Hook and modify stdout and stderr
npm install hook-stdimport assert from 'node:assert';
import {hookStdout} from 'hook-std';
const promise = hookStdout(output => {
promise.unhook();
assert.strictEqual(output.trim(), 'unicorn');
});
console.log('unicorn');
await promise;You can also unhook using the second transform method parameter:
import assert from 'node:assert';
import {hookStdout} from 'hook-std';
const promise = hookStdout((output, unhook) => {
unhook();
assert.strictEqual(output.trim(), 'unicorn');
});
console.log('unicorn');
await promise;Automatically collect output without a transform function:
import {hookStdout} from 'hook-std';
const promise = hookStdout();
console.log('unicorn');
console.log('rainbow');
console.log(promise.output); // 'unicorn\nrainbow\n'
promise.unhook();
await promise;Hook streams in streams option, or stdout and stderr if none are specified.
Returns a Promise with a unhook() method which, when called, unhooks both stdout and stderr and resolves the Promise with an empty result. The returned promise also has an output property to access the collected output.
When hooking multiple streams, the output property contains the interleaved output in the order the writes occurred:
import {hookStd} from 'hook-std';
const promise = hookStd();
process.stdout.write('A');
process.stderr.write('B');
process.stdout.write('C');
console.log(promise.output); // 'ABC' (interleaved in order)
promise.unhook();Hook stdout.
Returns a Promise with a unhook() method which, when called, unhooks stdout and resolves the Promise with an empty result. The returned promise also has an output property to access the collected output.
Hook stderr.
Returns a Promise with a unhook() method which, when called, unhooks stderr and resolves the Promise with an empty result. The returned promise also has an output property to access the collected output.
Type: object
Type: boolean
Default: true
Suppress stdout/stderr output.
Type: boolean
Default: false
Automatically unhook after the first call.
Type: stream.Writable[]
Default: [process.stdout, process.stderr]
The writable streams to hook. This can be useful for libraries allowing users to configure a writable stream to write to.
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(…).
Output is automatically collected and can be accessed via the output property of the returned promise, regardless of whether a transform function is provided.
