5
<title>Child Process Node.js v0.10.15 Manual & Documentation</title>
6
<link rel="stylesheet" href="assets/style.css">
7
<link rel="stylesheet" href="assets/sh.css">
8
<link rel="canonical" href="http://nodejs.org/api/child_process.html">
10
<body class="alt apidoc" id="api-section-child_process">
11
<div id="intro" class="interior">
12
<a href="/" title="Go back to the home page">
13
<img id="logo" src="http://nodejs.org/images/logo-light.png" alt="node.js">
16
<div id="content" class="clearfix">
17
<div id="column2" class="interior">
19
<li><a href="/" class="home">Home</a></li>
20
<li><a href="/download/" class="download">Download</a></li>
21
<li><a href="/about/" class="about">About</a></li>
22
<li><a href="http://npmjs.org/" class="npm">npm Registry</a></li>
23
<li><a href="http://nodejs.org/api/" class="docs current">Docs</a></li>
24
<li><a href="http://blog.nodejs.org" class="blog">Blog</a></li>
25
<li><a href="/community/" class="community">Community</a></li>
26
<li><a href="/logos/" class="logos">Logos</a></li>
27
<li><a href="http://jobs.nodejs.org/" class="jobs">Jobs</a></li>
29
<p class="twitter"><a href="http://twitter.com/nodejs">@nodejs</a></p>
32
<div id="column1" class="interior">
34
<h1>Node.js v0.10.15 Manual & Documentation</h1>
37
<a href="index.html" name="toc">Index</a> |
38
<a href="all.html">View on single page</a> |
39
<a href="child_process.json">View as JSON</a>
46
<h2>Table of Contents</h2>
48
<li><a href="#child_process_child_process">Child Process</a><ul>
49
<li><a href="#child_process_class_childprocess">Class: ChildProcess</a><ul>
50
<li><a href="#child_process_event_error">Event: 'error'</a></li>
51
<li><a href="#child_process_event_exit">Event: 'exit'</a></li>
52
<li><a href="#child_process_event_close">Event: 'close'</a></li>
53
<li><a href="#child_process_event_disconnect">Event: 'disconnect'</a></li>
54
<li><a href="#child_process_event_message">Event: 'message'</a></li>
55
<li><a href="#child_process_child_stdin">child.stdin</a></li>
56
<li><a href="#child_process_child_stdout">child.stdout</a></li>
57
<li><a href="#child_process_child_stderr">child.stderr</a></li>
58
<li><a href="#child_process_child_pid">child.pid</a></li>
59
<li><a href="#child_process_child_kill_signal">child.kill([signal])</a></li>
60
<li><a href="#child_process_child_send_message_sendhandle">child.send(message, [sendHandle])</a><ul>
61
<li><a href="#child_process_example_sending_server_object">Example: sending server object</a></li>
62
<li><a href="#child_process_example_sending_socket_object">Example: sending socket object</a></li>
65
<li><a href="#child_process_child_disconnect">child.disconnect()</a></li>
68
<li><a href="#child_process_child_process_spawn_command_args_options">child_process.spawn(command, [args], [options])</a></li>
69
<li><a href="#child_process_child_process_exec_command_options_callback">child_process.exec(command, [options], callback)</a></li>
70
<li><a href="#child_process_child_process_execfile_file_args_options_callback">child_process.execFile(file, args, options, callback)</a></li>
71
<li><a href="#child_process_child_process_fork_modulepath_args_options">child_process.fork(modulePath, [args], [options])</a></li>
79
<h1>Child Process<span><a class="mark" href="#child_process_child_process" id="child_process_child_process">#</a></span></h1>
80
<pre class="api_stability_3">Stability: 3 - Stable</pre><p>Node provides a tri-directional <code>popen(3)</code> facility through the
81
<code>child_process</code> module.
84
<p>It is possible to stream data through a child's <code>stdin</code>, <code>stdout</code>, and
85
<code>stderr</code> in a fully non-blocking way. (Note that some programs use
86
line-buffered I/O internally. That doesn't affect node.js but it means
87
data you send to the child process is not immediately consumed.)
90
<p>To create a child process use <code>require('child_process').spawn()</code> or
91
<code>require('child_process').fork()</code>. The semantics of each are slightly
92
different, and explained below.
95
<h2>Class: ChildProcess<span><a class="mark" href="#child_process_class_childprocess" id="child_process_class_childprocess">#</a></span></h2>
96
<p><code>ChildProcess</code> is an <a href="events.html#events_class_events_eventemitter">EventEmitter</a>.
99
<p>Child processes always have three streams associated with them. <code>child.stdin</code>,
100
<code>child.stdout</code>, and <code>child.stderr</code>. These may be shared with the stdio
101
streams of the parent process, or they may be separate stream objects
102
which can be piped to and from.
105
<p>The ChildProcess class is not intended to be used directly. Use the
106
<code>spawn()</code> or <code>fork()</code> methods to create a Child Process instance.
109
<h3>Event: 'error'<span><a class="mark" href="#child_process_event_error" id="child_process_event_error">#</a></span></h3>
110
<div class="signature"><ul>
111
<li><code>err</code> <span class="type">Error Object</span> the error.</li>
117
<li>The process could not be spawned, or</li>
118
<li>The process could not be killed, or</li>
119
<li>Sending a message to the child process failed for whatever reason.</li>
121
<p>See also <a href="#child_process_child_kill_signal"><code>ChildProcess#kill()</code></a> and
122
<a href="#child_process_child_send_message_sendhandle"><code>ChildProcess#send()</code></a>.
125
<h3>Event: 'exit'<span><a class="mark" href="#child_process_event_exit" id="child_process_event_exit">#</a></span></h3>
126
<div class="signature"><ul>
127
<li><code>code</code> <span class="type">Number</span> the exit code, if it exited normally.</li>
128
<li><code>signal</code> <span class="type">String</span> the signal passed to kill the child process, if it
129
was killed by the parent.</li>
131
<p>This event is emitted after the child process ends. If the process terminated
132
normally, <code>code</code> is the final exit code of the process, otherwise <code>null</code>. If
133
the process terminated due to receipt of a signal, <code>signal</code> is the string name
134
of the signal, otherwise <code>null</code>.
137
<p>Note that the child process stdio streams might still be open.
140
<p>See <code>waitpid(2)</code>.
143
<h3>Event: 'close'<span><a class="mark" href="#child_process_event_close" id="child_process_event_close">#</a></span></h3>
144
<div class="signature"><ul>
145
<li><code>code</code> <span class="type">Number</span> the exit code, if it exited normally.</li>
146
<li><code>signal</code> <span class="type">String</span> the signal passed to kill the child process, if it
147
was killed by the parent.</li>
149
<p>This event is emitted when the stdio streams of a child process have all
150
terminated. This is distinct from 'exit', since multiple processes
151
might share the same stdio streams.
154
<h3>Event: 'disconnect'<span><a class="mark" href="#child_process_event_disconnect" id="child_process_event_disconnect">#</a></span></h3>
155
<p>This event is emitted after using the <code>.disconnect()</code> method in the parent or
156
in the child. After disconnecting it is no longer possible to send messages.
157
An alternative way to check if you can send messages is to see if the
158
<code>child.connected</code> property is <code>true</code>.
161
<h3>Event: 'message'<span><a class="mark" href="#child_process_event_message" id="child_process_event_message">#</a></span></h3>
162
<div class="signature"><ul>
163
<li><code>message</code> <span class="type">Object</span> a parsed JSON object or primitive value</li>
164
<li><code>sendHandle</code> <span class="type">Handle object</span> a Socket or Server object</li>
166
<p>Messages send by <code>.send(message, [sendHandle])</code> are obtained using the
167
<code>message</code> event.
170
<h3>child.stdin<span><a class="mark" href="#child_process_child_stdin" id="child_process_child_stdin">#</a></span></h3>
171
<div class="signature"><ul>
172
<li><span class="type">Stream object</span></li>
174
<p>A <code>Writable Stream</code> that represents the child process's <code>stdin</code>.
175
Closing this stream via <code>end()</code> often causes the child process to terminate.
178
<p>If the child stdio streams are shared with the parent, then this will
182
<h3>child.stdout<span><a class="mark" href="#child_process_child_stdout" id="child_process_child_stdout">#</a></span></h3>
183
<div class="signature"><ul>
184
<li><span class="type">Stream object</span></li>
186
<p>A <code>Readable Stream</code> that represents the child process's <code>stdout</code>.
189
<p>If the child stdio streams are shared with the parent, then this will
193
<h3>child.stderr<span><a class="mark" href="#child_process_child_stderr" id="child_process_child_stderr">#</a></span></h3>
194
<div class="signature"><ul>
195
<li><span class="type">Stream object</span></li>
197
<p>A <code>Readable Stream</code> that represents the child process's <code>stderr</code>.
200
<p>If the child stdio streams are shared with the parent, then this will
204
<h3>child.pid<span><a class="mark" href="#child_process_child_pid" id="child_process_child_pid">#</a></span></h3>
205
<div class="signature"><ul>
206
<li><span class="type">Integer</span></li>
208
<p>The PID of the child process.
214
<pre><code>var spawn = require('child_process').spawn,
215
grep = spawn('grep', ['ssh']);
217
console.log('Spawned child pid: ' + grep.pid);
218
grep.stdin.end();</code></pre>
219
<h3>child.kill([signal])<span><a class="mark" href="#child_process_child_kill_signal" id="child_process_child_kill_signal">#</a></span></h3>
220
<div class="signature"><ul>
221
<li><code>signal</code> <span class="type">String</span></li>
223
<p>Send a signal to the child process. If no argument is given, the process will
224
be sent <code>'SIGTERM'</code>. See <code>signal(7)</code> for a list of available signals.
227
<pre><code>var spawn = require('child_process').spawn,
228
grep = spawn('grep', ['ssh']);
230
grep.on('close', function (code, signal) {
231
console.log('child process terminated due to receipt of signal '+signal);
234
// send SIGHUP to process
235
grep.kill('SIGHUP');</code></pre>
236
<p>May emit an <code>'error'</code> event when the signal cannot be delivered. Sending a
237
signal to a child process that has already exited is not an error but may
238
have unforeseen consequences: if the PID (the process ID) has been reassigned
239
to another process, the signal will be delivered to that process instead.
240
What happens next is anyone's guess.
243
<p>Note that while the function is called <code>kill</code>, the signal delivered to the
244
child process may not actually kill it. <code>kill</code> really just sends a signal
248
<p>See <code>kill(2)</code>
251
<h3>child.send(message, [sendHandle])<span><a class="mark" href="#child_process_child_send_message_sendhandle" id="child_process_child_send_message_sendhandle">#</a></span></h3>
252
<div class="signature"><ul>
253
<li><code>message</code> <span class="type">Object</span></li>
254
<li><code>sendHandle</code> <span class="type">Handle object</span></li>
256
<p>When using <code>child_process.fork()</code> you can write to the child using
257
<code>child.send(message, [sendHandle])</code> and messages are received by
258
a <code>'message'</code> event on the child.
264
<pre><code>var cp = require('child_process');
266
var n = cp.fork(__dirname + '/sub.js');
268
n.on('message', function(m) {
269
console.log('PARENT got message:', m);
272
n.send({ hello: 'world' });</code></pre>
273
<p>And then the child script, <code>'sub.js'</code> might look like this:
276
<pre><code>process.on('message', function(m) {
277
console.log('CHILD got message:', m);
280
process.send({ foo: 'bar' });</code></pre>
281
<p>In the child the <code>process</code> object will have a <code>send()</code> method, and <code>process</code>
282
will emit objects each time it receives a message on its channel.
285
<p>There is a special case when sending a <code>{cmd: 'NODE_foo'}</code> message. All messages
286
containing a <code>NODE_</code> prefix in its <code>cmd</code> property will not be emitted in
287
the <code>message</code> event, since they are internal messages used by node core.
288
Messages containing the prefix are emitted in the <code>internalMessage</code> event, you
289
should by all means avoid using this feature, it is subject to change without notice.
292
<p>The <code>sendHandle</code> option to <code>child.send()</code> is for sending a TCP server or
293
socket object to another process. The child will receive the object as its
294
second argument to the <code>message</code> event.
297
<p>Emits an <code>'error'</code> event if the message cannot be sent, for example because
298
the child process has already exited.
301
<h4>Example: sending server object<span><a class="mark" href="#child_process_example_sending_server_object" id="child_process_example_sending_server_object">#</a></span></h4>
302
<p>Here is an example of sending a server:
305
<pre><code>var child = require('child_process').fork('child.js');
307
// Open up the server object and send the handle.
308
var server = require('net').createServer();
309
server.on('connection', function (socket) {
310
socket.end('handled by parent');
312
server.listen(1337, function() {
313
child.send('server', server);
315
<p>And the child would the receive the server object as:
318
<pre><code>process.on('message', function(m, server) {
319
if (m === 'server') {
320
server.on('connection', function (socket) {
321
socket.end('handled by child');
325
<p>Note that the server is now shared between the parent and child, this means
326
that some connections will be handled by the parent and some by the child.
329
<p>For <code>dgram</code> servers the workflow is exactly the same. Here you listen on
330
a <code>message</code> event instead of <code>connection</code> and use <code>server.bind</code> instead of
331
<code>server.listen</code>. (Currently only supported on UNIX platforms.)
334
<h4>Example: sending socket object<span><a class="mark" href="#child_process_example_sending_socket_object" id="child_process_example_sending_socket_object">#</a></span></h4>
335
<p>Here is an example of sending a socket. It will spawn two children and handle
336
connections with the remote address <code>74.125.127.100</code> as VIP by sending the
337
socket to a "special" child process. Other sockets will go to a "normal" process.
340
<pre><code>var normal = require('child_process').fork('child.js', ['normal']);
341
var special = require('child_process').fork('child.js', ['special']);
343
// Open up the server and send sockets to child
344
var server = require('net').createServer();
345
server.on('connection', function (socket) {
348
if (socket.remoteAddress === '74.125.127.100') {
349
special.send('socket', socket);
352
// just the usual dudes
353
normal.send('socket', socket);
355
server.listen(1337);</code></pre>
356
<p>The <code>child.js</code> could look like this:
359
<pre><code>process.on('message', function(m, socket) {
360
if (m === 'socket') {
361
socket.end('You were handled as a ' + process.argv[2] + ' person');
364
<p>Note that once a single socket has been sent to a child the parent can no
365
longer keep track of when the socket is destroyed. To indicate this condition
366
the <code>.connections</code> property becomes <code>null</code>.
367
It is also recommended not to use <code>.maxConnections</code> in this condition.
370
<h3>child.disconnect()<span><a class="mark" href="#child_process_child_disconnect" id="child_process_child_disconnect">#</a></span></h3>
371
<p>To close the IPC connection between parent and child use the
372
<code>child.disconnect()</code> method. This allows the child to exit gracefully since
373
there is no IPC channel keeping it alive. When calling this method the
374
<code>disconnect</code> event will be emitted in both parent and child, and the
375
<code>connected</code> flag will be set to <code>false</code>. Please note that you can also call
376
<code>process.disconnect()</code> in the child process.
379
<h2>child_process.spawn(command, [args], [options])<span><a class="mark" href="#child_process_child_process_spawn_command_args_options" id="child_process_child_process_spawn_command_args_options">#</a></span></h2>
380
<div class="signature"><ul>
381
<li><code>command</code> <span class="type">String</span> The command to run</li>
382
<li><code>args</code> <span class="type">Array</span> List of string arguments</li>
383
<li><code>options</code> <span class="type">Object</span><ul>
384
<li><code>cwd</code> <span class="type">String</span> Current working directory of the child process</li>
385
<li><code>stdio</code> <span class="type">Array|String</span> Child's stdio configuration. (See below)</li>
386
<li><code>customFds</code> <span class="type">Array</span> <strong>Deprecated</strong> File descriptors for the child to use
387
for stdio. (See below)</li>
388
<li><code>env</code> <span class="type">Object</span> Environment key-value pairs</li>
389
<li><code>detached</code> <span class="type">Boolean</span> The child will be a process group leader. (See below)</li>
390
<li><code>uid</code> <span class="type">Number</span> Sets the user identity of the process. (See setuid(2).)</li>
391
<li><code>gid</code> <span class="type">Number</span> Sets the group identity of the process. (See setgid(2).)</li>
394
<li>return: <span class="type">ChildProcess object</span></li>
396
<p>Launches a new process with the given <code>command</code>, with command line arguments in <code>args</code>.
397
If omitted, <code>args</code> defaults to an empty Array.
400
<p>The third argument is used to specify additional options, which defaults to:
403
<pre><code>{ cwd: undefined,
406
<p><code>cwd</code> allows you to specify the working directory from which the process is spawned.
407
Use <code>env</code> to specify environment variables that will be visible to the new process.
410
<p>Example of running <code>ls -lh /usr</code>, capturing <code>stdout</code>, <code>stderr</code>, and the exit code:
413
<pre><code>var spawn = require('child_process').spawn,
414
ls = spawn('ls', ['-lh', '/usr']);
416
ls.stdout.on('data', function (data) {
417
console.log('stdout: ' + data);
420
ls.stderr.on('data', function (data) {
421
console.log('stderr: ' + data);
424
ls.on('close', function (code) {
425
console.log('child process exited with code ' + code);
427
<p>Example: A very elaborate way to run 'ps ax | grep ssh'
430
<pre><code>var spawn = require('child_process').spawn,
431
ps = spawn('ps', ['ax']),
432
grep = spawn('grep', ['ssh']);
434
ps.stdout.on('data', function (data) {
435
grep.stdin.write(data);
438
ps.stderr.on('data', function (data) {
439
console.log('ps stderr: ' + data);
442
ps.on('close', function (code) {
444
console.log('ps process exited with code ' + code);
449
grep.stdout.on('data', function (data) {
450
console.log('' + data);
453
grep.stderr.on('data', function (data) {
454
console.log('grep stderr: ' + data);
457
grep.on('close', function (code) {
459
console.log('grep process exited with code ' + code);
462
<p>Example of checking for failed exec:
465
<pre><code>var spawn = require('child_process').spawn,
466
child = spawn('bad_command');
468
child.stderr.setEncoding('utf8');
469
child.stderr.on('data', function (data) {
470
if (/^execvp\(\)/.test(data)) {
471
console.log('Failed to start child process.');
474
<p>Note that if spawn receives an empty options object, it will result in
475
spawning the process with an empty environment rather than using
476
<code>process.env</code>. This due to backwards compatibility issues with a deprecated
480
<p>The 'stdio' option to <code>child_process.spawn()</code> is an array where each
481
index corresponds to a fd in the child. The value is one of the following:
485
<li><code>'pipe'</code> - Create a pipe between the child process and the parent process.
486
The parent end of the pipe is exposed to the parent as a property on the
487
<code>child_process</code> object as <code>ChildProcess.stdio[fd]</code>. Pipes created for
488
fds 0 - 2 are also available as ChildProcess.stdin, ChildProcess.stdout
489
and ChildProcess.stderr, respectively.</li>
490
<li><code>'ipc'</code> - Create an IPC channel for passing messages/file descriptors
491
between parent and child. A ChildProcess may have at most <em>one</em> IPC stdio
492
file descriptor. Setting this option enables the ChildProcess.send() method.
493
If the child writes JSON messages to this file descriptor, then this will
494
trigger ChildProcess.on('message'). If the child is a Node.js program, then
495
the presence of an IPC channel will enable process.send() and
496
process.on('message').</li>
497
<li><code>'ignore'</code> - Do not set this file descriptor in the child. Note that Node
498
will always open fd 0 - 2 for the processes it spawns. When any of these is
499
ignored node will open <code>/dev/null</code> and attach it to the child's fd.</li>
500
<li><code>Stream</code> object - Share a readable or writable stream that refers to a tty,
501
file, socket, or a pipe with the child process. The stream's underlying
502
file descriptor is duplicated in the child process to the fd that
503
corresponds to the index in the <code>stdio</code> array.</li>
504
<li>Positive integer - The integer value is interpreted as a file descriptor
505
that is is currently open in the parent process. It is shared with the child
506
process, similar to how <code>Stream</code> objects can be shared.</li>
507
<li><code>null</code>, <code>undefined</code> - Use default value. For stdio fds 0, 1 and 2 (in other
508
words, stdin, stdout, and stderr) a pipe is created. For fd 3 and up, the
509
default is <code>'ignore'</code>.</li>
511
<p>As a shorthand, the <code>stdio</code> argument may also be one of the following
512
strings, rather than an array:
516
<li><code>ignore</code> - <code>['ignore', 'ignore', 'ignore']</code></li>
517
<li><code>pipe</code> - <code>['pipe', 'pipe', 'pipe']</code></li>
518
<li><code>inherit</code> - <code>[process.stdin, process.stdout, process.stderr]</code> or <code>[0,1,2]</code></li>
523
<pre><code>var spawn = require('child_process').spawn;
525
// Child will use parent's stdios
526
spawn('prg', [], { stdio: 'inherit' });
528
// Spawn child sharing only stderr
529
spawn('prg', [], { stdio: ['pipe', 'pipe', process.stderr] });
531
// Open an extra fd=4, to interact with programs present a
532
// startd-style interface.
533
spawn('prg', [], { stdio: ['pipe', null, null, null, 'pipe'] });</code></pre>
534
<p>If the <code>detached</code> option is set, the child process will be made the leader of a
535
new process group. This makes it possible for the child to continue running
536
after the parent exits.
539
<p>By default, the parent will wait for the detached child to exit. To prevent
540
the parent from waiting for a given <code>child</code>, use the <code>child.unref()</code> method,
541
and the parent's event loop will not include the child in its reference count.
544
<p>Example of detaching a long-running process and redirecting its output to a
548
<pre><code> var fs = require('fs'),
549
spawn = require('child_process').spawn,
550
out = fs.openSync('./out.log', 'a'),
551
err = fs.openSync('./out.log', 'a');
553
var child = spawn('prg', [], {
555
stdio: [ 'ignore', out, err ]
558
child.unref();</code></pre>
559
<p>When using the <code>detached</code> option to start a long-running process, the process
560
will not stay running in the background unless it is provided with a <code>stdio</code>
561
configuration that is not connected to the parent. If the parent's <code>stdio</code> is
562
inherited, the child will remain attached to the controlling terminal.
565
<p>There is a deprecated option called <code>customFds</code> which allows one to specify
566
specific file descriptors for the stdio of the child process. This API was
567
not portable to all platforms and therefore removed.
568
With <code>customFds</code> it was possible to hook up the new process' <code>[stdin, stdout,
569
stderr]</code> to existing streams; <code>-1</code> meant that a new stream should be created.
570
Use at your own risk.
573
<p>See also: <code>child_process.exec()</code> and <code>child_process.fork()</code>
576
<h2>child_process.exec(command, [options], callback)<span><a class="mark" href="#child_process_child_process_exec_command_options_callback" id="child_process_child_process_exec_command_options_callback">#</a></span></h2>
577
<div class="signature"><ul>
578
<li><code>command</code> <span class="type">String</span> The command to run, with space-separated arguments</li>
579
<li><code>options</code> <span class="type">Object</span><ul>
580
<li><code>cwd</code> <span class="type">String</span> Current working directory of the child process</li>
581
<li><code>env</code> <span class="type">Object</span> Environment key-value pairs</li>
582
<li><code>encoding</code> <span class="type">String</span> (Default: 'utf8')</li>
583
<li><code>timeout</code> <span class="type">Number</span> (Default: 0)</li>
584
<li><code>maxBuffer</code> <span class="type">Number</span> (Default: 200*1024)</li>
585
<li><code>killSignal</code> <span class="type">String</span> (Default: 'SIGTERM')</li>
588
<li><code>callback</code> <span class="type">Function</span> called with the output when process terminates<ul>
589
<li><code>error</code> <span class="type">Error</span></li>
590
<li><code>stdout</code> <span class="type">Buffer</span></li>
591
<li><code>stderr</code> <span class="type">Buffer</span></li>
594
<li>Return: ChildProcess object</li>
596
<p>Runs a command in a shell and buffers the output.
599
<pre><code>var exec = require('child_process').exec,
602
child = exec('cat *.js bad_file | wc -l',
603
function (error, stdout, stderr) {
604
console.log('stdout: ' + stdout);
605
console.log('stderr: ' + stderr);
606
if (error !== null) {
607
console.log('exec error: ' + error);
610
<p>The callback gets the arguments <code>(error, stdout, stderr)</code>. On success, <code>error</code>
611
will be <code>null</code>. On error, <code>error</code> will be an instance of <code>Error</code> and <code>err.code</code>
612
will be the exit code of the child process, and <code>err.signal</code> will be set to the
613
signal that terminated the process.
616
<p>There is a second optional argument to specify several options. The
620
<pre><code>{ encoding: 'utf8',
623
killSignal: 'SIGTERM',
625
env: null }</code></pre>
626
<p>If <code>timeout</code> is greater than 0, then it will kill the child process
627
if it runs longer than <code>timeout</code> milliseconds. The child process is killed with
628
<code>killSignal</code> (default: <code>'SIGTERM'</code>). <code>maxBuffer</code> specifies the largest
629
amount of data allowed on stdout or stderr - if this value is exceeded then
630
the child process is killed.
634
<h2>child_process.execFile(file, args, options, callback)<span><a class="mark" href="#child_process_child_process_execfile_file_args_options_callback" id="child_process_child_process_execfile_file_args_options_callback">#</a></span></h2>
635
<div class="signature"><ul>
636
<li><code>file</code> <span class="type">String</span> The filename of the program to run</li>
637
<li><code>args</code> <span class="type">Array</span> List of string arguments</li>
638
<li><code>options</code> <span class="type">Object</span><ul>
639
<li><code>cwd</code> <span class="type">String</span> Current working directory of the child process</li>
640
<li><code>env</code> <span class="type">Object</span> Environment key-value pairs</li>
641
<li><code>encoding</code> <span class="type">String</span> (Default: 'utf8')</li>
642
<li><code>timeout</code> <span class="type">Number</span> (Default: 0)</li>
643
<li><code>maxBuffer</code> <span class="type">Number</span> (Default: 200*1024)</li>
644
<li><code>killSignal</code> <span class="type">String</span> (Default: 'SIGTERM')</li>
647
<li><code>callback</code> <span class="type">Function</span> called with the output when process terminates<ul>
648
<li><code>error</code> <span class="type">Error</span></li>
649
<li><code>stdout</code> <span class="type">Buffer</span></li>
650
<li><code>stderr</code> <span class="type">Buffer</span></li>
653
<li>Return: ChildProcess object</li>
655
<p>This is similar to <code>child_process.exec()</code> except it does not execute a
656
subshell but rather the specified file directly. This makes it slightly
657
leaner than <code>child_process.exec</code>. It has the same options.
661
<h2>child_process.fork(modulePath, [args], [options])<span><a class="mark" href="#child_process_child_process_fork_modulepath_args_options" id="child_process_child_process_fork_modulepath_args_options">#</a></span></h2>
662
<div class="signature"><ul>
663
<li><code>modulePath</code> <span class="type">String</span> The module to run in the child</li>
664
<li><code>args</code> <span class="type">Array</span> List of string arguments</li>
665
<li><code>options</code> <span class="type">Object</span><ul>
666
<li><code>cwd</code> <span class="type">String</span> Current working directory of the child process</li>
667
<li><code>env</code> <span class="type">Object</span> Environment key-value pairs</li>
668
<li><code>encoding</code> <span class="type">String</span> (Default: 'utf8')</li>
669
<li><code>execPath</code> <span class="type">String</span> Executable used to create the child process</li>
672
<li>Return: ChildProcess object</li>
674
<p>This is a special case of the <code>spawn()</code> functionality for spawning Node
675
processes. In addition to having all the methods in a normal ChildProcess
676
instance, the returned object has a communication channel built-in. See
677
<code>child.send(message, [sendHandle])</code> for details.
680
<p>By default the spawned Node process will have the stdout, stderr associated
681
with the parent's. To change this behavior set the <code>silent</code> property in the
682
<code>options</code> object to <code>true</code>.
685
<p>The child process does not automatically exit once it's done, you need to call
686
<code>process.exit()</code> explicitly. This limitation may be lifted in the future.
689
<p>These child Nodes are still whole new instances of V8. Assume at least 30ms
690
startup and 10mb memory for each new Node. That is, you cannot create many
694
<p>The <code>execPath</code> property in the <code>options</code> object allows for a process to be
695
created for the child rather than the current <code>node</code> executable. This should be
696
done with care and by default will talk over the fd represented an
697
environmental variable <code>NODE_CHANNEL_FD</code> on the child process. The input and
698
output on this fd is expected to be line delimited JSON objects.
706
<a href="http://joyent.com" class="joyent-logo">Joyent</a>
707
<ul class="clearfix">
708
<li><a href="/">Node.js</a></li>
709
<li><a href="/download/">Download</a></li>
710
<li><a href="/about/">About</a></li>
711
<li><a href="http://npmjs.org/">npm Registry</a></li>
712
<li><a href="http://nodejs.org/api/">Docs</a></li>
713
<li><a href="http://blog.nodejs.org">Blog</a></li>
714
<li><a href="/community/">Community</a></li>
715
<li><a href="/logos/">Logos</a></li>
716
<li><a href="http://jobs.nodejs.org/">Jobs</a></li>
717
<li><a href="http://twitter.com/nodejs" class="twitter">@nodejs</a></li>
720
<p>Copyright <a href="http://joyent.com/">Joyent, Inc</a>, Node.js is a <a href="/trademark-policy.pdf">trademark</a> of Joyent, Inc. View <a href="https://raw.github.com/joyent/node/v0.10.15/LICENSE">license</a>.</p>
723
<script src="../sh_main.js"></script>
724
<script src="../sh_javascript.min.js"></script>
725
<script>highlight(undefined, undefined, 'pre');</script>
727
window._gaq = [['_setAccount', 'UA-10874194-2'], ['_trackPageview']];
729
var g = d.createElement(t),
730
s = d.getElementsByTagName(t)[0];
731
g.src = '//www.google-analytics.com/ga.js';
732
s.parentNode.insertBefore(g, s);
733
}(document, 'script'));
added
removed
doc/api/child_process.html
