Child process exit codes in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to listen for the child process exit event.

Node.js

childProcess.on('exit', (code) => {
  console.log('Child exited with code', [1]);
});

Drag options to blanks, or click blank then click option'

Astatus

Berror

Csignal

Dcode

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'error' or 'signal' instead of the exit code parameter.

Not using the parameter at all.

The 'exit' event provides the exit code as the first argument, which is commonly named code.

2fill in blank

medium

Complete the code to spawn a child process running 'ls' command.

Node.js

const { spawn } = require('child_process');
const ls = [1]('ls', ['-lh', '/usr']);

Drag options to blanks, or click blank then click option'

Aexec

Bfork

Cspawn

DexecFile

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'exec' which runs a shell command but does not take arguments as an array.

Using 'fork' which is for spawning new Node.js processes.

The spawn function is used to launch a new process with a given command and arguments.

3fill in blank

hard

Fix the error in the code to correctly check if the child process exited normally.

Node.js

childProcess.on('exit', (code, signal) => {
  if ([1] === null) {
    console.log('Exited normally with code', code);
  } else {
    console.log('Process killed by signal', signal);
  }
});

Drag options to blanks, or click blank then click option'

Acode

Bsignal

Ccode === 0

Dsignal === null

Attempts:

3 left

💡 Hint

Common Mistakes

Checking if code is null instead of signal.

Checking if code equals zero to determine normal exit.

The signal parameter is null if the process exited normally. Checking if signal === null tells us if the exit was normal.

4fill in blank

hard

Fill both blanks to create a dictionary of exit codes and their meanings.

Node.js

const exitCodes = {
  0: [1],
  1: [2]
};

Drag options to blanks, or click blank then click option'

A'Success'

B'General error'

C'Failure'

D'Unknown'

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the meanings of exit codes 0 and 1.

Using vague terms like 'Failure' instead of 'General error'.

Exit code 0 means success, and exit code 1 usually means a general error.

5fill in blank

hard

Fill all three blanks to create a filtered object of exit codes greater than zero.

Node.js

const filtered = Object.fromEntries(
  Object.entries(exitCodes).filter(([[1], [2]]) => [3] > 0)
);

Drag options to blanks, or click blank then click option'

Acode

Bmessage

CNumber(code)

Dmessage.length

Attempts:

3 left

💡 Hint

Common Mistakes

Not converting the key to a number before comparison.

Using the message variable in the comparison instead of the code.

We destructure the entries into code and message. We convert code to a number to compare it with 0.