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isaacs committed Feb 29, 2012
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2 changes: 1 addition & 1 deletion doc/about/index.html
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Expand Up @@ -102,7 +102,7 @@ <h1>Node's goal is to provide an easy way to build scalable
<p>But what about multiple-processor concurrency? Aren't
threads necessary to scale programs to multi-core computers?
You can start new processes via <code><a
href="http://nodejs.org/docs/latest/api/child_processes.html#child_process.fork">child_process.fork()</a></code>
href="http://nodejs.org/docs/latest/api/child_process.html#child_process.fork">child_process.fork()</a></code>
these other processes will be scheduled in parallel. For load
balancing incoming connections across multiple processes use
<a href="http://nodejs.org/docs/latest/api/cluster.html">the
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2 changes: 1 addition & 1 deletion doc/api/_toc.markdown
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Expand Up @@ -26,7 +26,7 @@
* [Readline](readline.html)
* [REPL](repl.html)
* [VM](vm.html)
* [Child Processes](child_processes.html)
* [Child Processes](child_process.html)
* [Assertion Testing](assert.html)
* [TTY](tty.html)
* [ZLIB](zlib.html)
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2 changes: 1 addition & 1 deletion doc/api/all.markdown
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Expand Up @@ -24,7 +24,7 @@
@include readline
@include repl
@include vm
@include child_processes
@include child_process
@include assert
@include tty
@include zlib
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173 changes: 137 additions & 36 deletions doc/api/child_processes.markdown → doc/api/child_process.markdown
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@@ -1,21 +1,32 @@
## Child Processes
# Child Process

Node provides a tri-directional `popen(3)` facility through the `ChildProcess`
class.
Node provides a tri-directional `popen(3)` facility through the
`child_process` module.

It is possible to stream data through the child's `stdin`, `stdout`, and
It is possible to stream data through a child's `stdin`, `stdout`, and
`stderr` in a fully non-blocking way.

To create a child process use `require('child_process').spawn()`.
To create a child process use `require('child_process').spawn()` or
`require('child_process').fork()`. The semantics of each are slightly
different, and explained below.

Child processes always have three streams associated with them. `child.stdin`,
`child.stdout`, and `child.stderr`.
## Class: ChildProcess

`ChildProcess` is an `EventEmitter`.

Child processes always have three streams associated with them. `child.stdin`,
`child.stdout`, and `child.stderr`. These may be shared with the stdio
streams of the parent process, or they may be separate stream objects
which can be piped to and from.

The ChildProcess class is not intended to be used directly. Use the
`spawn()` or `fork()` methods to create a Child Process instance.

### Event: 'exit'

`function (code, signal) {}`
* `code` {Number} the exit code, if it exited normally.
* `signal` {String} the signal passed to kill the child process, if it
was killed by the parent.

This event is emitted after the child process ends. If the process terminated
normally, `code` is the final exit code of the process, otherwise `null`. If
Expand All @@ -26,19 +37,36 @@ See `waitpid(2)`.

### child.stdin

* {Stream object}

A `Writable Stream` that represents the child process's `stdin`.
Closing this stream via `end()` often causes the child process to terminate.

If the child stdio streams are shared with the parent, then this will
not be set.

### child.stdout

* {Stream object}

A `Readable Stream` that represents the child process's `stdout`.

If the child stdio streams are shared with the parent, then this will
not be set.

### child.stderr

* {Stream object}

A `Readable Stream` that represents the child process's `stderr`.

If the child stdio streams are shared with the parent, then this will
not be set.

### child.pid

* {Integer}

The PID of the child process.

Example:
Expand All @@ -49,8 +77,48 @@ Example:
console.log('Spawned child pid: ' + grep.pid);
grep.stdin.end();

### child.kill([signal])

* `signal` {String}

Send a signal to the child process. If no argument is given, the process will
be sent `'SIGTERM'`. See `signal(7)` for a list of available signals.

var spawn = require('child_process').spawn,
grep = spawn('grep', ['ssh']);

grep.on('exit', function (code, signal) {
console.log('child process terminated due to receipt of signal '+signal);
});

// send SIGHUP to process
grep.kill('SIGHUP');

Note that while the function is called `kill`, the signal delivered to the child
process may not actually kill it. `kill` really just sends a signal to a process.

See `kill(2)`

### child.send(message, [sendHandle])

* `message` {Object}
* `sendHandle` {Handle object}

Send a message (and, optionally, a handle object) to a child process.

See `child_process.fork()` for details.

### child_process.spawn(command, [args], [options])
## child_process.spawn(command, [args], [options])

* `command` {String} The command to run
* `args` {Array} List of string arguments
* `options` {Object}
* `cwd` {String} Current working directory of the child process
* `customFds` {Array} **Deprecated** File descriptors for the child to use
for stdio. (See below)
* `env` {Object} Environment key-value pairs
* `setsid` {Boolean}
* return: {ChildProcess object}

Launches a new process with the given `command`, with command line arguments in `args`.
If omitted, `args` defaults to an empty Array.
Expand Down Expand Up @@ -140,17 +208,34 @@ API.
There is a deprecated option called `customFds` which allows one to specify
specific file descriptors for the stdio of the child process. This API was
not portable to all platforms and therefore removed.
With `customFds` it was possible to hook up the new process' [stdin, stdout,
stderr] to existing streams; `-1` meant that a new stream should be created.
With `customFds` it was possible to hook up the new process' `[stdin, stdout,
stderr]` to existing streams; `-1` meant that a new stream should be created.
Use at your own risk.

There are several internal options. In particular `stdinStream`,
`stdoutStream`, `stderrStream`. They are for INTERNAL USE ONLY. As with all
undocumented APIs in Node, they should not be used.

See also: `child_process.exec()`

### child_process.exec(command, [options], callback)
See also: `child_process.exec()` and `child_process.fork()`

## child_process.exec(command, [options], callback)

* `command` {String} The command to run, with space-separated arguments
* `options` {Object}
* `cwd` {String} Current working directory of the child process
* `customFds` {Array} **Deprecated** File descriptors for the child to use
for stdio. (See below)
* `env` {Object} Environment key-value pairs
* `setsid` {Boolean}
* `encoding` {String} (Default: 'utf8')
* `timeout` {Number} (Default: 0)
* `maxBuffer` {Number} (Default: 200*1024)
* `killSignal` {String} (Default: 'SIGTERM')
* `callback` {Function} called with the output when process terminates
* `code` {Integer} Exit code
* `stdout` {Buffer}
* `stderr` {Buffer}
* Return: ChildProcess object

Runs a command in a shell and buffers the output.

Expand All @@ -172,7 +257,8 @@ will be `null`. On error, `error` will be an instance of `Error` and `err.code`
will be the exit code of the child process, and `err.signal` will be set to the
signal that terminated the process.

There is a second optional argument to specify several options. The default options are
There is a second optional argument to specify several options. The
default options are

{ encoding: 'utf8',
timeout: 0,
Expand All @@ -188,14 +274,48 @@ amount of data allowed on stdout or stderr - if this value is exceeded then
the child process is killed.


### child_process.execFile(file, args, options, callback)
## child_process.execFile(file, args, options, callback)

* `file` {String} The filename of the program to run
* `args` {Array} List of string arguments
* `options` {Object}
* `cwd` {String} Current working directory of the child process
* `customFds` {Array} **Deprecated** File descriptors for the child to use
for stdio. (See below)
* `env` {Object} Environment key-value pairs
* `setsid` {Boolean}
* `encoding` {String} (Default: 'utf8')
* `timeout` {Number} (Default: 0)
* `maxBuffer` {Number} (Default: 200*1024)
* `killSignal` {String} (Default: 'SIGTERM')
* `callback` {Function} called with the output when process terminates
* `code` {Integer} Exit code
* `stdout` {Buffer}
* `stderr` {Buffer}
* Return: ChildProcess object

This is similar to `child_process.exec()` except it does not execute a
subshell but rather the specified file directly. This makes it slightly
leaner than `child_process.exec`. It has the same options.


### child_process.fork(modulePath, arguments, options)
## child_process.fork(modulePath, [args], [options])

* `modulePath` {String} The module to run in the child
* `args` {Array} List of string arguments
* `options` {Object}
* `cwd` {String} Current working directory of the child process
* `customFds` {Array} **Deprecated** File descriptors for the child to use
for stdio. (See below)
* `env` {Object} Environment key-value pairs
* `setsid` {Boolean}
* `encoding` {String} (Default: 'utf8')
* `timeout` {Number} (Default: 0)
* `callback` {Function} called with the output when process terminates
* `code` {Integer} Exit code
* `stdout` {Buffer}
* `stderr` {Buffer}
* Return: ChildProcess object

This is a special case of the `spawn()` functionality for spawning Node
processes. In addition to having all the methods in a normal ChildProcess
Expand Down Expand Up @@ -256,22 +376,3 @@ processes:



### child.kill([signal])

Send a signal to the child process. If no argument is given, the process will
be sent `'SIGTERM'`. See `signal(7)` for a list of available signals.

var spawn = require('child_process').spawn,
grep = spawn('grep', ['ssh']);

grep.on('exit', function (code, signal) {
console.log('child process terminated due to receipt of signal '+signal);
});

// send SIGHUP to process
grep.kill('SIGHUP');

Note that while the function is called `kill`, the signal delivered to the child
process may not actually kill it. `kill` really just sends a signal to a process.

See `kill(2)`

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