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

  • modulePath <string> 要在子进程中运行的模块。
  • args <string[]> 字符串参数的列表。
  • options <Object>

    • cwd <string> 子进程的当前工作目录。
    • env <Object> 环境变量的键值对。
    • execPath <string> 用于创建子进程的可执行文件。
    • execArgv <string[]> 传给可执行文件的字符串参数的列表。默认值: process.execArgv
    • silent <boolean> 如果为 true,则将子进程的 stdin、stdout 和 stderr 传给父进程,否则从父进程继承,参阅 child_process.spawn()stdio 中的 'pipe''inherit' 选项。默认值: false
    • stdio <Array> | <string> 参阅 child_process.spawn()stdio。如果提供了此选项,则覆盖 silent 选项。 如果使用了数组变量,则必须包含一个值为 'ipc' 的元素,否则将抛出错误。例如 [0, 1, 2, 'ipc']
    • windowsVerbatimArguments <boolean> 在 Windows 上是否为参数加上引号或转义。在 Unix 上忽略。默认值: false
    • uid <number> 设置进程的用户标识,参阅 setuid(2)
    • gid <number> 设置进程的群组标识,参阅 setgid(2)
  • 返回: <ChildProcess>

child_process.fork() 方法是 child_process.spawn() 的一个特例,专门用于衍生新的 Node.js 进程。 与 child_process.spawn() 一样返回 ChildProcess 对象。 返回的 ChildProcess 将内置一个额外的通信通道,允许消息在父进程和子进程之间来回传递。 有关详细信息,请参阅 subprocess.send()

注意,衍生的 Node.js 子进程独立于父进程,但两者之间建立的 IPC 通信通道除外。 每个进程都有自己的内存,带有自己的 V8 实例。 由于需要额外的资源分配,因此不建议衍生大量子 Node.js 进程。

默认情况下, child_process.fork() 将使用父进程的 process.execPath 衍生新的 Node.js 实例。 options 对象中的 execPath 属性允许使用备用的执行路径。

使用自定义的 execPath 启动的 Node.js 进程将使用在子进程上使用环境变量 NODE_CHANNEL_FD 标识的文件描述符(fd)与父进程通信。

fork(2) 的 POSIX 系统调用不同, child_process.fork() 不克隆当前进程。

child_process.fork() 不支持 child_process.spawn() 中可用的 shell 选项,如果设置则将被忽略。

  • modulePath <string> The module to run in the child.
  • args <string[]> List of string arguments.
  • options <Object>

    • cwd <string> Current working directory of the child process.
    • detached <boolean> Prepare child to run independently of its parent process. Specific behavior depends on the platform, see options.detached).
    • env <Object> Environment key-value pairs.
    • execPath <string> Executable used to create the child process.
    • execArgv <string[]> List of string arguments passed to the executable. Default: process.execArgv.
    • silent <boolean> If true, stdin, stdout, and stderr of the child will be piped to the parent, otherwise they will be inherited from the parent, see the 'pipe' and 'inherit' options for child_process.spawn()'s stdio for more details. Default: false.
    • stdio <Array> | <string> See child_process.spawn()'s stdio. When this option is provided, it overrides silent. If the array variant is used, it must contain exactly one item with value 'ipc' or an error will be thrown. For instance [0, 1, 2, 'ipc'].
    • windowsVerbatimArguments <boolean> No quoting or escaping of arguments is done on Windows. Ignored on Unix. Default: false.
    • uid <number> Sets the user identity of the process (see setuid(2)).
    • gid <number> Sets the group identity of the process (see setgid(2)).
  • Returns: <ChildProcess>

The child_process.fork() method is a special case of child_process.spawn() used specifically to spawn new Node.js processes. Like child_process.spawn(), a ChildProcess object is returned. The returned ChildProcess will have an additional communication channel built-in that allows messages to be passed back and forth between the parent and child. See subprocess.send() for details.

It is important to keep in mind that spawned Node.js child processes are independent of the parent with exception of the IPC communication channel that is established between the two. Each process has its own memory, with their own V8 instances. Because of the additional resource allocations required, spawning a large number of child Node.js processes is not recommended.

By default, child_process.fork() will spawn new Node.js instances using the process.execPath of the parent process. The execPath property in the options object allows for an alternative execution path to be used.

Node.js processes launched with a custom execPath will communicate with the parent process using the file descriptor (fd) identified using the environment variable NODE_CHANNEL_FD on the child process.

Unlike the fork(2) POSIX system call, child_process.fork() does not clone the current process.

The shell option available in child_process.spawn() is not supported by child_process.fork() and will be ignored if set.