Node.js — Processes

Child Process Module

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

exec

Runs a command in a shell:

exec('ls -la', (error, stdout, stderr) => {
    if (error) {
        console.error(`Error: ${error.message}`);
        return;
    }
    console.log(stdout);
});

spawn

Launches a new process:

const child = spawn('ls', ['-la']);

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

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

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

fork

Creates a new Node.js process:

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

const child = fork('worker.js');

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

child.send({ task: 'process' });

Environment

const child = spawn('node', ['script.js'], {
    env: { ...process.env, NODE_ENV: 'production' },
    cwd: '/path/to/directory'
});

Mini Practice

1. Execute a shell command
2. Spawn a child process
3. Fork a Node.js process
4. Communicate between processes

Up Next

Continue with Environment Variables — using env vars.