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Node.js v0.10.18 手册 & 文档


子进程#

稳定度: 3 - 稳定

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

Node 通过 child_process 模块提供了类似 popen(3) 的处理三向数据流(stdin/stdout/stderr)的功能。

It is possible to stream data through a child's stdin, stdout, and stderr in a fully non-blocking way. (Note that some programs use line-buffered I/O internally. That doesn't affect node.js but it means data you send to the child process is not immediately consumed.)

它能够以完全非阻塞的方式与子进程的 stdinstdoutstderr 以流式传递数据。(请注意,某些程序在内部使用行缓冲 I/O。这不会影响到 node.js,但您发送到子进程的数据不会被立即消费。)

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.

使用 require('child_process').spawn()require('child_process').fork() 创建子进程。这两种方法的语义有些区别,下文将会解释。

类: ChildProcess#

ChildProcess is an EventEmitter.

ChildProcess 是一个 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.

子进程有三个与之关联的流:child.stdinchild.stdoutchild.stderr。它们可以共享父进程的 stdio 流,也可以作为独立的被导流的流对象。

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

ChildProcess 类不能直接被使用, 使用 spawn() 或者 fork() 方法创建一个 Child Process 实例。

事件: 'error'#

  • err Error Object the error.

  • err Error Object 错误。

Emitted when:

发生于:

  1. The process could not be spawned, or
  2. The process could not be killed, or
  3. Sending a message to the child process failed for whatever reason.
  1. 进程不能被创建, 或者
  2. 进程不能被终止掉, 或者
  3. 由任何原因引起的数据发送到子进程失败.

See also ChildProcess#kill() and ChildProcess#send().

参阅 ChildProcess#kill()ChildProcess#send()

事件: 'exit'#

  • 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.

  • code Number 假如进程正常退出,则为它的退出代码。

  • signal String 假如是被父进程终止,则为所传入的终止子进程的信号。

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 the process terminated due to receipt of a signal, signal is the string name of the signal, otherwise null.

这个事件是在子进程被结束的时候触发的. 假如进程被正常结束,‘code’就是退出进程的指令代码, 否则为'null'. 假如进程是由于接受到signal结束的, signal 就代表着信号的名称, 否则为null.

Note that the child process stdio streams might still be open.

注意子进程的 stdio 流可能仍为开启状态。

See waitpid(2).

参阅waitpid(2).

事件: 'close'#

  • 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.

  • code Number 假如进程正常退出,则为它的退出代码。

  • signal String 假如是被父进程终止,则为所传入的终止子进程的信号。

This event is emitted when the stdio streams of a child process have all terminated. This is distinct from 'exit', since multiple processes might share the same stdio streams.

这个事件会在一个子进程的所有stdio流被终止时触发, 这和'exit'事件有明显的不同,因为多进程有时候会共享同一个stdio流

事件: 'disconnect'#

This event is emitted after using the .disconnect() method in the parent or in the child. After disconnecting it is no longer possible to send messages. An alternative way to check if you can send messages is to see if the child.connected property is true.

在子进程或父进程中使用使用.disconnect()方法后,这个事件会被触发,在断开之后,就不可能再相互发送信息了。可以通过检查子进程的child.connected属性是否为true去检查是否可以发送信息

事件: 'message'#

  • message Object a parsed JSON object or primitive value
  • sendHandle Handle object a Socket or Server object

  • message Object 一个已解析的JSON对象或者原始类型值

  • sendHandle Handle object 一个socket 或者 server对象

Messages send by .send(message, [sendHandle]) are obtained using the message event.

通过.send()发送的信息可以通过监听'message'事件获取到

child.stdin#

  • Stream object

  • Stream object

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

子进程的'stdin'是一个‘可写流’,通过end()方法关闭该可写流可以终止子进程,

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

假如子进程的stdio流与父线程共享,这个child.stdin不会被设置

child.stdout#

  • Stream object

  • Stream object

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

子进程的stdout是个可读流.

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

假如子进程的stdio流与父线程共享,这个child.stdin不会被设置

child.stderr#

  • Stream object

  • Stream object

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

子进程的stderr是一个可读流

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

假如子进程的stdio流与父线程共享,这个child.stdin不会被设置

child.pid#

  • Integer

  • Integer

The PID of the child process.

子进程的PID

Example:

示例:

console.log('Spawned child pid: ' + grep.pid);
grep.stdin.end();

child.kill([signal])#

  • signal String

  • 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.

发送一个信号给子线程. 假如没有给参数, 将会发送 'SIGTERM'. 参阅 signal(7) 查看所有可用的signals列表

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

May emit an 'error' event when the signal cannot be delivered. Sending a signal to a child process that has already exited is not an error but may have unforeseen consequences: if the PID (the process ID) has been reassigned to another process, the signal will be delivered to that process instead. What happens next is anyone's guess.

当一个signal不能被传递的时候,会触发一个'error'事件, 发送一个信号到已终止的子线程不会发生错误,但是可能引起不可预见的后果, 假如该子进程的ID已经重新分配给了其他进程,signal将会被发送到其他进程上面,大家可以猜想到这发生什么后果。

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.

注意,当函数调用‘kill’, 传递给子进程的信号不会去终结子进程, ‘kill’实际上只是发送一个信号到进程而已。

See kill(2)

See kill(2)

child.send(message, [sendHandle])#

  • message Object
  • sendHandle Handle object

  • message Object

  • sendHandle Handle object

When using child_process.fork() you can write to the child using child.send(message, [sendHandle]) and messages are received by a 'message' event on the child.

当使用 child_process.fork() 你可以使用 child.send(message, [sendHandle])向子进程写数据 and 数据将通过子进程上的‘message’事件接受.

For example:

例如:

n.send({ hello: 'world' });

And then the child script, 'sub.js' might look like this:

然后是子进程脚本的代码, 'sub.js' 代码如下:

process.send({ foo: 'bar' });

In the child the process object will have a send() method, and process will emit objects each time it receives a message on its channel.

在子进程脚本中'process'对象有‘send()’方法, ‘process’每次通过它的信道接收到信息都会触发事件,信息以对象形式返回。

There is a special case when sending a {cmd: 'NODE_foo'} message. All messages containing a NODE_ prefix in its cmd property will not be emitted in the message event, since they are internal messages used by node core. Messages containing the prefix are emitted in the internalMessage event, you should by all means avoid using this feature, it is subject to change without notice.

不过发送{cmd: 'NODE_foo'} 信息是个比较特殊的情况. 所有在‘cmd’属性中包含 a NODE_前缀的信息将不会触发‘message’事件, 因为他们是由node 核心使用的内部信息. 相反这种信息会触发 internalMessage 事件, 你应该通过各种方法避免使用这种特性, 他改变的时候不会接收到通知.

The sendHandle option to child.send() is for sending a TCP server or socket object to another process. The child will receive the object as its second argument to the message event.

child.send()sendHandle 选项是用来发送一个TCP服务或者socket对象到另一个线程的,子进程将会接收这个参数作为‘message’事件的第二个参数。

Emits an 'error' event if the message cannot be sent, for example because the child process has already exited.

假如信息不能被发送,将会触发一个‘error’事件, 比如说因为子线程已经退出了。

例子: 发送一个server对象#

Here is an example of sending a server:

这里是一个发送一个server对象的例子:

// 创建一个handle对象,发送一个句柄.
var server = require('net').createServer();
server.on('connection', function (socket) {
  socket.end('handled by parent');
});
server.listen(1337, function() {
  child.send('server', server);
});

And the child would the receive the server object as:

同时子进程将会以如下方式接收到这个server对象:

process.on('message', function(m, server) {
  if (m === 'server') {
    server.on('connection', function (socket) {
      socket.end('handled by child');
    });
  }
});

Note that the server is now shared between the parent and child, this means that some connections will be handled by the parent and some by the child.

注意,server对象现在有父进程和子进程共享,这意味着某些连接将会被父进程和子进程处理。

For dgram servers the workflow is exactly the same. Here you listen on a message event instead of connection and use server.bind instead of server.listen. (Currently only supported on UNIX platforms.)

对‘dgram’服务器,工作流程是一样的, 你监听的是‘message’事件,而不是 ‘connection’事件, 使用‘server.bind’ ,而不是‘server.listen’.(当前仅在UNIX平台支持)

示例: 发送socket对象#

Here is an example of sending a socket. It will spawn two children and handle connections with the remote address 74.125.127.100 as VIP by sending the socket to a "special" child process. Other sockets will go to a "normal" process.

这是个发送socket的例子. 他将创建两个子线程 ,同时处理连接,这是通过使用远程地址 74.125.127.100 作为 VIP 发送socket到一个‘特殊’的子线程. 其他的socket将会发送到‘正常’的线程里.

  // if this is a VIP
  if (socket.remoteAddress === '74.125.127.100') {
    special.send('socket', socket);
    return;
  }
  // just the usual dudes
  normal.send('socket', socket);
});
server.listen(1337);

The child.js could look like this:

child.js 文件代码如下:

process.on('message', function(m, socket) {
  if (m === 'socket') {
    socket.end('You were handled as a ' + process.argv[2] + ' person');
  }
});

Note that once a single socket has been sent to a child the parent can no longer keep track of when the socket is destroyed. To indicate this condition the .connections property becomes null. It is also recommended not to use .maxConnections in this condition.

注意,一旦单个的socket被发送到子进程,当这个socket被删除之后,父进程将不再对它保存跟踪,这表明了这个条件下‘.connetions’属性将变成'null', 在这个条件下同时也不推荐时间‘.maxConnections’

child.disconnect()#

To close the IPC connection between parent and child use the child.disconnect() method. This allows the child to exit gracefully since there is no IPC channel keeping it alive. When calling this method the disconnect event will be emitted in both parent and child, and the connected flag will be set to false. Please note that you can also call process.disconnect() in the child process.

使用child.disconnect() 方法关闭父进程与子进程的IPC连接. 他让子进程非常优雅的退出,因为已经没有活跃的IPC信道. 当调用这个方法,‘disconnect’事件将会同时在父进程和子进程内被触发,‘connected’的标签将会被设置成‘flase’, 请注意,你也可以在子进程中调用‘process.disconnect()’

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
    • stdio Array|String Child's stdio configuration. (See below)
    • customFds Array Deprecated File descriptors for the child to use for stdio. (See below)
    • env Object Environment key-value pairs
    • detached Boolean The child will be a process group leader. (See below)
    • uid Number Sets the user identity of the process. (See setuid(2).)
    • gid Number Sets the group identity of the process. (See setgid(2).)
  • return: ChildProcess object
  • command {String}要运行的命令
  • args {Array} 字符串参数列表
  • options {Object}
    • cwd {String} 子进程的当前的工作目录
    • stdio {Array|String} 子进程 stdio 配置. (参阅下文)
    • customFds {Array} Deprecated 作为子进程 stdio 使用的 文件标示符. (参阅下文)
    • env {Object} 环境变量的键值对
    • detached {Boolean} 子进程将会变成一个进程组的领导者. (参阅下文)
    • uid {Number} 设置用户进程的ID. (See setuid(2).)
    • gid {Number} 设置进程组的ID. (See setgid(2).)
  • 返回: {ChildProcess object}

Launches a new process with the given command, with command line arguments in args. If omitted, args defaults to an empty Array.

用给定的命令发布一个子进程,带有‘args’命令行参数,如果省略的话,‘args’默认为一个空数组

The third argument is used to specify additional options, which defaults to:

第三个参数被用来指定额外的设置,默认是:

{ cwd: undefined,
  env: process.env
}

cwd allows you to specify the working directory from which the process is spawned. Use env to specify environment variables that will be visible to the new process.

cwd允许你从被创建的子进程中指定一个工作目录. 使用 env 去指定在新进程中可用的环境变量.

Example of running ls -lh /usr, capturing stdout, stderr, and the exit code:

一个运行 ls -lh /usr的例子, 获取stdout, stderr, 和退出代码:

ls.on('close', function (code) {
  console.log('child process exited with code ' + code);
});

Example: A very elaborate way to run 'ps ax | grep ssh'

例子: 一个非常精巧的方法执行 'ps ax | grep ssh'

grep.on('close', function (code) {
  if (code !== 0) {
    console.log('grep process exited with code ' + code);
  }
});

Example of checking for failed exec:

检查执行错误的例子:

child.stderr.setEncoding('utf8');
child.stderr.on('data', function (data) {
  if (/^execvp\(\)/.test(data)) {
    console.log('Failed to start child process.');
  }
});

Note that if spawn receives an empty options object, it will result in spawning the process with an empty environment rather than using process.env. This due to backwards compatibility issues with a deprecated API.

注意,当在spawn过程中接收一个空对象,这会导致创建的进程使用空的环境变量而不是使用‘process.env’.这是由于与一个废弃API向后兼容的问题.

The 'stdio' option to child_process.spawn() is an array where each index corresponds to a fd in the child. The value is one of the following:

child_process.spawn() 中的 stdio 选项是一个数组,每个索引对应子进程中的一个文件标识符。可以是下列值之一:

  1. 'pipe' - Create a pipe between the child process and the parent process. The parent end of the pipe is exposed to the parent as a property on the child_process object as ChildProcess.stdio[fd]. Pipes created for fds 0 - 2 are also available as ChildProcess.stdin, ChildProcess.stdout and ChildProcess.stderr, respectively.
  2. 'ipc' - Create an IPC channel for passing messages/file descriptors between parent and child. A ChildProcess may have at most one IPC stdio file descriptor. Setting this option enables the ChildProcess.send() method. If the child writes JSON messages to this file descriptor, then this will trigger ChildProcess.on('message'). If the child is a Node.js program, then the presence of an IPC channel will enable process.send() and process.on('message').
  3. 'ignore' - Do not set this file descriptor in the child. Note that Node will always open fd 0 - 2 for the processes it spawns. When any of these is ignored node will open /dev/null and attach it to the child's fd.
  4. Stream object - Share a readable or writable stream that refers to a tty, file, socket, or a pipe with the child process. The stream's underlying file descriptor is duplicated in the child process to the fd that corresponds to the index in the stdio array.
  5. Positive integer - The integer value is interpreted as a file descriptor that is is currently open in the parent process. It is shared with the child process, similar to how Stream objects can be shared.
  6. null, undefined - Use default value. For stdio fds 0, 1 and 2 (in other words, stdin, stdout, and stderr) a pipe is created. For fd 3 and up, the default is 'ignore'.
  1. 'pipe' -在子进程与父进程之间创建一个管道,管道的父进程端以 child_process 的属性的形式暴露给父进程,如 ChildProcess.stdio[fd]。 为 文件标识(fds) 0 - 2 建立的管道也可以通过 ChildProcess.stdin,ChildProcess.stdout 及 ChildProcess.stderr 分别访问。

  2. 'ipc' - 创建一个IPC通道以在父进程与子进程之间传递 消息/文件标识符。一个子进程只能有最多一个 IPC stdio 文件标识。 设置该选项激活 ChildProcess.send() 方法。如果子进程向此文件标识符写JSON消息,则会触发 ChildProcess.on("message")。 如果子进程是一个nodejs程序,那么IPC通道的存在会激活process.send()和process.on('message')

  3. 'ignore' - 不在子进程中设置该文件标识。注意,Node 总是会为其spawn的进程打开 文件标识(fd) 0 - 2。 当其中任意一项被 ignored,node 会打开 /dev/null 并将其附给子进程的文件标识(fd)。

  4. Stream 对象 - 与子进程共享一个与tty,文件,socket,或者管道(pipe)相关的可读或可写流。 该流底层(underlying)的文件标识在子进程中被复制给stdio数组索引对应的文件标识(fd)

  5. 正数 - 该整形值被解释为父进程中打开的文件标识符。他与子进程共享,和Stream被共享的方式相似。

  6. null, undefined - 使用默认值。 对于stdio fds 0,1,2(或者说stdin,stdout和stderr),pipe管道被建立。对于fd 3及往后,默认为ignore

As a shorthand, the stdio argument may also be one of the following strings, rather than an array:

作为快捷方式,stdio 参数除了数组也可以是下列字符串之一:

  • ignore - ['ignore', 'ignore', 'ignore']
  • pipe - ['pipe', 'pipe', 'pipe']
  • inherit - [process.stdin, process.stdout, process.stderr] or [0,1,2]

  • ignore - ['ignore', 'ignore', 'ignore']

  • pipe - ['pipe', 'pipe', 'pipe']
  • inherit - [process.stdin, process.stdout, process.stderr][0,1,2]

Example:

示例:

// 开启一个额外的 fd=4 来与提供 startd 风格接口的程序进行交互。
spawn('prg', [], { stdio: ['pipe', null, null, null, 'pipe'] });

If the detached option is set, the child process will be made the leader of a new process group. This makes it possible for the child to continue running after the parent exits.

如果 detached 选项被设置,则子进程会被作为新进程组的 leader。这使得子进程可以在父进程退出后继续运行。

By default, the parent will wait for the detached child to exit. To prevent the parent from waiting for a given child, use the child.unref() method, and the parent's event loop will not include the child in its reference count.

缺省情况下,父进程会等待脱离了的子进程退出。要阻止父进程等待一个给出的子进程 child,使用 child.unref() 方法,则父进程的事件循环引用计数中将不会包含这个子进程。

Example of detaching a long-running process and redirecting its output to a file:

脱离一个长时间运行的进程并将它的输出重定向到一个文件的例子:

 child.unref();

When using the detached option to start a long-running process, the process will not stay running in the background unless it is provided with a stdio configuration that is not connected to the parent. If the parent's stdio is inherited, the child will remain attached to the controlling terminal.

当使用 detached 选项来启动一个长时间运行的进程,该进程不会在后台保持运行,除非向它提供了一个不连接到父进程的 stdio 配置。如果继承了父进程的 stdio,则子进程会继续附着在控制终端。

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. Use at your own risk.

有一个已废弃的选项 customFds 允许指定特定文件描述符作为子进程的 stdio。该 API 无法移植到所有平台,因此被移除。使用 customFds 可以将新进程的 [stdin, stdout, stderr] 钩到已有流上;-1 表示创建新流。自己承担使用风险。

See also: child_process.exec() and child_process.fork()

参阅:child_process.exec()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
    • env Object Environment key-value pairs
    • encoding String (Default: 'utf8')
    • shell String Shell to execute the command with (Default: '/bin/sh' on UNIX, 'cmd.exe' on Windows, The shell should understand the -c switch on UNIX or /s /c on Windows. On Windows, command line parsing should be compatible with cmd.exe.)
    • timeout Number (Default: 0)
    • maxBuffer Number (Default: 200*1024)
    • killSignal String (Default: 'SIGTERM')
  • callback Function called with the output when process terminates
    • error Error
    • stdout Buffer
    • stderr Buffer
  • Return: ChildProcess object

  • command String 将要执行的命令,用空格分隔参数

  • options Object
    • cwd String 子进程的当前工作目录
    • env Object 环境变量键值对
    • encoding String 编码(缺省为 'utf8')
    • shell String 运行命令的 shell(UNIX 上缺省为 '/bin/sh',Windows 上缺省为 'cmd.exe'。该 shell 在 UNIX 上应当接受 -c 开关,在 Windows 上应当接受 /s /c 开关。在 Windows 中,命令行解析应当兼容 cmd.exe。)
    • timeout Number 超时(缺省为 0)
    • maxBuffer Number 最大缓冲(缺省为 200*1024)
    • killSignal String 结束信号(缺省为 'SIGTERM')
  • callback Function 进程结束时回调并带上输出
    • error Error
    • stdout Buffer
    • stderr Buffer
  • 返回:ChildProcess 对象

Runs a command in a shell and buffers the output.

在 shell 中执行一个命令并缓冲输出。

child = exec('cat *.js bad_file | wc -l',
  function (error, stdout, stderr) {
    console.log('stdout: ' + stdout);
    console.log('stderr: ' + stderr);
    if (error !== null) {
      console.log('exec error: ' + error);
    }
});

The callback gets the arguments (error, stdout, stderr). On success, error 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.

回调参数为 (error, stdout, stderr)。当成功时,error 会是 null。当遇到错误时,error 会是一个 Error 实例,并且 err.code 会是子进程的退出代码,同时 err.signal 会被设置为结束进程的信号名。

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

第二个可选的参数用于指定一些选项,缺省选项为:

{ encoding: 'utf8',
  timeout: 0,
  maxBuffer: 200*1024,
  killSignal: 'SIGTERM',
  cwd: null,
  env: null }

If timeout is greater than 0, then it will kill the child process if it runs longer than timeout milliseconds. The child process is killed with killSignal (default: 'SIGTERM'). maxBuffer specifies the largest amount of data allowed on stdout or stderr - if this value is exceeded then the child process is killed.

如果 timeout 大于 0,则当进程运行超过 timeout 毫秒后会被终止。子进程使用 killSignal 信号结束(缺省为 'SIGTERM')。maxBuffer 指定了 stdout 或 stderr 所允许的最大数据量,如果超出这个值则子进程会被终止。

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
    • env Object Environment key-value pairs
    • 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
    • error Error
    • stdout Buffer
    • stderr Buffer
  • Return: ChildProcess object

  • file String 要运行的程序的文件名

  • args Array 字符串参数列表
  • options Object
    • cwd String 子进程的当前工作目录
    • env Object 环境变量键值对
    • encoding String 编码(缺省为 'utf8')
    • timeout Number 超时(缺省为 0)
    • maxBuffer Number 最大缓冲(缺省为 200*1024)
    • killSignal String 结束信号(缺省为 'SIGTERM')
  • callback Function 进程结束时回调并带上输出
    • error Error
    • stdout Buffer
    • stderr Buffer
  • 返回:ChildProcess 对象

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.

该方法类似于 child_process.exec(),但是它不会执行一个子 shell,而是直接执行所指定的文件。因此它稍微比 child_process.exec 精简,参数与之一致。

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
    • env Object Environment key-value pairs
    • encoding String (Default: 'utf8')
    • execPath String Executable used to create the child process
  • Return: ChildProcess object

  • modulePath String 子进程中运行的模块

  • args Array 字符串参数列表
  • options Object
    • cwd String 子进程的当前工作目录
    • env Object 环境变量键值对
    • encoding String 编码(缺省为 'utf8')
    • execPath String 创建子进程的可执行文件
  • 返回:ChildProcess 对象

This is a special case of the spawn() functionality for spawning Node processes. In addition to having all the methods in a normal ChildProcess instance, the returned object has a communication channel built-in. See child.send(message, [sendHandle]) for details.

该方法是 spawn() 的特殊情景,用于派生 Node 进程。除了普通 ChildProcess 实例所具有的所有方法,所返回的对象还具有内建的通讯通道。详见 child.send(message, [sendHandle])

By default the spawned Node process will have the stdout, stderr associated with the parent's. To change this behavior set the silent property in the options object to true.

缺省情况下所派生的 Node 进程的 stdout、stderr 会关联到父进程。要更改该行为,可将 options 对象中的 silent 属性设置为 true

The child process does not automatically exit once it's done, you need to call process.exit() explicitly. This limitation may be lifted in the future.

子进程运行完成时并不会自动退出,您需要明确地调用 process.exit()。该限制可能会在未来版本里接触。

These child Nodes are still whole new instances of V8. Assume at least 30ms startup and 10mb memory for each new Node. That is, you cannot create many thousands of them.

这些子 Node 是全新的 V8 实例,假设每个新的 Node 需要至少 30 毫秒的启动时间和 10MB 内存,就是说您不能创建成百上千个这样的实例。

The execPath property in the options object allows for a process to be created for the child rather than the current node executable. This should be done with care and by default will talk over the fd represented an environmental variable NODE_CHANNEL_FD on the child process. The input and output on this fd is expected to be line delimited JSON objects.

options 对象中的 execPath 属性可以用非当前 node 可执行文件来创建子进程。这需要小心使用,并且缺省情况下会使用子进程上的 NODE_CHANNEL_FD 环境变量所指定的文件描述符来通讯。该文件描述符的输入和输出假定为以行分割的 JSON 对象。