child_process

What is child_process?

The 'child_process' module in Node.js allows you to spawn new processes, execute commands, and communicate with those processes. It provides a way to run shell commands, scripts, and other programs from within a Node.js application.

What are child_process's main functionalities?

Spawning a new process

The 'spawn' function launches a new process with a given command. In this example, it runs the 'ls' command with the '-lh' and '/usr' arguments. The stdout and stderr streams are used to handle the output and errors, respectively.

const { spawn } = require('child_process');
const ls = spawn('ls', ['-lh', '/usr']);

ls.stdout.on('data', (data) => {
  console.log(`stdout: ${data}`);
});

ls.stderr.on('data', (data) => {
  console.error(`stderr: ${data}`);
});

ls.on('close', (code) => {
  console.log(`child process exited with code ${code}`);
});

Executing a command

The 'exec' function runs a command in a shell and buffers the output. This example executes the 'ls -lh /usr' command and logs the stdout and stderr outputs. If an error occurs, it is logged as well.

const { exec } = require('child_process');
exec('ls -lh /usr', (error, stdout, stderr) => {
  if (error) {
    console.error(`exec error: ${error}`);
    return;
  }
  console.log(`stdout: ${stdout}`);
  console.error(`stderr: ${stderr}`);
});

Forking a new Node.js process

The 'fork' function is a special case of 'spawn' used to create new Node.js processes. It allows for communication between the parent and child processes using the 'message' event. In this example, a new Node.js process is created to run 'child.js', and messages are exchanged between the parent and child.

const { fork } = require('child_process');
const child = fork('child.js');

child.on('message', (msg) => {
  console.log('Message from child', msg);
});

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

Other packages similar to child_process

execa

Execa is a modern alternative to 'child_process'. It provides a more user-friendly API for executing shell commands and handling their output. Execa supports promises, better error handling, and more features compared to the standard 'child_process' module.

cross-spawn

Cross-spawn is a package that provides a consistent API for spawning child processes across different platforms. It addresses issues with the default 'child_process' module, especially on Windows, making it easier to write cross-platform code.

shelljs

ShellJS is a portable (Windows/Linux/OS X) implementation of Unix shell commands on top of the Node.js API. It provides a higher-level API for executing shell commands and scripts, making it easier to work with the filesystem and other shell tasks.

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