spawn for streaming processes in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the spawn function from the child_process module.

Node.js

const { [1] } = require('child_process');

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Aexec

Bfork

Cspawn

DexecFile

Attempts:

3 left

💡 Hint

Common Mistakes

Using exec instead of spawn, which buffers output instead of streaming.

Trying to import a function that does not exist in child_process.

The spawn function is imported from the child_process module to create streaming child processes.

2fill in blank

medium

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

Node.js

const ls = spawn('[1]');

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Adir

Bshow

Clist

Dls

Attempts:

3 left

💡 Hint

Common Mistakes

Using Windows command 'dir' on Unix systems.

Using a non-existent command like 'list' or 'show'.

The ls command lists directory contents on Unix-like systems and is used here with spawn.

3fill in blank

hard

Fix the error in the code to correctly handle the data event from the child process stdout stream.

Node.js

ls.stdout.on('[1]', (data) => {
  console.log(`Output: ${data}`);
});

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Adata

Berror

Cmessage

Dclose

Attempts:

3 left

💡 Hint

Common Mistakes

Listening for 'message' which is not an event on stdout streams.

Using 'error' event to get output data.

The data event is emitted when the child process sends output data on stdout.

4fill in blank

hard

Fill both blanks to spawn a process running 'node' with arguments ['-v'] and handle its exit event.

Node.js

const proc = spawn('[1]', ['[2]']);
proc.on('exit', (code) => {
  console.log(`Process exited with code ${code}`);
});

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

Anode

B-v

C-h

Dnpm

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'npm' instead of 'node' for the command.

Using '-h' which shows help, not version.

The node command runs Node.js, and -v prints its version. The exit event tells when the process finishes.

5fill in blank

hard

Fill all three blanks to create a child process that runs 'grep' to filter 'error' from input, and handle its stdout data event.

Node.js

const grep = spawn('[1]', ['[2]']);
grep.stdout.on('[3]', (data) => {
  console.log(`Filtered output: ${data}`);
});

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

Agrep

Berror

Cdata

Dexit

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'exit' event instead of 'data' to read output.

Using wrong command or pattern strings.

grep filters input lines matching 'error'. The data event reads the filtered output stream.