>ChildProcess.disconnect()</code></a> from the parent process.</p> 1516<p>If the Node.js process was not spawned with an IPC channel, 1517<code>process.disconnect()</code> will be <code>undefined</code>.</p> 1518</section><section><h3><code>process.dlopen(module, filename[, flags])</code><span><a class="mark" href="#processdlopenmodule-filename-flags" id="processdlopenmodule-filename-flags">#</a></span><a aria-hidden="true" class="legacy" id="process_process_dlopen_module_filename_flags"></a></h3> 1519<div class="api_metadata"> 1520<details class="changelog"><summary>History</summary> 1521<table> 1522<tbody><tr><th>Version</th><th>Changes</th></tr> 1523<tr><td>v9.0.0</td> 1524<td><p>Added support for the <code>flags</code> argument.</p></td></tr> 1525<tr><td>v0.1.16</td> 1526<td><p><span>Added in: v0.1.16</span></p></td></tr> 1527</tbody></table> 1528</details> 1529</div> 1530<ul> 1531<li><code>module</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 1532<li><code>filename</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1533<li><code>flags</code> <a href="os.html#dlopen-constants" class="type"><os.constants.dlopen></a> <strong>Default:</strong> <code>os.constants.dlopen.RTLD_LAZY</code></li> 1534</ul> 1535<p>The <code>process.dlopen()</code> method allows dynamically loading shared objects. It is 1536primarily used by <code>require()</code> to load C++ Addons, and should not be used 1537directly, except in special cases. In other words, <a href="globals.html#require"><code>require()</code></a> should be 1538preferred over <code>process.dlopen()</code> unless there are specific reasons such as 1539custom dlopen flags or loading from ES modules.</p> 1540<p>The <code>flags</code> argument is an integer that allows to specify dlopen 1541behavior. See the <a href="os.html#dlopen-constants"><code>os.constants.dlopen</code></a> documentation for details.</p> 1542<p>An important requirement when calling <code>process.dlopen()</code> is that the <code>module</code> 1543instance must be passed. Functions exported by the C++ Addon are then 1544accessible via <code>module.exports</code>.</p> 1545<p>The example below shows how to load a C++ Addon, named <code>local.node</code>, 1546that exports a <code>foo</code> function. All the symbols are loaded before 1547the call returns, by passing the <code>RTLD_NOW</code> constant. In this example 1548the constant is assumed to be available.</p> 1549 1550<pre class="with-43-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { dlopen } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1551<span class="hljs-keyword">import</span> { constants } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:os'</span>; 1552<span class="hljs-keyword">import</span> { fileURLToPath } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:url'</span>; 1553 1554<span class="hljs-keyword">const</span> <span class="hljs-variable language_">module</span> = { <span class="hljs-attr">exports</span>: {} }; 1555<span class="hljs-title function_">dlopen</span>(<span class="hljs-variable language_">module</span>, <span class="hljs-title function_">fileURLToPath</span>(<span class="hljs-keyword">new</span> <span class="hljs-title function_">URL</span>(<span class="hljs-string">'local.node'</span>, <span class="hljs-keyword">import</span>.<span class="hljs-property">meta</span>.<span class="hljs-property">url</span>)), 1556 constants.<span class="hljs-property">dlopen</span>.<span class="hljs-property">RTLD_NOW</span>); 1557<span class="hljs-variable language_">module</span>.<span class="hljs-property">exports</span>.<span class="hljs-title function_">foo</span>();</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { dlopen } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1558<span class="hljs-keyword">const</span> { constants } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:os'</span>); 1559<span class="hljs-keyword">const</span> { join } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:path'</span>); 1560 1561<span class="hljs-keyword">const</span> <span class="hljs-variable language_">module</span> = { <span class="hljs-attr">exports</span>: {} }; 1562<span class="hljs-title function_">dlopen</span>(<span class="hljs-variable language_">module</span>, <span class="hljs-title function_">join</span>(__dirname, <span class="hljs-string">'local.node'</span>), constants.<span class="hljs-property">dlopen</span>.<span class="hljs-property">RTLD_NOW</span>); 1563<span class="hljs-variable language_">module</span>.<span class="hljs-property">exports</span>.<span class="hljs-title function_">foo</span>();</code><button class="copy-button">copy</button></pre> 1564</section><section><h3><code>process.emitWarning(warning[, options])</code><span><a class="mark" href="#processemitwarningwarning-options" id="processemitwarningwarning-options">#</a></span><a aria-hidden="true" class="legacy" id="process_process_emitwarning_warning_options"></a></h3> 1565<div class="api_metadata"> 1566<span>Added in: v8.0.0</span> 1567</div> 1568<ul> 1569<li><code>warning</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/Error" class="type"><Error></a> The warning to emit.</li> 1570<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1571<ul> 1572<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> When <code>warning</code> is a <code>String</code>, <code>type</code> is the name to use 1573for the <em>type</em> of warning being emitted. <strong>Default:</strong> <code>'Warning'</code>.</li> 1574<li><code>code</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A unique identifier for the warning instance being emitted.</li> 1575<li><code>ctor</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> When <code>warning</code> is a <code>String</code>, <code>ctor</code> is an optional 1576function used to limit the generated stack trace. <strong>Default:</strong> 1577<code>process.emitWarning</code>.</li> 1578<li><code>detail</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Additional text to include with the error.</li> 1579</ul> 1580</li> 1581</ul> 1582<p>The <code>process.emitWarning()</code> method can be used to emit custom or application 1583specific process warnings. These can be listened for by adding a handler to the 1584<a href="#event-warning"><code>'warning'</code></a> event.</p> 1585 1586<pre class="with-48-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { emitWarning } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1587 1588<span class="hljs-comment">// Emit a warning with a code and additional detail.</span> 1589<span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Something happened!'</span>, { 1590 <span class="hljs-attr">code</span>: <span class="hljs-string">'MY_WARNING'</span>, 1591 <span class="hljs-attr">detail</span>: <span class="hljs-string">'This is some additional information'</span>, 1592}); 1593<span class="hljs-comment">// Emits:</span> 1594<span class="hljs-comment">// (node:56338) [MY_WARNING] Warning: Something happened!</span> 1595<span class="hljs-comment">// This is some additional information</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { emitWarning } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1596 1597<span class="hljs-comment">// Emit a warning with a code and additional detail.</span> 1598<span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Something happened!'</span>, { 1599 <span class="hljs-attr">code</span>: <span class="hljs-string">'MY_WARNING'</span>, 1600 <span class="hljs-attr">detail</span>: <span class="hljs-string">'This is some additional information'</span>, 1601}); 1602<span class="hljs-comment">// Emits:</span> 1603<span class="hljs-comment">// (node:56338) [MY_WARNING] Warning: Something happened!</span> 1604<span class="hljs-comment">// This is some additional information</span></code><button class="copy-button">copy</button></pre> 1605<p>In this example, an <code>Error</code> object is generated internally by 1606<code>process.emitWarning()</code> and passed through to the 1607<a href="#event-warning"><code>'warning'</code></a> handler.</p> 1608 1609<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1610 1611process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'warning'</span>, <span class="hljs-function">(<span class="hljs-params">warning</span>) =></span> { 1612 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">name</span>); <span class="hljs-comment">// 'Warning'</span> 1613 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">message</span>); <span class="hljs-comment">// 'Something happened!'</span> 1614 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">code</span>); <span class="hljs-comment">// 'MY_WARNING'</span> 1615 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">stack</span>); <span class="hljs-comment">// Stack trace</span> 1616 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">detail</span>); <span class="hljs-comment">// 'This is some additional information'</span> 1617});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1618 1619process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'warning'</span>, <span class="hljs-function">(<span class="hljs-params">warning</span>) =></span> { 1620 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">name</span>); <span class="hljs-comment">// 'Warning'</span> 1621 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">message</span>); <span class="hljs-comment">// 'Something happened!'</span> 1622 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">code</span>); <span class="hljs-comment">// 'MY_WARNING'</span> 1623 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">stack</span>); <span class="hljs-comment">// Stack trace</span> 1624 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">detail</span>); <span class="hljs-comment">// 'This is some additional information'</span> 1625});</code><button class="copy-button">copy</button></pre> 1626<p>If <code>warning</code> is passed as an <code>Error</code> object, the <code>options</code> argument is ignored.</p> 1627</section><section><h3><code>process.emitWarning(warning[, type[, code]][, ctor])</code><span><a class="mark" href="#processemitwarningwarning-type-code-ctor" id="processemitwarningwarning-type-code-ctor">#</a></span><a aria-hidden="true" class="legacy" id="process_process_emitwarning_warning_type_code_ctor"></a></h3> 1628<div class="api_metadata"> 1629<span>Added in: v6.0.0</span> 1630</div> 1631<ul> 1632<li><code>warning</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/Error" class="type"><Error></a> The warning to emit.</li> 1633<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> When <code>warning</code> is a <code>String</code>, <code>type</code> is the name to use 1634for the <em>type</em> of warning being emitted. <strong>Default:</strong> <code>'Warning'</code>.</li> 1635<li><code>code</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A unique identifier for the warning instance being emitted.</li> 1636<li><code>ctor</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> When <code>warning</code> is a <code>String</code>, <code>ctor</code> is an optional 1637function used to limit the generated stack trace. <strong>Default:</strong> 1638<code>process.emitWarning</code>.</li> 1639</ul> 1640<p>The <code>process.emitWarning()</code> method can be used to emit custom or application 1641specific process warnings. These can be listened for by adding a handler to the 1642<a href="#event-warning"><code>'warning'</code></a> event.</p> 1643 1644<pre class="with-48-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { emitWarning } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1645 1646<span class="hljs-comment">// Emit a warning using a string.</span> 1647<span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Something happened!'</span>); 1648<span class="hljs-comment">// Emits: (node: 56338) Warning: Something happened!</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { emitWarning } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1649 1650<span class="hljs-comment">// Emit a warning using a string.</span> 1651<span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Something happened!'</span>); 1652<span class="hljs-comment">// Emits: (node: 56338) Warning: Something happened!</span></code><button class="copy-button">copy</button></pre> 1653 1654<pre class="with-48-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { emitWarning } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1655 1656<span class="hljs-comment">// Emit a warning using a string and a type.</span> 1657<span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Something Happened!'</span>, <span class="hljs-string">'CustomWarning'</span>); 1658<span class="hljs-comment">// Emits: (node:56338) CustomWarning: Something Happened!</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { emitWarning } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1659 1660<span class="hljs-comment">// Emit a warning using a string and a type.</span> 1661<span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Something Happened!'</span>, <span class="hljs-string">'CustomWarning'</span>); 1662<span class="hljs-comment">// Emits: (node:56338) CustomWarning: Something Happened!</span></code><button class="copy-button">copy</button></pre> 1663 1664<pre class="with-48-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { emitWarning } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1665 1666<span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Something happened!'</span>, <span class="hljs-string">'CustomWarning'</span>, <span class="hljs-string">'WARN001'</span>); 1667<span class="hljs-comment">// Emits: (node:56338) [WARN001] CustomWarning: Something happened!</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { emitWarning } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1668 1669process.<span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Something happened!'</span>, <span class="hljs-string">'CustomWarning'</span>, <span class="hljs-string">'WARN001'</span>); 1670<span class="hljs-comment">// Emits: (node:56338) [WARN001] CustomWarning: Something happened!</span></code><button class="copy-button">copy</button></pre> 1671<p>In each of the previous examples, an <code>Error</code> object is generated internally by 1672<code>process.emitWarning()</code> and passed through to the <a href="#event-warning"><code>'warning'</code></a> 1673handler.</p> 1674 1675<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1676 1677process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'warning'</span>, <span class="hljs-function">(<span class="hljs-params">warning</span>) =></span> { 1678 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">name</span>); 1679 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">message</span>); 1680 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">code</span>); 1681 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">stack</span>); 1682});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1683 1684process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'warning'</span>, <span class="hljs-function">(<span class="hljs-params">warning</span>) =></span> { 1685 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">name</span>); 1686 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">message</span>); 1687 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">code</span>); 1688 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">stack</span>); 1689});</code><button class="copy-button">copy</button></pre> 1690<p>If <code>warning</code> is passed as an <code>Error</code> object, it will be passed through to the 1691<code>'warning'</code> event handler unmodified (and the optional <code>type</code>, 1692<code>code</code> and <code>ctor</code> arguments will be ignored):</p> 1693 1694<pre class="with-48-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { emitWarning } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1695 1696<span class="hljs-comment">// Emit a warning using an Error object.</span> 1697<span class="hljs-keyword">const</span> myWarning = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Something happened!'</span>); 1698<span class="hljs-comment">// Use the Error name property to specify the type name</span> 1699myWarning.<span class="hljs-property">name</span> = <span class="hljs-string">'CustomWarning'</span>; 1700myWarning.<span class="hljs-property">code</span> = <span class="hljs-string">'WARN001'</span>; 1701 1702<span class="hljs-title function_">emitWarning</span>(myWarning); 1703<span class="hljs-comment">// Emits: (node:56338) [WARN001] CustomWarning: Something happened!</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { emitWarning } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1704 1705<span class="hljs-comment">// Emit a warning using an Error object.</span> 1706<span class="hljs-keyword">const</span> myWarning = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Something happened!'</span>); 1707<span class="hljs-comment">// Use the Error name property to specify the type name</span> 1708myWarning.<span class="hljs-property">name</span> = <span class="hljs-string">'CustomWarning'</span>; 1709myWarning.<span class="hljs-property">code</span> = <span class="hljs-string">'WARN001'</span>; 1710 1711<span class="hljs-title function_">emitWarning</span>(myWarning); 1712<span class="hljs-comment">// Emits: (node:56338) [WARN001] CustomWarning: Something happened!</span></code><button class="copy-button">copy</button></pre> 1713<p>A <code>TypeError</code> is thrown if <code>warning</code> is anything other than a string or <code>Error</code> 1714object.</p> 1715<p>While process warnings use <code>Error</code> objects, the process warning 1716mechanism is <strong>not</strong> a replacement for normal error handling mechanisms.</p> 1717<p>The following additional handling is implemented if the warning <code>type</code> is 1718<code>'DeprecationWarning'</code>:</p> 1719<ul> 1720<li>If the <code>--throw-deprecation</code> command-line flag is used, the deprecation 1721warning is thrown as an exception rather than being emitted as an event.</li> 1722<li>If the <code>--no-deprecation</code> command-line flag is used, the deprecation 1723warning is suppressed.</li> 1724<li>If the <code>--trace-deprecation</code> command-line flag is used, the deprecation 1725warning is printed to <code>stderr</code> along with the full stack trace.</li> 1726</ul> 1727<h4>Avoiding duplicate warnings<span><a class="mark" href="#avoiding-duplicate-warnings" id="avoiding-duplicate-warnings">#</a></span><a aria-hidden="true" class="legacy" id="process_avoiding_duplicate_warnings"></a></h4> 1728<p>As a best practice, warnings should be emitted only once per process. To do 1729so, place the <code>emitWarning()</code> behind a boolean.</p> 1730 1731<pre class="with-48-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { emitWarning } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1732 1733<span class="hljs-keyword">function</span> <span class="hljs-title function_">emitMyWarning</span>(<span class="hljs-params"></span>) { 1734 <span class="hljs-keyword">if</span> (!emitMyWarning.<span class="hljs-property">warned</span>) { 1735 emitMyWarning.<span class="hljs-property">warned</span> = <span class="hljs-literal">true</span>; 1736 <span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Only warn once!'</span>); 1737 } 1738} 1739<span class="hljs-title function_">emitMyWarning</span>(); 1740<span class="hljs-comment">// Emits: (node: 56339) Warning: Only warn once!</span> 1741<span class="hljs-title function_">emitMyWarning</span>(); 1742<span class="hljs-comment">// Emits nothing</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { emitWarning } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1743 1744<span class="hljs-keyword">function</span> <span class="hljs-title function_">emitMyWarning</span>(<span class="hljs-params"></span>) { 1745 <span class="hljs-keyword">if</span> (!emitMyWarning.<span class="hljs-property">warned</span>) { 1746 emitMyWarning.<span class="hljs-property">warned</span> = <span class="hljs-literal">true</span>; 1747 <span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Only warn once!'</span>); 1748 } 1749} 1750<span class="hljs-title function_">emitMyWarning</span>(); 1751<span class="hljs-comment">// Emits: (node: 56339) Warning: Only warn once!</span> 1752<span class="hljs-title function_">emitMyWarning</span>(); 1753<span class="hljs-comment">// Emits nothing</span></code><button class="copy-button">copy</button></pre> 1754</section><section><h3><code>process.env</code><span><a class="mark" href="#processenv" id="processenv">#</a></span><a aria-hidden="true" class="legacy" id="process_process_env"></a></h3> 1755<div class="api_metadata"> 1756<details class="changelog"><summary>History</summary> 1757<table> 1758<tbody><tr><th>Version</th><th>Changes</th></tr> 1759<tr><td>v11.14.0</td> 1760<td><p>Worker threads will now use a copy of the parent thread's <code>process.env</code> by default, configurable through the <code>env</code> option of the <code>Worker</code> constructor.</p></td></tr> 1761<tr><td>v10.0.0</td> 1762<td><p>Implicit conversion of variable value to string is deprecated.</p></td></tr> 1763<tr><td>v0.1.27</td> 1764<td><p><span>Added in: v0.1.27</span></p></td></tr> 1765</tbody></table> 1766</details> 1767</div> 1768<ul> 1769<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 1770</ul> 1771<p>The <code>process.env</code> property returns an object containing the user environment. 1772See <a href="http://man7.org/linux/man-pages/man7/environ.7.html"><code>environ(7)</code></a>.</p> 1773<p>An example of this object looks like:</p> 1774<!-- eslint-skip --> 1775<pre><code class="language-js">{ 1776 <span class="hljs-attr">TERM</span>: <span class="hljs-string">'xterm-256color'</span>, 1777 <span class="hljs-attr">SHELL</span>: <span class="hljs-string">'/usr/local/bin/bash'</span>, 1778 <span class="hljs-attr">USER</span>: <span class="hljs-string">'maciej'</span>, 1779 <span class="hljs-attr">PATH</span>: <span class="hljs-string">'~/.bin/:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin'</span>, 1780 <span class="hljs-attr">PWD</span>: <span class="hljs-string">'/Users/maciej'</span>, 1781 <span class="hljs-attr">EDITOR</span>: <span class="hljs-string">'vim'</span>, 1782 <span class="hljs-attr">SHLVL</span>: <span class="hljs-string">'1'</span>, 1783 <span class="hljs-attr">HOME</span>: <span class="hljs-string">'/Users/maciej'</span>, 1784 <span class="hljs-attr">LOGNAME</span>: <span class="hljs-string">'maciej'</span>, 1785 <span class="hljs-attr">_</span>: <span class="hljs-string">'/usr/local/bin/node'</span> 1786}</code> <button class="copy-button">copy</button></pre> 1787<p>It is possible to modify this object, but such modifications will not be 1788reflected outside the Node.js process, or (unless explicitly requested) 1789to other <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads. 1790In other words, the following example would not work:</p> 1791<pre><code class="language-console"><span class="hljs-meta prompt_">$ </span><span class="language-bash">node -e <span class="hljs-string">'process.env.foo = "bar"'</span> && <span class="hljs-built_in">echo</span> <span class="hljs-variable">$foo</span></span></code> <button class="copy-button">copy</button></pre> 1792<p>While the following will:</p> 1793 1794<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { env } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1795 1796env.<span class="hljs-property">foo</span> = <span class="hljs-string">'bar'</span>; 1797<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(env.<span class="hljs-property">foo</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { env } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1798 1799env.<span class="hljs-property">foo</span> = <span class="hljs-string">'bar'</span>; 1800<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(env.<span class="hljs-property">foo</span>);</code><button class="copy-button">copy</button></pre> 1801<p>Assigning a property on <code>process.env</code> will implicitly convert the value 1802to a string. <strong>This behavior is deprecated.</strong> Future versions of Node.js may 1803throw an error when the value is not a string, number, or boolean.</p> 1804 1805<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { env } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1806 1807env.<span class="hljs-property">test</span> = <span class="hljs-literal">null</span>; 1808<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(env.<span class="hljs-property">test</span>); 1809<span class="hljs-comment">// => 'null'</span> 1810env.<span class="hljs-property">test</span> = <span class="hljs-literal">undefined</span>; 1811<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(env.<span class="hljs-property">test</span>); 1812<span class="hljs-comment">// => 'undefined'</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { env } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1813 1814env.<span class="hljs-property">test</span> = <span class="hljs-literal">null</span>; 1815<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(env.<span class="hljs-property">test</span>); 1816<span class="hljs-comment">// => 'null'</span> 1817env.<span class="hljs-property">test</span> = <span class="hljs-literal">undefined</span>; 1818<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(env.<span class="hljs-property">test</span>); 1819<span class="hljs-comment">// => 'undefined'</span></code><button class="copy-button">copy</button></pre> 1820<p>Use <code>delete</code> to delete a property from <code>process.env</code>.</p> 1821 1822<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { env } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1823 1824env.<span class="hljs-property">TEST</span> = <span class="hljs-number">1</span>; 1825<span class="hljs-keyword">delete</span> env.<span class="hljs-property">TEST</span>; 1826<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(env.<span class="hljs-property">TEST</span>); 1827<span class="hljs-comment">// => undefined</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { env } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1828 1829env.<span class="hljs-property">TEST</span> = <span class="hljs-number">1</span>; 1830<span class="hljs-keyword">delete</span> env.<span class="hljs-property">TEST</span>; 1831<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(env.<span class="hljs-property">TEST</span>); 1832<span class="hljs-comment">// => undefined</span></code><button class="copy-button">copy</button></pre> 1833<p>On Windows operating systems, environment variables are case-insensitive.</p> 1834 1835<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { env } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1836 1837env.<span class="hljs-property">TEST</span> = <span class="hljs-number">1</span>; 1838<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(env.<span class="hljs-property">test</span>); 1839<span class="hljs-comment">// => 1</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { env } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1840 1841env.<span class="hljs-property">TEST</span> = <span class="hljs-number">1</span>; 1842<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(env.<span class="hljs-property">test</span>); 1843<span class="hljs-comment">// => 1</span></code><button class="copy-button">copy</button></pre> 1844<p>Unless explicitly specified when creating a <a href="worker_threads.html#class-worker"><code>Worker</code></a> instance, 1845each <a href="worker_threads.html#class-worker"><code>Worker</code></a> thread has its own copy of <code>process.env</code>, based on its 1846parent thread's <code>process.env</code>, or whatever was specified as the <code>env</code> option 1847to the <a href="worker_threads.html#class-worker"><code>Worker</code></a> constructor. Changes to <code>process.env</code> will not be visible 1848across <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads, and only the main thread can make changes that 1849are visible to the operating system or to native add-ons. On Windows, a copy of 1850<code>process.env</code> on a <a href="worker_threads.html#class-worker"><code>Worker</code></a> instance operates in a case-sensitive manner 1851unlike the main thread.</p> 1852</section><section><h3><code>process.execArgv</code><span><a class="mark" href="#processexecargv" id="processexecargv">#</a></span><a aria-hidden="true" class="legacy" id="process_process_execargv"></a></h3> 1853<div class="api_metadata"> 1854<span>Added in: v0.7.7</span> 1855</div> 1856<ul> 1857<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 1858</ul> 1859<p>The <code>process.execArgv</code> property returns the set of Node.js-specific command-line 1860options passed when the Node.js process was launched. These options do not 1861appear in the array returned by the <a href="#processargv"><code>process.argv</code></a> property, and do not 1862include the Node.js executable, the name of the script, or any options following 1863the script name. These options are useful in order to spawn child processes with 1864the same execution environment as the parent.</p> 1865<pre><code class="language-console"><span class="hljs-meta prompt_">$ </span><span class="language-bash">node --harmony script.js --version</span></code> <button class="copy-button">copy</button></pre> 1866<p>Results in <code>process.execArgv</code>:</p> 1867<!-- eslint-disable semi --> 1868<pre><code class="language-js">[<span class="hljs-string">'--harmony'</span>]</code> <button class="copy-button">copy</button></pre> 1869<p>And <code>process.argv</code>:</p> 1870<!-- eslint-disable semi --> 1871<pre><code class="language-js">[<span class="hljs-string">'/usr/local/bin/node'</span>, <span class="hljs-string">'script.js'</span>, <span class="hljs-string">'--version'</span>]</code> <button class="copy-button">copy</button></pre> 1872<p>Refer to <a href="worker_threads.html#new-workerfilename-options"><code>Worker</code> constructor</a> for the detailed behavior of worker 1873threads with this property.</p> 1874</section><section><h3><code>process.execPath</code><span><a class="mark" href="#processexecpath" id="processexecpath">#</a></span><a aria-hidden="true" class="legacy" id="process_process_execpath"></a></h3> 1875<div class="api_metadata"> 1876<span>Added in: v0.1.100</span> 1877</div> 1878<ul> 1879<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1880</ul> 1881<p>The <code>process.execPath</code> property returns the absolute pathname of the executable 1882that started the Node.js process. Symbolic links, if any, are resolved.</p> 1883<!-- eslint-disable semi --> 1884<pre><code class="language-js"><span class="hljs-string">'/usr/local/bin/node'</span></code> <button class="copy-button">copy</button></pre> 1885</section><section><h3><code>process.exit([code])</code><span><a class="mark" href="#processexitcode" id="processexitcode">#</a></span><a aria-hidden="true" class="legacy" id="process_process_exit_code"></a></h3> 1886<div class="api_metadata"> 1887<span>Added in: v0.1.13</span> 1888</div> 1889<ul> 1890<li><code>code</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The exit code. <strong>Default:</strong> <code>0</code>.</li> 1891</ul> 1892<p>The <code>process.exit()</code> method instructs Node.js to terminate the process 1893synchronously with an exit status of <code>code</code>. If <code>code</code> is omitted, exit uses 1894either the 'success' code <code>0</code> or the value of <code>process.exitCode</code> if it has been 1895set. Node.js will not terminate until all the <a href="#event-exit"><code>'exit'</code></a> event listeners are 1896called.</p> 1897<p>To exit with a 'failure' code:</p> 1898 1899<pre class="with-41-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { exit } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1900 1901<span class="hljs-title function_">exit</span>(<span class="hljs-number">1</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { exit } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1902 1903<span class="hljs-title function_">exit</span>(<span class="hljs-number">1</span>);</code><button class="copy-button">copy</button></pre> 1904<p>The shell that executed Node.js should see the exit code as <code>1</code>.</p> 1905<p>Calling <code>process.exit()</code> will force the process to exit as quickly as possible 1906even if there are still asynchronous operations pending that have not yet 1907completed fully, including I/O operations to <code>process.stdout</code> and 1908<code>process.stderr</code>.</p> 1909<p>In most situations, it is not actually necessary to call <code>process.exit()</code> 1910explicitly. The Node.js process will exit on its own <em>if there is no additional 1911work pending</em> in the event loop. The <code>process.exitCode</code> property can be set to 1912tell the process which exit code to use when the process exits gracefully.</p> 1913<p>For instance, the following example illustrates a <em>misuse</em> of the 1914<code>process.exit()</code> method that could lead to data printed to stdout being 1915truncated and lost:</p> 1916 1917<pre class="with-41-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { exit } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1918 1919<span class="hljs-comment">// This is an example of what *not* to do:</span> 1920<span class="hljs-keyword">if</span> (<span class="hljs-title function_">someConditionNotMet</span>()) { 1921 <span class="hljs-title function_">printUsageToStdout</span>(); 1922 <span class="hljs-title function_">exit</span>(<span class="hljs-number">1</span>); 1923}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { exit } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1924 1925<span class="hljs-comment">// This is an example of what *not* to do:</span> 1926<span class="hljs-keyword">if</span> (<span class="hljs-title function_">someConditionNotMet</span>()) { 1927 <span class="hljs-title function_">printUsageToStdout</span>(); 1928 <span class="hljs-title function_">exit</span>(<span class="hljs-number">1</span>); 1929}</code><button class="copy-button">copy</button></pre> 1930<p>The reason this is problematic is because writes to <code>process.stdout</code> in Node.js 1931are sometimes <em>asynchronous</em> and may occur over multiple ticks of the Node.js 1932event loop. Calling <code>process.exit()</code>, however, forces the process to exit 1933<em>before</em> those additional writes to <code>stdout</code> can be performed.</p> 1934<p>Rather than calling <code>process.exit()</code> directly, the code <em>should</em> set the 1935<code>process.exitCode</code> and allow the process to exit naturally by avoiding 1936scheduling any additional work for the event loop:</p> 1937 1938<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1939 1940<span class="hljs-comment">// How to properly set the exit code while letting</span> 1941<span class="hljs-comment">// the process exit gracefully.</span> 1942<span class="hljs-keyword">if</span> (<span class="hljs-title function_">someConditionNotMet</span>()) { 1943 <span class="hljs-title function_">printUsageToStdout</span>(); 1944 process.<span class="hljs-property">exitCode</span> = <span class="hljs-number">1</span>; 1945}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1946 1947<span class="hljs-comment">// How to properly set the exit code while letting</span> 1948<span class="hljs-comment">// the process exit gracefully.</span> 1949<span class="hljs-keyword">if</span> (<span class="hljs-title function_">someConditionNotMet</span>()) { 1950 <span class="hljs-title function_">printUsageToStdout</span>(); 1951 process.<span class="hljs-property">exitCode</span> = <span class="hljs-number">1</span>; 1952}</code><button class="copy-button">copy</button></pre> 1953<p>If it is necessary to terminate the Node.js process due to an error condition, 1954throwing an <em>uncaught</em> error and allowing the process to terminate accordingly 1955is safer than calling <code>process.exit()</code>.</p> 1956<p>In <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads, this function stops the current thread rather 1957than the current process.</p> 1958</section><section><h3><code>process.exitCode</code><span><a class="mark" href="#processexitcode_1" id="processexitcode_1">#</a></span><a aria-hidden="true" class="legacy" id="process_process_exitcode"></a></h3> 1959<div class="api_metadata"> 1960<span>Added in: v0.11.8</span> 1961</div> 1962<ul> 1963<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 1964</ul> 1965<p>A number which will be the process exit code, when the process either 1966exits gracefully, or is exited via <a href="#processexitcode"><code>process.exit()</code></a> without specifying 1967a code.</p> 1968<p>Specifying a code to <a href="#processexitcode"><code>process.exit(code)</code></a> will override any 1969previous setting of <code>process.exitCode</code>.</p> 1970</section><section><h3><code>process.getActiveResourcesInfo()</code><span><a class="mark" href="#processgetactiveresourcesinfo" id="processgetactiveresourcesinfo">#</a></span><a aria-hidden="true" class="legacy" id="process_process_getactiveresourcesinfo"></a></h3> 1971<div class="api_metadata"> 1972<span>Added in: v17.3.0, v16.14.0</span> 1973</div> 1974<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 1975<ul> 1976<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 1977</ul> 1978<p>The <code>process.getActiveResourcesInfo()</code> method returns an array of strings 1979containing the types of the active resources that are currently keeping the 1980event loop alive.</p> 1981 1982<pre class="with-59-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { getActiveResourcesInfo } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 1983<span class="hljs-keyword">import</span> { <span class="hljs-built_in">setTimeout</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:timers'</span>; 1984 1985<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Before:'</span>, <span class="hljs-title function_">getActiveResourcesInfo</span>()); 1986<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> {}, <span class="hljs-number">1000</span>); 1987<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'After:'</span>, <span class="hljs-title function_">getActiveResourcesInfo</span>()); 1988<span class="hljs-comment">// Prints:</span> 1989<span class="hljs-comment">// Before: [ 'CloseReq', 'TTYWrap', 'TTYWrap', 'TTYWrap' ]</span> 1990<span class="hljs-comment">// After: [ 'CloseReq', 'TTYWrap', 'TTYWrap', 'TTYWrap', 'Timeout' ]</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { getActiveResourcesInfo } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1991<span class="hljs-keyword">const</span> { <span class="hljs-built_in">setTimeout</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:timers'</span>); 1992 1993<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Before:'</span>, <span class="hljs-title function_">getActiveResourcesInfo</span>()); 1994<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> {}, <span class="hljs-number">1000</span>); 1995<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'After:'</span>, <span class="hljs-title function_">getActiveResourcesInfo</span>()); 1996<span class="hljs-comment">// Prints:</span> 1997<span class="hljs-comment">// Before: [ 'TTYWrap', 'TTYWrap', 'TTYWrap' ]</span> 1998<span class="hljs-comment">// After: [ 'TTYWrap', 'TTYWrap', 'TTYWrap', 'Timeout' ]</span></code><button class="copy-button">copy</button></pre> 1999</section><section><h3><code>process.getegid()</code><span><a class="mark" href="#processgetegid" id="processgetegid">#</a></span><a aria-hidden="true" class="legacy" id="process_process_getegid"></a></h3> 2000<div class="api_metadata"> 2001<span>Added in: v2.0.0</span> 2002</div> 2003<p>The <code>process.getegid()</code> method returns the numerical effective group identity 2004of the Node.js process. (See <a href="http://man7.org/linux/man-pages/man2/getegid.2.html"><code>getegid(2)</code></a>.)</p> 2005 2006<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2007 2008<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getegid</span>) { 2009 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current gid: <span class="hljs-subst">${process.getegid()}</span>`</span>); 2010}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2011 2012<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getegid</span>) { 2013 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current gid: <span class="hljs-subst">${process.getegid()}</span>`</span>); 2014}</code><button class="copy-button">copy</button></pre> 2015<p>This function is only available on POSIX platforms (i.e. not Windows or 2016Android).</p> 2017</section><section><h3><code>process.geteuid()</code><span><a class="mark" href="#processgeteuid" id="processgeteuid">#</a></span><a aria-hidden="true" class="legacy" id="process_process_geteuid"></a></h3> 2018<div class="api_metadata"> 2019<span>Added in: v2.0.0</span> 2020</div> 2021<ul> 2022<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 2023</ul> 2024<p>The <code>process.geteuid()</code> method returns the numerical effective user identity of 2025the process. (See <a href="http://man7.org/linux/man-pages/man2/geteuid.2.html"><code>geteuid(2)</code></a>.)</p> 2026 2027<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2028 2029<span class="hljs-keyword">if</span> (process.<span class="hljs-property">geteuid</span>) { 2030 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current uid: <span class="hljs-subst">${process.geteuid()}</span>`</span>); 2031}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2032 2033<span class="hljs-keyword">if</span> (process.<span class="hljs-property">geteuid</span>) { 2034 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current uid: <span class="hljs-subst">${process.geteuid()}</span>`</span>); 2035}</code><button class="copy-button">copy</button></pre> 2036<p>This function is only available on POSIX platforms (i.e. not Windows or 2037Android).</p> 2038</section><section><h3><code>process.getgid()</code><span><a class="mark" href="#processgetgid" id="processgetgid">#</a></span><a aria-hidden="true" class="legacy" id="process_process_getgid"></a></h3> 2039<div class="api_metadata"> 2040<span>Added in: v0.1.31</span> 2041</div> 2042<ul> 2043<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 2044</ul> 2045<p>The <code>process.getgid()</code> method returns the numerical group identity of the 2046process. (See <a href="http://man7.org/linux/man-pages/man2/getgid.2.html"><code>getgid(2)</code></a>.)</p> 2047 2048<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2049 2050<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getgid</span>) { 2051 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current gid: <span class="hljs-subst">${process.getgid()}</span>`</span>); 2052}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2053 2054<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getgid</span>) { 2055 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current gid: <span class="hljs-subst">${process.getgid()}</span>`</span>); 2056}</code><button class="copy-button">copy</button></pre> 2057<p>This function is only available on POSIX platforms (i.e. not Windows or 2058Android).</p> 2059</section><section><h3><code>process.getgroups()</code><span><a class="mark" href="#processgetgroups" id="processgetgroups">#</a></span><a aria-hidden="true" class="legacy" id="process_process_getgroups"></a></h3> 2060<div class="api_metadata"> 2061<span>Added in: v0.9.4</span> 2062</div> 2063<ul> 2064<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer[]></a></li> 2065</ul> 2066<p>The <code>process.getgroups()</code> method returns an array with the supplementary group 2067IDs. POSIX leaves it unspecified if the effective group ID is included but 2068Node.js ensures it always is.</p> 2069 2070<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2071 2072<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getgroups</span>) { 2073 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(process.<span class="hljs-title function_">getgroups</span>()); <span class="hljs-comment">// [ 16, 21, 297 ]</span> 2074}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2075 2076<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getgroups</span>) { 2077 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(process.<span class="hljs-title function_">getgroups</span>()); <span class="hljs-comment">// [ 16, 21, 297 ]</span> 2078}</code><button class="copy-button">copy</button></pre> 2079<p>This function is only available on POSIX platforms (i.e. not Windows or 2080Android).</p> 2081</section><section><h3><code>process.getuid()</code><span><a class="mark" href="#processgetuid" id="processgetuid">#</a></span><a aria-hidden="true" class="legacy" id="process_process_getuid"></a></h3> 2082<div class="api_metadata"> 2083<span>Added in: v0.1.28</span> 2084</div> 2085<ul> 2086<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2087</ul> 2088<p>The <code>process.getuid()</code> method returns the numeric user identity of the process. 2089(See <a href="http://man7.org/linux/man-pages/man2/getuid.2.html"><code>getuid(2)</code></a>.)</p> 2090 2091<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2092 2093<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getuid</span>) { 2094 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current uid: <span class="hljs-subst">${process.getuid()}</span>`</span>); 2095}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2096 2097<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getuid</span>) { 2098 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current uid: <span class="hljs-subst">${process.getuid()}</span>`</span>); 2099}</code><button class="copy-button">copy</button></pre> 2100<p>This function is only available on POSIX platforms (i.e. not Windows or 2101Android).</p> 2102</section><section><h3><code>process.hasUncaughtExceptionCaptureCallback()</code><span><a class="mark" href="#processhasuncaughtexceptioncapturecallback" id="processhasuncaughtexceptioncapturecallback">#</a></span><a aria-hidden="true" class="legacy" id="process_process_hasuncaughtexceptioncapturecallback"></a></h3> 2103<div class="api_metadata"> 2104<span>Added in: v9.3.0</span> 2105</div> 2106<ul> 2107<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2108</ul> 2109<p>Indicates whether a callback has been set using 2110<a href="#processsetuncaughtexceptioncapturecallbackfn"><code>process.setUncaughtExceptionCaptureCallback()</code></a>.</p> 2111</section><section><h3><code>process.hrtime([time])</code><span><a class="mark" href="#processhrtimetime" id="processhrtimetime">#</a></span><a aria-hidden="true" class="legacy" id="process_process_hrtime_time"></a></h3> 2112<div class="api_metadata"> 2113<span>Added in: v0.7.6</span> 2114</div> 2115<p></p><div class="api_stability api_stability_3"><a href="documentation.html#stability-index">Stability: 3</a> - Legacy. Use <a href="#processhrtimebigint"><code>process.hrtime.bigint()</code></a> instead.</div><p></p> 2116<ul> 2117<li><code>time</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer[]></a> The result of a previous call to <code>process.hrtime()</code></li> 2118<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer[]></a></li> 2119</ul> 2120<p>This is the legacy version of <a href="#processhrtimebigint"><code>process.hrtime.bigint()</code></a> 2121before <code>bigint</code> was introduced in JavaScript.</p> 2122<p>The <code>process.hrtime()</code> method returns the current high-resolution real time 2123in a <code>[seconds, nanoseconds]</code> tuple <code>Array</code>, where <code>nanoseconds</code> is the 2124remaining part of the real time that can't be represented in second precision.</p> 2125<p><code>time</code> is an optional parameter that must be the result of a previous 2126<code>process.hrtime()</code> call to diff with the current time. If the parameter 2127passed in is not a tuple <code>Array</code>, a <code>TypeError</code> will be thrown. Passing in a 2128user-defined array instead of the result of a previous call to 2129<code>process.hrtime()</code> will lead to undefined behavior.</p> 2130<p>These times are relative to an arbitrary time in the 2131past, and not related to the time of day and therefore not subject to clock 2132drift. The primary use is for measuring performance between intervals:</p> 2133 2134<pre class="with-43-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { hrtime } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2135 2136<span class="hljs-keyword">const</span> <span class="hljs-variable constant_">NS_PER_SEC</span> = <span class="hljs-number">1e9</span>; 2137<span class="hljs-keyword">const</span> time = <span class="hljs-title function_">hrtime</span>(); 2138<span class="hljs-comment">// [ 1800216, 25 ]</span> 2139 2140<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 2141 <span class="hljs-keyword">const</span> diff = <span class="hljs-title function_">hrtime</span>(time); 2142 <span class="hljs-comment">// [ 1, 552 ]</span> 2143 2144 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Benchmark took <span class="hljs-subst">${diff[<span class="hljs-number">0</span>] * NS_PER_SEC + diff[<span class="hljs-number">1</span>]}</span> nanoseconds`</span>); 2145 <span class="hljs-comment">// Benchmark took 1000000552 nanoseconds</span> 2146}, <span class="hljs-number">1000</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { hrtime } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2147 2148<span class="hljs-keyword">const</span> <span class="hljs-variable constant_">NS_PER_SEC</span> = <span class="hljs-number">1e9</span>; 2149<span class="hljs-keyword">const</span> time = <span class="hljs-title function_">hrtime</span>(); 2150<span class="hljs-comment">// [ 1800216, 25 ]</span> 2151 2152<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 2153 <span class="hljs-keyword">const</span> diff = <span class="hljs-title function_">hrtime</span>(time); 2154 <span class="hljs-comment">// [ 1, 552 ]</span> 2155 2156 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Benchmark took <span class="hljs-subst">${diff[<span class="hljs-number">0</span>] * NS_PER_SEC + diff[<span class="hljs-number">1</span>]}</span> nanoseconds`</span>); 2157 <span class="hljs-comment">// Benchmark took 1000000552 nanoseconds</span> 2158}, <span class="hljs-number">1000</span>);</code><button class="copy-button">copy</button></pre> 2159</section><section><h3><code>process.hrtime.bigint()</code><span><a class="mark" href="#processhrtimebigint" id="processhrtimebigint">#</a></span><a aria-hidden="true" class="legacy" id="process_process_hrtime_bigint"></a></h3> 2160<div class="api_metadata"> 2161<span>Added in: v10.7.0</span> 2162</div> 2163<ul> 2164<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt" class="type"><bigint></a></li> 2165</ul> 2166<p>The <code>bigint</code> version of the <a href="#processhrtimetime"><code>process.hrtime()</code></a> method returning the 2167current high-resolution real time in nanoseconds as a <code>bigint</code>.</p> 2168<p>Unlike <a href="#processhrtimetime"><code>process.hrtime()</code></a>, it does not support an additional <code>time</code> 2169argument since the difference can just be computed directly 2170by subtraction of the two <code>bigint</code>s.</p> 2171 2172<pre class="with-43-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { hrtime } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2173 2174<span class="hljs-keyword">const</span> start = hrtime.<span class="hljs-title function_">bigint</span>(); 2175<span class="hljs-comment">// 191051479007711n</span> 2176 2177<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 2178 <span class="hljs-keyword">const</span> end = hrtime.<span class="hljs-title function_">bigint</span>(); 2179 <span class="hljs-comment">// 191052633396993n</span> 2180 2181 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Benchmark took <span class="hljs-subst">${end - start}</span> nanoseconds`</span>); 2182 <span class="hljs-comment">// Benchmark took 1154389282 nanoseconds</span> 2183}, <span class="hljs-number">1000</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { hrtime } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2184 2185<span class="hljs-keyword">const</span> start = hrtime.<span class="hljs-title function_">bigint</span>(); 2186<span class="hljs-comment">// 191051479007711n</span> 2187 2188<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 2189 <span class="hljs-keyword">const</span> end = hrtime.<span class="hljs-title function_">bigint</span>(); 2190 <span class="hljs-comment">// 191052633396993n</span> 2191 2192 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Benchmark took <span class="hljs-subst">${end - start}</span> nanoseconds`</span>); 2193 <span class="hljs-comment">// Benchmark took 1154389282 nanoseconds</span> 2194}, <span class="hljs-number">1000</span>);</code><button class="copy-button">copy</button></pre> 2195</section><section><h3><code>process.initgroups(user, extraGroup)</code><span><a class="mark" href="#processinitgroupsuser-extragroup" id="processinitgroupsuser-extragroup">#</a></span><a aria-hidden="true" class="legacy" id="process_process_initgroups_user_extragroup"></a></h3> 2196<div class="api_metadata"> 2197<span>Added in: v0.9.4</span> 2198</div> 2199<ul> 2200<li><code>user</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"><number></a> The user name or numeric identifier.</li> 2201<li><code>extraGroup</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"><number></a> A group name or numeric identifier.</li> 2202</ul> 2203<p>The <code>process.initgroups()</code> method reads the <code>/etc/group</code> file and initializes 2204the group access list, using all groups of which the user is a member. This is 2205a privileged operation that requires that the Node.js process either have <code>root</code> 2206access or the <code>CAP_SETGID</code> capability.</p> 2207<p>Use care when dropping privileges:</p> 2208 2209<pre class="with-66-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { getgroups, initgroups, setgid } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2210 2211<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">getgroups</span>()); <span class="hljs-comment">// [ 0 ]</span> 2212<span class="hljs-title function_">initgroups</span>(<span class="hljs-string">'nodeuser'</span>, <span class="hljs-number">1000</span>); <span class="hljs-comment">// switch user</span> 2213<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">getgroups</span>()); <span class="hljs-comment">// [ 27, 30, 46, 1000, 0 ]</span> 2214<span class="hljs-title function_">setgid</span>(<span class="hljs-number">1000</span>); <span class="hljs-comment">// drop root gid</span> 2215<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">getgroups</span>()); <span class="hljs-comment">// [ 27, 30, 46, 1000 ]</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { getgroups, initgroups, setgid } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2216 2217<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">getgroups</span>()); <span class="hljs-comment">// [ 0 ]</span> 2218<span class="hljs-title function_">initgroups</span>(<span class="hljs-string">'nodeuser'</span>, <span class="hljs-number">1000</span>); <span class="hljs-comment">// switch user</span> 2219<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">getgroups</span>()); <span class="hljs-comment">// [ 27, 30, 46, 1000, 0 ]</span> 2220<span class="hljs-title function_">setgid</span>(<span class="hljs-number">1000</span>); <span class="hljs-comment">// drop root gid</span> 2221<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">getgroups</span>()); <span class="hljs-comment">// [ 27, 30, 46, 1000 ]</span></code><button class="copy-button">copy</button></pre> 2222<p>This function is only available on POSIX platforms (i.e. not Windows or 2223Android). 2224This feature is not available in <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 2225</section><section><h3><code>process.kill(pid[, signal])</code><span><a class="mark" href="#processkillpid-signal" id="processkillpid-signal">#</a></span><a aria-hidden="true" class="legacy" id="process_process_kill_pid_signal"></a></h3> 2226<div class="api_metadata"> 2227<span>Added in: v0.0.6</span> 2228</div> 2229<ul> 2230<li><code>pid</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> A process ID</li> 2231<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#Number_type" class="type"><number></a> The signal to send, either as a string or number. 2232<strong>Default:</strong> <code>'SIGTERM'</code>.</li> 2233</ul> 2234<p>The <code>process.kill()</code> method sends the <code>signal</code> to the process identified by 2235<code>pid</code>.</p> 2236<p>Signal names are strings such as <code>'SIGINT'</code> or <code>'SIGHUP'</code>. See <a href="#signal-events">Signal Events</a> 2237and <a href="http://man7.org/linux/man-pages/man2/kill.2.html"><code>kill(2)</code></a> for more information.</p> 2238<p>This method will throw an error if the target <code>pid</code> does not exist. As a special 2239case, a signal of <code>0</code> can be used to test for the existence of a process. 2240Windows platforms will throw an error if the <code>pid</code> is used to kill a process 2241group.</p> 2242<p>Even though the name of this function is <code>process.kill()</code>, it is really just a 2243signal sender, like the <code>kill</code> system call. The signal sent may do something 2244other than kill the target process.</p> 2245 2246<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process, { kill } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2247 2248process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'SIGHUP'</span>, <span class="hljs-function">() =></span> { 2249 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Got SIGHUP signal.'</span>); 2250}); 2251 2252<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 2253 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Exiting.'</span>); 2254 process.<span class="hljs-title function_">exit</span>(<span class="hljs-number">0</span>); 2255}, <span class="hljs-number">100</span>); 2256 2257<span class="hljs-title function_">kill</span>(process.<span class="hljs-property">pid</span>, <span class="hljs-string">'SIGHUP'</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2258 2259process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'SIGHUP'</span>, <span class="hljs-function">() =></span> { 2260 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Got SIGHUP signal.'</span>); 2261}); 2262 2263<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 2264 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Exiting.'</span>); 2265 process.<span class="hljs-title function_">exit</span>(<span class="hljs-number">0</span>); 2266}, <span class="hljs-number">100</span>); 2267 2268process.<span class="hljs-title function_">kill</span>(process.<span class="hljs-property">pid</span>, <span class="hljs-string">'SIGHUP'</span>);</code><button class="copy-button">copy</button></pre> 2269<p>When <code>SIGUSR1</code> is received by a Node.js process, Node.js will start the 2270debugger. See <a href="#signal-events">Signal Events</a>.</p> 2271</section><section><h3><code>process.mainModule</code><span><a class="mark" href="#processmainmodule" id="processmainmodule">#</a></span><a aria-hidden="true" class="legacy" id="process_process_mainmodule"></a></h3> 2272<div class="api_metadata"> 2273<span>Added in: v0.1.17</span><span>Deprecated since: v14.0.0</span> 2274</div> 2275<p></p><div class="api_stability api_stability_0"><a href="documentation.html#stability-index">Stability: 0</a> - Deprecated: Use <a href="modules.html#accessing-the-main-module"><code>require.main</code></a> instead.</div><p></p> 2276<ul> 2277<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 2278</ul> 2279<p>The <code>process.mainModule</code> property provides an alternative way of retrieving 2280<a href="modules.html#accessing-the-main-module"><code>require.main</code></a>. The difference is that if the main module changes at 2281runtime, <a href="modules.html#accessing-the-main-module"><code>require.main</code></a> may still refer to the original main module in 2282modules that were required before the change occurred. Generally, it's 2283safe to assume that the two refer to the same module.</p> 2284<p>As with <a href="modules.html#accessing-the-main-module"><code>require.main</code></a>, <code>process.mainModule</code> will be <code>undefined</code> if there 2285is no entry script.</p> 2286</section><section><h3><code>process.memoryUsage()</code><span><a class="mark" href="#processmemoryusage" id="processmemoryusage">#</a></span><a aria-hidden="true" class="legacy" id="process_process_memoryusage"></a></h3> 2287<div class="api_metadata"> 2288<details class="changelog"><summary>History</summary> 2289<table> 2290<tbody><tr><th>Version</th><th>Changes</th></tr> 2291<tr><td>v13.9.0, v12.17.0</td> 2292<td><p>Added <code>arrayBuffers</code> to the returned object.</p></td></tr> 2293<tr><td>v7.2.0</td> 2294<td><p>Added <code>external</code> to the returned object.</p></td></tr> 2295<tr><td>v0.1.16</td> 2296<td><p><span>Added in: v0.1.16</span></p></td></tr> 2297</tbody></table> 2298</details> 2299</div> 2300<ul> 2301<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 2302<ul> 2303<li><code>rss</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2304<li><code>heapTotal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2305<li><code>heapUsed</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2306<li><code>external</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2307<li><code>arrayBuffers</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2308</ul> 2309</li> 2310</ul> 2311<p>Returns an object describing the memory usage of the Node.js process measured in 2312bytes.</p> 2313 2314<pre class="with-48-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { memoryUsage } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2315 2316<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">memoryUsage</span>()); 2317<span class="hljs-comment">// Prints:</span> 2318<span class="hljs-comment">// {</span> 2319<span class="hljs-comment">// rss: 4935680,</span> 2320<span class="hljs-comment">// heapTotal: 1826816,</span> 2321<span class="hljs-comment">// heapUsed: 650472,</span> 2322<span class="hljs-comment">// external: 49879,</span> 2323<span class="hljs-comment">// arrayBuffers: 9386</span> 2324<span class="hljs-comment">// }</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { memoryUsage } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2325 2326<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">memoryUsage</span>()); 2327<span class="hljs-comment">// Prints:</span> 2328<span class="hljs-comment">// {</span> 2329<span class="hljs-comment">// rss: 4935680,</span> 2330<span class="hljs-comment">// heapTotal: 1826816,</span> 2331<span class="hljs-comment">// heapUsed: 650472,</span> 2332<span class="hljs-comment">// external: 49879,</span> 2333<span class="hljs-comment">// arrayBuffers: 9386</span> 2334<span class="hljs-comment">// }</span></code><button class="copy-button">copy</button></pre> 2335<ul> 2336<li><code>heapTotal</code> and <code>heapUsed</code> refer to V8's memory usage.</li> 2337<li><code>external</code> refers to the memory usage of C++ objects bound to JavaScript 2338objects managed by V8.</li> 2339<li><code>rss</code>, Resident Set Size, is the amount of space occupied in the main 2340memory device (that is a subset of the total allocated memory) for the 2341process, including all C++ and JavaScript objects and code.</li> 2342<li><code>arrayBuffers</code> refers to memory allocated for <code>ArrayBuffer</code>s and 2343<code>SharedArrayBuffer</code>s, including all Node.js <a href="buffer.html"><code>Buffer</code></a>s. 2344This is also included in the <code>external</code> value. When Node.js is used as an 2345embedded library, this value may be <code>0</code> because allocations for <code>ArrayBuffer</code>s 2346may not be tracked in that case.</li> 2347</ul> 2348<p>When using <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads, <code>rss</code> will be a value that is valid for the 2349entire process, while the other fields will only refer to the current thread.</p> 2350<p>The <code>process.memoryUsage()</code> method iterates over each page to gather 2351information about memory usage which might be slow depending on the 2352program memory allocations.</p> 2353</section><section><h3><code>process.memoryUsage.rss()</code><span><a class="mark" href="#processmemoryusagerss" id="processmemoryusagerss">#</a></span><a aria-hidden="true" class="legacy" id="process_process_memoryusage_rss"></a></h3> 2354<div class="api_metadata"> 2355<span>Added in: v15.6.0, v14.18.0</span> 2356</div> 2357<ul> 2358<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2359</ul> 2360<p>The <code>process.memoryUsage.rss()</code> method returns an integer representing the 2361Resident Set Size (RSS) in bytes.</p> 2362<p>The Resident Set Size, is the amount of space occupied in the main 2363memory device (that is a subset of the total allocated memory) for the 2364process, including all C++ and JavaScript objects and code.</p> 2365<p>This is the same value as the <code>rss</code> property provided by <code>process.memoryUsage()</code> 2366but <code>process.memoryUsage.rss()</code> is faster.</p> 2367 2368<pre class="with-48-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { memoryUsage } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2369 2370<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(memoryUsage.<span class="hljs-title function_">rss</span>()); 2371<span class="hljs-comment">// 35655680</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { memoryUsage } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2372 2373<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(memoryUsage.<span class="hljs-title function_">rss</span>()); 2374<span class="hljs-comment">// 35655680</span></code><button class="copy-button">copy</button></pre> 2375</section><section><h3><code>process.nextTick(callback[, ...args])</code><span><a class="mark" href="#processnexttickcallback-args" id="processnexttickcallback-args">#</a></span><a aria-hidden="true" class="legacy" id="process_process_nexttick_callback_args"></a></h3> 2376<div class="api_metadata"> 2377<details class="changelog"><summary>History</summary> 2378<table> 2379<tbody><tr><th>Version</th><th>Changes</th></tr> 2380<tr><td>v18.0.0</td> 2381<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 2382<tr><td>v1.8.1</td> 2383<td><p>Additional arguments after <code>callback</code> are now supported.</p></td></tr> 2384<tr><td>v0.1.26</td> 2385<td><p><span>Added in: v0.1.26</span></p></td></tr> 2386</tbody></table> 2387</details> 2388</div> 2389<ul> 2390<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 2391<li><code>...args</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> Additional arguments to pass when invoking the <code>callback</code></li> 2392</ul> 2393<p><code>process.nextTick()</code> adds <code>callback</code> to the "next tick queue". This queue is 2394fully drained after the current operation on the JavaScript stack runs to 2395completion and before the event loop is allowed to continue. It's possible to 2396create an infinite loop if one were to recursively call <code>process.nextTick()</code>. 2397See the <a href="https://nodejs.org/en/docs/guides/event-loop-timers-and-nexttick/#process-nexttick">Event Loop</a> guide for more background.</p> 2398 2399<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { nextTick } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2400 2401<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'start'</span>); 2402<span class="hljs-title function_">nextTick</span>(<span class="hljs-function">() =></span> { 2403 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'nextTick callback'</span>); 2404}); 2405<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'scheduled'</span>); 2406<span class="hljs-comment">// Output:</span> 2407<span class="hljs-comment">// start</span> 2408<span class="hljs-comment">// scheduled</span> 2409<span class="hljs-comment">// nextTick callback</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { nextTick } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2410 2411<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'start'</span>); 2412<span class="hljs-title function_">nextTick</span>(<span class="hljs-function">() =></span> { 2413 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'nextTick callback'</span>); 2414}); 2415<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'scheduled'</span>); 2416<span class="hljs-comment">// Output:</span> 2417<span class="hljs-comment">// start</span> 2418<span class="hljs-comment">// scheduled</span> 2419<span class="hljs-comment">// nextTick callback</span></code><button class="copy-button">copy</button></pre> 2420<p>This is important when developing APIs in order to give users the opportunity 2421to assign event handlers <em>after</em> an object has been constructed but before any 2422I/O has occurred:</p> 2423 2424<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { nextTick } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2425 2426<span class="hljs-keyword">function</span> <span class="hljs-title function_">MyThing</span>(<span class="hljs-params">options</span>) { 2427 <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">setupOptions</span>(options); 2428 2429 <span class="hljs-title function_">nextTick</span>(<span class="hljs-function">() =></span> { 2430 <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">startDoingStuff</span>(); 2431 }); 2432} 2433 2434<span class="hljs-keyword">const</span> thing = <span class="hljs-keyword">new</span> <span class="hljs-title class_">MyThing</span>(); 2435thing.<span class="hljs-title function_">getReadyForStuff</span>(); 2436 2437<span class="hljs-comment">// thing.startDoingStuff() gets called now, not before.</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { nextTick } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2438 2439<span class="hljs-keyword">function</span> <span class="hljs-title function_">MyThing</span>(<span class="hljs-params">options</span>) { 2440 <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">setupOptions</span>(options); 2441 2442 <span class="hljs-title function_">nextTick</span>(<span class="hljs-function">() =></span> { 2443 <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">startDoingStuff</span>(); 2444 }); 2445} 2446 2447<span class="hljs-keyword">const</span> thing = <span class="hljs-keyword">new</span> <span class="hljs-title class_">MyThing</span>(); 2448thing.<span class="hljs-title function_">getReadyForStuff</span>(); 2449 2450<span class="hljs-comment">// thing.startDoingStuff() gets called now, not before.</span></code><button class="copy-button">copy</button></pre> 2451<p>It is very important for APIs to be either 100% synchronous or 100% 2452asynchronous. Consider this example:</p> 2453<pre><code class="language-js"><span class="hljs-comment">// WARNING! DO NOT USE! BAD UNSAFE HAZARD!</span> 2454<span class="hljs-keyword">function</span> <span class="hljs-title function_">maybeSync</span>(<span class="hljs-params">arg, cb</span>) { 2455 <span class="hljs-keyword">if</span> (arg) { 2456 <span class="hljs-title function_">cb</span>(); 2457 <span class="hljs-keyword">return</span>; 2458 } 2459 2460 fs.<span class="hljs-title function_">stat</span>(<span class="hljs-string">'file'</span>, cb); 2461}</code> <button class="copy-button">copy</button></pre> 2462<p>This API is hazardous because in the following case:</p> 2463<pre><code class="language-js"><span class="hljs-keyword">const</span> maybeTrue = <span class="hljs-title class_">Math</span>.<span class="hljs-title function_">random</span>() > <span class="hljs-number">0.5</span>; 2464 2465<span class="hljs-title function_">maybeSync</span>(maybeTrue, <span class="hljs-function">() =></span> { 2466 <span class="hljs-title function_">foo</span>(); 2467}); 2468 2469<span class="hljs-title function_">bar</span>();</code> <button class="copy-button">copy</button></pre> 2470<p>It is not clear whether <code>foo()</code> or <code>bar()</code> will be called first.</p> 2471<p>The following approach is much better:</p> 2472 2473<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { nextTick } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2474 2475<span class="hljs-keyword">function</span> <span class="hljs-title function_">definitelyAsync</span>(<span class="hljs-params">arg, cb</span>) { 2476 <span class="hljs-keyword">if</span> (arg) { 2477 <span class="hljs-title function_">nextTick</span>(cb); 2478 <span class="hljs-keyword">return</span>; 2479 } 2480 2481 fs.<span class="hljs-title function_">stat</span>(<span class="hljs-string">'file'</span>, cb); 2482}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { nextTick } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2483 2484<span class="hljs-keyword">function</span> <span class="hljs-title function_">definitelyAsync</span>(<span class="hljs-params">arg, cb</span>) { 2485 <span class="hljs-keyword">if</span> (arg) { 2486 <span class="hljs-title function_">nextTick</span>(cb); 2487 <span class="hljs-keyword">return</span>; 2488 } 2489 2490 fs.<span class="hljs-title function_">stat</span>(<span class="hljs-string">'file'</span>, cb); 2491}</code><button class="copy-button">copy</button></pre> 2492<h4>When to use <code>queueMicrotask()</code> vs. <code>process.nextTick()</code><span><a class="mark" href="#when-to-use-queuemicrotask-vs-processnexttick" id="when-to-use-queuemicrotask-vs-processnexttick">#</a></span><a aria-hidden="true" class="legacy" id="process_when_to_use_queuemicrotask_vs_process_nexttick"></a></h4> 2493<p>The <a href="globals.html#queuemicrotaskcallback"><code>queueMicrotask()</code></a> API is an alternative to <code>process.nextTick()</code> that 2494also defers execution of a function using the same microtask queue used to 2495execute the then, catch, and finally handlers of resolved promises. Within 2496Node.js, every time the "next tick queue" is drained, the microtask queue 2497is drained immediately after.</p> 2498 2499<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { nextTick } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2500 2501<span class="hljs-title class_">Promise</span>.<span class="hljs-title function_">resolve</span>().<span class="hljs-title function_">then</span>(<span class="hljs-function">() =></span> <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-number">2</span>)); 2502<span class="hljs-title function_">queueMicrotask</span>(<span class="hljs-function">() =></span> <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-number">3</span>)); 2503<span class="hljs-title function_">nextTick</span>(<span class="hljs-function">() =></span> <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-number">1</span>)); 2504<span class="hljs-comment">// Output:</span> 2505<span class="hljs-comment">// 1</span> 2506<span class="hljs-comment">// 2</span> 2507<span class="hljs-comment">// 3</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { nextTick } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2508 2509<span class="hljs-title class_">Promise</span>.<span class="hljs-title function_">resolve</span>().<span class="hljs-title function_">then</span>(<span class="hljs-function">() =></span> <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-number">2</span>)); 2510<span class="hljs-title function_">queueMicrotask</span>(<span class="hljs-function">() =></span> <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-number">3</span>)); 2511<span class="hljs-title function_">nextTick</span>(<span class="hljs-function">() =></span> <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-number">1</span>)); 2512<span class="hljs-comment">// Output:</span> 2513<span class="hljs-comment">// 1</span> 2514<span class="hljs-comment">// 2</span> 2515<span class="hljs-comment">// 3</span></code><button class="copy-button">copy</button></pre> 2516<p>For <em>most</em> userland use cases, the <code>queueMicrotask()</code> API provides a portable 2517and reliable mechanism for deferring execution that works across multiple 2518JavaScript platform environments and should be favored over <code>process.nextTick()</code>. 2519In simple scenarios, <code>queueMicrotask()</code> can be a drop-in replacement for 2520<code>process.nextTick()</code>.</p> 2521<pre><code class="language-js"><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'start'</span>); 2522<span class="hljs-title function_">queueMicrotask</span>(<span class="hljs-function">() =></span> { 2523 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'microtask callback'</span>); 2524}); 2525<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'scheduled'</span>); 2526<span class="hljs-comment">// Output:</span> 2527<span class="hljs-comment">// start</span> 2528<span class="hljs-comment">// scheduled</span> 2529<span class="hljs-comment">// microtask callback</span></code> <button class="copy-button">copy</button></pre> 2530<p>One note-worthy difference between the two APIs is that <code>process.nextTick()</code> 2531allows specifying additional values that will be passed as arguments to the 2532deferred function when it is called. Achieving the same result with 2533<code>queueMicrotask()</code> requires using either a closure or a bound function:</p> 2534<pre><code class="language-js"><span class="hljs-keyword">function</span> <span class="hljs-title function_">deferred</span>(<span class="hljs-params">a, b</span>) { 2535 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'microtask'</span>, a + b); 2536} 2537 2538<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'start'</span>); 2539<span class="hljs-title function_">queueMicrotask</span>(deferred.<span class="hljs-title function_">bind</span>(<span class="hljs-literal">undefined</span>, <span class="hljs-number">1</span>, <span class="hljs-number">2</span>)); 2540<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'scheduled'</span>); 2541<span class="hljs-comment">// Output:</span> 2542<span class="hljs-comment">// start</span> 2543<span class="hljs-comment">// scheduled</span> 2544<span class="hljs-comment">// microtask 3</span></code> <button class="copy-button">copy</button></pre> 2545<p>There are minor differences in the way errors raised from within the next tick 2546queue and microtask queue are handled. Errors thrown within a queued microtask 2547callback should be handled within the queued callback when possible. If they are 2548not, the <code>process.on('uncaughtException')</code> event handler can be used to capture 2549and handle the errors.</p> 2550<p>When in doubt, unless the specific capabilities of <code>process.nextTick()</code> are 2551needed, use <code>queueMicrotask()</code>.</p> 2552</section><section><h3><code>process.noDeprecation</code><span><a class="mark" href="#processnodeprecation" id="processnodeprecation">#</a></span><a aria-hidden="true" class="legacy" id="process_process_nodeprecation"></a></h3> 2553<div class="api_metadata"> 2554<span>Added in: v0.8.0</span> 2555</div> 2556<ul> 2557<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2558</ul> 2559<p>The <code>process.noDeprecation</code> property indicates whether the <code>--no-deprecation</code> 2560flag is set on the current Node.js process. See the documentation for 2561the <a href="#event-warning"><code>'warning'</code> event</a> and the 2562<a href="#processemitwarningwarning-type-code-ctor"><code>emitWarning()</code> method</a> for more information about this 2563flag's behavior.</p> 2564</section><section><h3><code>process.pid</code><span><a class="mark" href="#processpid" id="processpid">#</a></span><a aria-hidden="true" class="legacy" id="process_process_pid"></a></h3> 2565<div class="api_metadata"> 2566<span>Added in: v0.1.15</span> 2567</div> 2568<ul> 2569<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2570</ul> 2571<p>The <code>process.pid</code> property returns the PID of the process.</p> 2572 2573<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { pid } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2574 2575<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`This process is pid <span class="hljs-subst">${pid}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { pid } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2576 2577<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`This process is pid <span class="hljs-subst">${pid}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2578</section><section><h3><code>process.platform</code><span><a class="mark" href="#processplatform" id="processplatform">#</a></span><a aria-hidden="true" class="legacy" id="process_process_platform"></a></h3> 2579<div class="api_metadata"> 2580<span>Added in: v0.1.16</span> 2581</div> 2582<ul> 2583<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 2584</ul> 2585<p>The <code>process.platform</code> property returns a string identifying the operating 2586system platform for which the Node.js binary was compiled.</p> 2587<p>Currently possible values are:</p> 2588<ul> 2589<li><code>'aix'</code></li> 2590<li><code>'darwin'</code></li> 2591<li><code>'freebsd'</code></li> 2592<li><code>'linux'</code></li> 2593<li><code>'openbsd'</code></li> 2594<li><code>'sunos'</code></li> 2595<li><code>'win32'</code></li> 2596</ul> 2597 2598<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { platform } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2599 2600<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`This platform is <span class="hljs-subst">${platform}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { platform } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2601 2602<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`This platform is <span class="hljs-subst">${platform}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2603<p>The value <code>'android'</code> may also be returned if the Node.js is built on the 2604Android operating system. However, Android support in Node.js 2605<a href="https://github.com/nodejs/node/blob/HEAD/BUILDING.md#androidandroid-based-devices-eg-firefox-os">is experimental</a>.</p> 2606</section><section><h3><code>process.ppid</code><span><a class="mark" href="#processppid" id="processppid">#</a></span><a aria-hidden="true" class="legacy" id="process_process_ppid"></a></h3> 2607<div class="api_metadata"> 2608<span>Added in: v9.2.0, v8.10.0, v6.13.0</span> 2609</div> 2610<ul> 2611<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2612</ul> 2613<p>The <code>process.ppid</code> property returns the PID of the parent of the 2614current process.</p> 2615 2616<pre class="with-41-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { ppid } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2617 2618<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`The parent process is pid <span class="hljs-subst">${ppid}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { ppid } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2619 2620<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`The parent process is pid <span class="hljs-subst">${ppid}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2621</section><section><h3><code>process.release</code><span><a class="mark" href="#processrelease" id="processrelease">#</a></span><a aria-hidden="true" class="legacy" id="process_process_release"></a></h3> 2622<div class="api_metadata"> 2623<details class="changelog"><summary>History</summary> 2624<table> 2625<tbody><tr><th>Version</th><th>Changes</th></tr> 2626<tr><td>v4.2.0</td> 2627<td><p>The <code>lts</code> property is now supported.</p></td></tr> 2628<tr><td>v3.0.0</td> 2629<td><p><span>Added in: v3.0.0</span></p></td></tr> 2630</tbody></table> 2631</details> 2632</div> 2633<ul> 2634<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 2635</ul> 2636<p>The <code>process.release</code> property returns an <code>Object</code> containing metadata related 2637to the current release, including URLs for the source tarball and headers-only 2638tarball.</p> 2639<p><code>process.release</code> contains the following properties:</p> 2640<ul> 2641<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A value that will always be <code>'node'</code>.</li> 2642<li><code>sourceUrl</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> an absolute URL pointing to a <em><code>.tar.gz</code></em> file containing 2643the source code of the current release.</li> 2644<li><code>headersUrl</code><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> an absolute URL pointing to a <em><code>.tar.gz</code></em> file containing 2645only the source header files for the current release. This file is 2646significantly smaller than the full source file and can be used for compiling 2647Node.js native add-ons.</li> 2648<li><code>libUrl</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#Undefined_type" class="type"><undefined></a> an absolute URL pointing to a <em><code>node.lib</code></em> file 2649matching the architecture and version of the current release. This file is 2650used for compiling Node.js native add-ons. <em>This property is only present on 2651Windows builds of Node.js and will be missing on all other platforms.</em></li> 2652<li><code>lts</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#Undefined_type" class="type"><undefined></a> a string label identifying the <a href="https://github.com/nodejs/Release">LTS</a> label for this 2653release. This property only exists for LTS releases and is <code>undefined</code> for all 2654other release types, including <em>Current</em> releases. Valid values include the 2655LTS Release code names (including those that are no longer supported). 2656<ul> 2657<li><code>'Fermium'</code> for the 14.x LTS line beginning with 14.15.0.</li> 2658<li><code>'Gallium'</code> for the 16.x LTS line beginning with 16.13.0.</li> 2659<li><code>'Hydrogen'</code> for the 18.x LTS line beginning with 18.12.0. 2660For other LTS Release code names, see <a href="https://github.com/nodejs/node/blob/HEAD/doc/changelogs/CHANGELOG_ARCHIVE.md">Node.js Changelog Archive</a></li> 2661</ul> 2662</li> 2663</ul> 2664<!-- eslint-skip --> 2665<pre><code class="language-js">{ 2666 <span class="hljs-attr">name</span>: <span class="hljs-string">'node'</span>, 2667 <span class="hljs-attr">lts</span>: <span class="hljs-string">'Hydrogen'</span>, 2668 <span class="hljs-attr">sourceUrl</span>: <span class="hljs-string">'https://nodejs.org/download/release/v18.12.0/node-v18.12.0.tar.gz'</span>, 2669 <span class="hljs-attr">headersUrl</span>: <span class="hljs-string">'https://nodejs.org/download/release/v18.12.0/node-v18.12.0-headers.tar.gz'</span>, 2670 <span class="hljs-attr">libUrl</span>: <span class="hljs-string">'https://nodejs.org/download/release/v18.12.0/win-x64/node.lib'</span> 2671}</code> <button class="copy-button">copy</button></pre> 2672<p>In custom builds from non-release versions of the source tree, only the 2673<code>name</code> property may be present. The additional properties should not be 2674relied upon to exist.</p> 2675</section><section><h3><code>process.report</code><span><a class="mark" href="#processreport" id="processreport">#</a></span><a aria-hidden="true" class="legacy" id="process_process_report"></a></h3> 2676<div class="api_metadata"> 2677<details class="changelog"><summary>History</summary> 2678<table> 2679<tbody><tr><th>Version</th><th>Changes</th></tr> 2680<tr><td>v13.12.0, v12.17.0</td> 2681<td><p>This API is no longer experimental.</p></td></tr> 2682<tr><td>v11.8.0</td> 2683<td><p><span>Added in: v11.8.0</span></p></td></tr> 2684</tbody></table> 2685</details> 2686</div> 2687<ul> 2688<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 2689</ul> 2690<p><code>process.report</code> is an object whose methods are used to generate diagnostic 2691reports for the current process. Additional documentation is available in the 2692<a href="report.html">report documentation</a>.</p> 2693<h4><code>process.report.compact</code><span><a class="mark" href="#processreportcompact" id="processreportcompact">#</a></span><a aria-hidden="true" class="legacy" id="process_process_report_compact"></a></h4> 2694<div class="api_metadata"> 2695<span>Added in: v13.12.0, v12.17.0</span> 2696</div> 2697<ul> 2698<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2699</ul> 2700<p>Write reports in a compact format, single-line JSON, more easily consumable 2701by log processing systems than the default multi-line format designed for 2702human consumption.</p> 2703 2704<pre class="with-43-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { report } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2705 2706<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Reports are compact? <span class="hljs-subst">${report.compact}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { report } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2707 2708<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Reports are compact? <span class="hljs-subst">${report.compact}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2709<h4><code>process.report.directory</code><span><a class="mark" href="#processreportdirectory" id="processreportdirectory">#</a></span><a aria-hidden="true" class="legacy" id="process_process_report_directory"></a></h4> 2710<div class="api_metadata"> 2711<details class="changelog"><summary>History</summary> 2712<table> 2713<tbody><tr><th>Version</th><th>Changes</th></tr> 2714<tr><td>v13.12.0, v12.17.0</td> 2715<td><p>This API is no longer experimental.</p></td></tr> 2716<tr><td>v11.12.0</td> 2717<td><p><span>Added in: v11.12.0</span></p></td></tr> 2718</tbody></table> 2719</details> 2720</div> 2721<ul> 2722<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 2723</ul> 2724<p>Directory where the report is written. The default value is the empty string, 2725indicating that reports are written to the current working directory of the 2726Node.js process.</p> 2727 2728<pre class="with-43-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { report } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2729 2730<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report directory is <span class="hljs-subst">${report.directory}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { report } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2731 2732<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report directory is <span class="hljs-subst">${report.directory}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2733<h4><code>process.report.filename</code><span><a class="mark" href="#processreportfilename" id="processreportfilename">#</a></span><a aria-hidden="true" class="legacy" id="process_process_report_filename"></a></h4> 2734<div class="api_metadata"> 2735<details class="changelog"><summary>History</summary> 2736<table> 2737<tbody><tr><th>Version</th><th>Changes</th></tr> 2738<tr><td>v13.12.0, v12.17.0</td> 2739<td><p>This API is no longer experimental.</p></td></tr> 2740<tr><td>v11.12.0</td> 2741<td><p><span>Added in: v11.12.0</span></p></td></tr> 2742</tbody></table> 2743</details> 2744</div> 2745<ul> 2746<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 2747</ul> 2748<p>Filename where the report is written. If set to the empty string, the output 2749filename will be comprised of a timestamp, PID, and sequence number. The default 2750value is the empty string.</p> 2751<p>If the value of <code>process.report.filename</code> is set to <code>'stdout'</code> or <code>'stderr'</code>, 2752the report is written to the stdout or stderr of the process respectively.</p> 2753 2754<pre class="with-43-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { report } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2755 2756<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report filename is <span class="hljs-subst">${report.filename}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { report } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2757 2758<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report filename is <span class="hljs-subst">${report.filename}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2759<h4><code>process.report.getReport([err])</code><span><a class="mark" href="#processreportgetreporterr" id="processreportgetreporterr">#</a></span><a aria-hidden="true" class="legacy" id="process_process_report_getreport_err"></a></h4> 2760<div class="api_metadata"> 2761<details class="changelog"><summary>History</summary> 2762<table> 2763<tbody><tr><th>Version</th><th>Changes</th></tr> 2764<tr><td>v13.12.0, v12.17.0</td> 2765<td><p>This API is no longer experimental.</p></td></tr> 2766<tr><td>v11.8.0</td> 2767<td><p><span>Added in: v11.8.0</span></p></td></tr> 2768</tbody></table> 2769</details> 2770</div> 2771<ul> 2772<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a> A custom error used for reporting the JavaScript stack.</li> 2773<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 2774</ul> 2775<p>Returns a JavaScript Object representation of a diagnostic report for the 2776running process. The report's JavaScript stack trace is taken from <code>err</code>, if 2777present.</p> 2778 2779<pre class="with-43-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { report } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2780<span class="hljs-keyword">import</span> util <span class="hljs-keyword">from</span> <span class="hljs-string">'node:util'</span>; 2781 2782<span class="hljs-keyword">const</span> data = report.<span class="hljs-title function_">getReport</span>(); 2783<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(data.<span class="hljs-property">header</span>.<span class="hljs-property">nodejsVersion</span>); 2784 2785<span class="hljs-comment">// Similar to process.report.writeReport()</span> 2786<span class="hljs-keyword">import</span> fs <span class="hljs-keyword">from</span> <span class="hljs-string">'node:fs'</span>; 2787fs.<span class="hljs-title function_">writeFileSync</span>(<span class="hljs-string">'my-report.log'</span>, util.<span class="hljs-title function_">inspect</span>(data), <span class="hljs-string">'utf8'</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { report } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2788<span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:util'</span>); 2789 2790<span class="hljs-keyword">const</span> data = report.<span class="hljs-title function_">getReport</span>(); 2791<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(data.<span class="hljs-property">header</span>.<span class="hljs-property">nodejsVersion</span>); 2792 2793<span class="hljs-comment">// Similar to process.report.writeReport()</span> 2794<span class="hljs-keyword">const</span> fs = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:fs'</span>); 2795fs.<span class="hljs-title function_">writeFileSync</span>(<span class="hljs-string">'my-report.log'</span>, util.<span class="hljs-title function_">inspect</span>(data), <span class="hljs-string">'utf8'</span>);</code><button class="copy-button">copy</button></pre> 2796<p>Additional documentation is available in the <a href="report.html">report documentation</a>.</p> 2797<h4><code>process.report.reportOnFatalError</code><span><a class="mark" href="#processreportreportonfatalerror" id="processreportreportonfatalerror">#</a></span><a aria-hidden="true" class="legacy" id="process_process_report_reportonfatalerror"></a></h4> 2798<div class="api_metadata"> 2799<details class="changelog"><summary>History</summary> 2800<table> 2801<tbody><tr><th>Version</th><th>Changes</th></tr> 2802<tr><td>v15.0.0, v14.17.0</td> 2803<td><p>This API is no longer experimental.</p></td></tr> 2804<tr><td>v11.12.0</td> 2805<td><p><span>Added in: v11.12.0</span></p></td></tr> 2806</tbody></table> 2807</details> 2808</div> 2809<ul> 2810<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2811</ul> 2812<p>If <code>true</code>, a diagnostic report is generated on fatal errors, such as out of 2813memory errors or failed C++ assertions.</p> 2814 2815<pre class="with-43-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { report } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2816 2817<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report on fatal error: <span class="hljs-subst">${report.reportOnFatalError}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { report } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2818 2819<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report on fatal error: <span class="hljs-subst">${report.reportOnFatalError}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2820<h4><code>process.report.reportOnSignal</code><span><a class="mark" href="#processreportreportonsignal" id="processreportreportonsignal">#</a></span><a aria-hidden="true" class="legacy" id="process_process_report_reportonsignal"></a></h4> 2821<div class="api_metadata"> 2822<details class="changelog"><summary>History</summary> 2823<table> 2824<tbody><tr><th>Version</th><th>Changes</th></tr> 2825<tr><td>v13.12.0, v12.17.0</td> 2826<td><p>This API is no longer experimental.</p></td></tr> 2827<tr><td>v11.12.0</td> 2828<td><p><span>Added in: v11.12.0</span></p></td></tr> 2829</tbody></table> 2830</details> 2831</div> 2832<ul> 2833<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2834</ul> 2835<p>If <code>true</code>, a diagnostic report is generated when the process receives the 2836signal specified by <code>process.report.signal</code>.</p> 2837 2838<pre class="with-43-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { report } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2839 2840<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report on signal: <span class="hljs-subst">${report.reportOnSignal}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { report } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2841 2842<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report on signal: <span class="hljs-subst">${report.reportOnSignal}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2843<h4><code>process.report.reportOnUncaughtException</code><span><a class="mark" href="#processreportreportonuncaughtexception" id="processreportreportonuncaughtexception">#</a></span><a aria-hidden="true" class="legacy" id="process_process_report_reportonuncaughtexception"></a></h4> 2844<div class="api_metadata"> 2845<details class="changelog"><summary>History</summary> 2846<table> 2847<tbody><tr><th>Version</th><th>Changes</th></tr> 2848<tr><td>v13.12.0, v12.17.0</td> 2849<td><p>This API is no longer experimental.</p></td></tr> 2850<tr><td>v11.12.0</td> 2851<td><p><span>Added in: v11.12.0</span></p></td></tr> 2852</tbody></table> 2853</details> 2854</div> 2855<ul> 2856<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2857</ul> 2858<p>If <code>true</code>, a diagnostic report is generated on uncaught exception.</p> 2859 2860<pre class="with-43-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { report } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2861 2862<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report on exception: <span class="hljs-subst">${report.reportOnUncaughtException}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { report } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2863 2864<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report on exception: <span class="hljs-subst">${report.reportOnUncaughtException}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2865<h4><code>process.report.signal</code><span><a class="mark" href="#processreportsignal" id="processreportsignal">#</a></span><a aria-hidden="true" class="legacy" id="process_process_report_signal"></a></h4> 2866<div class="api_metadata"> 2867<details class="changelog"><summary>History</summary> 2868<table> 2869<tbody><tr><th>Version</th><th>Changes</th></tr> 2870<tr><td>v13.12.0, v12.17.0</td> 2871<td><p>This API is no longer experimental.</p></td></tr> 2872<tr><td>v11.12.0</td> 2873<td><p><span>Added in: v11.12.0</span></p></td></tr> 2874</tbody></table> 2875</details> 2876</div> 2877<ul> 2878<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 2879</ul> 2880<p>The signal used to trigger the creation of a diagnostic report. Defaults to 2881<code>'SIGUSR2'</code>.</p> 2882 2883<pre class="with-43-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { report } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2884 2885<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report signal: <span class="hljs-subst">${report.signal}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { report } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2886 2887<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report signal: <span class="hljs-subst">${report.signal}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2888<h4><code>process.report.writeReport([filename][, err])</code><span><a class="mark" href="#processreportwritereportfilename-err" id="processreportwritereportfilename-err">#</a></span><a aria-hidden="true" class="legacy" id="process_process_report_writereport_filename_err"></a></h4> 2889<div class="api_metadata"> 2890<details class="changelog"><summary>History</summary> 2891<table> 2892<tbody><tr><th>Version</th><th>Changes</th></tr> 2893<tr><td>v13.12.0, v12.17.0</td> 2894<td><p>This API is no longer experimental.</p></td></tr> 2895<tr><td>v11.8.0</td> 2896<td><p><span>Added in: v11.8.0</span></p></td></tr> 2897</tbody></table> 2898</details> 2899</div> 2900<ul> 2901<li> 2902<p><code>filename</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Name of the file where the report is written. This 2903should be a relative path, that will be appended to the directory specified in 2904<code>process.report.directory</code>, or the current working directory of the Node.js 2905process, if unspecified.</p> 2906</li> 2907<li> 2908<p><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a> A custom error used for reporting the JavaScript stack.</p> 2909</li> 2910<li> 2911<p>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Returns the filename of the generated report.</p> 2912</li> 2913</ul> 2914<p>Writes a diagnostic report to a file. If <code>filename</code> is not provided, the default 2915filename includes the date, time, PID, and a sequence number. The report's 2916JavaScript stack trace is taken from <code>err</code>, if present.</p> 2917<p>If the value of <code>filename</code> is set to <code>'stdout'</code> or <code>'stderr'</code>, the report is 2918written to the stdout or stderr of the process respectively.</p> 2919 2920<pre class="with-43-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { report } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2921 2922report.<span class="hljs-title function_">writeReport</span>();</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { report } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2923 2924report.<span class="hljs-title function_">writeReport</span>();</code><button class="copy-button">copy</button></pre> 2925<p>Additional documentation is available in the <a href="report.html">report documentation</a>.</p> 2926</section><section><h3><code>process.resourceUsage()</code><span><a class="mark" href="#processresourceusage" id="processresourceusage">#</a></span><a aria-hidden="true" class="legacy" id="process_process_resourceusage"></a></h3> 2927<div class="api_metadata"> 2928<span>Added in: v12.6.0</span> 2929</div> 2930<ul> 2931<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> the resource usage for the current process. All of these 2932values come from the <code>uv_getrusage</code> call which returns 2933a <a href="https://docs.libuv.org/en/v1.x/misc.html#c.uv_rusage_t"><code>uv_rusage_t</code> struct</a>. 2934<ul> 2935<li><code>userCPUTime</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> maps to <code>ru_utime</code> computed in microseconds. 2936It is the same value as <a href="#processcpuusagepreviousvalue"><code>process.cpuUsage().user</code></a>.</li> 2937<li><code>systemCPUTime</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> maps to <code>ru_stime</code> computed in microseconds. 2938It is the same value as <a href="#processcpuusagepreviousvalue"><code>process.cpuUsage().system</code></a>.</li> 2939<li><code>maxRSS</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> maps to <code>ru_maxrss</code> which is the maximum resident set 2940size used in kilobytes.</li> 2941<li><code>sharedMemorySize</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> maps to <code>ru_ixrss</code> but is not supported by 2942any platform.</li> 2943<li><code>unsharedDataSize</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> maps to <code>ru_idrss</code> but is not supported by 2944any platform.</li> 2945<li><code>unsharedStackSize</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> maps to <code>ru_isrss</code> but is not supported by 2946any platform.</li> 2947<li><code>minorPageFault</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> maps to <code>ru_minflt</code> which is the number of 2948minor page faults for the process, see 2949<a href="https://en.wikipedia.org/wiki/Page_fault#Minor">this article for more details</a>.</li> 2950<li><code>majorPageFault</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> maps to <code>ru_majflt</code> which is the number of 2951major page faults for the process, see 2952<a href="https://en.wikipedia.org/wiki/Page_fault#Major">this article for more details</a>. This field is not 2953supported on Windows.</li> 2954<li><code>swappedOut</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> maps to <code>ru_nswap</code> but is not supported by any 2955platform.</li> 2956<li><code>fsRead</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> maps to <code>ru_inblock</code> which is the number of times the 2957file system had to perform input.</li> 2958<li><code>fsWrite</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> maps to <code>ru_oublock</code> which is the number of times the 2959file system had to perform output.</li> 2960<li><code>ipcSent</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> maps to <code>ru_msgsnd</code> but is not supported by any 2961platform.</li> 2962<li><code>ipcReceived</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> maps to <code>ru_msgrcv</code> but is not supported by any 2963platform.</li> 2964<li><code>signalsCount</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> maps to <code>ru_nsignals</code> but is not supported by any 2965platform.</li> 2966<li><code>voluntaryContextSwitches</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> maps to <code>ru_nvcsw</code> which is the 2967number of times a CPU context switch resulted due to a process voluntarily 2968giving up the processor before its time slice was completed (usually to 2969await availability of a resource). This field is not supported on Windows.</li> 2970<li><code>involuntaryContextSwitches</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> maps to <code>ru_nivcsw</code> which is the 2971number of times a CPU context switch resulted due to a higher priority 2972process becoming runnable or because the current process exceeded its 2973time slice. This field is not supported on Windows.</li> 2974</ul> 2975</li> 2976</ul> 2977 2978<pre class="with-50-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { resourceUsage } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 2979 2980<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">resourceUsage</span>()); 2981<span class="hljs-comment">/* 2982 Will output: 2983 { 2984 userCPUTime: 82872, 2985 systemCPUTime: 4143, 2986 maxRSS: 33164, 2987 sharedMemorySize: 0, 2988 unsharedDataSize: 0, 2989 unsharedStackSize: 0, 2990 minorPageFault: 2469, 2991 majorPageFault: 0, 2992 swappedOut: 0, 2993 fsRead: 0, 2994 fsWrite: 8, 2995 ipcSent: 0, 2996 ipcReceived: 0, 2997 signalsCount: 0, 2998 voluntaryContextSwitches: 79, 2999 involuntaryContextSwitches: 1 3000 } 3001*/</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { resourceUsage } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3002 3003<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">resourceUsage</span>()); 3004<span class="hljs-comment">/* 3005 Will output: 3006 { 3007 userCPUTime: 82872, 3008 systemCPUTime: 4143, 3009 maxRSS: 33164, 3010 sharedMemorySize: 0, 3011 unsharedDataSize: 0, 3012 unsharedStackSize: 0, 3013 minorPageFault: 2469, 3014 majorPageFault: 0, 3015 swappedOut: 0, 3016 fsRead: 0, 3017 fsWrite: 8, 3018 ipcSent: 0, 3019 ipcReceived: 0, 3020 signalsCount: 0, 3021 voluntaryContextSwitches: 79, 3022 involuntaryContextSwitches: 1 3023 } 3024*/</span></code><button class="copy-button">copy</button></pre> 3025</section><section><h3><code>process.send(message[, sendHandle[, options]][, callback])</code><span><a class="mark" href="#processsendmessage-sendhandle-options-callback" id="processsendmessage-sendhandle-options-callback">#</a></span><a aria-hidden="true" class="legacy" id="process_process_send_message_sendhandle_options_callback"></a></h3> 3026<div class="api_metadata"> 3027<span>Added in: v0.5.9</span> 3028</div> 3029<ul> 3030<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 3031<li><code>sendHandle</code> <a href="net.html#class-netserver" class="type"><net.Server></a> | <a href="net.html#class-netsocket" class="type"><net.Socket></a></li> 3032<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> used to parameterize the sending of certain types of 3033handles.<code>options</code> supports the following properties: 3034<ul> 3035<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 3036<code>net.Socket</code>. When <code>true</code>, the socket is kept open in the sending process. 3037<strong>Default:</strong> <code>false</code>.</li> 3038</ul> 3039</li> 3040<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 3041<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 3042</ul> 3043<p>If Node.js is spawned with an IPC channel, the <code>process.send()</code> method can be 3044used to send messages to the parent process. Messages will be received as a 3045<a href="child_process.html#event-message"><code>'message'</code></a> event on the parent's <a href="child_process.html#class-childprocess"><code>ChildProcess</code></a> object.</p> 3046<p>If Node.js was not spawned with an IPC channel, <code>process.send</code> will be 3047<code>undefined</code>.</p> 3048<p>The message goes through serialization and parsing. The resulting message might 3049not be the same as what is originally sent.</p> 3050</section><section><h3><code>process.setegid(id)</code><span><a class="mark" href="#processsetegidid" id="processsetegidid">#</a></span><a aria-hidden="true" class="legacy" id="process_process_setegid_id"></a></h3> 3051<div class="api_metadata"> 3052<span>Added in: v2.0.0</span> 3053</div> 3054<ul> 3055<li><code>id</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"><number></a> A group name or ID</li> 3056</ul> 3057<p>The <code>process.setegid()</code> method sets the effective group identity of the process. 3058(See <a href="http://man7.org/linux/man-pages/man2/setegid.2.html"><code>setegid(2)</code></a>.) The <code>id</code> can be passed as either a numeric ID or a group 3059name string. If a group name is specified, this method blocks while resolving 3060the associated a numeric ID.</p> 3061 3062<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 3063 3064<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getegid</span> && process.<span class="hljs-property">setegid</span>) { 3065 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current gid: <span class="hljs-subst">${process.getegid()}</span>`</span>); 3066 <span class="hljs-keyword">try</span> { 3067 process.<span class="hljs-title function_">setegid</span>(<span class="hljs-number">501</span>); 3068 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New gid: <span class="hljs-subst">${process.getegid()}</span>`</span>); 3069 } <span class="hljs-keyword">catch</span> (err) { 3070 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`Failed to set gid: <span class="hljs-subst">${err}</span>`</span>); 3071 } 3072}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3073 3074<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getegid</span> && process.<span class="hljs-property">setegid</span>) { 3075 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current gid: <span class="hljs-subst">${process.getegid()}</span>`</span>); 3076 <span class="hljs-keyword">try</span> { 3077 process.<span class="hljs-title function_">setegid</span>(<span class="hljs-number">501</span>); 3078 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New gid: <span class="hljs-subst">${process.getegid()}</span>`</span>); 3079 } <span class="hljs-keyword">catch</span> (err) { 3080 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`Failed to set gid: <span class="hljs-subst">${err}</span>`</span>); 3081 } 3082}</code><button class="copy-button">copy</button></pre> 3083<p>This function is only available on POSIX platforms (i.e. not Windows or 3084Android). 3085This feature is not available in <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 3086</section><section><h3><code>process.seteuid(id)</code><span><a class="mark" href="#processseteuidid" id="processseteuidid">#</a></span><a aria-hidden="true" class="legacy" id="process_process_seteuid_id"></a></h3> 3087<div class="api_metadata"> 3088<span>Added in: v2.0.0</span> 3089</div> 3090<ul> 3091<li><code>id</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"><number></a> A user name or ID</li> 3092</ul> 3093<p>The <code>process.seteuid()</code> method sets the effective user identity of the process. 3094(See <a href="http://man7.org/linux/man-pages/man2/seteuid.2.html"><code>seteuid(2)</code></a>.) The <code>id</code> can be passed as either a numeric ID or a username 3095string. If a username is specified, the method blocks while resolving the 3096associated numeric ID.</p> 3097 3098<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 3099 3100<span class="hljs-keyword">if</span> (process.<span class="hljs-property">geteuid</span> && process.<span class="hljs-property">seteuid</span>) { 3101 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current uid: <span class="hljs-subst">${process.geteuid()}</span>`</span>); 3102 <span class="hljs-keyword">try</span> { 3103 process.<span class="hljs-title function_">seteuid</span>(<span class="hljs-number">501</span>); 3104 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New uid: <span class="hljs-subst">${process.geteuid()}</span>`</span>); 3105 } <span class="hljs-keyword">catch</span> (err) { 3106 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`Failed to set uid: <span class="hljs-subst">${err}</span>`</span>); 3107 } 3108}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3109 3110<span class="hljs-keyword">if</span> (process.<span class="hljs-property">geteuid</span> && process.<span class="hljs-property">seteuid</span>) { 3111 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current uid: <span class="hljs-subst">${process.geteuid()}</span>`</span>); 3112 <span class="hljs-keyword">try</span> { 3113 process.<span class="hljs-title function_">seteuid</span>(<span class="hljs-number">501</span>); 3114 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New uid: <span class="hljs-subst">${process.geteuid()}</span>`</span>); 3115 } <span class="hljs-keyword">catch</span> (err) { 3116 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`Failed to set uid: <span class="hljs-subst">${err}</span>`</span>); 3117 } 3118}</code><button class="copy-button">copy</button></pre> 3119<p>This function is only available on POSIX platforms (i.e. not Windows or 3120Android). 3121This feature is not available in <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 3122</section><section><h3><code>process.setgid(id)</code><span><a class="mark" href="#processsetgidid" id="processsetgidid">#</a></span><a aria-hidden="true" class="legacy" id="process_process_setgid_id"></a></h3> 3123<div class="api_metadata"> 3124<span>Added in: v0.1.31</span> 3125</div> 3126<ul> 3127<li><code>id</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"><number></a> The group name or ID</li> 3128</ul> 3129<p>The <code>process.setgid()</code> method sets the group identity of the process. (See 3130<a href="http://man7.org/linux/man-pages/man2/setgid.2.html"><code>setgid(2)</code></a>.) The <code>id</code> can be passed as either a numeric ID or a group name 3131string. If a group name is specified, this method blocks while resolving the 3132associated numeric ID.</p> 3133 3134<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 3135 3136<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getgid</span> && process.<span class="hljs-property">setgid</span>) { 3137 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current gid: <span class="hljs-subst">${process.getgid()}</span>`</span>); 3138 <span class="hljs-keyword">try</span> { 3139 process.<span class="hljs-title function_">setgid</span>(<span class="hljs-number">501</span>); 3140 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New gid: <span class="hljs-subst">${process.getgid()}</span>`</span>); 3141 } <span class="hljs-keyword">catch</span> (err) { 3142 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`Failed to set gid: <span class="hljs-subst">${err}</span>`</span>); 3143 } 3144}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3145 3146<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getgid</span> && process.<span class="hljs-property">setgid</span>) { 3147 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current gid: <span class="hljs-subst">${process.getgid()}</span>`</span>); 3148 <span class="hljs-keyword">try</span> { 3149 process.<span class="hljs-title function_">setgid</span>(<span class="hljs-number">501</span>); 3150 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New gid: <span class="hljs-subst">${process.getgid()}</span>`</span>); 3151 } <span class="hljs-keyword">catch</span> (err) { 3152 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`Failed to set gid: <span class="hljs-subst">${err}</span>`</span>); 3153 } 3154}</code><button class="copy-button">copy</button></pre> 3155<p>This function is only available on POSIX platforms (i.e. not Windows or 3156Android). 3157This feature is not available in <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 3158</section><section><h3><code>process.setgroups(groups)</code><span><a class="mark" href="#processsetgroupsgroups" id="processsetgroupsgroups">#</a></span><a aria-hidden="true" class="legacy" id="process_process_setgroups_groups"></a></h3> 3159<div class="api_metadata"> 3160<span>Added in: v0.9.4</span> 3161</div> 3162<ul> 3163<li><code>groups</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer[]></a></li> 3164</ul> 3165<p>The <code>process.setgroups()</code> method sets the supplementary group IDs for the 3166Node.js process. This is a privileged operation that requires the Node.js 3167process to have <code>root</code> or the <code>CAP_SETGID</code> capability.</p> 3168<p>The <code>groups</code> array can contain numeric group IDs, group names, or both.</p> 3169 3170<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 3171 3172<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getgroups</span> && process.<span class="hljs-property">setgroups</span>) { 3173 <span class="hljs-keyword">try</span> { 3174 process.<span class="hljs-title function_">setgroups</span>([<span class="hljs-number">501</span>]); 3175 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(process.<span class="hljs-title function_">getgroups</span>()); <span class="hljs-comment">// new groups</span> 3176 } <span class="hljs-keyword">catch</span> (err) { 3177 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`Failed to set groups: <span class="hljs-subst">${err}</span>`</span>); 3178 } 3179}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3180 3181<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getgroups</span> && process.<span class="hljs-property">setgroups</span>) { 3182 <span class="hljs-keyword">try</span> { 3183 process.<span class="hljs-title function_">setgroups</span>([<span class="hljs-number">501</span>]); 3184 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(process.<span class="hljs-title function_">getgroups</span>()); <span class="hljs-comment">// new groups</span> 3185 } <span class="hljs-keyword">catch</span> (err) { 3186 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`Failed to set groups: <span class="hljs-subst">${err}</span>`</span>); 3187 } 3188}</code><button class="copy-button">copy</button></pre> 3189<p>This function is only available on POSIX platforms (i.e. not Windows or 3190Android). 3191This feature is not available in <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 3192</section><section><h3><code>process.setuid(id)</code><span><a class="mark" href="#processsetuidid" id="processsetuidid">#</a></span><a aria-hidden="true" class="legacy" id="process_process_setuid_id"></a></h3> 3193<div class="api_metadata"> 3194<span>Added in: v0.1.28</span> 3195</div> 3196<ul> 3197<li><code>id</code> <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#String_type" class="type"><string></a></li> 3198</ul> 3199<p>The <code>process.setuid(id)</code> method sets the user identity of the process. (See 3200<a href="http://man7.org/linux/man-pages/man2/setuid.2.html"><code>setuid(2)</code></a>.) The <code>id</code> can be passed as either a numeric ID or a username string. 3201If a username is specified, the method blocks while resolving the associated 3202numeric ID.</p> 3203 3204<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 3205 3206<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getuid</span> && process.<span class="hljs-property">setuid</span>) { 3207 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current uid: <span class="hljs-subst">${process.getuid()}</span>`</span>); 3208 <span class="hljs-keyword">try</span> { 3209 process.<span class="hljs-title function_">setuid</span>(<span class="hljs-number">501</span>); 3210 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New uid: <span class="hljs-subst">${process.getuid()}</span>`</span>); 3211 } <span class="hljs-keyword">catch</span> (err) { 3212 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`Failed to set uid: <span class="hljs-subst">${err}</span>`</span>); 3213 } 3214}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3215 3216<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getuid</span> && process.<span class="hljs-property">setuid</span>) { 3217 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current uid: <span class="hljs-subst">${process.getuid()}</span>`</span>); 3218 <span class="hljs-keyword">try</span> { 3219 process.<span class="hljs-title function_">setuid</span>(<span class="hljs-number">501</span>); 3220 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New uid: <span class="hljs-subst">${process.getuid()}</span>`</span>); 3221 } <span class="hljs-keyword">catch</span> (err) { 3222 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`Failed to set uid: <span class="hljs-subst">${err}</span>`</span>); 3223 } 3224}</code><button class="copy-button">copy</button></pre> 3225<p>This function is only available on POSIX platforms (i.e. not Windows or 3226Android). 3227This feature is not available in <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 3228</section><section><h3><code>process.setSourceMapsEnabled(val)</code><span><a class="mark" href="#processsetsourcemapsenabledval" id="processsetsourcemapsenabledval">#</a></span><a aria-hidden="true" class="legacy" id="process_process_setsourcemapsenabled_val"></a></h3> 3229<div class="api_metadata"> 3230<span>Added in: v16.6.0, v14.18.0</span> 3231</div> 3232<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 3233<ul> 3234<li><code>val</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 3235</ul> 3236<p>This function enables or disables the <a href="https://sourcemaps.info/spec.html">Source Map v3</a> support for 3237stack traces.</p> 3238<p>It provides same features as launching Node.js process with commandline options 3239<code>--enable-source-maps</code>.</p> 3240<p>Only source maps in JavaScript files that are loaded after source maps has been 3241enabled will be parsed and loaded.</p> 3242</section><section><h3><code>process.setUncaughtExceptionCaptureCallback(fn)</code><span><a class="mark" href="#processsetuncaughtexceptioncapturecallbackfn" id="processsetuncaughtexceptioncapturecallbackfn">#</a></span><a aria-hidden="true" class="legacy" id="process_process_setuncaughtexceptioncapturecallback_fn"></a></h3> 3243<div class="api_metadata"> 3244<span>Added in: v9.3.0</span> 3245</div> 3246<ul> 3247<li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Null_type" class="type"><null></a></li> 3248</ul> 3249<p>The <code>process.setUncaughtExceptionCaptureCallback()</code> function sets a function 3250that will be invoked when an uncaught exception occurs, which will receive the 3251exception value itself as its first argument.</p> 3252<p>If such a function is set, the <a href="#event-uncaughtexception"><code>'uncaughtException'</code></a> event will 3253not be emitted. If <code>--abort-on-uncaught-exception</code> was passed from the 3254command line or set through <a href="v8.html#v8setflagsfromstringflags"><code>v8.setFlagsFromString()</code></a>, the process will 3255not abort. Actions configured to take place on exceptions such as report 3256generations will be affected too</p> 3257<p>To unset the capture function, 3258<code>process.setUncaughtExceptionCaptureCallback(null)</code> may be used. Calling this 3259method with a non-<code>null</code> argument while another capture function is set will 3260throw an error.</p> 3261<p>Using this function is mutually exclusive with using the deprecated 3262<a href="domain.html"><code>domain</code></a> built-in module.</p> 3263</section><section><h3><code>process.sourceMapsEnabled</code><span><a class="mark" href="#processsourcemapsenabled" id="processsourcemapsenabled">#</a></span><a aria-hidden="true" class="legacy" id="process_process_sourcemapsenabled"></a></h3> 3264<div class="api_metadata"> 3265<span>Added in: v18.19.0</span> 3266</div> 3267<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 3268<ul> 3269<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 3270</ul> 3271<p>The <code>process.sourceMapsEnabled</code> property returns whether the 3272<a href="https://sourcemaps.info/spec.html">Source Map v3</a> support for stack traces is enabled.</p> 3273</section><section><h3><code>process.stderr</code><span><a class="mark" href="#processstderr" id="processstderr">#</a></span><a aria-hidden="true" class="legacy" id="process_process_stderr"></a></h3> 3274<ul> 3275<li><a href="stream.html#stream" class="type"><Stream></a></li> 3276</ul> 3277<p>The <code>process.stderr</code> property returns a stream connected to 3278<code>stderr</code> (fd <code>2</code>). It is a <a href="net.html#class-netsocket"><code>net.Socket</code></a> (which is a <a href="stream.html#duplex-and-transform-streams">Duplex</a> 3279stream) unless fd <code>2</code> refers to a file, in which case it is 3280a <a href="stream.html#writable-streams">Writable</a> stream.</p> 3281<p><code>process.stderr</code> differs from other Node.js streams in important ways. See 3282<a href="#a-note-on-process-io">note on process I/O</a> for more information.</p> 3283<h4><code>process.stderr.fd</code><span><a class="mark" href="#processstderrfd" id="processstderrfd">#</a></span><a aria-hidden="true" class="legacy" id="process_process_stderr_fd"></a></h4> 3284<ul> 3285<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 3286</ul> 3287<p>This property refers to the value of underlying file descriptor of 3288<code>process.stderr</code>. The value is fixed at <code>2</code>. In <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads, 3289this field does not exist.</p> 3290</section><section><h3><code>process.stdin</code><span><a class="mark" href="#processstdin" id="processstdin">#</a></span><a aria-hidden="true" class="legacy" id="process_process_stdin"></a></h3> 3291<ul> 3292<li><a href="stream.html#stream" class="type"><Stream></a></li> 3293</ul> 3294<p>The <code>process.stdin</code> property returns a stream connected to 3295<code>stdin</code> (fd <code>0</code>). It is a <a href="net.html#class-netsocket"><code>net.Socket</code></a> (which is a <a href="stream.html#duplex-and-transform-streams">Duplex</a> 3296stream) unless fd <code>0</code> refers to a file, in which case it is 3297a <a href="stream.html#readable-streams">Readable</a> stream.</p> 3298<p>For details of how to read from <code>stdin</code> see <a href="stream.html#readablereadsize"><code>readable.read()</code></a>.</p> 3299<p>As a <a href="stream.html#duplex-and-transform-streams">Duplex</a> stream, <code>process.stdin</code> can also be used in "old" mode that 3300is compatible with scripts written for Node.js prior to v0.10. 3301For more information see <a href="stream.html#compatibility-with-older-nodejs-versions">Stream compatibility</a>.</p> 3302<p>In "old" streams mode the <code>stdin</code> stream is paused by default, so one 3303must call <code>process.stdin.resume()</code> to read from it. Note also that calling 3304<code>process.stdin.resume()</code> itself would switch stream to "old" mode.</p> 3305<h4><code>process.stdin.fd</code><span><a class="mark" href="#processstdinfd" id="processstdinfd">#</a></span><a aria-hidden="true" class="legacy" id="process_process_stdin_fd"></a></h4> 3306<ul> 3307<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 3308</ul> 3309<p>This property refers to the value of underlying file descriptor of 3310<code>process.stdin</code>. The value is fixed at <code>0</code>. In <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads, 3311this field does not exist.</p> 3312</section><section><h3><code>process.stdout</code><span><a class="mark" href="#processstdout" id="processstdout">#</a></span><a aria-hidden="true" class="legacy" id="process_process_stdout"></a></h3> 3313<ul> 3314<li><a href="stream.html#stream" class="type"><Stream></a></li> 3315</ul> 3316<p>The <code>process.stdout</code> property returns a stream connected to 3317<code>stdout</code> (fd <code>1</code>). It is a <a href="net.html#class-netsocket"><code>net.Socket</code></a> (which is a <a href="stream.html#duplex-and-transform-streams">Duplex</a> 3318stream) unless fd <code>1</code> refers to a file, in which case it is 3319a <a href="stream.html#writable-streams">Writable</a> stream.</p> 3320<p>For example, to copy <code>process.stdin</code> to <code>process.stdout</code>:</p> 3321 3322<pre class="with-50-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { stdin, stdout } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 3323 3324stdin.<span class="hljs-title function_">pipe</span>(stdout);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { stdin, stdout } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3325 3326stdin.<span class="hljs-title function_">pipe</span>(stdout);</code><button class="copy-button">copy</button></pre> 3327<p><code>process.stdout</code> differs from other Node.js streams in important ways. See 3328<a href="#a-note-on-process-io">note on process I/O</a> for more information.</p> 3329<h4><code>process.stdout.fd</code><span><a class="mark" href="#processstdoutfd" id="processstdoutfd">#</a></span><a aria-hidden="true" class="legacy" id="process_process_stdout_fd"></a></h4> 3330<ul> 3331<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 3332</ul> 3333<p>This property refers to the value of underlying file descriptor of 3334<code>process.stdout</code>. The value is fixed at <code>1</code>. In <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads, 3335this field does not exist.</p> 3336<h4>A note on process I/O<span><a class="mark" href="#a-note-on-process-io" id="a-note-on-process-io">#</a></span><a aria-hidden="true" class="legacy" id="process_a_note_on_process_i_o"></a></h4> 3337<p><code>process.stdout</code> and <code>process.stderr</code> differ from other Node.js streams in 3338important ways:</p> 3339<ol> 3340<li>They are used internally by <a href="console.html#consolelogdata-args"><code>console.log()</code></a> and <a href="console.html#consoleerrordata-args"><code>console.error()</code></a>, 3341respectively.</li> 3342<li>Writes may be synchronous depending on what the stream is connected to 3343and whether the system is Windows or POSIX: 3344<ul> 3345<li>Files: <em>synchronous</em> on Windows and POSIX</li> 3346<li>TTYs (Terminals): <em>asynchronous</em> on Windows, <em>synchronous</em> on POSIX</li> 3347<li>Pipes (and sockets): <em>synchronous</em> on Windows, <em>asynchronous</em> on POSIX</li> 3348</ul> 3349</li> 3350</ol> 3351<p>These behaviors are partly for historical reasons, as changing them would 3352create backward incompatibility, but they are also expected by some users.</p> 3353<p>Synchronous writes avoid problems such as output written with <code>console.log()</code> or 3354<code>console.error()</code> being unexpectedly interleaved, or not written at all if 3355<code>process.exit()</code> is called before an asynchronous write completes. See 3356<a href="#processexitcode"><code>process.exit()</code></a> for more information.</p> 3357<p><em><strong>Warning</strong></em>: Synchronous writes block the event loop until the write has 3358completed. This can be near instantaneous in the case of output to a file, but 3359under high system load, pipes that are not being read at the receiving end, or 3360with slow terminals or file systems, it's possible for the event loop to be 3361blocked often enough and long enough to have severe negative performance 3362impacts. This may not be a problem when writing to an interactive terminal 3363session, but consider this particularly careful when doing production logging to 3364the process output streams.</p> 3365<p>To check if a stream is connected to a <a href="tty.html#tty">TTY</a> context, check the <code>isTTY</code> 3366property.</p> 3367<p>For instance:</p> 3368<pre><code class="language-console"><span class="hljs-meta prompt_">$ </span><span class="language-bash">node -p <span class="hljs-string">"Boolean(process.stdin.isTTY)"</span></span> 3369true 3370<span class="hljs-meta prompt_">$ </span><span class="language-bash"><span class="hljs-built_in">echo</span> <span class="hljs-string">"foo"</span> | node -p <span class="hljs-string">"Boolean(process.stdin.isTTY)"</span></span> 3371false 3372<span class="hljs-meta prompt_">$ </span><span class="language-bash">node -p <span class="hljs-string">"Boolean(process.stdout.isTTY)"</span></span> 3373true 3374<span class="hljs-meta prompt_">$ </span><span class="language-bash">node -p <span class="hljs-string">"Boolean(process.stdout.isTTY)"</span> | <span class="hljs-built_in">cat</span></span> 3375false</code> <button class="copy-button">copy</button></pre> 3376<p>See the <a href="tty.html#tty">TTY</a> documentation for more information.</p> 3377</section><section><h3><code>process.throwDeprecation</code><span><a class="mark" href="#processthrowdeprecation" id="processthrowdeprecation">#</a></span><a aria-hidden="true" class="legacy" id="process_process_throwdeprecation"></a></h3> 3378<div class="api_metadata"> 3379<span>Added in: v0.9.12</span> 3380</div> 3381<ul> 3382<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 3383</ul> 3384<p>The initial value of <code>process.throwDeprecation</code> indicates whether the 3385<code>--throw-deprecation</code> flag is set on the current Node.js process. 3386<code>process.throwDeprecation</code> is mutable, so whether or not deprecation 3387warnings result in errors may be altered at runtime. See the 3388documentation for the <a href="#event-warning"><code>'warning'</code> event</a> and the 3389<a href="#processemitwarningwarning-type-code-ctor"><code>emitWarning()</code> method</a> for more information.</p> 3390<pre><code class="language-console"><span class="hljs-meta prompt_">$ </span><span class="language-bash">node --throw-deprecation -p <span class="hljs-string">"process.throwDeprecation"</span></span> 3391true 3392<span class="hljs-meta prompt_">$ </span><span class="language-bash">node -p <span class="hljs-string">"process.throwDeprecation"</span></span> 3393undefined 3394<span class="hljs-meta prompt_">$ </span><span class="language-bash">node</span> 3395<span class="hljs-meta prompt_">> </span><span class="language-bash">process.emitWarning(<span class="hljs-string">'test'</span>, <span class="hljs-string">'DeprecationWarning'</span>);</span> 3396undefined 3397<span class="hljs-meta prompt_">> </span><span class="language-bash">(node:26598) DeprecationWarning: <span class="hljs-built_in">test</span></span> 3398<span class="hljs-meta prompt_">> </span><span class="language-bash">process.throwDeprecation = <span class="hljs-literal">true</span>;</span> 3399true 3400<span class="hljs-meta prompt_">> </span><span class="language-bash">process.emitWarning(<span class="hljs-string">'test'</span>, <span class="hljs-string">'DeprecationWarning'</span>);</span> 3401Thrown: 3402[DeprecationWarning: test] { name: 'DeprecationWarning' }</code> <button class="copy-button">copy</button></pre> 3403</section><section><h3><code>process.title</code><span><a class="mark" href="#processtitle" id="processtitle">#</a></span><a aria-hidden="true" class="legacy" id="process_process_title"></a></h3> 3404<div class="api_metadata"> 3405<span>Added in: v0.1.104</span> 3406</div> 3407<ul> 3408<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 3409</ul> 3410<p>The <code>process.title</code> property returns the current process title (i.e. returns 3411the current value of <code>ps</code>). Assigning a new value to <code>process.title</code> modifies 3412the current value of <code>ps</code>.</p> 3413<p>When a new value is assigned, different platforms will impose different maximum 3414length restrictions on the title. Usually such restrictions are quite limited. 3415For instance, on Linux and macOS, <code>process.title</code> is limited to the size of the 3416binary name plus the length of the command-line arguments because setting the 3417<code>process.title</code> overwrites the <code>argv</code> memory of the process. Node.js v0.8 3418allowed for longer process title strings by also overwriting the <code>environ</code> 3419memory but that was potentially insecure and confusing in some (rather obscure) 3420cases.</p> 3421<p>Assigning a value to <code>process.title</code> might not result in an accurate label 3422within process manager applications such as macOS Activity Monitor or Windows 3423Services Manager.</p> 3424</section><section><h3><code>process.traceDeprecation</code><span><a class="mark" href="#processtracedeprecation" id="processtracedeprecation">#</a></span><a aria-hidden="true" class="legacy" id="process_process_tracedeprecation"></a></h3> 3425<div class="api_metadata"> 3426<span>Added in: v0.8.0</span> 3427</div> 3428<ul> 3429<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 3430</ul> 3431<p>The <code>process.traceDeprecation</code> property indicates whether the 3432<code>--trace-deprecation</code> flag is set on the current Node.js process. See the 3433documentation for the <a href="#event-warning"><code>'warning'</code> event</a> and the 3434<a href="#processemitwarningwarning-type-code-ctor"><code>emitWarning()</code> method</a> for more information about this 3435flag's behavior.</p> 3436</section><section><h3><code>process.umask()</code><span><a class="mark" href="#processumask" id="processumask">#</a></span><a aria-hidden="true" class="legacy" id="process_process_umask"></a></h3> 3437<div class="api_metadata"> 3438<details class="changelog"><summary>History</summary> 3439<table> 3440<tbody><tr><th>Version</th><th>Changes</th></tr> 3441<tr><td>v14.0.0, v12.19.0</td> 3442<td><p>Calling <code>process.umask()</code> with no arguments is deprecated.</p></td></tr> 3443<tr><td>v0.1.19</td> 3444<td><p><span>Added in: v0.1.19</span></p></td></tr> 3445</tbody></table> 3446</details> 3447</div> 3448<p></p><div class="api_stability api_stability_0"><a href="documentation.html#stability-index">Stability: 0</a> - Deprecated. Calling <code>process.umask()</code> with no argument causes 3449the process-wide umask to be written twice. This introduces a race condition 3450between threads, and is a potential security vulnerability. There is no safe, 3451cross-platform alternative API.</div><p></p> 3452<p><code>process.umask()</code> returns the Node.js process's file mode creation mask. Child 3453processes inherit the mask from the parent process.</p> 3454</section><section><h3><code>process.umask(mask)</code><span><a class="mark" href="#processumaskmask" id="processumaskmask">#</a></span><a aria-hidden="true" class="legacy" id="process_process_umask_mask"></a></h3> 3455<div class="api_metadata"> 3456<span>Added in: v0.1.19</span> 3457</div> 3458<ul> 3459<li><code>mask</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></li> 3460</ul> 3461<p><code>process.umask(mask)</code> sets the Node.js process's file mode creation mask. Child 3462processes inherit the mask from the parent process. Returns the previous mask.</p> 3463 3464<pre class="with-42-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { umask } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 3465 3466<span class="hljs-keyword">const</span> newmask = <span class="hljs-number">0o022</span>; 3467<span class="hljs-keyword">const</span> oldmask = <span class="hljs-title function_">umask</span>(newmask); 3468<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>( 3469 <span class="hljs-string">`Changed umask from <span class="hljs-subst">${oldmask.toString(<span class="hljs-number">8</span>)}</span> to <span class="hljs-subst">${newmask.toString(<span class="hljs-number">8</span>)}</span>`</span>, 3470);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { umask } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3471 3472<span class="hljs-keyword">const</span> newmask = <span class="hljs-number">0o022</span>; 3473<span class="hljs-keyword">const</span> oldmask = <span class="hljs-title function_">umask</span>(newmask); 3474<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>( 3475 <span class="hljs-string">`Changed umask from <span class="hljs-subst">${oldmask.toString(<span class="hljs-number">8</span>)}</span> to <span class="hljs-subst">${newmask.toString(<span class="hljs-number">8</span>)}</span>`</span>, 3476);</code><button class="copy-button">copy</button></pre> 3477<p>In <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads, <code>process.umask(mask)</code> will throw an exception.</p> 3478</section><section><h3><code>process.uptime()</code><span><a class="mark" href="#processuptime" id="processuptime">#</a></span><a aria-hidden="true" class="legacy" id="process_process_uptime"></a></h3> 3479<div class="api_metadata"> 3480<span>Added in: v0.5.0</span> 3481</div> 3482<ul> 3483<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 3484</ul> 3485<p>The <code>process.uptime()</code> method returns the number of seconds the current Node.js 3486process has been running.</p> 3487<p>The return value includes fractions of a second. Use <code>Math.floor()</code> to get whole 3488seconds.</p> 3489</section><section><h3><code>process.version</code><span><a class="mark" href="#processversion" id="processversion">#</a></span><a aria-hidden="true" class="legacy" id="process_process_version"></a></h3> 3490<div class="api_metadata"> 3491<span>Added in: v0.1.3</span> 3492</div> 3493<ul> 3494<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 3495</ul> 3496<p>The <code>process.version</code> property contains the Node.js version string.</p> 3497 3498<pre class="with-44-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { version } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 3499 3500<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Version: <span class="hljs-subst">${version}</span>`</span>); 3501<span class="hljs-comment">// Version: v14.8.0</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { version } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3502 3503<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Version: <span class="hljs-subst">${version}</span>`</span>); 3504<span class="hljs-comment">// Version: v14.8.0</span></code><button class="copy-button">copy</button></pre> 3505<p>To get the version string without the prepended <em>v</em>, use 3506<code>process.versions.node</code>.</p> 3507</section><section><h3><code>process.versions</code><span><a class="mark" href="#processversions" id="processversions">#</a></span><a aria-hidden="true" class="legacy" id="process_process_versions"></a></h3> 3508<div class="api_metadata"> 3509<details class="changelog"><summary>History</summary> 3510<table> 3511<tbody><tr><th>Version</th><th>Changes</th></tr> 3512<tr><td>v9.0.0</td> 3513<td><p>The <code>v8</code> property now includes a Node.js specific suffix.</p></td></tr> 3514<tr><td>v4.2.0</td> 3515<td><p>The <code>icu</code> property is now supported.</p></td></tr> 3516<tr><td>v0.2.0</td> 3517<td><p><span>Added in: v0.2.0</span></p></td></tr> 3518</tbody></table> 3519</details> 3520</div> 3521<ul> 3522<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 3523</ul> 3524<p>The <code>process.versions</code> property returns an object listing the version strings of 3525Node.js and its dependencies. <code>process.versions.modules</code> indicates the current 3526ABI version, which is increased whenever a C++ API changes. Node.js will refuse 3527to load modules that were compiled against a different module ABI version.</p> 3528 3529<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { versions } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 3530 3531<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(versions);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { versions } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3532 3533<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(versions);</code><button class="copy-button">copy</button></pre> 3534<p>Will generate an object similar to:</p> 3535<pre><code class="language-console">{ node: '11.13.0', 3536 v8: '7.0.276.38-node.18', 3537 uv: '1.27.0', 3538 zlib: '1.2.11', 3539 brotli: '1.0.7', 3540 ares: '1.15.0', 3541 modules: '67', 3542 nghttp2: '1.34.0', 3543 napi: '4', 3544 llhttp: '1.1.1', 3545 openssl: '1.1.1b', 3546 cldr: '34.0', 3547 icu: '63.1', 3548 tz: '2018e', 3549 unicode: '11.0' }</code> <button class="copy-button">copy</button></pre> 3550</section><section><h3>Exit codes<span><a class="mark" href="#exit-codes" id="exit-codes">#</a></span><a aria-hidden="true" class="legacy" id="process_exit_codes"></a></h3> 3551<p>Node.js will normally exit with a <code>0</code> status code when no more async 3552operations are pending. The following status codes are used in other 3553cases:</p> 3554<ul> 3555<li><code>1</code> <strong>Uncaught Fatal Exception</strong>: There was an uncaught exception, 3556and it was not handled by a domain or an <a href="#event-uncaughtexception"><code>'uncaughtException'</code></a> event 3557handler.</li> 3558<li><code>2</code>: Unused (reserved by Bash for builtin misuse)</li> 3559<li><code>3</code> <strong>Internal JavaScript Parse Error</strong>: The JavaScript source code 3560internal in the Node.js bootstrapping process caused a parse error. This 3561is extremely rare, and generally can only happen during development 3562of Node.js itself.</li> 3563<li><code>4</code> <strong>Internal JavaScript Evaluation Failure</strong>: The JavaScript 3564source code internal in the Node.js bootstrapping process failed to 3565return a function value when evaluated. This is extremely rare, and 3566generally can only happen during development of Node.js itself.</li> 3567<li><code>5</code> <strong>Fatal Error</strong>: There was a fatal unrecoverable error in V8. 3568Typically a message will be printed to stderr with the prefix <code>FATAL ERROR</code>.</li> 3569<li><code>6</code> <strong>Non-function Internal Exception Handler</strong>: There was an 3570uncaught exception, but the internal fatal exception handler 3571function was somehow set to a non-function, and could not be called.</li> 3572<li><code>7</code> <strong>Internal Exception Handler Run-Time Failure</strong>: There was an 3573uncaught exception, and the internal fatal exception handler 3574function itself threw an error while attempting to handle it. This 3575can happen, for example, if an <a href="#event-uncaughtexception"><code>'uncaughtException'</code></a> or 3576<code>domain.on('error')</code> handler throws an error.</li> 3577<li><code>8</code>: Unused. In previous versions of Node.js, exit code 8 sometimes 3578indicated an uncaught exception.</li> 3579<li><code>9</code> <strong>Invalid Argument</strong>: Either an unknown option was specified, 3580or an option requiring a value was provided without a value.</li> 3581<li><code>10</code> <strong>Internal JavaScript Run-Time Failure</strong>: The JavaScript 3582source code internal in the Node.js bootstrapping process threw an error 3583when the bootstrapping function was called. This is extremely rare, 3584and generally can only happen during development of Node.js itself.</li> 3585<li><code>12</code> <strong>Invalid Debug Argument</strong>: The <code>--inspect</code> and/or <code>--inspect-brk</code> 3586options were set, but the port number chosen was invalid or unavailable.</li> 3587<li><code>13</code> <strong>Unfinished Top-Level Await</strong>: <code>await</code> was used outside of a function 3588in the top-level code, but the passed <code>Promise</code> never resolved.</li> 3589<li><code>14</code> <strong>Snapshot Failure</strong>: Node.js was started to build a V8 startup 3590snapshot and it failed because certain requirements of the state of 3591the application were not met.</li> 3592<li><code>>128</code> <strong>Signal Exits</strong>: If Node.js receives a fatal signal such as 3593<code>SIGKILL</code> or <code>SIGHUP</code>, then its exit code will be <code>128</code> plus the 3594value of the signal code. This is a standard POSIX practice, since 3595exit codes are defined to be 7-bit integers, and signal exits set 3596the high-order bit, and then contain the value of the signal code. 3597For example, signal <code>SIGABRT</code> has value <code>6</code>, so the expected exit 3598code will be <code>128</code> + <code>6</code>, or <code>134</code>.</li> 3599</ul></section> 3600 <!-- API END --> 3601 </div> 3602 </div> 3603 </div> 3604</body> 3605</html> 3606