stdout-stderr

What is stdout-stderr?

The stdout-stderr npm package is a utility for capturing and manipulating the standard output (stdout) and standard error (stderr) streams in Node.js applications. It is particularly useful for testing and debugging purposes, allowing developers to intercept and inspect the output of their code.

What are stdout-stderr's main functionalities?

Capture stdout

This feature allows you to capture the standard output (stdout) stream. The code sample demonstrates how to start capturing stdout, print a message, stop capturing, and then inspect the captured output.

const stdio = require('stdout-stderr');

stdio.stdout.start();
console.log('Hello, World!');
stdio.stdout.stop();
console.log(stdio.stdout.output); // ['Hello, World!\n']

Capture stderr

This feature allows you to capture the standard error (stderr) stream. The code sample demonstrates how to start capturing stderr, print an error message, stop capturing, and then inspect the captured output.

const stdio = require('stdout-stderr');

stdio.stderr.start();
console.error('An error occurred!');
stdio.stderr.stop();
console.log(stdio.stderr.output); // ['An error occurred!\n']

Combined stdout and stderr capture

This feature allows you to capture both stdout and stderr streams simultaneously. The code sample demonstrates how to start capturing both streams, print messages to both stdout and stderr, stop capturing, and then inspect the combined output.

const stdio = require('stdout-stderr');

stdio.start();
console.log('Hello, World!');
console.error('An error occurred!');
stdio.stop();
console.log(stdio.output); // ['Hello, World!\n', 'An error occurred!\n']

Suppress output

This feature allows you to suppress the output to stdout or stderr. The code sample demonstrates how to suppress stdout, print a message that will not be shown, restore stdout, and then print a message that will be shown.

const stdio = require('stdout-stderr');

stdio.stdout.suppress();
console.log('This will not be shown');
stdio.stdout.restore();
console.log('This will be shown');

Other packages similar to stdout-stderr

capture-console

The capture-console package provides similar functionality for capturing and manipulating stdout and stderr streams. It offers methods to capture, suppress, and restore console output, making it a good alternative to stdout-stderr.

intercept-stdout

The intercept-stdout package enables you to intercept and capture stdout and stderr streams. It provides a straightforward API to intercept output and perform custom actions, making it a versatile alternative to stdout-stderr.

README

stdout-stderr

mock stdout and stderr

Usage:

const {stdout, stderr} = require('stdout-stderr')

stdout.start()                                // start mocking stdout
console.log('writing to stdout')              // this will not be displayed
stdout.stop()                                 // stop mocking stdout
assert(stdout.output === 'writing to stdout') // view the output


/* options */
stdout.stripColor = false // disable automatic ansi code stripping
stdout.print = true       // also output to screen

This uses the debug module so you can also see the output by setting DEBUG=stdout|stderr|*.