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Child Processes in Node.js

Node.js provides the child_process module to enable the creation of new processes, allowing your application to perform tasks outside the main event loop.

Why use Child Processes?

Offload Heavy Tasks: Run CPU-intensive operations in separate processes.
Run External Commands: Execute scripts or system binaries.
Scalability: Utilize multi-core systems by spawning multiple processes.

Core Methods

1. `spawn()`

Launches a command in a new process. It’s asynchronous and returns a stream. Use this for large amounts of data.

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

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

2. `exec()`

Spawns a shell and runs a command within that shell. It buffers the output and returns it in a callback.

const { exec } = require('child_process');

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

3. `execFile()`

Similar to exec() but does not spawn a shell, making it more efficient and secure for running executables.

4. `fork()`

A special case of spawn() that creates a new Node.js process with a communication channel (IPC) established between 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' });

Best Practices

Security: Always sanitize inputs to prevent command injection.
Error Handling: Listen for error and exit events.
Resource Management: Properly close processes when they are no longer needed.