hook-std

Hook and modify stdout and stderr

Install

$ npm install hook-std

Usage

const assert = require('assert');
const hookStd = require('hook-std');

(async () => {
    const promise = hookStd.stdout(output => {
        promise.unhook();
        assert.strictEqual(output.trim(), 'unicorn');
    });

    console.log('unicorn');
    await promise;
})();

You can also unhook using the second transform method parameter:

(async () => {
    const promise = hookStd.stdout((output, unhook) => {
        unhook();
        assert.strictEqual(output.trim(), 'unicorn');
    });

    console.log('unicorn');
    await promise;
})();

API

hookStd([options], transform)

Hook streams in streams option, by default stdout and stderr.

Returns a Promise with a unhook() method which, when called, unhooks both stdout and stderr and resolves the Promise with an empty result.

hookStd.stdout([options], transform)

Hook stdout.

Returns a Promise with a unhook() method which, when called, resolves the Promise with an empty result.

hookStd.stderr([options], transform)

Hook stderr.

Returns a Promise with a unhook() method which, when called, resolves the Promise with an empty result.

options

Type: Object

silent

Type: boolean
Default: true

Suppress stdout/stderr output.

once

Type: boolean
Default: false

Automatically unhooks after the first call.

streams

Type: stream.Writable[]
Default: [process.stdout, process.stderr]

Writable streams to hook. This can be useful for libraries allowing users to configure a Writable Stream to write to.

transform

Type: Function

Receives stdout/stderr as the first argument and the unhook method as the second argument. Return a string to modify it. Optionally, when in silent mode, you may return a boolean to influence the return value of .write(...).

License

MIT © Sindre Sorhus