Child process exit codes in Node.js - Mini Project: Build & Apply

Child Process Exit Codes in Node.js

📖 Scenario: You are building a Node.js script that runs a child process to execute a simple command. You want to check the exit code of the child process to know if it ran successfully or if there was an error.

🎯 Goal: Create a Node.js script that spawns a child process to run the ls command, captures its exit code, and prints a message based on whether the command succeeded or failed.

📋 What You'll Learn

Use the child_process module to spawn a child process

Run the ls command using spawn

Listen for the exit event to get the exit code

Print Success if exit code is 0, otherwise print Failure

💡 Why This Matters

🌍 Real World

Developers often run other programs from Node.js scripts and need to know if those programs finished successfully.

💼 Career

Understanding child process exit codes is important for building reliable automation scripts, deployment tools, and server-side applications.

1

Import the child_process module and create the child process

Write code to import spawn from the child_process module and create a child process called lsProcess that runs the ls command with no arguments.

Node.js

const { spawn } = require('child_process');
// Create lsProcess to run 'ls' command
// Your code here

Need a hint?

Use const { spawn } = require('child_process') to import spawn. Then call spawn('ls') to run the command.

2

Add a variable to hold the exit code

Create a variable called exitCode and set it to null. This will store the exit code of the child process.

Node.js

const { spawn } = require('child_process');
const lsProcess = spawn('ls');
// Create exitCode variable
// Your code here

Need a hint?

Use let exitCode = null to create the variable.

3

Listen for the exit event and save the exit code

Add an event listener on lsProcess for the exit event. Use (code) => as the callback parameter and assign code to the exitCode variable.

Node.js

const { spawn } = require('child_process');
const lsProcess = spawn('ls');
let exitCode = null;
// Listen for exit event and save code
// Your code here

Need a hint?

Use lsProcess.on('exit', (code) => { exitCode = code; }) to capture the exit code.

4

Print success or failure based on the exit code

Add an event listener on lsProcess for the close event. Inside the callback, check if exitCode is 0. If yes, print Success. Otherwise, print Failure.

Node.js

const { spawn } = require('child_process');
const lsProcess = spawn('ls');
let exitCode = null;
lsProcess.on('exit', (code) => {
    exitCode = code;
});
// Listen for close event and print result
// Your code here

Need a hint?

Use lsProcess.on('close', () => { if (exitCode === 0) console.log('Success'); else console.log('Failure'); }).