Skip to main content
fork - child_process - Node documentation
function fork

Usage in Deno

import { fork } from "node:child_process";
fork(
modulePath: string | URL,
options?: ForkOptions,
): ChildProcess

The child_process.fork() method is a special case of spawn used specifically to spawn new Node.js processes. Like 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.

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 spawn is not supported by child_process.fork() and will be ignored if set.

If the signal option is enabled, calling .abort() on the corresponding AbortController is similar to calling .kill() on the child process except the error passed to the callback will be an AbortError:

if (process.argv[2] === 'child') {
  setTimeout(() => {
    console.log(`Hello from ${process.argv[2]}!`);
  }, 1_000);
} else {
  import { fork } from 'node:child_process';
  const controller = new AbortController();
  const { signal } = controller;
  const child = fork(__filename, ['child'], { signal });
  child.on('error', (err) => {
    // This will be called with err being an AbortError if the controller aborts
  });
  controller.abort(); // Stops the child process
}

Parameters

modulePath: string | URL

The module to run in the child.

optional
options: ForkOptions

Return Type

fork(
modulePath: string | URL,
args?: readonly string[],
options?: ForkOptions,
): ChildProcess

Parameters

modulePath: string | URL
optional
args: readonly string[]
optional
options: ForkOptions

Return Type