Child Processes
📌 Covered in this chapter:
exec vs spawn vs fork · Running Shell Commands · Process Communication · Security
Spawn and communicate with external OS processes from Node.js using exec, spawn, and fork.
1Child Processes — What You'll Learn
Spawn and communicate with external OS processes from Node.js using exec, spawn, and fork.
Here's everything this chapter covers, in the order you'll learn it:
- What a child process is
- exec() for running shell commands and capturing output
- spawn() for streaming large output
- fork() for spawning another Node.js process
- Reading process output
- Handling process errors
- Security risks of shell execution
- Preventing command injection
- Communicating between parent and child processes
2Working Example
💻 Example: Child Processes
JavaScript
▶ Run in Compiler
import { exec } from "node:child_process";
exec("node --version", (error, stdout, stderr) => {
if (error) {
console.error(error.message);
return;
}
console.log("Node version:", stdout.trim());
});3Best Practices & Common Pitfalls
💡 Key things to remember:
- Never pass unsanitized user input directly into exec() — it runs through a shell and is vulnerable to command injection. Prefer spawn() with an argument array instead.
❓ Frequently Asked Questions (FAQ)
Q What's the most important thing to understand about child processes?
Focus on: exec vs spawn vs fork · Running Shell Commands · Process Communication · Security. These are the core building blocks this chapter's examples are built around, and they show up repeatedly in later chapters of this course.
Q Do I need external npm packages for child processes?
Only where explicitly shown in the code examples above (like Express, Zod, or Socket.IO) — otherwise, this chapter relies entirely on Node.js's own built-in capabilities.