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id="gtoc"> 113 <ul> 114 <li class="pinned-header">Node.js v18.18.2</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><a href="#processstderr"><code>process.stderr</code></a> 228<ul> 229<li><a href="#processstderrfd"><code>process.stderr.fd</code></a></li> 230</ul> 231</li> 232<li><a href="#processstdin"><code>process.stdin</code></a> 233<ul> 234<li><a href="#processstdinfd"><code>process.stdin.fd</code></a></li> 235</ul> 236</li> 237<li><a href="#processstdout"><code>process.stdout</code></a> 238<ul> 239<li><a href="#processstdoutfd"><code>process.stdout.fd</code></a></li> 240<li><a href="#a-note-on-process-io">A note on process I/O</a></li> 241</ul> 242</li> 243<li><a href="#processthrowdeprecation"><code>process.throwDeprecation</code></a></li> 244<li><a href="#processtitle"><code>process.title</code></a></li> 245<li><a href="#processtracedeprecation"><code>process.traceDeprecation</code></a></li> 246<li><span class="stability_0"><a href="#processumask"><code>process.umask()</code></a></span></li> 247<li><a href="#processumaskmask"><code>process.umask(mask)</code></a></li> 248<li><a href="#processuptime"><code>process.uptime()</code></a></li> 249<li><a href="#processversion"><code>process.version</code></a></li> 250<li><a href="#processversions"><code>process.versions</code></a></li> 251<li><a href="#exit-codes">Exit codes</a></li> 252</ul> 253</li> 254</ul></div></div> 255 </li> 256 257 258 <li class="picker-header"> 259 <a href="#"> 260 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 261 Index 262 </a> 263 264 <div class="picker"><ul> 265<li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> 266<li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> 267 268 <li> 269 <a href="index.html">Index</a> 270 </li> 271 </ul> 272 273<hr class="line"> 274<ul> 275<li><a href="assert.html" class="nav-assert">Assertion testing</a></li> 276<li><a href="async_context.html" class="nav-async_context">Asynchronous context tracking</a></li> 277<li><a href="async_hooks.html" class="nav-async_hooks">Async hooks</a></li> 278<li><a href="buffer.html" class="nav-buffer">Buffer</a></li> 279<li><a href="addons.html" class="nav-addons">C++ 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runner</a></li> 321<li><a href="timers.html" class="nav-timers">Timers</a></li> 322<li><a href="tls.html" class="nav-tls">TLS/SSL</a></li> 323<li><a href="tracing.html" class="nav-tracing">Trace events</a></li> 324<li><a href="tty.html" class="nav-tty">TTY</a></li> 325<li><a href="dgram.html" class="nav-dgram">UDP/datagram</a></li> 326<li><a href="url.html" class="nav-url">URL</a></li> 327<li><a href="util.html" class="nav-util">Utilities</a></li> 328<li><a href="v8.html" class="nav-v8">V8</a></li> 329<li><a href="vm.html" class="nav-vm">VM</a></li> 330<li><a href="wasi.html" class="nav-wasi">WASI</a></li> 331<li><a href="webcrypto.html" class="nav-webcrypto">Web Crypto API</a></li> 332<li><a href="webstreams.html" class="nav-webstreams">Web Streams API</a></li> 333<li><a href="worker_threads.html" class="nav-worker_threads">Worker threads</a></li> 334<li><a href="zlib.html" class="nav-zlib">Zlib</a></li> 335</ul> 336<hr class="line"> 337<ul> 338<li><a href="https://github.com/nodejs/node" class="nav-https-github-com-nodejs-node">Code repository and issue tracker</a></li> 339</ul></div> 340 </li> 341 342 343 <li class="picker-header"> 344 <a href="#"> 345 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 346 Other versions 347 </a> 348 <div class="picker"><ol id="alt-docs"><li><a href="https://nodejs.org/docs/latest-v20.x/api/process.html">20.x</a></li> 349<li><a href="https://nodejs.org/docs/latest-v19.x/api/process.html">19.x</a></li> 350<li><a href="https://nodejs.org/docs/latest-v18.x/api/process.html">18.x <b>LTS</b></a></li> 351<li><a href="https://nodejs.org/docs/latest-v17.x/api/process.html">17.x</a></li> 352<li><a href="https://nodejs.org/docs/latest-v16.x/api/process.html">16.x</a></li> 353<li><a href="https://nodejs.org/docs/latest-v15.x/api/process.html">15.x</a></li> 354<li><a href="https://nodejs.org/docs/latest-v14.x/api/process.html">14.x</a></li> 355<li><a href="https://nodejs.org/docs/latest-v13.x/api/process.html">13.x</a></li> 356<li><a href="https://nodejs.org/docs/latest-v12.x/api/process.html">12.x</a></li> 357<li><a href="https://nodejs.org/docs/latest-v11.x/api/process.html">11.x</a></li> 358<li><a href="https://nodejs.org/docs/latest-v10.x/api/process.html">10.x</a></li> 359<li><a href="https://nodejs.org/docs/latest-v9.x/api/process.html">9.x</a></li> 360<li><a href="https://nodejs.org/docs/latest-v8.x/api/process.html">8.x</a></li> 361<li><a href="https://nodejs.org/docs/latest-v7.x/api/process.html">7.x</a></li> 362<li><a href="https://nodejs.org/docs/latest-v6.x/api/process.html">6.x</a></li> 363<li><a href="https://nodejs.org/docs/latest-v5.x/api/process.html">5.x</a></li> 364<li><a href="https://nodejs.org/docs/latest-v4.x/api/process.html">4.x</a></li> 365<li><a href="https://nodejs.org/docs/latest-v0.12.x/api/process.html">0.12.x</a></li> 366<li><a href="https://nodejs.org/docs/latest-v0.10.x/api/process.html">0.10.x</a></li></ol></div> 367 </li> 368 369 <li class="picker-header"> 370 <a href="#"> 371 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 372 Options 373 </a> 374 375 <div class="picker"> 376 <ul> 377 <li> 378 <a href="all.html">View on single page</a> 379 </li> 380 <li> 381 <a href="process.json">View as JSON</a> 382 </li> 383 <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/main/doc/api/process.md">Edit on GitHub</a></li> 384 </ul> 385 </div> 386 </li> 387 </ul> 388 </div> 389 <hr> 390 </header> 391 392 <details id="toc" open><summary>Table of contents</summary><ul> 393<li><a href="#process">Process</a> 394<ul> 395<li><a href="#process-events">Process events</a> 396<ul> 397<li><a href="#event-beforeexit">Event: <code>'beforeExit'</code></a></li> 398<li><a href="#event-disconnect">Event: <code>'disconnect'</code></a></li> 399<li><a href="#event-exit">Event: <code>'exit'</code></a></li> 400<li><a href="#event-message">Event: <code>'message'</code></a></li> 401<li><span class="stability_0"><a href="#event-multipleresolves">Event: <code>'multipleResolves'</code></a></span></li> 402<li><a href="#event-rejectionhandled">Event: <code>'rejectionHandled'</code></a></li> 403<li><a href="#event-uncaughtexception">Event: <code>'uncaughtException'</code></a> 404<ul> 405<li><a href="#warning-using-uncaughtexception-correctly">Warning: Using <code>'uncaughtException'</code> correctly</a></li> 406</ul> 407</li> 408<li><a href="#event-uncaughtexceptionmonitor">Event: <code>'uncaughtExceptionMonitor'</code></a></li> 409<li><a href="#event-unhandledrejection">Event: <code>'unhandledRejection'</code></a></li> 410<li><a href="#event-warning">Event: <code>'warning'</code></a></li> 411<li><a href="#event-worker">Event: <code>'worker'</code></a> 412<ul> 413<li><a href="#emitting-custom-warnings">Emitting custom warnings</a></li> 414<li><a href="#nodejs-warning-names">Node.js warning names</a></li> 415</ul> 416</li> 417<li><a href="#signal-events">Signal events</a></li> 418</ul> 419</li> 420<li><a href="#processabort"><code>process.abort()</code></a></li> 421<li><a href="#processallowednodeenvironmentflags"><code>process.allowedNodeEnvironmentFlags</code></a></li> 422<li><a href="#processarch"><code>process.arch</code></a></li> 423<li><a href="#processargv"><code>process.argv</code></a></li> 424<li><a href="#processargv0"><code>process.argv0</code></a></li> 425<li><a href="#processchannel"><code>process.channel</code></a> 426<ul> 427<li><a href="#processchannelref"><code>process.channel.ref()</code></a></li> 428<li><a href="#processchannelunref"><code>process.channel.unref()</code></a></li> 429</ul> 430</li> 431<li><a href="#processchdirdirectory"><code>process.chdir(directory)</code></a></li> 432<li><a href="#processconfig"><code>process.config</code></a></li> 433<li><a href="#processconnected"><code>process.connected</code></a></li> 434<li><span class="stability_1"><a href="#processconstrainedmemory"><code>process.constrainedMemory()</code></a></span></li> 435<li><a href="#processcpuusagepreviousvalue"><code>process.cpuUsage([previousValue])</code></a></li> 436<li><a href="#processcwd"><code>process.cwd()</code></a></li> 437<li><a href="#processdebugport"><code>process.debugPort</code></a></li> 438<li><a href="#processdisconnect"><code>process.disconnect()</code></a></li> 439<li><a href="#processdlopenmodule-filename-flags"><code>process.dlopen(module, filename[, flags])</code></a></li> 440<li><a href="#processemitwarningwarning-options"><code>process.emitWarning(warning[, options])</code></a></li> 441<li><a href="#processemitwarningwarning-type-code-ctor"><code>process.emitWarning(warning[, type[, code]][, ctor])</code></a> 442<ul> 443<li><a href="#avoiding-duplicate-warnings">Avoiding duplicate warnings</a></li> 444</ul> 445</li> 446<li><a href="#processenv"><code>process.env</code></a></li> 447<li><a href="#processexecargv"><code>process.execArgv</code></a></li> 448<li><a href="#processexecpath"><code>process.execPath</code></a></li> 449<li><a href="#processexitcode"><code>process.exit([code])</code></a></li> 450<li><a href="#processexitcode_1"><code>process.exitCode</code></a></li> 451<li><span class="stability_1"><a href="#processgetactiveresourcesinfo"><code>process.getActiveResourcesInfo()</code></a></span></li> 452<li><a href="#processgetegid"><code>process.getegid()</code></a></li> 453<li><a href="#processgeteuid"><code>process.geteuid()</code></a></li> 454<li><a href="#processgetgid"><code>process.getgid()</code></a></li> 455<li><a href="#processgetgroups"><code>process.getgroups()</code></a></li> 456<li><a href="#processgetuid"><code>process.getuid()</code></a></li> 457<li><a href="#processhasuncaughtexceptioncapturecallback"><code>process.hasUncaughtExceptionCaptureCallback()</code></a></li> 458<li><span class="stability_3"><a href="#processhrtimetime"><code>process.hrtime([time])</code></a></span></li> 459<li><a href="#processhrtimebigint"><code>process.hrtime.bigint()</code></a></li> 460<li><a href="#processinitgroupsuser-extragroup"><code>process.initgroups(user, extraGroup)</code></a></li> 461<li><a href="#processkillpid-signal"><code>process.kill(pid[, signal])</code></a></li> 462<li><span class="stability_0"><a href="#processmainmodule"><code>process.mainModule</code></a></span></li> 463<li><a href="#processmemoryusage"><code>process.memoryUsage()</code></a></li> 464<li><a href="#processmemoryusagerss"><code>process.memoryUsage.rss()</code></a></li> 465<li><a href="#processnexttickcallback-args"><code>process.nextTick(callback[, ...args])</code></a> 466<ul> 467<li><a href="#when-to-use-queuemicrotask-vs-processnexttick">When to use <code>queueMicrotask()</code> vs. <code>process.nextTick()</code></a></li> 468</ul> 469</li> 470<li><a href="#processnodeprecation"><code>process.noDeprecation</code></a></li> 471<li><a href="#processpid"><code>process.pid</code></a></li> 472<li><a href="#processplatform"><code>process.platform</code></a></li> 473<li><a href="#processppid"><code>process.ppid</code></a></li> 474<li><a href="#processrelease"><code>process.release</code></a></li> 475<li><a href="#processreport"><code>process.report</code></a> 476<ul> 477<li><a href="#processreportcompact"><code>process.report.compact</code></a></li> 478<li><a href="#processreportdirectory"><code>process.report.directory</code></a></li> 479<li><a href="#processreportfilename"><code>process.report.filename</code></a></li> 480<li><a href="#processreportgetreporterr"><code>process.report.getReport([err])</code></a></li> 481<li><a href="#processreportreportonfatalerror"><code>process.report.reportOnFatalError</code></a></li> 482<li><a href="#processreportreportonsignal"><code>process.report.reportOnSignal</code></a></li> 483<li><a href="#processreportreportonuncaughtexception"><code>process.report.reportOnUncaughtException</code></a></li> 484<li><a href="#processreportsignal"><code>process.report.signal</code></a></li> 485<li><a href="#processreportwritereportfilename-err"><code>process.report.writeReport([filename][, err])</code></a></li> 486</ul> 487</li> 488<li><a href="#processresourceusage"><code>process.resourceUsage()</code></a></li> 489<li><a href="#processsendmessage-sendhandle-options-callback"><code>process.send(message[, sendHandle[, options]][, callback])</code></a></li> 490<li><a href="#processsetegidid"><code>process.setegid(id)</code></a></li> 491<li><a href="#processseteuidid"><code>process.seteuid(id)</code></a></li> 492<li><a href="#processsetgidid"><code>process.setgid(id)</code></a></li> 493<li><a href="#processsetgroupsgroups"><code>process.setgroups(groups)</code></a></li> 494<li><a href="#processsetuidid"><code>process.setuid(id)</code></a></li> 495<li><span class="stability_1"><a href="#processsetsourcemapsenabledval"><code>process.setSourceMapsEnabled(val)</code></a></span></li> 496<li><a href="#processsetuncaughtexceptioncapturecallbackfn"><code>process.setUncaughtExceptionCaptureCallback(fn)</code></a></li> 497<li><a href="#processstderr"><code>process.stderr</code></a> 498<ul> 499<li><a href="#processstderrfd"><code>process.stderr.fd</code></a></li> 500</ul> 501</li> 502<li><a href="#processstdin"><code>process.stdin</code></a> 503<ul> 504<li><a href="#processstdinfd"><code>process.stdin.fd</code></a></li> 505</ul> 506</li> 507<li><a href="#processstdout"><code>process.stdout</code></a> 508<ul> 509<li><a href="#processstdoutfd"><code>process.stdout.fd</code></a></li> 510<li><a href="#a-note-on-process-io">A note on process I/O</a></li> 511</ul> 512</li> 513<li><a href="#processthrowdeprecation"><code>process.throwDeprecation</code></a></li> 514<li><a href="#processtitle"><code>process.title</code></a></li> 515<li><a href="#processtracedeprecation"><code>process.traceDeprecation</code></a></li> 516<li><span class="stability_0"><a href="#processumask"><code>process.umask()</code></a></span></li> 517<li><a href="#processumaskmask"><code>process.umask(mask)</code></a></li> 518<li><a href="#processuptime"><code>process.uptime()</code></a></li> 519<li><a href="#processversion"><code>process.version</code></a></li> 520<li><a href="#processversions"><code>process.versions</code></a></li> 521<li><a href="#exit-codes">Exit codes</a></li> 522</ul> 523</li> 524</ul></details> 525 526 <div id="apicontent"> 527 <h2>Process<span><a class="mark" href="#process" id="process">#</a></span><a aria-hidden="true" class="legacy" id="process_process"></a></h2> 528 529 530<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v18.18.2/lib/process.js">lib/process.js</a></p> 531<p>The <code>process</code> object provides information about, and control over, the current 532Node.js process.</p> 533 534<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> 535<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> 536<p>The <code>process</code> object is an instance of <a href="events.html#class-eventemitter"><code>EventEmitter</code></a>.</p> 537<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> 538<div class="api_metadata"> 539<span>Added in: v0.11.12</span> 540</div> 541<p>The <code>'beforeExit'</code> event is emitted when Node.js empties its event loop and has 542no additional work to schedule. Normally, the Node.js process will exit when 543there is no work scheduled, but a listener registered on the <code>'beforeExit'</code> 544event can make asynchronous calls, and thereby cause the Node.js process to 545continue.</p> 546<p>The listener callback function is invoked with the value of 547<a href="#processexitcode_1"><code>process.exitCode</code></a> passed as the only argument.</p> 548<p>The <code>'beforeExit'</code> event is <em>not</em> emitted for conditions causing explicit 549termination, such as calling <a href="#processexitcode"><code>process.exit()</code></a> or uncaught exceptions.</p> 550<p>The <code>'beforeExit'</code> should <em>not</em> be used as an alternative to the <code>'exit'</code> event 551unless the intention is to schedule additional work.</p> 552 553<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>; 554 555process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'beforeExit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 556 <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); 557}); 558 559process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'exit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 560 <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); 561}); 562 563<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'This message is displayed first.'</span>); 564 565<span class="hljs-comment">// Prints:</span> 566<span class="hljs-comment">// This message is displayed first.</span> 567<span class="hljs-comment">// Process beforeExit event with code: 0</span> 568<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>); 569 570process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'beforeExit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 571 <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); 572}); 573 574process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'exit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 575 <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); 576}); 577 578<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'This message is displayed first.'</span>); 579 580<span class="hljs-comment">// Prints:</span> 581<span class="hljs-comment">// This message is displayed first.</span> 582<span class="hljs-comment">// Process beforeExit event with code: 0</span> 583<span class="hljs-comment">// Process exit event with code: 0</span></code><button class="copy-button">copy</button></pre> 584<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> 585<div class="api_metadata"> 586<span>Added in: v0.7.7</span> 587</div> 588<p>If the Node.js process is spawned with an IPC channel (see the <a href="child_process.html">Child Process</a> 589and <a href="cluster.html">Cluster</a> documentation), the <code>'disconnect'</code> event will be emitted when 590the IPC channel is closed.</p> 591<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> 592<div class="api_metadata"> 593<span>Added in: v0.1.7</span> 594</div> 595<ul> 596<li><code>code</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 597</ul> 598<p>The <code>'exit'</code> event is emitted when the Node.js process is about to exit as a 599result of either:</p> 600<ul> 601<li>The <code>process.exit()</code> method being called explicitly;</li> 602<li>The Node.js event loop no longer having any additional work to perform.</li> 603</ul> 604<p>There is no way to prevent the exiting of the event loop at this point, and once 605all <code>'exit'</code> listeners have finished running the Node.js process will terminate.</p> 606<p>The listener callback function is invoked with the exit code specified either 607by the <a href="#processexitcode_1"><code>process.exitCode</code></a> property, or the <code>exitCode</code> argument passed to the 608<a href="#processexitcode"><code>process.exit()</code></a> method.</p> 609 610<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>; 611 612process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'exit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 613 <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">${code}</span>`</span>); 614});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 615 616process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'exit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 617 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`About to exit with code: <span class="hljs-subst">${code}</span>`</span>); 618});</code><button class="copy-button">copy</button></pre> 619<p>Listener functions <strong>must</strong> only perform <strong>synchronous</strong> operations. The Node.js 620process will exit immediately after calling the <code>'exit'</code> event listeners 621causing any additional work still queued in the event loop to be abandoned. 622In the following example, for instance, the timeout will never occur:</p> 623 624<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>; 625 626process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'exit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 627 <span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 628 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'This will not run'</span>); 629 }, <span class="hljs-number">0</span>); 630});</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>); 631 632process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'exit'</span>, <span class="hljs-function">(<span class="hljs-params">code</span>) =></span> { 633 <span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 634 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'This will not run'</span>); 635 }, <span class="hljs-number">0</span>); 636});</code><button class="copy-button">copy</button></pre> 637<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> 638<div class="api_metadata"> 639<span>Added in: v0.5.10</span> 640</div> 641<ul> 642<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 643or a serializable primitive value.</li> 644<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> 645object, or undefined.</li> 646</ul> 647<p>If the Node.js process is spawned with an IPC channel (see the <a href="child_process.html">Child Process</a> 648and <a href="cluster.html">Cluster</a> documentation), the <code>'message'</code> event is emitted whenever a 649message sent by a parent process using <a href="child_process.html#subprocesssendmessage-sendhandle-options-callback"><code>childprocess.send()</code></a> is received by 650the child process.</p> 651<p>The message goes through serialization and parsing. The resulting message might 652not be the same as what is originally sent.</p> 653<p>If the <code>serialization</code> option was set to <code>advanced</code> used when spawning the 654process, the <code>message</code> argument can contain data that JSON is not able 655to represent. 656See <a href="child_process.html#advanced-serialization">Advanced serialization for <code>child_process</code></a> for more details.</p> 657<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> 658<div class="api_metadata"> 659<span>Added in: v10.12.0</span><span>Deprecated since: v17.6.0</span> 660</div> 661<p></p><div class="api_stability api_stability_0"><a href="documentation.html#stability-index">Stability: 0</a> - Deprecated</div><p></p> 662<ul> 663<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> 664<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> 665<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 666rejected after the original resolve.</li> 667</ul> 668<p>The <code>'multipleResolves'</code> event is emitted whenever a <code>Promise</code> has been either:</p> 669<ul> 670<li>Resolved more than once.</li> 671<li>Rejected more than once.</li> 672<li>Rejected after resolve.</li> 673<li>Resolved after reject.</li> 674</ul> 675<p>This is useful for tracking potential errors in an application while using the 676<code>Promise</code> constructor, as multiple resolutions are silently swallowed. However, 677the occurrence of this event does not necessarily indicate an error. For 678example, <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> 679<p>Because of the unreliability of the event in cases like the 680<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> 681 682<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>; 683 684process.<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> { 685 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(type, promise, reason); 686 <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>)); 687}); 688 689<span class="hljs-keyword">async</span> <span class="hljs-keyword">function</span> <span class="hljs-title function_">main</span>(<span class="hljs-params"></span>) { 690 <span class="hljs-keyword">try</span> { 691 <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> { 692 <span class="hljs-title function_">resolve</span>(<span class="hljs-string">'First call'</span>); 693 <span class="hljs-title function_">resolve</span>(<span class="hljs-string">'Swallowed resolve'</span>); 694 <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>)); 695 }); 696 } <span class="hljs-keyword">catch</span> { 697 <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>); 698 } 699} 700 701<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>); 702<span class="hljs-comment">// resolve: Promise { 'First call' } 'Swallowed resolve'</span> 703<span class="hljs-comment">// reject: Promise { 'First call' } Error: Swallowed reject</span> 704<span class="hljs-comment">// at Promise (*)</span> 705<span class="hljs-comment">// at new Promise (<anonymous>)</span> 706<span class="hljs-comment">// at main (*)</span> 707<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>); 708 709process.<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> { 710 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(type, promise, reason); 711 <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>)); 712}); 713 714<span class="hljs-keyword">async</span> <span class="hljs-keyword">function</span> <span class="hljs-title function_">main</span>(<span class="hljs-params"></span>) { 715 <span class="hljs-keyword">try</span> { 716 <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> { 717 <span class="hljs-title function_">resolve</span>(<span class="hljs-string">'First call'</span>); 718 <span class="hljs-title function_">resolve</span>(<span class="hljs-string">'Swallowed resolve'</span>); 719 <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>)); 720 }); 721 } <span class="hljs-keyword">catch</span> { 722 <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>); 723 } 724} 725 726<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>); 727<span class="hljs-comment">// resolve: Promise { 'First call' } 'Swallowed resolve'</span> 728<span class="hljs-comment">// reject: Promise { 'First call' } Error: Swallowed reject</span> 729<span class="hljs-comment">// at Promise (*)</span> 730<span class="hljs-comment">// at new Promise (<anonymous>)</span> 731<span class="hljs-comment">// at main (*)</span> 732<span class="hljs-comment">// First call</span></code><button class="copy-button">copy</button></pre> 733<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> 734<div class="api_metadata"> 735<span>Added in: v1.4.1</span> 736</div> 737<ul> 738<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> 739</ul> 740<p>The <code>'rejectionHandled'</code> event is emitted whenever a <code>Promise</code> has been rejected 741and 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 742example) later than one turn of the Node.js event loop.</p> 743<p>The <code>Promise</code> object would have previously been emitted in an 744<code>'unhandledRejection'</code> event, but during the course of processing gained a 745rejection handler.</p> 746<p>There is no notion of a top level for a <code>Promise</code> chain at which rejections can 747always be handled. Being inherently asynchronous in nature, a <code>Promise</code> 748rejection can be handled at a future point in time, possibly much later than 749the event loop turn it takes for the <code>'unhandledRejection'</code> event to be emitted.</p> 750<p>Another way of stating this is that, unlike in synchronous code where there is 751an ever-growing list of unhandled exceptions, with Promises there can be a 752growing-and-shrinking list of unhandled rejections.</p> 753<p>In synchronous code, the <code>'uncaughtException'</code> event is emitted when the list of 754unhandled exceptions grows.</p> 755<p>In asynchronous code, the <code>'unhandledRejection'</code> event is emitted when the list 756of unhandled rejections grows, and the <code>'rejectionHandled'</code> event is emitted 757when the list of unhandled rejections shrinks.</p> 758 759<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>; 760 761<span class="hljs-keyword">const</span> unhandledRejections = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Map</span>(); 762process.<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> { 763 unhandledRejections.<span class="hljs-title function_">set</span>(promise, reason); 764}); 765process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'rejectionHandled'</span>, <span class="hljs-function">(<span class="hljs-params">promise</span>) =></span> { 766 unhandledRejections.<span class="hljs-title function_">delete</span>(promise); 767});</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>); 768 769<span class="hljs-keyword">const</span> unhandledRejections = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Map</span>(); 770process.<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> { 771 unhandledRejections.<span class="hljs-title function_">set</span>(promise, reason); 772}); 773process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'rejectionHandled'</span>, <span class="hljs-function">(<span class="hljs-params">promise</span>) =></span> { 774 unhandledRejections.<span class="hljs-title function_">delete</span>(promise); 775});</code><button class="copy-button">copy</button></pre> 776<p>In this example, the <code>unhandledRejections</code> <code>Map</code> will grow and shrink over time, 777reflecting rejections that start unhandled and then become handled. It is 778possible to record such errors in an error log, either periodically (which is 779likely best for long-running application) or upon process exit (which is likely 780most convenient for scripts).</p> 781<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> 782<div class="api_metadata"> 783<details class="changelog"><summary>History</summary> 784<table> 785<tbody><tr><th>Version</th><th>Changes</th></tr> 786<tr><td>v12.0.0, v10.17.0</td> 787<td><p>Added the <code>origin</code> argument.</p></td></tr> 788<tr><td>v0.1.18</td> 789<td><p><span>Added in: v0.1.18</span></p></td></tr> 790</tbody></table> 791</details> 792</div> 793<ul> 794<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> 795<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 796rejection or from a synchronous error. Can either be <code>'uncaughtException'</code> or 797<code>'unhandledRejection'</code>. The latter is used when an exception happens in a 798<code>Promise</code> based async context (or if a <code>Promise</code> is rejected) and 799<a href="cli.html#--unhandled-rejectionsmode"><code>--unhandled-rejections</code></a> flag set to <code>strict</code> or <code>throw</code> (which is the 800default) and the rejection is not handled, or when a rejection happens during 801the command line entry point's ES module static loading phase.</li> 802</ul> 803<p>The <code>'uncaughtException'</code> event is emitted when an uncaught JavaScript 804exception bubbles all the way back to the event loop. By default, Node.js 805handles such exceptions by printing the stack trace to <code>stderr</code> and exiting 806with code 1, overriding any previously set <a href="#processexitcode_1"><code>process.exitCode</code></a>. 807Adding a handler for the <code>'uncaughtException'</code> event overrides this default 808behavior. Alternatively, change the <a href="#processexitcode_1"><code>process.exitCode</code></a> in the 809<code>'uncaughtException'</code> handler which will result in the process exiting with the 810provided exit code. Otherwise, in the presence of such handler the process will 811exit with 0.</p> 812 813<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>; 814 815process.<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> { 816 fs.<span class="hljs-title function_">writeSync</span>( 817 process.<span class="hljs-property">stderr</span>.<span class="hljs-property">fd</span>, 818 <span class="hljs-string">`Caught exception: <span class="hljs-subst">${err}</span>\n`</span> + 819 <span class="hljs-string">`Exception origin: <span class="hljs-subst">${origin}</span>`</span>, 820 ); 821}); 822 823<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 824 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'This will still run.'</span>); 825}, <span class="hljs-number">500</span>); 826 827<span class="hljs-comment">// Intentionally cause an exception, but don't catch it.</span> 828<span class="hljs-title function_">nonexistentFunc</span>(); 829<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>); 830 831process.<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> { 832 fs.<span class="hljs-title function_">writeSync</span>( 833 process.<span class="hljs-property">stderr</span>.<span class="hljs-property">fd</span>, 834 <span class="hljs-string">`Caught exception: <span class="hljs-subst">${err}</span>\n`</span> + 835 <span class="hljs-string">`Exception origin: <span class="hljs-subst">${origin}</span>`</span>, 836 ); 837}); 838 839<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 840 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'This will still run.'</span>); 841}, <span class="hljs-number">500</span>); 842 843<span class="hljs-comment">// Intentionally cause an exception, but don't catch it.</span> 844<span class="hljs-title function_">nonexistentFunc</span>(); 845<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> 846<p>It is possible to monitor <code>'uncaughtException'</code> events without overriding the 847default behavior to exit the process by installing a 848<code>'uncaughtExceptionMonitor'</code> listener.</p> 849<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> 850<p><code>'uncaughtException'</code> is a crude mechanism for exception handling 851intended to be used only as a last resort. The event <em>should not</em> be used as 852an equivalent to <code>On Error Resume Next</code>. Unhandled exceptions inherently mean 853that an application is in an undefined state. Attempting to resume application 854code without properly recovering from the exception can cause additional 855unforeseen and unpredictable issues.</p> 856<p>Exceptions thrown from within the event handler will not be caught. Instead the 857process will exit with a non-zero exit code and the stack trace will be printed. 858This is to avoid infinite recursion.</p> 859<p>Attempting to resume normally after an uncaught exception can be similar to 860pulling out the power cord when upgrading a computer. Nine out of ten 861times, nothing happens. But the tenth time, the system becomes corrupted.</p> 862<p>The correct use of <code>'uncaughtException'</code> is to perform synchronous cleanup 863of allocated resources (e.g. file descriptors, handles, etc) before shutting 864down the process. <strong>It is not safe to resume normal operation after 865<code>'uncaughtException'</code>.</strong></p> 866<p>To restart a crashed application in a more reliable way, whether 867<code>'uncaughtException'</code> is emitted or not, an external monitor should be employed 868in a separate process to detect application failures and recover or restart as 869needed.</p> 870<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> 871<div class="api_metadata"> 872<span>Added in: v13.7.0, v12.17.0</span> 873</div> 874<ul> 875<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> 876<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 877rejection or from synchronous errors. Can either be <code>'uncaughtException'</code> or 878<code>'unhandledRejection'</code>. The latter is used when an exception happens in a 879<code>Promise</code> based async context (or if a <code>Promise</code> is rejected) and 880<a href="cli.html#--unhandled-rejectionsmode"><code>--unhandled-rejections</code></a> flag set to <code>strict</code> or <code>throw</code> (which is the 881default) and the rejection is not handled, or when a rejection happens during 882the command line entry point's ES module static loading phase.</li> 883</ul> 884<p>The <code>'uncaughtExceptionMonitor'</code> event is emitted before an 885<code>'uncaughtException'</code> event is emitted or a hook installed via 886<a href="#processsetuncaughtexceptioncapturecallbackfn"><code>process.setUncaughtExceptionCaptureCallback()</code></a> is called.</p> 887<p>Installing an <code>'uncaughtExceptionMonitor'</code> listener does not change the behavior 888once an <code>'uncaughtException'</code> event is emitted. The process will 889still crash if no <code>'uncaughtException'</code> listener is installed.</p> 890 891<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>; 892 893process.<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> { 894 <span class="hljs-title class_">MyMonitoringTool</span>.<span class="hljs-title function_">logSync</span>(err, origin); 895}); 896 897<span class="hljs-comment">// Intentionally cause an exception, but don't catch it.</span> 898<span class="hljs-title function_">nonexistentFunc</span>(); 899<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>); 900 901process.<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> { 902 <span class="hljs-title class_">MyMonitoringTool</span>.<span class="hljs-title function_">logSync</span>(err, origin); 903}); 904 905<span class="hljs-comment">// Intentionally cause an exception, but don't catch it.</span> 906<span class="hljs-title function_">nonexistentFunc</span>(); 907<span class="hljs-comment">// Still crashes Node.js</span></code><button class="copy-button">copy</button></pre> 908<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> 909<div class="api_metadata"> 910<details class="changelog"><summary>History</summary> 911<table> 912<tbody><tr><th>Version</th><th>Changes</th></tr> 913<tr><td>v7.0.0</td> 914<td><p>Not handling <code>Promise</code> rejections is deprecated.</p></td></tr> 915<tr><td>v6.6.0</td> 916<td><p>Unhandled <code>Promise</code> rejections will now emit a process warning.</p></td></tr> 917<tr><td>v1.4.1</td> 918<td><p><span>Added in: v1.4.1</span></p></td></tr> 919</tbody></table> 920</details> 921</div> 922<ul> 923<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 924(typically an <a href="errors.html#class-error"><code>Error</code></a> object).</li> 925<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> 926</ul> 927<p>The <code>'unhandledRejection'</code> event is emitted whenever a <code>Promise</code> is rejected and 928no error handler is attached to the promise within a turn of the event loop. 929When programming with Promises, exceptions are encapsulated as "rejected 930promises". 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 931are propagated through a <code>Promise</code> chain. The <code>'unhandledRejection'</code> event is 932useful for detecting and keeping track of promises that were rejected whose 933rejections have not yet been handled.</p> 934 935<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>; 936 937process.<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> { 938 <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); 939 <span class="hljs-comment">// Application specific logging, throwing an error, or other logic here</span> 940}); 941 942somePromise.<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">res</span>) =></span> { 943 <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> 944}); <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>); 945 946process.<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> { 947 <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); 948 <span class="hljs-comment">// Application specific logging, throwing an error, or other logic here</span> 949}); 950 951somePromise.<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">res</span>) =></span> { 952 <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> 953}); <span class="hljs-comment">// No `.catch()` or `.then()`</span></code><button class="copy-button">copy</button></pre> 954<p>The following will also trigger the <code>'unhandledRejection'</code> event to be 955emitted:</p> 956 957<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>; 958 959<span class="hljs-keyword">function</span> <span class="hljs-title function_">SomeResource</span>(<span class="hljs-params"></span>) { 960 <span class="hljs-comment">// Initially set the loaded status to a rejected promise</span> 961 <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>)); 962} 963 964<span class="hljs-keyword">const</span> resource = <span class="hljs-keyword">new</span> <span class="hljs-title class_">SomeResource</span>(); 965<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>); 966 967<span class="hljs-keyword">function</span> <span class="hljs-title function_">SomeResource</span>(<span class="hljs-params"></span>) { 968 <span class="hljs-comment">// Initially set the loaded status to a rejected promise</span> 969 <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>)); 970} 971 972<span class="hljs-keyword">const</span> resource = <span class="hljs-keyword">new</span> <span class="hljs-title class_">SomeResource</span>(); 973<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> 974<p>In this example case, it is possible to track the rejection as a developer error 975as would typically be the case for other <code>'unhandledRejection'</code> events. To 976address such failures, a non-operational 977<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 978<code>resource.loaded</code>, which would prevent the <code>'unhandledRejection'</code> event from 979being emitted.</p> 980<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> 981<div class="api_metadata"> 982<span>Added in: v6.0.0</span> 983</div> 984<ul> 985<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: 986<ul> 987<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> 988<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> 989<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 990was issued.</li> 991</ul> 992</li> 993</ul> 994<p>The <code>'warning'</code> event is emitted whenever Node.js emits a process warning.</p> 995<p>A process warning is similar to an error in that it describes exceptional 996conditions that are being brought to the user's attention. However, warnings 997are not part of the normal Node.js and JavaScript error handling flow. 998Node.js can emit warnings whenever it detects bad coding practices that could 999lead to sub-optimal application performance, bugs, or security vulnerabilities.</p> 1000 1001<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>; 1002 1003process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'warning'</span>, <span class="hljs-function">(<span class="hljs-params">warning</span>) =></span> { 1004 <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> 1005 <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> 1006 <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> 1007});</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>); 1008 1009process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'warning'</span>, <span class="hljs-function">(<span class="hljs-params">warning</span>) =></span> { 1010 <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> 1011 <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> 1012 <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> 1013});</code><button class="copy-button">copy</button></pre> 1014<p>By default, Node.js will print process warnings to <code>stderr</code>. The <code>--no-warnings</code> 1015command-line option can be used to suppress the default console output but the 1016<code>'warning'</code> event will still be emitted by the <code>process</code> object.</p> 1017<p>The following example illustrates the warning that is printed to <code>stderr</code> when 1018too many listeners have been added to an event:</p> 1019<pre><code class="language-console"><span class="hljs-meta prompt_">$ </span><span class="language-bash">node</span> 1020<span class="hljs-meta prompt_">> </span><span class="language-bash">events.defaultMaxListeners = 1;</span> 1021<span class="hljs-meta prompt_">> </span><span class="language-bash">process.on(<span class="hljs-string">'foo'</span>, () => {});</span> 1022<span class="hljs-meta prompt_">> </span><span class="language-bash">process.on(<span class="hljs-string">'foo'</span>, () => {});</span> 1023<span class="hljs-meta prompt_">> </span><span class="language-bash">(node:38638) MaxListenersExceededWarning: Possible EventEmitter memory leak</span> 1024detected. 2 foo listeners added. Use emitter.setMaxListeners() to increase limit</code> <button class="copy-button">copy</button></pre> 1025<p>In contrast, the following example turns off the default warning output and 1026adds a custom handler to the <code>'warning'</code> event:</p> 1027<pre><code class="language-console"><span class="hljs-meta prompt_">$ </span><span class="language-bash">node --no-warnings</span> 1028<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> 1029<span class="hljs-meta prompt_">> </span><span class="language-bash">events.defaultMaxListeners = 1;</span> 1030<span class="hljs-meta prompt_">> </span><span class="language-bash">process.on(<span class="hljs-string">'foo'</span>, () => {});</span> 1031<span class="hljs-meta prompt_">> </span><span class="language-bash">process.on(<span class="hljs-string">'foo'</span>, () => {});</span> 1032<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> 1033<p>The <code>--trace-warnings</code> command-line option can be used to have the default 1034console output for warnings include the full stack trace of the warning.</p> 1035<p>Launching Node.js using the <code>--throw-deprecation</code> command-line flag will 1036cause custom deprecation warnings to be thrown as exceptions.</p> 1037<p>Using the <code>--trace-deprecation</code> command-line flag will cause the custom 1038deprecation to be printed to <code>stderr</code> along with the stack trace.</p> 1039<p>Using the <code>--no-deprecation</code> command-line flag will suppress all reporting 1040of the custom deprecation.</p> 1041<p>The <code>*-deprecation</code> command-line flags only affect warnings that use the name 1042<code>'DeprecationWarning'</code>.</p> 1043<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> 1044<div class="api_metadata"> 1045<span>Added in: v16.2.0, v14.18.0</span> 1046</div> 1047<ul> 1048<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> 1049</ul> 1050<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> 1051<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> 1052<p>See the <a href="#processemitwarningwarning-type-code-ctor"><code>process.emitWarning()</code></a> method for issuing 1053custom or application-specific warnings.</p> 1054<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> 1055<p>There are no strict guidelines for warning types (as identified by the <code>name</code> 1056property) emitted by Node.js. New types of warnings can be added at any time. 1057A few of the warning types that are most common include:</p> 1058<ul> 1059<li><code>'DeprecationWarning'</code> - Indicates use of a deprecated Node.js API or feature. 1060Such warnings must include a <code>'code'</code> property identifying the 1061<a href="deprecations.html">deprecation code</a>.</li> 1062<li><code>'ExperimentalWarning'</code> - Indicates use of an experimental Node.js API or 1063feature. Such features must be used with caution as they may change at any 1064time and are not subject to the same strict semantic-versioning and long-term 1065support policies as supported features.</li> 1066<li><code>'MaxListenersExceededWarning'</code> - Indicates that too many listeners for a 1067given event have been registered on either an <code>EventEmitter</code> or <code>EventTarget</code>. 1068This is often an indication of a memory leak.</li> 1069<li><code>'TimeoutOverflowWarning'</code> - Indicates that a numeric value that cannot fit 1070within a 32-bit signed integer has been provided to either the <code>setTimeout()</code> 1071or <code>setInterval()</code> functions.</li> 1072<li><code>'UnsupportedWarning'</code> - Indicates use of an unsupported option or feature 1073that will be ignored rather than treated as an error. One example is use of 1074the HTTP response status message when using the HTTP/2 compatibility API.</li> 1075</ul> 1076<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> 1077 1078 1079<p>Signal events will be emitted when the Node.js process receives a signal. Please 1080refer 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 1081<code>'SIGINT'</code>, <code>'SIGHUP'</code>, etc.</p> 1082<p>Signals are not available on <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 1083<p>The signal handler will receive the signal's name (<code>'SIGINT'</code>, 1084<code>'SIGTERM'</code>, etc.) as the first argument.</p> 1085<p>The name of each event will be the uppercase common name for the signal (e.g. 1086<code>'SIGINT'</code> for <code>SIGINT</code> signals).</p> 1087 1088<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>; 1089 1090<span class="hljs-comment">// Begin reading from stdin so the process does not exit.</span> 1091process.<span class="hljs-property">stdin</span>.<span class="hljs-title function_">resume</span>(); 1092 1093process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'SIGINT'</span>, <span class="hljs-function">() =></span> { 1094 <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>); 1095}); 1096 1097<span class="hljs-comment">// Using a single function to handle multiple signals</span> 1098<span class="hljs-keyword">function</span> <span class="hljs-title function_">handle</span>(<span class="hljs-params">signal</span>) { 1099 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Received <span class="hljs-subst">${signal}</span>`</span>); 1100} 1101 1102process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'SIGINT'</span>, handle); 1103process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'SIGTERM'</span>, handle);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1104 1105<span class="hljs-comment">// Begin reading from stdin so the process does not exit.</span> 1106process.<span class="hljs-property">stdin</span>.<span class="hljs-title function_">resume</span>(); 1107 1108process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'SIGINT'</span>, <span class="hljs-function">() =></span> { 1109 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Received SIGINT. Press Control-D to exit.'</span>); 1110}); 1111 1112<span class="hljs-comment">// Using a single function to handle multiple signals</span> 1113<span class="hljs-keyword">function</span> <span class="hljs-title function_">handle</span>(<span class="hljs-params">signal</span>) { 1114 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Received <span class="hljs-subst">${signal}</span>`</span>); 1115} 1116 1117process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'SIGINT'</span>, handle); 1118process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'SIGTERM'</span>, handle);</code><button class="copy-button">copy</button></pre> 1119<ul> 1120<li><code>'SIGUSR1'</code> is reserved by Node.js to start the <a href="debugger.html">debugger</a>. It's possible to 1121install a listener but doing so might interfere with the debugger.</li> 1122<li><code>'SIGTERM'</code> and <code>'SIGINT'</code> have default handlers on non-Windows platforms that 1123reset the terminal mode before exiting with code <code>128 + signal number</code>. If one 1124of these signals has a listener installed, its default behavior will be 1125removed (Node.js will no longer exit).</li> 1126<li><code>'SIGPIPE'</code> is ignored by default. It can have a listener installed.</li> 1127<li><code>'SIGHUP'</code> is generated on Windows when the console window is closed, and on 1128other 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 1129listener installed, however Node.js will be unconditionally terminated by 1130Windows about 10 seconds later. On non-Windows platforms, the default 1131behavior of <code>SIGHUP</code> is to terminate Node.js, but once a listener has been 1132installed its default behavior will be removed.</li> 1133<li><code>'SIGTERM'</code> is not supported on Windows, it can be listened on.</li> 1134<li><code>'SIGINT'</code> from the terminal is supported on all platforms, and can usually be 1135generated with <kbd>Ctrl</kbd>+<kbd>C</kbd> (though this may be configurable). 1136It is not generated when <a href="tty.html#readstreamsetrawmodemode">terminal raw mode</a> is enabled 1137and <kbd>Ctrl</kbd>+<kbd>C</kbd> is used.</li> 1138<li><code>'SIGBREAK'</code> is delivered on Windows when <kbd>Ctrl</kbd>+<kbd>Break</kbd> is 1139pressed. On non-Windows platforms, it can be listened on, but there is no way 1140to send or generate it.</li> 1141<li><code>'SIGWINCH'</code> is delivered when the console has been resized. On Windows, this 1142will only happen on write to the console when the cursor is being moved, or 1143when a readable tty is used in raw mode.</li> 1144<li><code>'SIGKILL'</code> cannot have a listener installed, it will unconditionally 1145terminate Node.js on all platforms.</li> 1146<li><code>'SIGSTOP'</code> cannot have a listener installed.</li> 1147<li><code>'SIGBUS'</code>, <code>'SIGFPE'</code>, <code>'SIGSEGV'</code>, and <code>'SIGILL'</code>, when not raised 1148artificially 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 1149which it is not safe to call JS listeners. Doing so might cause the process 1150to stop responding.</li> 1151<li><code>0</code> can be sent to test for the existence of a process, it has no effect if 1152the process exists, but will throw an error if the process does not exist.</li> 1153</ul> 1154<p>Windows does not support signals so has no equivalent to termination by signal, 1155but Node.js offers some emulation with <a href="#processkillpid-signal"><code>process.kill()</code></a>, and 1156<a href="child_process.html#subprocesskillsignal"><code>subprocess.kill()</code></a>:</p> 1157<ul> 1158<li>Sending <code>SIGINT</code>, <code>SIGTERM</code>, and <code>SIGKILL</code> will cause the unconditional 1159termination of the target process, and afterwards, subprocess will report that 1160the process was terminated by signal.</li> 1161<li>Sending signal <code>0</code> can be used as a platform independent way to test for the 1162existence of a process.</li> 1163</ul> 1164</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> 1165<div class="api_metadata"> 1166<span>Added in: v0.7.0</span> 1167</div> 1168<p>The <code>process.abort()</code> method causes the Node.js process to exit immediately and 1169generate a core file.</p> 1170<p>This feature is not available in <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 1171</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> 1172<div class="api_metadata"> 1173<span>Added in: v10.10.0</span> 1174</div> 1175<ul> 1176<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set" class="type"><Set></a></li> 1177</ul> 1178<p>The <code>process.allowedNodeEnvironmentFlags</code> property is a special, 1179read-only <code>Set</code> of flags allowable within the <a href="cli.html#node_optionsoptions"><code>NODE_OPTIONS</code></a> 1180environment variable.</p> 1181<p><code>process.allowedNodeEnvironmentFlags</code> extends <code>Set</code>, but overrides 1182<code>Set.prototype.has</code> to recognize several different possible flag 1183representations. <code>process.allowedNodeEnvironmentFlags.has()</code> will 1184return <code>true</code> in the following cases:</p> 1185<ul> 1186<li>Flags may omit leading single (<code>-</code>) or double (<code>--</code>) dashes; e.g., 1187<code>inspect-brk</code> for <code>--inspect-brk</code>, or <code>r</code> for <code>-r</code>.</li> 1188<li>Flags passed through to V8 (as listed in <code>--v8-options</code>) may replace 1189one or more <em>non-leading</em> dashes for an underscore, or vice-versa; 1190e.g., <code>--perf_basic_prof</code>, <code>--perf-basic-prof</code>, <code>--perf_basic-prof</code>, 1191etc.</li> 1192<li>Flags may contain one or more equals (<code>=</code>) characters; all 1193characters after and including the first equals will be ignored; 1194e.g., <code>--stack-trace-limit=100</code>.</li> 1195<li>Flags <em>must</em> be allowable within <a href="cli.html#node_optionsoptions"><code>NODE_OPTIONS</code></a>.</li> 1196</ul> 1197<p>When iterating over <code>process.allowedNodeEnvironmentFlags</code>, flags will 1198appear only <em>once</em>; each will begin with one or more dashes. Flags 1199passed through to V8 will contain underscores instead of non-leading 1200dashes:</p> 1201 1202<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>; 1203 1204allowedNodeEnvironmentFlags.<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">flag</span>) =></span> { 1205 <span class="hljs-comment">// -r</span> 1206 <span class="hljs-comment">// --inspect-brk</span> 1207 <span class="hljs-comment">// --abort_on_uncaught_exception</span> 1208 <span class="hljs-comment">// ...</span> 1209});</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>); 1210 1211allowedNodeEnvironmentFlags.<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">flag</span>) =></span> { 1212 <span class="hljs-comment">// -r</span> 1213 <span class="hljs-comment">// --inspect-brk</span> 1214 <span class="hljs-comment">// --abort_on_uncaught_exception</span> 1215 <span class="hljs-comment">// ...</span> 1216});</code><button class="copy-button">copy</button></pre> 1217<p>The methods <code>add()</code>, <code>clear()</code>, and <code>delete()</code> of 1218<code>process.allowedNodeEnvironmentFlags</code> do nothing, and will fail 1219silently.</p> 1220<p>If Node.js was compiled <em>without</em> <a href="cli.html#node_optionsoptions"><code>NODE_OPTIONS</code></a> support (shown in 1221<a href="#processconfig"><code>process.config</code></a>), <code>process.allowedNodeEnvironmentFlags</code> will 1222contain what <em>would have</em> been allowable.</p> 1223</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> 1224<div class="api_metadata"> 1225<span>Added in: v0.5.0</span> 1226</div> 1227<ul> 1228<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1229</ul> 1230<p>The operating system CPU architecture for which the Node.js binary was compiled. 1231Possible values are: <code>'arm'</code>, <code>'arm64'</code>, <code>'ia32'</code>, <code>'mips'</code>,<code>'mipsel'</code>, <code>'ppc'</code>, 1232<code>'ppc64'</code>, <code>'s390'</code>, <code>'s390x'</code>, and <code>'x64'</code>.</p> 1233 1234<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>; 1235 1236<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">${arch}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { arch } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1237 1238<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`This processor architecture is <span class="hljs-subst">${arch}</span>`</span>);</code><button class="copy-button">copy</button></pre> 1239</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> 1240<div class="api_metadata"> 1241<span>Added in: v0.1.27</span> 1242</div> 1243<ul> 1244<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 1245</ul> 1246<p>The <code>process.argv</code> property returns an array containing the command-line 1247arguments passed when the Node.js process was launched. The first element will 1248be <a href="#processexecpath"><code>process.execPath</code></a>. See <code>process.argv0</code> if access to the original value 1249of <code>argv[0]</code> is needed. The second element will be the path to the JavaScript 1250file being executed. The remaining elements will be any additional command-line 1251arguments.</p> 1252<p>For example, assuming the following script for <code>process-args.js</code>:</p> 1253 1254<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>; 1255 1256<span class="hljs-comment">// print process.argv</span> 1257argv.<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">val, index</span>) =></span> { 1258 <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>); 1259});</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>); 1260 1261<span class="hljs-comment">// print process.argv</span> 1262argv.<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">val, index</span>) =></span> { 1263 <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>); 1264});</code><button class="copy-button">copy</button></pre> 1265<p>Launching the Node.js process as:</p> 1266<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> 1267<p>Would generate the output:</p> 1268<pre><code class="language-text">0: /usr/local/bin/node 12691: /Users/mjr/work/node/process-args.js 12702: one 12713: two=three 12724: four</code> <button class="copy-button">copy</button></pre> 1273</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> 1274<div class="api_metadata"> 1275<span>Added in: v6.4.0</span> 1276</div> 1277<ul> 1278<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1279</ul> 1280<p>The <code>process.argv0</code> property stores a read-only copy of the original value of 1281<code>argv[0]</code> passed when Node.js starts.</p> 1282<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> 1283<span class="hljs-meta prompt_">> </span><span class="language-bash">process.argv[0]</span> 1284'/Volumes/code/external/node/out/Release/node' 1285<span class="hljs-meta prompt_">> </span><span class="language-bash">process.argv0</span> 1286'customArgv0'</code> <button class="copy-button">copy</button></pre> 1287</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> 1288<div class="api_metadata"> 1289<details class="changelog"><summary>History</summary> 1290<table> 1291<tbody><tr><th>Version</th><th>Changes</th></tr> 1292<tr><td>v14.0.0</td> 1293<td><p>The object no longer accidentally exposes native C++ bindings.</p></td></tr> 1294<tr><td>v7.1.0</td> 1295<td><p><span>Added in: v7.1.0</span></p></td></tr> 1296</tbody></table> 1297</details> 1298</div> 1299<ul> 1300<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 1301</ul> 1302<p>If the Node.js process was spawned with an IPC channel (see the 1303<a href="child_process.html">Child Process</a> documentation), the <code>process.channel</code> 1304property is a reference to the IPC channel. If no IPC channel exists, this 1305property is <code>undefined</code>.</p> 1306<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> 1307<div class="api_metadata"> 1308<span>Added in: v7.1.0</span> 1309</div> 1310<p>This method makes the IPC channel keep the event loop of the process 1311running if <code>.unref()</code> has been called before.</p> 1312<p>Typically, this is managed through the number of <code>'disconnect'</code> and <code>'message'</code> 1313listeners on the <code>process</code> object. However, this method can be used to 1314explicitly request a specific behavior.</p> 1315<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> 1316<div class="api_metadata"> 1317<span>Added in: v7.1.0</span> 1318</div> 1319<p>This method makes the IPC channel not keep the event loop of the process 1320running, and lets it finish even while the channel is open.</p> 1321<p>Typically, this is managed through the number of <code>'disconnect'</code> and <code>'message'</code> 1322listeners on the <code>process</code> object. However, this method can be used to 1323explicitly request a specific behavior.</p> 1324</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> 1325<div class="api_metadata"> 1326<span>Added in: v0.1.17</span> 1327</div> 1328<ul> 1329<li><code>directory</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1330</ul> 1331<p>The <code>process.chdir()</code> method changes the current working directory of the 1332Node.js process or throws an exception if doing so fails (for instance, if 1333the specified <code>directory</code> does not exist).</p> 1334 1335<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>; 1336 1337<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Starting directory: <span class="hljs-subst">${cwd()}</span>`</span>); 1338<span class="hljs-keyword">try</span> { 1339 <span class="hljs-title function_">chdir</span>(<span class="hljs-string">'/tmp'</span>); 1340 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New directory: <span class="hljs-subst">${cwd()}</span>`</span>); 1341} <span class="hljs-keyword">catch</span> (err) { 1342 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`chdir: <span class="hljs-subst">${err}</span>`</span>); 1343}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { chdir, cwd } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1344 1345<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Starting directory: <span class="hljs-subst">${cwd()}</span>`</span>); 1346<span class="hljs-keyword">try</span> { 1347 <span class="hljs-title function_">chdir</span>(<span class="hljs-string">'/tmp'</span>); 1348 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New directory: <span class="hljs-subst">${cwd()}</span>`</span>); 1349} <span class="hljs-keyword">catch</span> (err) { 1350 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`chdir: <span class="hljs-subst">${err}</span>`</span>); 1351}</code><button class="copy-button">copy</button></pre> 1352<p>This feature is not available in <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 1353</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> 1354<div class="api_metadata"> 1355<details class="changelog"><summary>History</summary> 1356<table> 1357<tbody><tr><th>Version</th><th>Changes</th></tr> 1358<tr><td>v16.0.0</td> 1359<td><p>Modifying process.config has been deprecated.</p></td></tr> 1360<tr><td>v0.7.7</td> 1361<td><p><span>Added in: v0.7.7</span></p></td></tr> 1362</tbody></table> 1363</details> 1364</div> 1365<ul> 1366<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 1367</ul> 1368<p>The <code>process.config</code> property returns an <code>Object</code> containing the JavaScript 1369representation of the configure options used to compile the current Node.js 1370executable. This is the same as the <code>config.gypi</code> file that was produced when 1371running the <code>./configure</code> script.</p> 1372<p>An example of the possible output looks like:</p> 1373<!-- eslint-skip --> 1374<pre><code class="language-js">{ 1375 <span class="hljs-attr">target_defaults</span>: 1376 { <span class="hljs-attr">cflags</span>: [], 1377 <span class="hljs-attr">default_configuration</span>: <span class="hljs-string">'Release'</span>, 1378 <span class="hljs-attr">defines</span>: [], 1379 <span class="hljs-attr">include_dirs</span>: [], 1380 <span class="hljs-attr">libraries</span>: [] }, 1381 <span class="hljs-attr">variables</span>: 1382 { 1383 <span class="hljs-attr">host_arch</span>: <span class="hljs-string">'x64'</span>, 1384 <span class="hljs-attr">napi_build_version</span>: <span class="hljs-number">5</span>, 1385 <span class="hljs-attr">node_install_npm</span>: <span class="hljs-string">'true'</span>, 1386 <span class="hljs-attr">node_prefix</span>: <span class="hljs-string">''</span>, 1387 <span class="hljs-attr">node_shared_cares</span>: <span class="hljs-string">'false'</span>, 1388 <span class="hljs-attr">node_shared_http_parser</span>: <span class="hljs-string">'false'</span>, 1389 <span class="hljs-attr">node_shared_libuv</span>: <span class="hljs-string">'false'</span>, 1390 <span class="hljs-attr">node_shared_zlib</span>: <span class="hljs-string">'false'</span>, 1391 <span class="hljs-attr">node_use_dtrace</span>: <span class="hljs-string">'false'</span>, 1392 <span class="hljs-attr">node_use_openssl</span>: <span class="hljs-string">'true'</span>, 1393 <span class="hljs-attr">node_shared_openssl</span>: <span class="hljs-string">'false'</span>, 1394 <span class="hljs-attr">strict_aliasing</span>: <span class="hljs-string">'true'</span>, 1395 <span class="hljs-attr">target_arch</span>: <span class="hljs-string">'x64'</span>, 1396 <span class="hljs-attr">v8_use_snapshot</span>: <span class="hljs-number">1</span> 1397 } 1398}</code> <button class="copy-button">copy</button></pre> 1399<p>The <code>process.config</code> property is <strong>not</strong> read-only and there are existing 1400modules in the ecosystem that are known to extend, modify, or entirely replace 1401the value of <code>process.config</code>.</p> 1402<p>Modifying the <code>process.config</code> property, or any child-property of the 1403<code>process.config</code> object has been deprecated. The <code>process.config</code> will be made 1404read-only in a future release.</p> 1405</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> 1406<div class="api_metadata"> 1407<span>Added in: v0.7.2</span> 1408</div> 1409<ul> 1410<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1411</ul> 1412<p>If the Node.js process is spawned with an IPC channel (see the <a href="child_process.html">Child Process</a> 1413and <a href="cluster.html">Cluster</a> documentation), the <code>process.connected</code> property will return 1414<code>true</code> so long as the IPC channel is connected and will return <code>false</code> after 1415<code>process.disconnect()</code> is called.</p> 1416<p>Once <code>process.connected</code> is <code>false</code>, it is no longer possible to send messages 1417over the IPC channel using <code>process.send()</code>.</p> 1418</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> 1419<div class="api_metadata"> 1420<span>Added in: v18.15.0</span> 1421</div> 1422<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 1423<ul> 1424<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> 1425</ul> 1426<p>Gets the amount of memory available to the process (in bytes) based on 1427limits imposed by the OS. If there is no such constraint, or the constraint 1428is unknown, <code>undefined</code> is returned.</p> 1429<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 1430information.</p> 1431</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> 1432<div class="api_metadata"> 1433<span>Added in: v6.1.0</span> 1434</div> 1435<ul> 1436<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 1437<code>process.cpuUsage()</code></li> 1438<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1439<ul> 1440<li><code>user</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 1441<li><code>system</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 1442</ul> 1443</li> 1444</ul> 1445<p>The <code>process.cpuUsage()</code> method returns the user and system CPU time usage of 1446the current process, in an object with properties <code>user</code> and <code>system</code>, whose 1447values are microsecond values (millionth of a second). These values measure time 1448spent in user and system code respectively, and may end up being greater than 1449actual elapsed time if multiple CPU cores are performing work for this process.</p> 1450<p>The result of a previous call to <code>process.cpuUsage()</code> can be passed as the 1451argument to the function, to get a diff reading.</p> 1452 1453<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>; 1454 1455<span class="hljs-keyword">const</span> startUsage = <span class="hljs-title function_">cpuUsage</span>(); 1456<span class="hljs-comment">// { user: 38579, system: 6986 }</span> 1457 1458<span class="hljs-comment">// spin the CPU for 500 milliseconds</span> 1459<span class="hljs-keyword">const</span> now = <span class="hljs-title class_">Date</span>.<span class="hljs-title function_">now</span>(); 1460<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>); 1461 1462<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">cpuUsage</span>(startUsage)); 1463<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>); 1464 1465<span class="hljs-keyword">const</span> startUsage = <span class="hljs-title function_">cpuUsage</span>(); 1466<span class="hljs-comment">// { user: 38579, system: 6986 }</span> 1467 1468<span class="hljs-comment">// spin the CPU for 500 milliseconds</span> 1469<span class="hljs-keyword">const</span> now = <span class="hljs-title class_">Date</span>.<span class="hljs-title function_">now</span>(); 1470<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>); 1471 1472<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">cpuUsage</span>(startUsage)); 1473<span class="hljs-comment">// { user: 514883, system: 11226 }</span></code><button class="copy-button">copy</button></pre> 1474</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> 1475<div class="api_metadata"> 1476<span>Added in: v0.1.8</span> 1477</div> 1478<ul> 1479<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1480</ul> 1481<p>The <code>process.cwd()</code> method returns the current working directory of the Node.js 1482process.</p> 1483 1484<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>; 1485 1486<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current directory: <span class="hljs-subst">${cwd()}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { cwd } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 1487 1488<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current directory: <span class="hljs-subst">${cwd()}</span>`</span>);</code><button class="copy-button">copy</button></pre> 1489</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> 1490<div class="api_metadata"> 1491<span>Added in: v0.7.2</span> 1492</div> 1493<ul> 1494<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1495</ul> 1496<p>The port used by the Node.js debugger when enabled.</p> 1497 1498<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>; 1499 1500process.<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>); 1501 1502process.<span class="hljs-property">debugPort</span> = <span class="hljs-number">5858</span>;</code><button class="copy-button">copy</button></pre> 1503</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> 1504<div class="api_metadata"> 1505<span>Added in: v0.7.2</span> 1506</div> 1507<p>If the Node.js process is spawned with an IPC channel (see the <a href="child_process.html">Child Process</a> 1508and <a href="cluster.html">Cluster</a> documentation), the <code>process.disconnect()</code> method will close the 1509IPC channel to the parent process, allowing the child process to exit gracefully 1510once there are no other connections keeping it alive.</p> 1511<p>The effect of calling <code>process.disconnect()</code> is the same as calling 1512<a href="child_process.html#subprocessdisconnect"><code>ChildProcess.disconnect()</code></a> from the parent process.</p> 1513<p>If the Node.js process was not spawned with an IPC channel, 1514<code>process.disconnect()</code> will be <code>undefined</code>.</p> 1515</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> 1516<div class="api_metadata"> 1517<details class="changelog"><summary>History</summary> 1518<table> 1519<tbody><tr><th>Version</th><th>Changes</th></tr> 1520<tr><td>v9.0.0</td> 1521<td><p>Added support for the <code>flags</code> argument.</p></td></tr> 1522<tr><td>v0.1.16</td> 1523<td><p><span>Added in: v0.1.16</span></p></td></tr> 1524</tbody></table> 1525</details> 1526</div> 1527<ul> 1528<li><code>module</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 1529<li><code>filename</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1530<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> 1531</ul> 1532<p>The <code>process.dlopen()</code> method allows dynamically loading shared objects. It is 1533primarily used by <code>require()</code> to load C++ Addons, and should not be used 1534directly, except in special cases. In other words, <a href="globals.html#require"><code>require()</code></a> should be 1535preferred over <code>process.dlopen()</code> unless there are specific reasons such as 1536custom dlopen flags or loading from ES modules.</p> 1537<p>The <code>flags</code> argument is an integer that allows to specify dlopen 1538behavior. See the <a href="os.html#dlopen-constants"><code>os.constants.dlopen</code></a> documentation for details.</p> 1539<p>An important requirement when calling <code>process.dlopen()</code> is that the <code>module</code> 1540instance must be passed. Functions exported by the C++ Addon are then 1541accessible via <code>module.exports</code>.</p> 1542<p>The example below shows how to load a C++ Addon, named <code>local.node</code>, 1543that exports a <code>foo</code> function. All the symbols are loaded before 1544the call returns, by passing the <code>RTLD_NOW</code> constant. In this example 1545the constant is assumed to be available.</p> 1546 1547<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>; 1548<span class="hljs-keyword">import</span> { constants } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:os'</span>; 1549<span class="hljs-keyword">import</span> { fileURLToPath } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:url'</span>; 1550 1551<span class="hljs-keyword">const</span> <span class="hljs-variable language_">module</span> = { <span class="hljs-attr">exports</span>: {} }; 1552<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>)), 1553 constants.<span class="hljs-property">dlopen</span>.<span class="hljs-property">RTLD_NOW</span>); 1554<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>); 1555<span class="hljs-keyword">const</span> { constants } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:os'</span>); 1556<span class="hljs-keyword">const</span> { join } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:path'</span>); 1557 1558<span class="hljs-keyword">const</span> <span class="hljs-variable language_">module</span> = { <span class="hljs-attr">exports</span>: {} }; 1559<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>); 1560<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> 1561</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> 1562<div class="api_metadata"> 1563<span>Added in: v8.0.0</span> 1564</div> 1565<ul> 1566<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> 1567<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1568<ul> 1569<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 1570for the <em>type</em> of warning being emitted. <strong>Default:</strong> <code>'Warning'</code>.</li> 1571<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> 1572<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 1573function used to limit the generated stack trace. <strong>Default:</strong> 1574<code>process.emitWarning</code>.</li> 1575<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> 1576</ul> 1577</li> 1578</ul> 1579<p>The <code>process.emitWarning()</code> method can be used to emit custom or application 1580specific process warnings. These can be listened for by adding a handler to the 1581<a href="#event-warning"><code>'warning'</code></a> event.</p> 1582 1583<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>; 1584 1585<span class="hljs-comment">// Emit a warning with a code and additional detail.</span> 1586<span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Something happened!'</span>, { 1587 <span class="hljs-attr">code</span>: <span class="hljs-string">'MY_WARNING'</span>, 1588 <span class="hljs-attr">detail</span>: <span class="hljs-string">'This is some additional information'</span>, 1589}); 1590<span class="hljs-comment">// Emits:</span> 1591<span class="hljs-comment">// (node:56338) [MY_WARNING] Warning: Something happened!</span> 1592<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>); 1593 1594<span class="hljs-comment">// Emit a warning with a code and additional detail.</span> 1595<span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Something happened!'</span>, { 1596 <span class="hljs-attr">code</span>: <span class="hljs-string">'MY_WARNING'</span>, 1597 <span class="hljs-attr">detail</span>: <span class="hljs-string">'This is some additional information'</span>, 1598}); 1599<span class="hljs-comment">// Emits:</span> 1600<span class="hljs-comment">// (node:56338) [MY_WARNING] Warning: Something happened!</span> 1601<span class="hljs-comment">// This is some additional information</span></code><button class="copy-button">copy</button></pre> 1602<p>In this example, an <code>Error</code> object is generated internally by 1603<code>process.emitWarning()</code> and passed through to the 1604<a href="#event-warning"><code>'warning'</code></a> handler.</p> 1605 1606<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>; 1607 1608process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'warning'</span>, <span class="hljs-function">(<span class="hljs-params">warning</span>) =></span> { 1609 <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> 1610 <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> 1611 <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> 1612 <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> 1613 <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> 1614});</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>); 1615 1616process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'warning'</span>, <span class="hljs-function">(<span class="hljs-params">warning</span>) =></span> { 1617 <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> 1618 <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> 1619 <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> 1620 <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> 1621 <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> 1622});</code><button class="copy-button">copy</button></pre> 1623<p>If <code>warning</code> is passed as an <code>Error</code> object, the <code>options</code> argument is ignored.</p> 1624</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> 1625<div class="api_metadata"> 1626<span>Added in: v6.0.0</span> 1627</div> 1628<ul> 1629<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> 1630<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 1631for the <em>type</em> of warning being emitted. <strong>Default:</strong> <code>'Warning'</code>.</li> 1632<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> 1633<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 1634function used to limit the generated stack trace. <strong>Default:</strong> 1635<code>process.emitWarning</code>.</li> 1636</ul> 1637<p>The <code>process.emitWarning()</code> method can be used to emit custom or application 1638specific process warnings. These can be listened for by adding a handler to the 1639<a href="#event-warning"><code>'warning'</code></a> event.</p> 1640 1641<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>; 1642 1643<span class="hljs-comment">// Emit a warning using a string.</span> 1644<span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Something happened!'</span>); 1645<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>); 1646 1647<span class="hljs-comment">// Emit a warning using a string.</span> 1648<span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Something happened!'</span>); 1649<span class="hljs-comment">// Emits: (node: 56338) Warning: Something happened!</span></code><button class="copy-button">copy</button></pre> 1650 1651<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>; 1652 1653<span class="hljs-comment">// Emit a warning using a string and a type.</span> 1654<span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Something Happened!'</span>, <span class="hljs-string">'CustomWarning'</span>); 1655<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>); 1656 1657<span class="hljs-comment">// Emit a warning using a string and a type.</span> 1658<span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Something Happened!'</span>, <span class="hljs-string">'CustomWarning'</span>); 1659<span class="hljs-comment">// Emits: (node:56338) CustomWarning: Something Happened!</span></code><button class="copy-button">copy</button></pre> 1660 1661<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>; 1662 1663<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>); 1664<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>); 1665 1666process.<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><button class="copy-button">copy</button></pre> 1668<p>In each of the previous examples, an <code>Error</code> object is generated internally by 1669<code>process.emitWarning()</code> and passed through to the <a href="#event-warning"><code>'warning'</code></a> 1670handler.</p> 1671 1672<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>; 1673 1674process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'warning'</span>, <span class="hljs-function">(<span class="hljs-params">warning</span>) =></span> { 1675 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">name</span>); 1676 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">message</span>); 1677 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">code</span>); 1678 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">stack</span>); 1679});</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>); 1680 1681process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'warning'</span>, <span class="hljs-function">(<span class="hljs-params">warning</span>) =></span> { 1682 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">name</span>); 1683 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">message</span>); 1684 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">code</span>); 1685 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">warn</span>(warning.<span class="hljs-property">stack</span>); 1686});</code><button class="copy-button">copy</button></pre> 1687<p>If <code>warning</code> is passed as an <code>Error</code> object, it will be passed through to the 1688<code>'warning'</code> event handler unmodified (and the optional <code>type</code>, 1689<code>code</code> and <code>ctor</code> arguments will be ignored):</p> 1690 1691<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>; 1692 1693<span class="hljs-comment">// Emit a warning using an Error object.</span> 1694<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>); 1695<span class="hljs-comment">// Use the Error name property to specify the type name</span> 1696myWarning.<span class="hljs-property">name</span> = <span class="hljs-string">'CustomWarning'</span>; 1697myWarning.<span class="hljs-property">code</span> = <span class="hljs-string">'WARN001'</span>; 1698 1699<span class="hljs-title function_">emitWarning</span>(myWarning); 1700<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>); 1701 1702<span class="hljs-comment">// Emit a warning using an Error object.</span> 1703<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>); 1704<span class="hljs-comment">// Use the Error name property to specify the type name</span> 1705myWarning.<span class="hljs-property">name</span> = <span class="hljs-string">'CustomWarning'</span>; 1706myWarning.<span class="hljs-property">code</span> = <span class="hljs-string">'WARN001'</span>; 1707 1708<span class="hljs-title function_">emitWarning</span>(myWarning); 1709<span class="hljs-comment">// Emits: (node:56338) [WARN001] CustomWarning: Something happened!</span></code><button class="copy-button">copy</button></pre> 1710<p>A <code>TypeError</code> is thrown if <code>warning</code> is anything other than a string or <code>Error</code> 1711object.</p> 1712<p>While process warnings use <code>Error</code> objects, the process warning 1713mechanism is <strong>not</strong> a replacement for normal error handling mechanisms.</p> 1714<p>The following additional handling is implemented if the warning <code>type</code> is 1715<code>'DeprecationWarning'</code>:</p> 1716<ul> 1717<li>If the <code>--throw-deprecation</code> command-line flag is used, the deprecation 1718warning is thrown as an exception rather than being emitted as an event.</li> 1719<li>If the <code>--no-deprecation</code> command-line flag is used, the deprecation 1720warning is suppressed.</li> 1721<li>If the <code>--trace-deprecation</code> command-line flag is used, the deprecation 1722warning is printed to <code>stderr</code> along with the full stack trace.</li> 1723</ul> 1724<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> 1725<p>As a best practice, warnings should be emitted only once per process. To do 1726so, place the <code>emitWarning()</code> behind a boolean.</p> 1727 1728<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>; 1729 1730<span class="hljs-keyword">function</span> <span class="hljs-title function_">emitMyWarning</span>(<span class="hljs-params"></span>) { 1731 <span class="hljs-keyword">if</span> (!emitMyWarning.<span class="hljs-property">warned</span>) { 1732 emitMyWarning.<span class="hljs-property">warned</span> = <span class="hljs-literal">true</span>; 1733 <span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Only warn once!'</span>); 1734 } 1735} 1736<span class="hljs-title function_">emitMyWarning</span>(); 1737<span class="hljs-comment">// Emits: (node: 56339) Warning: Only warn once!</span> 1738<span class="hljs-title function_">emitMyWarning</span>(); 1739<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>); 1740 1741<span class="hljs-keyword">function</span> <span class="hljs-title function_">emitMyWarning</span>(<span class="hljs-params"></span>) { 1742 <span class="hljs-keyword">if</span> (!emitMyWarning.<span class="hljs-property">warned</span>) { 1743 emitMyWarning.<span class="hljs-property">warned</span> = <span class="hljs-literal">true</span>; 1744 <span class="hljs-title function_">emitWarning</span>(<span class="hljs-string">'Only warn once!'</span>); 1745 } 1746} 1747<span class="hljs-title function_">emitMyWarning</span>(); 1748<span class="hljs-comment">// Emits: (node: 56339) Warning: Only warn once!</span> 1749<span class="hljs-title function_">emitMyWarning</span>(); 1750<span class="hljs-comment">// Emits nothing</span></code><button class="copy-button">copy</button></pre> 1751</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> 1752<div class="api_metadata"> 1753<details class="changelog"><summary>History</summary> 1754<table> 1755<tbody><tr><th>Version</th><th>Changes</th></tr> 1756<tr><td>v11.14.0</td> 1757<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> 1758<tr><td>v10.0.0</td> 1759<td><p>Implicit conversion of variable value to string is deprecated.</p></td></tr> 1760<tr><td>v0.1.27</td> 1761<td><p><span>Added in: v0.1.27</span></p></td></tr> 1762</tbody></table> 1763</details> 1764</div> 1765<ul> 1766<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 1767</ul> 1768<p>The <code>process.env</code> property returns an object containing the user environment. 1769See <a href="http://man7.org/linux/man-pages/man7/environ.7.html"><code>environ(7)</code></a>.</p> 1770<p>An example of this object looks like:</p> 1771<!-- eslint-skip --> 1772<pre><code class="language-js">{ 1773 <span class="hljs-attr">TERM</span>: <span class="hljs-string">'xterm-256color'</span>, 1774 <span class="hljs-attr">SHELL</span>: <span class="hljs-string">'/usr/local/bin/bash'</span>, 1775 <span class="hljs-attr">USER</span>: <span class="hljs-string">'maciej'</span>, 1776 <span class="hljs-attr">PATH</span>: <span class="hljs-string">'~/.bin/:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin'</span>, 1777 <span class="hljs-attr">PWD</span>: <span class="hljs-string">'/Users/maciej'</span>, 1778 <span class="hljs-attr">EDITOR</span>: <span class="hljs-string">'vim'</span>, 1779 <span class="hljs-attr">SHLVL</span>: <span class="hljs-string">'1'</span>, 1780 <span class="hljs-attr">HOME</span>: <span class="hljs-string">'/Users/maciej'</span>, 1781 <span class="hljs-attr">LOGNAME</span>: <span class="hljs-string">'maciej'</span>, 1782 <span class="hljs-attr">_</span>: <span class="hljs-string">'/usr/local/bin/node'</span> 1783}</code> <button class="copy-button">copy</button></pre> 1784<p>It is possible to modify this object, but such modifications will not be 1785reflected outside the Node.js process, or (unless explicitly requested) 1786to other <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads. 1787In other words, the following example would not work:</p> 1788<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> 1789<p>While the following will:</p> 1790 1791<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>; 1792 1793env.<span class="hljs-property">foo</span> = <span class="hljs-string">'bar'</span>; 1794<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>); 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><button class="copy-button">copy</button></pre> 1798<p>Assigning a property on <code>process.env</code> will implicitly convert the value 1799to a string. <strong>This behavior is deprecated.</strong> Future versions of Node.js may 1800throw an error when the value is not a string, number, or boolean.</p> 1801 1802<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>; 1803 1804env.<span class="hljs-property">test</span> = <span class="hljs-literal">null</span>; 1805<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(env.<span class="hljs-property">test</span>); 1806<span class="hljs-comment">// => 'null'</span> 1807env.<span class="hljs-property">test</span> = <span class="hljs-literal">undefined</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">// => '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>); 1810 1811env.<span class="hljs-property">test</span> = <span class="hljs-literal">null</span>; 1812<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(env.<span class="hljs-property">test</span>); 1813<span class="hljs-comment">// => 'null'</span> 1814env.<span class="hljs-property">test</span> = <span class="hljs-literal">undefined</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">// => 'undefined'</span></code><button class="copy-button">copy</button></pre> 1817<p>Use <code>delete</code> to delete a property from <code>process.env</code>.</p> 1818 1819<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>; 1820 1821env.<span class="hljs-property">TEST</span> = <span class="hljs-number">1</span>; 1822<span class="hljs-keyword">delete</span> env.<span class="hljs-property">TEST</span>; 1823<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(env.<span class="hljs-property">TEST</span>); 1824<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>); 1825 1826env.<span class="hljs-property">TEST</span> = <span class="hljs-number">1</span>; 1827<span class="hljs-keyword">delete</span> env.<span class="hljs-property">TEST</span>; 1828<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(env.<span class="hljs-property">TEST</span>); 1829<span class="hljs-comment">// => undefined</span></code><button class="copy-button">copy</button></pre> 1830<p>On Windows operating systems, environment variables are case-insensitive.</p> 1831 1832<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>; 1833 1834env.<span class="hljs-property">TEST</span> = <span class="hljs-number">1</span>; 1835<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(env.<span class="hljs-property">test</span>); 1836<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>); 1837 1838env.<span class="hljs-property">TEST</span> = <span class="hljs-number">1</span>; 1839<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(env.<span class="hljs-property">test</span>); 1840<span class="hljs-comment">// => 1</span></code><button class="copy-button">copy</button></pre> 1841<p>Unless explicitly specified when creating a <a href="worker_threads.html#class-worker"><code>Worker</code></a> instance, 1842each <a href="worker_threads.html#class-worker"><code>Worker</code></a> thread has its own copy of <code>process.env</code>, based on its 1843parent thread's <code>process.env</code>, or whatever was specified as the <code>env</code> option 1844to the <a href="worker_threads.html#class-worker"><code>Worker</code></a> constructor. Changes to <code>process.env</code> will not be visible 1845across <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads, and only the main thread can make changes that 1846are visible to the operating system or to native add-ons.</p> 1847</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> 1848<div class="api_metadata"> 1849<span>Added in: v0.7.7</span> 1850</div> 1851<ul> 1852<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 1853</ul> 1854<p>The <code>process.execArgv</code> property returns the set of Node.js-specific command-line 1855options passed when the Node.js process was launched. These options do not 1856appear in the array returned by the <a href="#processargv"><code>process.argv</code></a> property, and do not 1857include the Node.js executable, the name of the script, or any options following 1858the script name. These options are useful in order to spawn child processes with 1859the same execution environment as the parent.</p> 1860<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> 1861<p>Results in <code>process.execArgv</code>:</p> 1862<!-- eslint-disable semi --> 1863<pre><code class="language-js">[<span class="hljs-string">'--harmony'</span>]</code> <button class="copy-button">copy</button></pre> 1864<p>And <code>process.argv</code>:</p> 1865<!-- eslint-disable semi --> 1866<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> 1867<p>Refer to <a href="worker_threads.html#new-workerfilename-options"><code>Worker</code> constructor</a> for the detailed behavior of worker 1868threads with this property.</p> 1869</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> 1870<div class="api_metadata"> 1871<span>Added in: v0.1.100</span> 1872</div> 1873<ul> 1874<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1875</ul> 1876<p>The <code>process.execPath</code> property returns the absolute pathname of the executable 1877that started the Node.js process. Symbolic links, if any, are resolved.</p> 1878<!-- eslint-disable semi --> 1879<pre><code class="language-js"><span class="hljs-string">'/usr/local/bin/node'</span></code> <button class="copy-button">copy</button></pre> 1880</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> 1881<div class="api_metadata"> 1882<span>Added in: v0.1.13</span> 1883</div> 1884<ul> 1885<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> 1886</ul> 1887<p>The <code>process.exit()</code> method instructs Node.js to terminate the process 1888synchronously with an exit status of <code>code</code>. If <code>code</code> is omitted, exit uses 1889either the 'success' code <code>0</code> or the value of <code>process.exitCode</code> if it has been 1890set. Node.js will not terminate until all the <a href="#event-exit"><code>'exit'</code></a> event listeners are 1891called.</p> 1892<p>To exit with a 'failure' code:</p> 1893 1894<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>; 1895 1896<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>); 1897 1898<span class="hljs-title function_">exit</span>(<span class="hljs-number">1</span>);</code><button class="copy-button">copy</button></pre> 1899<p>The shell that executed Node.js should see the exit code as <code>1</code>.</p> 1900<p>Calling <code>process.exit()</code> will force the process to exit as quickly as possible 1901even if there are still asynchronous operations pending that have not yet 1902completed fully, including I/O operations to <code>process.stdout</code> and 1903<code>process.stderr</code>.</p> 1904<p>In most situations, it is not actually necessary to call <code>process.exit()</code> 1905explicitly. The Node.js process will exit on its own <em>if there is no additional 1906work pending</em> in the event loop. The <code>process.exitCode</code> property can be set to 1907tell the process which exit code to use when the process exits gracefully.</p> 1908<p>For instance, the following example illustrates a <em>misuse</em> of the 1909<code>process.exit()</code> method that could lead to data printed to stdout being 1910truncated and lost:</p> 1911 1912<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>; 1913 1914<span class="hljs-comment">// This is an example of what *not* to do:</span> 1915<span class="hljs-keyword">if</span> (<span class="hljs-title function_">someConditionNotMet</span>()) { 1916 <span class="hljs-title function_">printUsageToStdout</span>(); 1917 <span class="hljs-title function_">exit</span>(<span class="hljs-number">1</span>); 1918}</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>); 1919 1920<span class="hljs-comment">// This is an example of what *not* to do:</span> 1921<span class="hljs-keyword">if</span> (<span class="hljs-title function_">someConditionNotMet</span>()) { 1922 <span class="hljs-title function_">printUsageToStdout</span>(); 1923 <span class="hljs-title function_">exit</span>(<span class="hljs-number">1</span>); 1924}</code><button class="copy-button">copy</button></pre> 1925<p>The reason this is problematic is because writes to <code>process.stdout</code> in Node.js 1926are sometimes <em>asynchronous</em> and may occur over multiple ticks of the Node.js 1927event loop. Calling <code>process.exit()</code>, however, forces the process to exit 1928<em>before</em> those additional writes to <code>stdout</code> can be performed.</p> 1929<p>Rather than calling <code>process.exit()</code> directly, the code <em>should</em> set the 1930<code>process.exitCode</code> and allow the process to exit naturally by avoiding 1931scheduling any additional work for the event loop:</p> 1932 1933<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>; 1934 1935<span class="hljs-comment">// How to properly set the exit code while letting</span> 1936<span class="hljs-comment">// the process exit gracefully.</span> 1937<span class="hljs-keyword">if</span> (<span class="hljs-title function_">someConditionNotMet</span>()) { 1938 <span class="hljs-title function_">printUsageToStdout</span>(); 1939 process.<span class="hljs-property">exitCode</span> = <span class="hljs-number">1</span>; 1940}</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>); 1941 1942<span class="hljs-comment">// How to properly set the exit code while letting</span> 1943<span class="hljs-comment">// the process exit gracefully.</span> 1944<span class="hljs-keyword">if</span> (<span class="hljs-title function_">someConditionNotMet</span>()) { 1945 <span class="hljs-title function_">printUsageToStdout</span>(); 1946 process.<span class="hljs-property">exitCode</span> = <span class="hljs-number">1</span>; 1947}</code><button class="copy-button">copy</button></pre> 1948<p>If it is necessary to terminate the Node.js process due to an error condition, 1949throwing an <em>uncaught</em> error and allowing the process to terminate accordingly 1950is safer than calling <code>process.exit()</code>.</p> 1951<p>In <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads, this function stops the current thread rather 1952than the current process.</p> 1953</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> 1954<div class="api_metadata"> 1955<span>Added in: v0.11.8</span> 1956</div> 1957<ul> 1958<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 1959</ul> 1960<p>A number which will be the process exit code, when the process either 1961exits gracefully, or is exited via <a href="#processexitcode"><code>process.exit()</code></a> without specifying 1962a code.</p> 1963<p>Specifying a code to <a href="#processexitcode"><code>process.exit(code)</code></a> will override any 1964previous setting of <code>process.exitCode</code>.</p> 1965</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> 1966<div class="api_metadata"> 1967<span>Added in: v17.3.0, v16.14.0</span> 1968</div> 1969<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 1970<ul> 1971<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 1972</ul> 1973<p>The <code>process.getActiveResourcesInfo()</code> method returns an array of strings 1974containing the types of the active resources that are currently keeping the 1975event loop alive.</p> 1976 1977<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>; 1978<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>; 1979 1980<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>()); 1981<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> {}, <span class="hljs-number">1000</span>); 1982<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>()); 1983<span class="hljs-comment">// Prints:</span> 1984<span class="hljs-comment">// Before: [ 'CloseReq', 'TTYWrap', 'TTYWrap', 'TTYWrap' ]</span> 1985<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>); 1986<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>); 1987 1988<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>()); 1989<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> {}, <span class="hljs-number">1000</span>); 1990<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>()); 1991<span class="hljs-comment">// Prints:</span> 1992<span class="hljs-comment">// Before: [ 'TTYWrap', 'TTYWrap', 'TTYWrap' ]</span> 1993<span class="hljs-comment">// After: [ 'TTYWrap', 'TTYWrap', 'TTYWrap', 'Timeout' ]</span></code><button class="copy-button">copy</button></pre> 1994</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> 1995<div class="api_metadata"> 1996<span>Added in: v2.0.0</span> 1997</div> 1998<p>The <code>process.getegid()</code> method returns the numerical effective group identity 1999of the Node.js process. (See <a href="http://man7.org/linux/man-pages/man2/getegid.2.html"><code>getegid(2)</code></a>.)</p> 2000 2001<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>; 2002 2003<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getegid</span>) { 2004 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current gid: <span class="hljs-subst">${process.getegid()}</span>`</span>); 2005}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2006 2007<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getegid</span>) { 2008 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current gid: <span class="hljs-subst">${process.getegid()}</span>`</span>); 2009}</code><button class="copy-button">copy</button></pre> 2010<p>This function is only available on POSIX platforms (i.e. not Windows or 2011Android).</p> 2012</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> 2013<div class="api_metadata"> 2014<span>Added in: v2.0.0</span> 2015</div> 2016<ul> 2017<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 2018</ul> 2019<p>The <code>process.geteuid()</code> method returns the numerical effective user identity of 2020the process. (See <a href="http://man7.org/linux/man-pages/man2/geteuid.2.html"><code>geteuid(2)</code></a>.)</p> 2021 2022<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>; 2023 2024<span class="hljs-keyword">if</span> (process.<span class="hljs-property">geteuid</span>) { 2025 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current uid: <span class="hljs-subst">${process.geteuid()}</span>`</span>); 2026}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2027 2028<span class="hljs-keyword">if</span> (process.<span class="hljs-property">geteuid</span>) { 2029 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current uid: <span class="hljs-subst">${process.geteuid()}</span>`</span>); 2030}</code><button class="copy-button">copy</button></pre> 2031<p>This function is only available on POSIX platforms (i.e. not Windows or 2032Android).</p> 2033</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> 2034<div class="api_metadata"> 2035<span>Added in: v0.1.31</span> 2036</div> 2037<ul> 2038<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 2039</ul> 2040<p>The <code>process.getgid()</code> method returns the numerical group identity of the 2041process. (See <a href="http://man7.org/linux/man-pages/man2/getgid.2.html"><code>getgid(2)</code></a>.)</p> 2042 2043<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>; 2044 2045<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getgid</span>) { 2046 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current gid: <span class="hljs-subst">${process.getgid()}</span>`</span>); 2047}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2048 2049<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getgid</span>) { 2050 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current gid: <span class="hljs-subst">${process.getgid()}</span>`</span>); 2051}</code><button class="copy-button">copy</button></pre> 2052<p>This function is only available on POSIX platforms (i.e. not Windows or 2053Android).</p> 2054</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> 2055<div class="api_metadata"> 2056<span>Added in: v0.9.4</span> 2057</div> 2058<ul> 2059<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer[]></a></li> 2060</ul> 2061<p>The <code>process.getgroups()</code> method returns an array with the supplementary group 2062IDs. POSIX leaves it unspecified if the effective group ID is included but 2063Node.js ensures it always is.</p> 2064 2065<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>; 2066 2067<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getgroups</span>) { 2068 <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> 2069}</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>); 2070 2071<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getgroups</span>) { 2072 <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> 2073}</code><button class="copy-button">copy</button></pre> 2074<p>This function is only available on POSIX platforms (i.e. not Windows or 2075Android).</p> 2076</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> 2077<div class="api_metadata"> 2078<span>Added in: v0.1.28</span> 2079</div> 2080<ul> 2081<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2082</ul> 2083<p>The <code>process.getuid()</code> method returns the numeric user identity of the process. 2084(See <a href="http://man7.org/linux/man-pages/man2/getuid.2.html"><code>getuid(2)</code></a>.)</p> 2085 2086<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>; 2087 2088<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getuid</span>) { 2089 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current uid: <span class="hljs-subst">${process.getuid()}</span>`</span>); 2090}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2091 2092<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getuid</span>) { 2093 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current uid: <span class="hljs-subst">${process.getuid()}</span>`</span>); 2094}</code><button class="copy-button">copy</button></pre> 2095<p>This function is only available on POSIX platforms (i.e. not Windows or 2096Android).</p> 2097</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> 2098<div class="api_metadata"> 2099<span>Added in: v9.3.0</span> 2100</div> 2101<ul> 2102<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2103</ul> 2104<p>Indicates whether a callback has been set using 2105<a href="#processsetuncaughtexceptioncapturecallbackfn"><code>process.setUncaughtExceptionCaptureCallback()</code></a>.</p> 2106</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> 2107<div class="api_metadata"> 2108<span>Added in: v0.7.6</span> 2109</div> 2110<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> 2111<ul> 2112<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> 2113<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer[]></a></li> 2114</ul> 2115<p>This is the legacy version of <a href="#processhrtimebigint"><code>process.hrtime.bigint()</code></a> 2116before <code>bigint</code> was introduced in JavaScript.</p> 2117<p>The <code>process.hrtime()</code> method returns the current high-resolution real time 2118in a <code>[seconds, nanoseconds]</code> tuple <code>Array</code>, where <code>nanoseconds</code> is the 2119remaining part of the real time that can't be represented in second precision.</p> 2120<p><code>time</code> is an optional parameter that must be the result of a previous 2121<code>process.hrtime()</code> call to diff with the current time. If the parameter 2122passed in is not a tuple <code>Array</code>, a <code>TypeError</code> will be thrown. Passing in a 2123user-defined array instead of the result of a previous call to 2124<code>process.hrtime()</code> will lead to undefined behavior.</p> 2125<p>These times are relative to an arbitrary time in the 2126past, and not related to the time of day and therefore not subject to clock 2127drift. The primary use is for measuring performance between intervals:</p> 2128 2129<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>; 2130 2131<span class="hljs-keyword">const</span> <span class="hljs-variable constant_">NS_PER_SEC</span> = <span class="hljs-number">1e9</span>; 2132<span class="hljs-keyword">const</span> time = <span class="hljs-title function_">hrtime</span>(); 2133<span class="hljs-comment">// [ 1800216, 25 ]</span> 2134 2135<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 2136 <span class="hljs-keyword">const</span> diff = <span class="hljs-title function_">hrtime</span>(time); 2137 <span class="hljs-comment">// [ 1, 552 ]</span> 2138 2139 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Benchmark took <span class="hljs-subst">${diff[<span class="hljs-number">0</span>] * NS_PER_SEC + diff[<span class="hljs-number">1</span>]}</span> nanoseconds`</span>); 2140 <span class="hljs-comment">// Benchmark took 1000000552 nanoseconds</span> 2141}, <span class="hljs-number">1000</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { hrtime } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2142 2143<span class="hljs-keyword">const</span> <span class="hljs-variable constant_">NS_PER_SEC</span> = <span class="hljs-number">1e9</span>; 2144<span class="hljs-keyword">const</span> time = <span class="hljs-title function_">hrtime</span>(); 2145<span class="hljs-comment">// [ 1800216, 25 ]</span> 2146 2147<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 2148 <span class="hljs-keyword">const</span> diff = <span class="hljs-title function_">hrtime</span>(time); 2149 <span class="hljs-comment">// [ 1, 552 ]</span> 2150 2151 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Benchmark took <span class="hljs-subst">${diff[<span class="hljs-number">0</span>] * NS_PER_SEC + diff[<span class="hljs-number">1</span>]}</span> nanoseconds`</span>); 2152 <span class="hljs-comment">// Benchmark took 1000000552 nanoseconds</span> 2153}, <span class="hljs-number">1000</span>);</code><button class="copy-button">copy</button></pre> 2154</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> 2155<div class="api_metadata"> 2156<span>Added in: v10.7.0</span> 2157</div> 2158<ul> 2159<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt" class="type"><bigint></a></li> 2160</ul> 2161<p>The <code>bigint</code> version of the <a href="#processhrtimetime"><code>process.hrtime()</code></a> method returning the 2162current high-resolution real time in nanoseconds as a <code>bigint</code>.</p> 2163<p>Unlike <a href="#processhrtimetime"><code>process.hrtime()</code></a>, it does not support an additional <code>time</code> 2164argument since the difference can just be computed directly 2165by subtraction of the two <code>bigint</code>s.</p> 2166 2167<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>; 2168 2169<span class="hljs-keyword">const</span> start = hrtime.<span class="hljs-title function_">bigint</span>(); 2170<span class="hljs-comment">// 191051479007711n</span> 2171 2172<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 2173 <span class="hljs-keyword">const</span> end = hrtime.<span class="hljs-title function_">bigint</span>(); 2174 <span class="hljs-comment">// 191052633396993n</span> 2175 2176 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Benchmark took <span class="hljs-subst">${end - start}</span> nanoseconds`</span>); 2177 <span class="hljs-comment">// Benchmark took 1154389282 nanoseconds</span> 2178}, <span class="hljs-number">1000</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { hrtime } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2179 2180<span class="hljs-keyword">const</span> start = hrtime.<span class="hljs-title function_">bigint</span>(); 2181<span class="hljs-comment">// 191051479007711n</span> 2182 2183<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 2184 <span class="hljs-keyword">const</span> end = hrtime.<span class="hljs-title function_">bigint</span>(); 2185 <span class="hljs-comment">// 191052633396993n</span> 2186 2187 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Benchmark took <span class="hljs-subst">${end - start}</span> nanoseconds`</span>); 2188 <span class="hljs-comment">// Benchmark took 1154389282 nanoseconds</span> 2189}, <span class="hljs-number">1000</span>);</code><button class="copy-button">copy</button></pre> 2190</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> 2191<div class="api_metadata"> 2192<span>Added in: v0.9.4</span> 2193</div> 2194<ul> 2195<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> 2196<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> 2197</ul> 2198<p>The <code>process.initgroups()</code> method reads the <code>/etc/group</code> file and initializes 2199the group access list, using all groups of which the user is a member. This is 2200a privileged operation that requires that the Node.js process either have <code>root</code> 2201access or the <code>CAP_SETGID</code> capability.</p> 2202<p>Use care when dropping privileges:</p> 2203 2204<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>; 2205 2206<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> 2207<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> 2208<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> 2209<span class="hljs-title function_">setgid</span>(<span class="hljs-number">1000</span>); <span class="hljs-comment">// drop root gid</span> 2210<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>); 2211 2212<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> 2213<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> 2214<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> 2215<span class="hljs-title function_">setgid</span>(<span class="hljs-number">1000</span>); <span class="hljs-comment">// drop root gid</span> 2216<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> 2217<p>This function is only available on POSIX platforms (i.e. not Windows or 2218Android). 2219This feature is not available in <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 2220</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> 2221<div class="api_metadata"> 2222<span>Added in: v0.0.6</span> 2223</div> 2224<ul> 2225<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> 2226<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. 2227<strong>Default:</strong> <code>'SIGTERM'</code>.</li> 2228</ul> 2229<p>The <code>process.kill()</code> method sends the <code>signal</code> to the process identified by 2230<code>pid</code>.</p> 2231<p>Signal names are strings such as <code>'SIGINT'</code> or <code>'SIGHUP'</code>. See <a href="#signal-events">Signal Events</a> 2232and <a href="http://man7.org/linux/man-pages/man2/kill.2.html"><code>kill(2)</code></a> for more information.</p> 2233<p>This method will throw an error if the target <code>pid</code> does not exist. As a special 2234case, a signal of <code>0</code> can be used to test for the existence of a process. 2235Windows platforms will throw an error if the <code>pid</code> is used to kill a process 2236group.</p> 2237<p>Even though the name of this function is <code>process.kill()</code>, it is really just a 2238signal sender, like the <code>kill</code> system call. The signal sent may do something 2239other than kill the target process.</p> 2240 2241<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>; 2242 2243process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'SIGHUP'</span>, <span class="hljs-function">() =></span> { 2244 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Got SIGHUP signal.'</span>); 2245}); 2246 2247<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 2248 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Exiting.'</span>); 2249 process.<span class="hljs-title function_">exit</span>(<span class="hljs-number">0</span>); 2250}, <span class="hljs-number">100</span>); 2251 2252<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>); 2253 2254process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'SIGHUP'</span>, <span class="hljs-function">() =></span> { 2255 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Got SIGHUP signal.'</span>); 2256}); 2257 2258<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 2259 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Exiting.'</span>); 2260 process.<span class="hljs-title function_">exit</span>(<span class="hljs-number">0</span>); 2261}, <span class="hljs-number">100</span>); 2262 2263process.<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> 2264<p>When <code>SIGUSR1</code> is received by a Node.js process, Node.js will start the 2265debugger. See <a href="#signal-events">Signal Events</a>.</p> 2266</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> 2267<div class="api_metadata"> 2268<span>Added in: v0.1.17</span><span>Deprecated since: v14.0.0</span> 2269</div> 2270<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> 2271<ul> 2272<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 2273</ul> 2274<p>The <code>process.mainModule</code> property provides an alternative way of retrieving 2275<a href="modules.html#accessing-the-main-module"><code>require.main</code></a>. The difference is that if the main module changes at 2276runtime, <a href="modules.html#accessing-the-main-module"><code>require.main</code></a> may still refer to the original main module in 2277modules that were required before the change occurred. Generally, it's 2278safe to assume that the two refer to the same module.</p> 2279<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 2280is no entry script.</p> 2281</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> 2282<div class="api_metadata"> 2283<details class="changelog"><summary>History</summary> 2284<table> 2285<tbody><tr><th>Version</th><th>Changes</th></tr> 2286<tr><td>v13.9.0, v12.17.0</td> 2287<td><p>Added <code>arrayBuffers</code> to the returned object.</p></td></tr> 2288<tr><td>v7.2.0</td> 2289<td><p>Added <code>external</code> to the returned object.</p></td></tr> 2290<tr><td>v0.1.16</td> 2291<td><p><span>Added in: v0.1.16</span></p></td></tr> 2292</tbody></table> 2293</details> 2294</div> 2295<ul> 2296<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 2297<ul> 2298<li><code>rss</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2299<li><code>heapTotal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2300<li><code>heapUsed</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2301<li><code>external</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2302<li><code>arrayBuffers</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2303</ul> 2304</li> 2305</ul> 2306<p>Returns an object describing the memory usage of the Node.js process measured in 2307bytes.</p> 2308 2309<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>; 2310 2311<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">memoryUsage</span>()); 2312<span class="hljs-comment">// Prints:</span> 2313<span class="hljs-comment">// {</span> 2314<span class="hljs-comment">// rss: 4935680,</span> 2315<span class="hljs-comment">// heapTotal: 1826816,</span> 2316<span class="hljs-comment">// heapUsed: 650472,</span> 2317<span class="hljs-comment">// external: 49879,</span> 2318<span class="hljs-comment">// arrayBuffers: 9386</span> 2319<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>); 2320 2321<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">memoryUsage</span>()); 2322<span class="hljs-comment">// Prints:</span> 2323<span class="hljs-comment">// {</span> 2324<span class="hljs-comment">// rss: 4935680,</span> 2325<span class="hljs-comment">// heapTotal: 1826816,</span> 2326<span class="hljs-comment">// heapUsed: 650472,</span> 2327<span class="hljs-comment">// external: 49879,</span> 2328<span class="hljs-comment">// arrayBuffers: 9386</span> 2329<span class="hljs-comment">// }</span></code><button class="copy-button">copy</button></pre> 2330<ul> 2331<li><code>heapTotal</code> and <code>heapUsed</code> refer to V8's memory usage.</li> 2332<li><code>external</code> refers to the memory usage of C++ objects bound to JavaScript 2333objects managed by V8.</li> 2334<li><code>rss</code>, Resident Set Size, is the amount of space occupied in the main 2335memory device (that is a subset of the total allocated memory) for the 2336process, including all C++ and JavaScript objects and code.</li> 2337<li><code>arrayBuffers</code> refers to memory allocated for <code>ArrayBuffer</code>s and 2338<code>SharedArrayBuffer</code>s, including all Node.js <a href="buffer.html"><code>Buffer</code></a>s. 2339This is also included in the <code>external</code> value. When Node.js is used as an 2340embedded library, this value may be <code>0</code> because allocations for <code>ArrayBuffer</code>s 2341may not be tracked in that case.</li> 2342</ul> 2343<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 2344entire process, while the other fields will only refer to the current thread.</p> 2345<p>The <code>process.memoryUsage()</code> method iterates over each page to gather 2346information about memory usage which might be slow depending on the 2347program memory allocations.</p> 2348</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> 2349<div class="api_metadata"> 2350<span>Added in: v15.6.0, v14.18.0</span> 2351</div> 2352<ul> 2353<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2354</ul> 2355<p>The <code>process.memoryUsage.rss()</code> method returns an integer representing the 2356Resident Set Size (RSS) in bytes.</p> 2357<p>The Resident Set Size, is the amount of space occupied in the main 2358memory device (that is a subset of the total allocated memory) for the 2359process, including all C++ and JavaScript objects and code.</p> 2360<p>This is the same value as the <code>rss</code> property provided by <code>process.memoryUsage()</code> 2361but <code>process.memoryUsage.rss()</code> is faster.</p> 2362 2363<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>; 2364 2365<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(memoryUsage.<span class="hljs-title function_">rss</span>()); 2366<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>); 2367 2368<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(memoryUsage.<span class="hljs-title function_">rss</span>()); 2369<span class="hljs-comment">// 35655680</span></code><button class="copy-button">copy</button></pre> 2370</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> 2371<div class="api_metadata"> 2372<details class="changelog"><summary>History</summary> 2373<table> 2374<tbody><tr><th>Version</th><th>Changes</th></tr> 2375<tr><td>v18.0.0</td> 2376<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> 2377<tr><td>v1.8.1</td> 2378<td><p>Additional arguments after <code>callback</code> are now supported.</p></td></tr> 2379<tr><td>v0.1.26</td> 2380<td><p><span>Added in: v0.1.26</span></p></td></tr> 2381</tbody></table> 2382</details> 2383</div> 2384<ul> 2385<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 2386<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> 2387</ul> 2388<p><code>process.nextTick()</code> adds <code>callback</code> to the "next tick queue". This queue is 2389fully drained after the current operation on the JavaScript stack runs to 2390completion and before the event loop is allowed to continue. It's possible to 2391create an infinite loop if one were to recursively call <code>process.nextTick()</code>. 2392See the <a href="https://nodejs.org/en/docs/guides/event-loop-timers-and-nexttick/#process-nexttick">Event Loop</a> guide for more background.</p> 2393 2394<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>; 2395 2396<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'start'</span>); 2397<span class="hljs-title function_">nextTick</span>(<span class="hljs-function">() =></span> { 2398 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'nextTick callback'</span>); 2399}); 2400<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'scheduled'</span>); 2401<span class="hljs-comment">// Output:</span> 2402<span class="hljs-comment">// start</span> 2403<span class="hljs-comment">// scheduled</span> 2404<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>); 2405 2406<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'start'</span>); 2407<span class="hljs-title function_">nextTick</span>(<span class="hljs-function">() =></span> { 2408 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'nextTick callback'</span>); 2409}); 2410<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'scheduled'</span>); 2411<span class="hljs-comment">// Output:</span> 2412<span class="hljs-comment">// start</span> 2413<span class="hljs-comment">// scheduled</span> 2414<span class="hljs-comment">// nextTick callback</span></code><button class="copy-button">copy</button></pre> 2415<p>This is important when developing APIs in order to give users the opportunity 2416to assign event handlers <em>after</em> an object has been constructed but before any 2417I/O has occurred:</p> 2418 2419<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>; 2420 2421<span class="hljs-keyword">function</span> <span class="hljs-title function_">MyThing</span>(<span class="hljs-params">options</span>) { 2422 <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">setupOptions</span>(options); 2423 2424 <span class="hljs-title function_">nextTick</span>(<span class="hljs-function">() =></span> { 2425 <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">startDoingStuff</span>(); 2426 }); 2427} 2428 2429<span class="hljs-keyword">const</span> thing = <span class="hljs-keyword">new</span> <span class="hljs-title class_">MyThing</span>(); 2430thing.<span class="hljs-title function_">getReadyForStuff</span>(); 2431 2432<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>); 2433 2434<span class="hljs-keyword">function</span> <span class="hljs-title function_">MyThing</span>(<span class="hljs-params">options</span>) { 2435 <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">setupOptions</span>(options); 2436 2437 <span class="hljs-title function_">nextTick</span>(<span class="hljs-function">() =></span> { 2438 <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">startDoingStuff</span>(); 2439 }); 2440} 2441 2442<span class="hljs-keyword">const</span> thing = <span class="hljs-keyword">new</span> <span class="hljs-title class_">MyThing</span>(); 2443thing.<span class="hljs-title function_">getReadyForStuff</span>(); 2444 2445<span class="hljs-comment">// thing.startDoingStuff() gets called now, not before.</span></code><button class="copy-button">copy</button></pre> 2446<p>It is very important for APIs to be either 100% synchronous or 100% 2447asynchronous. Consider this example:</p> 2448<pre><code class="language-js"><span class="hljs-comment">// WARNING! DO NOT USE! BAD UNSAFE HAZARD!</span> 2449<span class="hljs-keyword">function</span> <span class="hljs-title function_">maybeSync</span>(<span class="hljs-params">arg, cb</span>) { 2450 <span class="hljs-keyword">if</span> (arg) { 2451 <span class="hljs-title function_">cb</span>(); 2452 <span class="hljs-keyword">return</span>; 2453 } 2454 2455 fs.<span class="hljs-title function_">stat</span>(<span class="hljs-string">'file'</span>, cb); 2456}</code> <button class="copy-button">copy</button></pre> 2457<p>This API is hazardous because in the following case:</p> 2458<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>; 2459 2460<span class="hljs-title function_">maybeSync</span>(maybeTrue, <span class="hljs-function">() =></span> { 2461 <span class="hljs-title function_">foo</span>(); 2462}); 2463 2464<span class="hljs-title function_">bar</span>();</code> <button class="copy-button">copy</button></pre> 2465<p>It is not clear whether <code>foo()</code> or <code>bar()</code> will be called first.</p> 2466<p>The following approach is much better:</p> 2467 2468<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>; 2469 2470<span class="hljs-keyword">function</span> <span class="hljs-title function_">definitelyAsync</span>(<span class="hljs-params">arg, cb</span>) { 2471 <span class="hljs-keyword">if</span> (arg) { 2472 <span class="hljs-title function_">nextTick</span>(cb); 2473 <span class="hljs-keyword">return</span>; 2474 } 2475 2476 fs.<span class="hljs-title function_">stat</span>(<span class="hljs-string">'file'</span>, cb); 2477}</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>); 2478 2479<span class="hljs-keyword">function</span> <span class="hljs-title function_">definitelyAsync</span>(<span class="hljs-params">arg, cb</span>) { 2480 <span class="hljs-keyword">if</span> (arg) { 2481 <span class="hljs-title function_">nextTick</span>(cb); 2482 <span class="hljs-keyword">return</span>; 2483 } 2484 2485 fs.<span class="hljs-title function_">stat</span>(<span class="hljs-string">'file'</span>, cb); 2486}</code><button class="copy-button">copy</button></pre> 2487<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> 2488<p>The <a href="globals.html#queuemicrotaskcallback"><code>queueMicrotask()</code></a> API is an alternative to <code>process.nextTick()</code> that 2489also defers execution of a function using the same microtask queue used to 2490execute the then, catch, and finally handlers of resolved promises. Within 2491Node.js, every time the "next tick queue" is drained, the microtask queue 2492is drained immediately after.</p> 2493 2494<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>; 2495 2496<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>)); 2497<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>)); 2498<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>)); 2499<span class="hljs-comment">// Output:</span> 2500<span class="hljs-comment">// 1</span> 2501<span class="hljs-comment">// 2</span> 2502<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>); 2503 2504<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>)); 2505<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>)); 2506<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>)); 2507<span class="hljs-comment">// Output:</span> 2508<span class="hljs-comment">// 1</span> 2509<span class="hljs-comment">// 2</span> 2510<span class="hljs-comment">// 3</span></code><button class="copy-button">copy</button></pre> 2511<p>For <em>most</em> userland use cases, the <code>queueMicrotask()</code> API provides a portable 2512and reliable mechanism for deferring execution that works across multiple 2513JavaScript platform environments and should be favored over <code>process.nextTick()</code>. 2514In simple scenarios, <code>queueMicrotask()</code> can be a drop-in replacement for 2515<code>process.nextTick()</code>.</p> 2516<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>); 2517<span class="hljs-title function_">queueMicrotask</span>(<span class="hljs-function">() =></span> { 2518 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'microtask callback'</span>); 2519}); 2520<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'scheduled'</span>); 2521<span class="hljs-comment">// Output:</span> 2522<span class="hljs-comment">// start</span> 2523<span class="hljs-comment">// scheduled</span> 2524<span class="hljs-comment">// microtask callback</span></code> <button class="copy-button">copy</button></pre> 2525<p>One note-worthy difference between the two APIs is that <code>process.nextTick()</code> 2526allows specifying additional values that will be passed as arguments to the 2527deferred function when it is called. Achieving the same result with 2528<code>queueMicrotask()</code> requires using either a closure or a bound function:</p> 2529<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>) { 2530 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'microtask'</span>, a + b); 2531} 2532 2533<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'start'</span>); 2534<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>)); 2535<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'scheduled'</span>); 2536<span class="hljs-comment">// Output:</span> 2537<span class="hljs-comment">// start</span> 2538<span class="hljs-comment">// scheduled</span> 2539<span class="hljs-comment">// microtask 3</span></code> <button class="copy-button">copy</button></pre> 2540<p>There are minor differences in the way errors raised from within the next tick 2541queue and microtask queue are handled. Errors thrown within a queued microtask 2542callback should be handled within the queued callback when possible. If they are 2543not, the <code>process.on('uncaughtException')</code> event handler can be used to capture 2544and handle the errors.</p> 2545<p>When in doubt, unless the specific capabilities of <code>process.nextTick()</code> are 2546needed, use <code>queueMicrotask()</code>.</p> 2547</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> 2548<div class="api_metadata"> 2549<span>Added in: v0.8.0</span> 2550</div> 2551<ul> 2552<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2553</ul> 2554<p>The <code>process.noDeprecation</code> property indicates whether the <code>--no-deprecation</code> 2555flag is set on the current Node.js process. See the documentation for 2556the <a href="#event-warning"><code>'warning'</code> event</a> and the 2557<a href="#processemitwarningwarning-type-code-ctor"><code>emitWarning()</code> method</a> for more information about this 2558flag's behavior.</p> 2559</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> 2560<div class="api_metadata"> 2561<span>Added in: v0.1.15</span> 2562</div> 2563<ul> 2564<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2565</ul> 2566<p>The <code>process.pid</code> property returns the PID of the process.</p> 2567 2568<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>; 2569 2570<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">${pid}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { pid } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2571 2572<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`This process is pid <span class="hljs-subst">${pid}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2573</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> 2574<div class="api_metadata"> 2575<span>Added in: v0.1.16</span> 2576</div> 2577<ul> 2578<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 2579</ul> 2580<p>The <code>process.platform</code> property returns a string identifying the operating 2581system platform for which the Node.js binary was compiled.</p> 2582<p>Currently possible values are:</p> 2583<ul> 2584<li><code>'aix'</code></li> 2585<li><code>'darwin'</code></li> 2586<li><code>'freebsd'</code></li> 2587<li><code>'linux'</code></li> 2588<li><code>'openbsd'</code></li> 2589<li><code>'sunos'</code></li> 2590<li><code>'win32'</code></li> 2591</ul> 2592 2593<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>; 2594 2595<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">${platform}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { platform } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2596 2597<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`This platform is <span class="hljs-subst">${platform}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2598<p>The value <code>'android'</code> may also be returned if the Node.js is built on the 2599Android operating system. However, Android support in Node.js 2600<a href="https://github.com/nodejs/node/blob/HEAD/BUILDING.md#androidandroid-based-devices-eg-firefox-os">is experimental</a>.</p> 2601</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> 2602<div class="api_metadata"> 2603<span>Added in: v9.2.0, v8.10.0, v6.13.0</span> 2604</div> 2605<ul> 2606<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 2607</ul> 2608<p>The <code>process.ppid</code> property returns the PID of the parent of the 2609current process.</p> 2610 2611<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>; 2612 2613<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">${ppid}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { ppid } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2614 2615<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`The parent process is pid <span class="hljs-subst">${ppid}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2616</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> 2617<div class="api_metadata"> 2618<details class="changelog"><summary>History</summary> 2619<table> 2620<tbody><tr><th>Version</th><th>Changes</th></tr> 2621<tr><td>v4.2.0</td> 2622<td><p>The <code>lts</code> property is now supported.</p></td></tr> 2623<tr><td>v3.0.0</td> 2624<td><p><span>Added in: v3.0.0</span></p></td></tr> 2625</tbody></table> 2626</details> 2627</div> 2628<ul> 2629<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 2630</ul> 2631<p>The <code>process.release</code> property returns an <code>Object</code> containing metadata related 2632to the current release, including URLs for the source tarball and headers-only 2633tarball.</p> 2634<p><code>process.release</code> contains the following properties:</p> 2635<ul> 2636<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> 2637<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 2638the source code of the current release.</li> 2639<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 2640only the source header files for the current release. This file is 2641significantly smaller than the full source file and can be used for compiling 2642Node.js native add-ons.</li> 2643<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 2644matching the architecture and version of the current release. This file is 2645used for compiling Node.js native add-ons. <em>This property is only present on 2646Windows builds of Node.js and will be missing on all other platforms.</em></li> 2647<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 2648release. This property only exists for LTS releases and is <code>undefined</code> for all 2649other release types, including <em>Current</em> releases. Valid values include the 2650LTS Release code names (including those that are no longer supported). 2651<ul> 2652<li><code>'Fermium'</code> for the 14.x LTS line beginning with 14.15.0.</li> 2653<li><code>'Gallium'</code> for the 16.x LTS line beginning with 16.13.0.</li> 2654<li><code>'Hydrogen'</code> for the 18.x LTS line beginning with 18.12.0. 2655For 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> 2656</ul> 2657</li> 2658</ul> 2659<!-- eslint-skip --> 2660<pre><code class="language-js">{ 2661 <span class="hljs-attr">name</span>: <span class="hljs-string">'node'</span>, 2662 <span class="hljs-attr">lts</span>: <span class="hljs-string">'Hydrogen'</span>, 2663 <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>, 2664 <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>, 2665 <span class="hljs-attr">libUrl</span>: <span class="hljs-string">'https://nodejs.org/download/release/v18.12.0/win-x64/node.lib'</span> 2666}</code> <button class="copy-button">copy</button></pre> 2667<p>In custom builds from non-release versions of the source tree, only the 2668<code>name</code> property may be present. The additional properties should not be 2669relied upon to exist.</p> 2670</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> 2671<div class="api_metadata"> 2672<details class="changelog"><summary>History</summary> 2673<table> 2674<tbody><tr><th>Version</th><th>Changes</th></tr> 2675<tr><td>v13.12.0, v12.17.0</td> 2676<td><p>This API is no longer experimental.</p></td></tr> 2677<tr><td>v11.8.0</td> 2678<td><p><span>Added in: v11.8.0</span></p></td></tr> 2679</tbody></table> 2680</details> 2681</div> 2682<ul> 2683<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 2684</ul> 2685<p><code>process.report</code> is an object whose methods are used to generate diagnostic 2686reports for the current process. Additional documentation is available in the 2687<a href="report.html">report documentation</a>.</p> 2688<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> 2689<div class="api_metadata"> 2690<span>Added in: v13.12.0, v12.17.0</span> 2691</div> 2692<ul> 2693<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2694</ul> 2695<p>Write reports in a compact format, single-line JSON, more easily consumable 2696by log processing systems than the default multi-line format designed for 2697human consumption.</p> 2698 2699<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>; 2700 2701<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">${report.compact}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { report } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2702 2703<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Reports are compact? <span class="hljs-subst">${report.compact}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2704<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> 2705<div class="api_metadata"> 2706<details class="changelog"><summary>History</summary> 2707<table> 2708<tbody><tr><th>Version</th><th>Changes</th></tr> 2709<tr><td>v13.12.0, v12.17.0</td> 2710<td><p>This API is no longer experimental.</p></td></tr> 2711<tr><td>v11.12.0</td> 2712<td><p><span>Added in: v11.12.0</span></p></td></tr> 2713</tbody></table> 2714</details> 2715</div> 2716<ul> 2717<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 2718</ul> 2719<p>Directory where the report is written. The default value is the empty string, 2720indicating that reports are written to the current working directory of the 2721Node.js process.</p> 2722 2723<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>; 2724 2725<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">${report.directory}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { report } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2726 2727<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report directory is <span class="hljs-subst">${report.directory}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2728<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> 2729<div class="api_metadata"> 2730<details class="changelog"><summary>History</summary> 2731<table> 2732<tbody><tr><th>Version</th><th>Changes</th></tr> 2733<tr><td>v13.12.0, v12.17.0</td> 2734<td><p>This API is no longer experimental.</p></td></tr> 2735<tr><td>v11.12.0</td> 2736<td><p><span>Added in: v11.12.0</span></p></td></tr> 2737</tbody></table> 2738</details> 2739</div> 2740<ul> 2741<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 2742</ul> 2743<p>Filename where the report is written. If set to the empty string, the output 2744filename will be comprised of a timestamp, PID, and sequence number. The default 2745value is the empty string.</p> 2746<p>If the value of <code>process.report.filename</code> is set to <code>'stdout'</code> or <code>'stderr'</code>, 2747the report is written to the stdout or stderr of the process respectively.</p> 2748 2749<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>; 2750 2751<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">${report.filename}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { report } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2752 2753<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report filename is <span class="hljs-subst">${report.filename}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2754<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> 2755<div class="api_metadata"> 2756<details class="changelog"><summary>History</summary> 2757<table> 2758<tbody><tr><th>Version</th><th>Changes</th></tr> 2759<tr><td>v13.12.0, v12.17.0</td> 2760<td><p>This API is no longer experimental.</p></td></tr> 2761<tr><td>v11.8.0</td> 2762<td><p><span>Added in: v11.8.0</span></p></td></tr> 2763</tbody></table> 2764</details> 2765</div> 2766<ul> 2767<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> 2768<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 2769</ul> 2770<p>Returns a JavaScript Object representation of a diagnostic report for the 2771running process. The report's JavaScript stack trace is taken from <code>err</code>, if 2772present.</p> 2773 2774<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>; 2775<span class="hljs-keyword">import</span> util <span class="hljs-keyword">from</span> <span class="hljs-string">'node:util'</span>; 2776 2777<span class="hljs-keyword">const</span> data = report.<span class="hljs-title function_">getReport</span>(); 2778<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>); 2779 2780<span class="hljs-comment">// Similar to process.report.writeReport()</span> 2781<span class="hljs-keyword">import</span> fs <span class="hljs-keyword">from</span> <span class="hljs-string">'node:fs'</span>; 2782fs.<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>); 2783<span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:util'</span>); 2784 2785<span class="hljs-keyword">const</span> data = report.<span class="hljs-title function_">getReport</span>(); 2786<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>); 2787 2788<span class="hljs-comment">// Similar to process.report.writeReport()</span> 2789<span class="hljs-keyword">const</span> fs = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:fs'</span>); 2790fs.<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> 2791<p>Additional documentation is available in the <a href="report.html">report documentation</a>.</p> 2792<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> 2793<div class="api_metadata"> 2794<details class="changelog"><summary>History</summary> 2795<table> 2796<tbody><tr><th>Version</th><th>Changes</th></tr> 2797<tr><td>v15.0.0, v14.17.0</td> 2798<td><p>This API is no longer experimental.</p></td></tr> 2799<tr><td>v11.12.0</td> 2800<td><p><span>Added in: v11.12.0</span></p></td></tr> 2801</tbody></table> 2802</details> 2803</div> 2804<ul> 2805<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2806</ul> 2807<p>If <code>true</code>, a diagnostic report is generated on fatal errors, such as out of 2808memory errors or failed C++ assertions.</p> 2809 2810<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>; 2811 2812<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">${report.reportOnFatalError}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { report } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2813 2814<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report on fatal error: <span class="hljs-subst">${report.reportOnFatalError}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2815<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> 2816<div class="api_metadata"> 2817<details class="changelog"><summary>History</summary> 2818<table> 2819<tbody><tr><th>Version</th><th>Changes</th></tr> 2820<tr><td>v13.12.0, v12.17.0</td> 2821<td><p>This API is no longer experimental.</p></td></tr> 2822<tr><td>v11.12.0</td> 2823<td><p><span>Added in: v11.12.0</span></p></td></tr> 2824</tbody></table> 2825</details> 2826</div> 2827<ul> 2828<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2829</ul> 2830<p>If <code>true</code>, a diagnostic report is generated when the process receives the 2831signal specified by <code>process.report.signal</code>.</p> 2832 2833<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>; 2834 2835<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">${report.reportOnSignal}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { report } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2836 2837<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report on signal: <span class="hljs-subst">${report.reportOnSignal}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2838<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> 2839<div class="api_metadata"> 2840<details class="changelog"><summary>History</summary> 2841<table> 2842<tbody><tr><th>Version</th><th>Changes</th></tr> 2843<tr><td>v13.12.0, v12.17.0</td> 2844<td><p>This API is no longer experimental.</p></td></tr> 2845<tr><td>v11.12.0</td> 2846<td><p><span>Added in: v11.12.0</span></p></td></tr> 2847</tbody></table> 2848</details> 2849</div> 2850<ul> 2851<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2852</ul> 2853<p>If <code>true</code>, a diagnostic report is generated on uncaught exception.</p> 2854 2855<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>; 2856 2857<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">${report.reportOnUncaughtException}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { report } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2858 2859<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report on exception: <span class="hljs-subst">${report.reportOnUncaughtException}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2860<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> 2861<div class="api_metadata"> 2862<details class="changelog"><summary>History</summary> 2863<table> 2864<tbody><tr><th>Version</th><th>Changes</th></tr> 2865<tr><td>v13.12.0, v12.17.0</td> 2866<td><p>This API is no longer experimental.</p></td></tr> 2867<tr><td>v11.12.0</td> 2868<td><p><span>Added in: v11.12.0</span></p></td></tr> 2869</tbody></table> 2870</details> 2871</div> 2872<ul> 2873<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 2874</ul> 2875<p>The signal used to trigger the creation of a diagnostic report. Defaults to 2876<code>'SIGUSR2'</code>.</p> 2877 2878<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>; 2879 2880<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report signal: <span class="hljs-subst">${report.signal}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { report } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 2881 2882<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Report signal: <span class="hljs-subst">${report.signal}</span>`</span>);</code><button class="copy-button">copy</button></pre> 2883<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> 2884<div class="api_metadata"> 2885<details class="changelog"><summary>History</summary> 2886<table> 2887<tbody><tr><th>Version</th><th>Changes</th></tr> 2888<tr><td>v13.12.0, v12.17.0</td> 2889<td><p>This API is no longer experimental.</p></td></tr> 2890<tr><td>v11.8.0</td> 2891<td><p><span>Added in: v11.8.0</span></p></td></tr> 2892</tbody></table> 2893</details> 2894</div> 2895<ul> 2896<li> 2897<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 2898should be a relative path, that will be appended to the directory specified in 2899<code>process.report.directory</code>, or the current working directory of the Node.js 2900process, if unspecified.</p> 2901</li> 2902<li> 2903<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> 2904</li> 2905<li> 2906<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> 2907</li> 2908</ul> 2909<p>Writes a diagnostic report to a file. If <code>filename</code> is not provided, the default 2910filename includes the date, time, PID, and a sequence number. The report's 2911JavaScript stack trace is taken from <code>err</code>, if present.</p> 2912<p>If the value of <code>filename</code> is set to <code>'stdout'</code> or <code>'stderr'</code>, the report is 2913written to the stdout or stderr of the process respectively.</p> 2914 2915<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>; 2916 2917report.<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>); 2918 2919report.<span class="hljs-title function_">writeReport</span>();</code><button class="copy-button">copy</button></pre> 2920<p>Additional documentation is available in the <a href="report.html">report documentation</a>.</p> 2921</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> 2922<div class="api_metadata"> 2923<span>Added in: v12.6.0</span> 2924</div> 2925<ul> 2926<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 2927values come from the <code>uv_getrusage</code> call which returns 2928a <a href="https://docs.libuv.org/en/v1.x/misc.html#c.uv_rusage_t"><code>uv_rusage_t</code> struct</a>. 2929<ul> 2930<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. 2931It is the same value as <a href="#processcpuusagepreviousvalue"><code>process.cpuUsage().user</code></a>.</li> 2932<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. 2933It is the same value as <a href="#processcpuusagepreviousvalue"><code>process.cpuUsage().system</code></a>.</li> 2934<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 2935size used in kilobytes.</li> 2936<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 2937any platform.</li> 2938<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 2939any platform.</li> 2940<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 2941any platform.</li> 2942<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 2943minor page faults for the process, see 2944<a href="https://en.wikipedia.org/wiki/Page_fault#Minor">this article for more details</a>.</li> 2945<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 2946major page faults for the process, see 2947<a href="https://en.wikipedia.org/wiki/Page_fault#Major">this article for more details</a>. This field is not 2948supported on Windows.</li> 2949<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 2950platform.</li> 2951<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 2952file system had to perform input.</li> 2953<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 2954file system had to perform output.</li> 2955<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 2956platform.</li> 2957<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 2958platform.</li> 2959<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 2960platform.</li> 2961<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 2962number of times a CPU context switch resulted due to a process voluntarily 2963giving up the processor before its time slice was completed (usually to 2964await availability of a resource). This field is not supported on Windows.</li> 2965<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 2966number of times a CPU context switch resulted due to a higher priority 2967process becoming runnable or because the current process exceeded its 2968time slice. This field is not supported on Windows.</li> 2969</ul> 2970</li> 2971</ul> 2972 2973<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>; 2974 2975<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">resourceUsage</span>()); 2976<span class="hljs-comment">/* 2977 Will output: 2978 { 2979 userCPUTime: 82872, 2980 systemCPUTime: 4143, 2981 maxRSS: 33164, 2982 sharedMemorySize: 0, 2983 unsharedDataSize: 0, 2984 unsharedStackSize: 0, 2985 minorPageFault: 2469, 2986 majorPageFault: 0, 2987 swappedOut: 0, 2988 fsRead: 0, 2989 fsWrite: 8, 2990 ipcSent: 0, 2991 ipcReceived: 0, 2992 signalsCount: 0, 2993 voluntaryContextSwitches: 79, 2994 involuntaryContextSwitches: 1 2995 } 2996*/</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>); 2997 2998<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">resourceUsage</span>()); 2999<span class="hljs-comment">/* 3000 Will output: 3001 { 3002 userCPUTime: 82872, 3003 systemCPUTime: 4143, 3004 maxRSS: 33164, 3005 sharedMemorySize: 0, 3006 unsharedDataSize: 0, 3007 unsharedStackSize: 0, 3008 minorPageFault: 2469, 3009 majorPageFault: 0, 3010 swappedOut: 0, 3011 fsRead: 0, 3012 fsWrite: 8, 3013 ipcSent: 0, 3014 ipcReceived: 0, 3015 signalsCount: 0, 3016 voluntaryContextSwitches: 79, 3017 involuntaryContextSwitches: 1 3018 } 3019*/</span></code><button class="copy-button">copy</button></pre> 3020</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> 3021<div class="api_metadata"> 3022<span>Added in: v0.5.9</span> 3023</div> 3024<ul> 3025<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 3026<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> 3027<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 3028handles.<code>options</code> supports the following properties: 3029<ul> 3030<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 3031<code>net.Socket</code>. When <code>true</code>, the socket is kept open in the sending process. 3032<strong>Default:</strong> <code>false</code>.</li> 3033</ul> 3034</li> 3035<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 3036<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 3037</ul> 3038<p>If Node.js is spawned with an IPC channel, the <code>process.send()</code> method can be 3039used to send messages to the parent process. Messages will be received as a 3040<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> 3041<p>If Node.js was not spawned with an IPC channel, <code>process.send</code> will be 3042<code>undefined</code>.</p> 3043<p>The message goes through serialization and parsing. The resulting message might 3044not be the same as what is originally sent.</p> 3045</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> 3046<div class="api_metadata"> 3047<span>Added in: v2.0.0</span> 3048</div> 3049<ul> 3050<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> 3051</ul> 3052<p>The <code>process.setegid()</code> method sets the effective group identity of the process. 3053(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 3054name string. If a group name is specified, this method blocks while resolving 3055the associated a numeric ID.</p> 3056 3057<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>; 3058 3059<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getegid</span> && process.<span class="hljs-property">setegid</span>) { 3060 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current gid: <span class="hljs-subst">${process.getegid()}</span>`</span>); 3061 <span class="hljs-keyword">try</span> { 3062 process.<span class="hljs-title function_">setegid</span>(<span class="hljs-number">501</span>); 3063 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New gid: <span class="hljs-subst">${process.getegid()}</span>`</span>); 3064 } <span class="hljs-keyword">catch</span> (err) { 3065 <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">${err}</span>`</span>); 3066 } 3067}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3068 3069<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getegid</span> && process.<span class="hljs-property">setegid</span>) { 3070 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current gid: <span class="hljs-subst">${process.getegid()}</span>`</span>); 3071 <span class="hljs-keyword">try</span> { 3072 process.<span class="hljs-title function_">setegid</span>(<span class="hljs-number">501</span>); 3073 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New gid: <span class="hljs-subst">${process.getegid()}</span>`</span>); 3074 } <span class="hljs-keyword">catch</span> (err) { 3075 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`Failed to set gid: <span class="hljs-subst">${err}</span>`</span>); 3076 } 3077}</code><button class="copy-button">copy</button></pre> 3078<p>This function is only available on POSIX platforms (i.e. not Windows or 3079Android). 3080This feature is not available in <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 3081</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> 3082<div class="api_metadata"> 3083<span>Added in: v2.0.0</span> 3084</div> 3085<ul> 3086<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> 3087</ul> 3088<p>The <code>process.seteuid()</code> method sets the effective user identity of the process. 3089(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 3090string. If a username is specified, the method blocks while resolving the 3091associated numeric ID.</p> 3092 3093<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>; 3094 3095<span class="hljs-keyword">if</span> (process.<span class="hljs-property">geteuid</span> && process.<span class="hljs-property">seteuid</span>) { 3096 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current uid: <span class="hljs-subst">${process.geteuid()}</span>`</span>); 3097 <span class="hljs-keyword">try</span> { 3098 process.<span class="hljs-title function_">seteuid</span>(<span class="hljs-number">501</span>); 3099 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New uid: <span class="hljs-subst">${process.geteuid()}</span>`</span>); 3100 } <span class="hljs-keyword">catch</span> (err) { 3101 <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">${err}</span>`</span>); 3102 } 3103}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3104 3105<span class="hljs-keyword">if</span> (process.<span class="hljs-property">geteuid</span> && process.<span class="hljs-property">seteuid</span>) { 3106 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current uid: <span class="hljs-subst">${process.geteuid()}</span>`</span>); 3107 <span class="hljs-keyword">try</span> { 3108 process.<span class="hljs-title function_">seteuid</span>(<span class="hljs-number">501</span>); 3109 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New uid: <span class="hljs-subst">${process.geteuid()}</span>`</span>); 3110 } <span class="hljs-keyword">catch</span> (err) { 3111 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`Failed to set uid: <span class="hljs-subst">${err}</span>`</span>); 3112 } 3113}</code><button class="copy-button">copy</button></pre> 3114<p>This function is only available on POSIX platforms (i.e. not Windows or 3115Android). 3116This feature is not available in <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 3117</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> 3118<div class="api_metadata"> 3119<span>Added in: v0.1.31</span> 3120</div> 3121<ul> 3122<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> 3123</ul> 3124<p>The <code>process.setgid()</code> method sets the group identity of the process. (See 3125<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 3126string. If a group name is specified, this method blocks while resolving the 3127associated numeric ID.</p> 3128 3129<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>; 3130 3131<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getgid</span> && process.<span class="hljs-property">setgid</span>) { 3132 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current gid: <span class="hljs-subst">${process.getgid()}</span>`</span>); 3133 <span class="hljs-keyword">try</span> { 3134 process.<span class="hljs-title function_">setgid</span>(<span class="hljs-number">501</span>); 3135 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New gid: <span class="hljs-subst">${process.getgid()}</span>`</span>); 3136 } <span class="hljs-keyword">catch</span> (err) { 3137 <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">${err}</span>`</span>); 3138 } 3139}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3140 3141<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getgid</span> && process.<span class="hljs-property">setgid</span>) { 3142 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current gid: <span class="hljs-subst">${process.getgid()}</span>`</span>); 3143 <span class="hljs-keyword">try</span> { 3144 process.<span class="hljs-title function_">setgid</span>(<span class="hljs-number">501</span>); 3145 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New gid: <span class="hljs-subst">${process.getgid()}</span>`</span>); 3146 } <span class="hljs-keyword">catch</span> (err) { 3147 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`Failed to set gid: <span class="hljs-subst">${err}</span>`</span>); 3148 } 3149}</code><button class="copy-button">copy</button></pre> 3150<p>This function is only available on POSIX platforms (i.e. not Windows or 3151Android). 3152This feature is not available in <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 3153</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> 3154<div class="api_metadata"> 3155<span>Added in: v0.9.4</span> 3156</div> 3157<ul> 3158<li><code>groups</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer[]></a></li> 3159</ul> 3160<p>The <code>process.setgroups()</code> method sets the supplementary group IDs for the 3161Node.js process. This is a privileged operation that requires the Node.js 3162process to have <code>root</code> or the <code>CAP_SETGID</code> capability.</p> 3163<p>The <code>groups</code> array can contain numeric group IDs, group names, or both.</p> 3164 3165<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>; 3166 3167<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getgroups</span> && process.<span class="hljs-property">setgroups</span>) { 3168 <span class="hljs-keyword">try</span> { 3169 process.<span class="hljs-title function_">setgroups</span>([<span class="hljs-number">501</span>]); 3170 <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> 3171 } <span class="hljs-keyword">catch</span> (err) { 3172 <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">${err}</span>`</span>); 3173 } 3174}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3175 3176<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getgroups</span> && process.<span class="hljs-property">setgroups</span>) { 3177 <span class="hljs-keyword">try</span> { 3178 process.<span class="hljs-title function_">setgroups</span>([<span class="hljs-number">501</span>]); 3179 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(process.<span class="hljs-title function_">getgroups</span>()); <span class="hljs-comment">// new groups</span> 3180 } <span class="hljs-keyword">catch</span> (err) { 3181 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`Failed to set groups: <span class="hljs-subst">${err}</span>`</span>); 3182 } 3183}</code><button class="copy-button">copy</button></pre> 3184<p>This function is only available on POSIX platforms (i.e. not Windows or 3185Android). 3186This feature is not available in <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 3187</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> 3188<div class="api_metadata"> 3189<span>Added in: v0.1.28</span> 3190</div> 3191<ul> 3192<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> 3193</ul> 3194<p>The <code>process.setuid(id)</code> method sets the user identity of the process. (See 3195<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. 3196If a username is specified, the method blocks while resolving the associated 3197numeric ID.</p> 3198 3199<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>; 3200 3201<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getuid</span> && process.<span class="hljs-property">setuid</span>) { 3202 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current uid: <span class="hljs-subst">${process.getuid()}</span>`</span>); 3203 <span class="hljs-keyword">try</span> { 3204 process.<span class="hljs-title function_">setuid</span>(<span class="hljs-number">501</span>); 3205 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New uid: <span class="hljs-subst">${process.getuid()}</span>`</span>); 3206 } <span class="hljs-keyword">catch</span> (err) { 3207 <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">${err}</span>`</span>); 3208 } 3209}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> process = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3210 3211<span class="hljs-keyword">if</span> (process.<span class="hljs-property">getuid</span> && process.<span class="hljs-property">setuid</span>) { 3212 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Current uid: <span class="hljs-subst">${process.getuid()}</span>`</span>); 3213 <span class="hljs-keyword">try</span> { 3214 process.<span class="hljs-title function_">setuid</span>(<span class="hljs-number">501</span>); 3215 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`New uid: <span class="hljs-subst">${process.getuid()}</span>`</span>); 3216 } <span class="hljs-keyword">catch</span> (err) { 3217 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(<span class="hljs-string">`Failed to set uid: <span class="hljs-subst">${err}</span>`</span>); 3218 } 3219}</code><button class="copy-button">copy</button></pre> 3220<p>This function is only available on POSIX platforms (i.e. not Windows or 3221Android). 3222This feature is not available in <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads.</p> 3223</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> 3224<div class="api_metadata"> 3225<span>Added in: v16.6.0, v14.18.0</span> 3226</div> 3227<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 3228<ul> 3229<li><code>val</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 3230</ul> 3231<p>This function enables or disables the <a href="https://sourcemaps.info/spec.html">Source Map v3</a> support for 3232stack traces.</p> 3233<p>It provides same features as launching Node.js process with commandline options 3234<code>--enable-source-maps</code>.</p> 3235<p>Only source maps in JavaScript files that are loaded after source maps has been 3236enabled will be parsed and loaded.</p> 3237</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> 3238<div class="api_metadata"> 3239<span>Added in: v9.3.0</span> 3240</div> 3241<ul> 3242<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> 3243</ul> 3244<p>The <code>process.setUncaughtExceptionCaptureCallback()</code> function sets a function 3245that will be invoked when an uncaught exception occurs, which will receive the 3246exception value itself as its first argument.</p> 3247<p>If such a function is set, the <a href="#event-uncaughtexception"><code>'uncaughtException'</code></a> event will 3248not be emitted. If <code>--abort-on-uncaught-exception</code> was passed from the 3249command line or set through <a href="v8.html#v8setflagsfromstringflags"><code>v8.setFlagsFromString()</code></a>, the process will 3250not abort. Actions configured to take place on exceptions such as report 3251generations will be affected too</p> 3252<p>To unset the capture function, 3253<code>process.setUncaughtExceptionCaptureCallback(null)</code> may be used. Calling this 3254method with a non-<code>null</code> argument while another capture function is set will 3255throw an error.</p> 3256<p>Using this function is mutually exclusive with using the deprecated 3257<a href="domain.html"><code>domain</code></a> built-in module.</p> 3258</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> 3259<ul> 3260<li><a href="stream.html#stream" class="type"><Stream></a></li> 3261</ul> 3262<p>The <code>process.stderr</code> property returns a stream connected to 3263<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> 3264stream) unless fd <code>2</code> refers to a file, in which case it is 3265a <a href="stream.html#writable-streams">Writable</a> stream.</p> 3266<p><code>process.stderr</code> differs from other Node.js streams in important ways. See 3267<a href="#a-note-on-process-io">note on process I/O</a> for more information.</p> 3268<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> 3269<ul> 3270<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 3271</ul> 3272<p>This property refers to the value of underlying file descriptor of 3273<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, 3274this field does not exist.</p> 3275</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> 3276<ul> 3277<li><a href="stream.html#stream" class="type"><Stream></a></li> 3278</ul> 3279<p>The <code>process.stdin</code> property returns a stream connected to 3280<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> 3281stream) unless fd <code>0</code> refers to a file, in which case it is 3282a <a href="stream.html#readable-streams">Readable</a> stream.</p> 3283<p>For details of how to read from <code>stdin</code> see <a href="stream.html#readablereadsize"><code>readable.read()</code></a>.</p> 3284<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 3285is compatible with scripts written for Node.js prior to v0.10. 3286For more information see <a href="stream.html#compatibility-with-older-nodejs-versions">Stream compatibility</a>.</p> 3287<p>In "old" streams mode the <code>stdin</code> stream is paused by default, so one 3288must call <code>process.stdin.resume()</code> to read from it. Note also that calling 3289<code>process.stdin.resume()</code> itself would switch stream to "old" mode.</p> 3290<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> 3291<ul> 3292<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 3293</ul> 3294<p>This property refers to the value of underlying file descriptor of 3295<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, 3296this field does not exist.</p> 3297</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> 3298<ul> 3299<li><a href="stream.html#stream" class="type"><Stream></a></li> 3300</ul> 3301<p>The <code>process.stdout</code> property returns a stream connected to 3302<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> 3303stream) unless fd <code>1</code> refers to a file, in which case it is 3304a <a href="stream.html#writable-streams">Writable</a> stream.</p> 3305<p>For example, to copy <code>process.stdin</code> to <code>process.stdout</code>:</p> 3306 3307<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>; 3308 3309stdin.<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>); 3310 3311stdin.<span class="hljs-title function_">pipe</span>(stdout);</code><button class="copy-button">copy</button></pre> 3312<p><code>process.stdout</code> differs from other Node.js streams in important ways. See 3313<a href="#a-note-on-process-io">note on process I/O</a> for more information.</p> 3314<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> 3315<ul> 3316<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 3317</ul> 3318<p>This property refers to the value of underlying file descriptor of 3319<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, 3320this field does not exist.</p> 3321<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> 3322<p><code>process.stdout</code> and <code>process.stderr</code> differ from other Node.js streams in 3323important ways:</p> 3324<ol> 3325<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>, 3326respectively.</li> 3327<li>Writes may be synchronous depending on what the stream is connected to 3328and whether the system is Windows or POSIX: 3329<ul> 3330<li>Files: <em>synchronous</em> on Windows and POSIX</li> 3331<li>TTYs (Terminals): <em>asynchronous</em> on Windows, <em>synchronous</em> on POSIX</li> 3332<li>Pipes (and sockets): <em>synchronous</em> on Windows, <em>asynchronous</em> on POSIX</li> 3333</ul> 3334</li> 3335</ol> 3336<p>These behaviors are partly for historical reasons, as changing them would 3337create backward incompatibility, but they are also expected by some users.</p> 3338<p>Synchronous writes avoid problems such as output written with <code>console.log()</code> or 3339<code>console.error()</code> being unexpectedly interleaved, or not written at all if 3340<code>process.exit()</code> is called before an asynchronous write completes. See 3341<a href="#processexitcode"><code>process.exit()</code></a> for more information.</p> 3342<p><em><strong>Warning</strong></em>: Synchronous writes block the event loop until the write has 3343completed. This can be near instantaneous in the case of output to a file, but 3344under high system load, pipes that are not being read at the receiving end, or 3345with slow terminals or file systems, it's possible for the event loop to be 3346blocked often enough and long enough to have severe negative performance 3347impacts. This may not be a problem when writing to an interactive terminal 3348session, but consider this particularly careful when doing production logging to 3349the process output streams.</p> 3350<p>To check if a stream is connected to a <a href="tty.html#tty">TTY</a> context, check the <code>isTTY</code> 3351property.</p> 3352<p>For instance:</p> 3353<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> 3354true 3355<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> 3356false 3357<span class="hljs-meta prompt_">$ </span><span class="language-bash">node -p <span class="hljs-string">"Boolean(process.stdout.isTTY)"</span></span> 3358true 3359<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> 3360false</code> <button class="copy-button">copy</button></pre> 3361<p>See the <a href="tty.html#tty">TTY</a> documentation for more information.</p> 3362</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> 3363<div class="api_metadata"> 3364<span>Added in: v0.9.12</span> 3365</div> 3366<ul> 3367<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 3368</ul> 3369<p>The initial value of <code>process.throwDeprecation</code> indicates whether the 3370<code>--throw-deprecation</code> flag is set on the current Node.js process. 3371<code>process.throwDeprecation</code> is mutable, so whether or not deprecation 3372warnings result in errors may be altered at runtime. See the 3373documentation for the <a href="#event-warning"><code>'warning'</code> event</a> and the 3374<a href="#processemitwarningwarning-type-code-ctor"><code>emitWarning()</code> method</a> for more information.</p> 3375<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> 3376true 3377<span class="hljs-meta prompt_">$ </span><span class="language-bash">node -p <span class="hljs-string">"process.throwDeprecation"</span></span> 3378undefined 3379<span class="hljs-meta prompt_">$ </span><span class="language-bash">node</span> 3380<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> 3381undefined 3382<span class="hljs-meta prompt_">> </span><span class="language-bash">(node:26598) DeprecationWarning: <span class="hljs-built_in">test</span></span> 3383<span class="hljs-meta prompt_">> </span><span class="language-bash">process.throwDeprecation = <span class="hljs-literal">true</span>;</span> 3384true 3385<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> 3386Thrown: 3387[DeprecationWarning: test] { name: 'DeprecationWarning' }</code> <button class="copy-button">copy</button></pre> 3388</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> 3389<div class="api_metadata"> 3390<span>Added in: v0.1.104</span> 3391</div> 3392<ul> 3393<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 3394</ul> 3395<p>The <code>process.title</code> property returns the current process title (i.e. returns 3396the current value of <code>ps</code>). Assigning a new value to <code>process.title</code> modifies 3397the current value of <code>ps</code>.</p> 3398<p>When a new value is assigned, different platforms will impose different maximum 3399length restrictions on the title. Usually such restrictions are quite limited. 3400For instance, on Linux and macOS, <code>process.title</code> is limited to the size of the 3401binary name plus the length of the command-line arguments because setting the 3402<code>process.title</code> overwrites the <code>argv</code> memory of the process. Node.js v0.8 3403allowed for longer process title strings by also overwriting the <code>environ</code> 3404memory but that was potentially insecure and confusing in some (rather obscure) 3405cases.</p> 3406<p>Assigning a value to <code>process.title</code> might not result in an accurate label 3407within process manager applications such as macOS Activity Monitor or Windows 3408Services Manager.</p> 3409</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> 3410<div class="api_metadata"> 3411<span>Added in: v0.8.0</span> 3412</div> 3413<ul> 3414<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 3415</ul> 3416<p>The <code>process.traceDeprecation</code> property indicates whether the 3417<code>--trace-deprecation</code> flag is set on the current Node.js process. See the 3418documentation for the <a href="#event-warning"><code>'warning'</code> event</a> and the 3419<a href="#processemitwarningwarning-type-code-ctor"><code>emitWarning()</code> method</a> for more information about this 3420flag's behavior.</p> 3421</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> 3422<div class="api_metadata"> 3423<details class="changelog"><summary>History</summary> 3424<table> 3425<tbody><tr><th>Version</th><th>Changes</th></tr> 3426<tr><td>v14.0.0, v12.19.0</td> 3427<td><p>Calling <code>process.umask()</code> with no arguments is deprecated.</p></td></tr> 3428<tr><td>v0.1.19</td> 3429<td><p><span>Added in: v0.1.19</span></p></td></tr> 3430</tbody></table> 3431</details> 3432</div> 3433<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 3434the process-wide umask to be written twice. This introduces a race condition 3435between threads, and is a potential security vulnerability. There is no safe, 3436cross-platform alternative API.</div><p></p> 3437<p><code>process.umask()</code> returns the Node.js process's file mode creation mask. Child 3438processes inherit the mask from the parent process.</p> 3439</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> 3440<div class="api_metadata"> 3441<span>Added in: v0.1.19</span> 3442</div> 3443<ul> 3444<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> 3445</ul> 3446<p><code>process.umask(mask)</code> sets the Node.js process's file mode creation mask. Child 3447processes inherit the mask from the parent process. Returns the previous mask.</p> 3448 3449<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>; 3450 3451<span class="hljs-keyword">const</span> newmask = <span class="hljs-number">0o022</span>; 3452<span class="hljs-keyword">const</span> oldmask = <span class="hljs-title function_">umask</span>(newmask); 3453<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>( 3454 <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>, 3455);</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>); 3456 3457<span class="hljs-keyword">const</span> newmask = <span class="hljs-number">0o022</span>; 3458<span class="hljs-keyword">const</span> oldmask = <span class="hljs-title function_">umask</span>(newmask); 3459<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>( 3460 <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>, 3461);</code><button class="copy-button">copy</button></pre> 3462<p>In <a href="worker_threads.html#class-worker"><code>Worker</code></a> threads, <code>process.umask(mask)</code> will throw an exception.</p> 3463</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> 3464<div class="api_metadata"> 3465<span>Added in: v0.5.0</span> 3466</div> 3467<ul> 3468<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 3469</ul> 3470<p>The <code>process.uptime()</code> method returns the number of seconds the current Node.js 3471process has been running.</p> 3472<p>The return value includes fractions of a second. Use <code>Math.floor()</code> to get whole 3473seconds.</p> 3474</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> 3475<div class="api_metadata"> 3476<span>Added in: v0.1.3</span> 3477</div> 3478<ul> 3479<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 3480</ul> 3481<p>The <code>process.version</code> property contains the Node.js version string.</p> 3482 3483<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>; 3484 3485<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Version: <span class="hljs-subst">${version}</span>`</span>); 3486<span class="hljs-comment">// Version: v14.8.0</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> { version } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:process'</span>); 3487 3488<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Version: <span class="hljs-subst">${version}</span>`</span>); 3489<span class="hljs-comment">// Version: v14.8.0</span></code><button class="copy-button">copy</button></pre> 3490<p>To get the version string without the prepended <em>v</em>, use 3491<code>process.versions.node</code>.</p> 3492</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> 3493<div class="api_metadata"> 3494<details class="changelog"><summary>History</summary> 3495<table> 3496<tbody><tr><th>Version</th><th>Changes</th></tr> 3497<tr><td>v9.0.0</td> 3498<td><p>The <code>v8</code> property now includes a Node.js specific suffix.</p></td></tr> 3499<tr><td>v4.2.0</td> 3500<td><p>The <code>icu</code> property is now supported.</p></td></tr> 3501<tr><td>v0.2.0</td> 3502<td><p><span>Added in: v0.2.0</span></p></td></tr> 3503</tbody></table> 3504</details> 3505</div> 3506<ul> 3507<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 3508</ul> 3509<p>The <code>process.versions</code> property returns an object listing the version strings of 3510Node.js and its dependencies. <code>process.versions.modules</code> indicates the current 3511ABI version, which is increased whenever a C++ API changes. Node.js will refuse 3512to load modules that were compiled against a different module ABI version.</p> 3513 3514<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>; 3515 3516<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>); 3517 3518<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(versions);</code><button class="copy-button">copy</button></pre> 3519<p>Will generate an object similar to:</p> 3520<pre><code class="language-console">{ node: '11.13.0', 3521 v8: '7.0.276.38-node.18', 3522 uv: '1.27.0', 3523 zlib: '1.2.11', 3524 brotli: '1.0.7', 3525 ares: '1.15.0', 3526 modules: '67', 3527 nghttp2: '1.34.0', 3528 napi: '4', 3529 llhttp: '1.1.1', 3530 openssl: '1.1.1b', 3531 cldr: '34.0', 3532 icu: '63.1', 3533 tz: '2018e', 3534 unicode: '11.0' }</code> <button class="copy-button">copy</button></pre> 3535</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> 3536<p>Node.js will normally exit with a <code>0</code> status code when no more async 3537operations are pending. The following status codes are used in other 3538cases:</p> 3539<ul> 3540<li><code>1</code> <strong>Uncaught Fatal Exception</strong>: There was an uncaught exception, 3541and it was not handled by a domain or an <a href="#event-uncaughtexception"><code>'uncaughtException'</code></a> event 3542handler.</li> 3543<li><code>2</code>: Unused (reserved by Bash for builtin misuse)</li> 3544<li><code>3</code> <strong>Internal JavaScript Parse Error</strong>: The JavaScript source code 3545internal in the Node.js bootstrapping process caused a parse error. This 3546is extremely rare, and generally can only happen during development 3547of Node.js itself.</li> 3548<li><code>4</code> <strong>Internal JavaScript Evaluation Failure</strong>: The JavaScript 3549source code internal in the Node.js bootstrapping process failed to 3550return a function value when evaluated. This is extremely rare, and 3551generally can only happen during development of Node.js itself.</li> 3552<li><code>5</code> <strong>Fatal Error</strong>: There was a fatal unrecoverable error in V8. 3553Typically a message will be printed to stderr with the prefix <code>FATAL ERROR</code>.</li> 3554<li><code>6</code> <strong>Non-function Internal Exception Handler</strong>: There was an 3555uncaught exception, but the internal fatal exception handler 3556function was somehow set to a non-function, and could not be called.</li> 3557<li><code>7</code> <strong>Internal Exception Handler Run-Time Failure</strong>: There was an 3558uncaught exception, and the internal fatal exception handler 3559function itself threw an error while attempting to handle it. This 3560can happen, for example, if an <a href="#event-uncaughtexception"><code>'uncaughtException'</code></a> or 3561<code>domain.on('error')</code> handler throws an error.</li> 3562<li><code>8</code>: Unused. In previous versions of Node.js, exit code 8 sometimes 3563indicated an uncaught exception.</li> 3564<li><code>9</code> <strong>Invalid Argument</strong>: Either an unknown option was specified, 3565or an option requiring a value was provided without a value.</li> 3566<li><code>10</code> <strong>Internal JavaScript Run-Time Failure</strong>: The JavaScript 3567source code internal in the Node.js bootstrapping process threw an error 3568when the bootstrapping function was called. This is extremely rare, 3569and generally can only happen during development of Node.js itself.</li> 3570<li><code>12</code> <strong>Invalid Debug Argument</strong>: The <code>--inspect</code> and/or <code>--inspect-brk</code> 3571options were set, but the port number chosen was invalid or unavailable.</li> 3572<li><code>13</code> <strong>Unfinished Top-Level Await</strong>: <code>await</code> was used outside of a function 3573in the top-level code, but the passed <code>Promise</code> never resolved.</li> 3574<li><code>14</code> <strong>Snapshot Failure</strong>: Node.js was started to build a V8 startup 3575snapshot and it failed because certain requirements of the state of 3576the application were not met.</li> 3577<li><code>>128</code> <strong>Signal Exits</strong>: If Node.js receives a fatal signal such as 3578<code>SIGKILL</code> or <code>SIGHUP</code>, then its exit code will be <code>128</code> plus the 3579value of the signal code. This is a standard POSIX practice, since 3580exit codes are defined to be 7-bit integers, and signal exits set 3581the high-order bit, and then contain the value of the signal code. 3582For example, signal <code>SIGABRT</code> has value <code>6</code>, so the expected exit 3583code will be <code>128</code> + <code>6</code>, or <code>134</code>.</li> 3584</ul></section> 3585 <!-- API END --> 3586 </div> 3587 </div> 3588 </div> 3589</body> 3590</html> 3591