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dots.node.fs.read-stream

Instances of fs.ReadStream are created and returned using the {@link createReadStream } function.

Instances of `fs.ReadStream` are created and returned using the {@link createReadStream } function.
raw docstring

add-listenercljs

(add-listener read-stream event listener)

events.EventEmitter

  1. open
  2. close
  3. ready

Parameters:

  • event: string | symbol
  • listener: (...args: any[]) => void

Returns: ReadStream

events.EventEmitter
  1. open
  2. close
  3. ready

**Parameters:**
- `event`: `string | symbol`
- `listener`: `(...args: any[]) => void`

**Returns:** `ReadStream`
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as-indexed-pairscljs

(as-indexed-pairs read-stream)
(as-indexed-pairs read-stream options)

This method returns a new stream with chunks of the underlying stream paired with a counter in the form [index, chunk]. The first index value is 0 and it increases by 1 for each chunk produced.

Parameters:

  • options: Pick<ArrayOptions, "signal"> | undefined

Returns: Readable - a stream of indexed pairs.

This method returns a new stream with chunks of the underlying stream paired with a counter
in the form `[index, chunk]`. The first index value is `0` and it increases by 1 for each chunk produced.

**Parameters:**
- `options`: `Pick<ArrayOptions, "signal"> | undefined`

**Returns:** `Readable` - a stream of indexed pairs.
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bytes-readcljs

(bytes-read read-stream)

The number of bytes that have been read so far.

The number of bytes that have been read so far.
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closecljs

(close read-stream)
(close read-stream callback)

Parameters:

  • callback: ((err?: ErrnoException | null | undefined) => void) | undefined

Returns: void

**Parameters:**
- `callback`: `((err?: ErrnoException | null | undefined) => void) | undefined`

**Returns:** `void`
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closed?cljs

(closed? read-stream)

Is true after 'close' has been emitted.

Is `true` after `'close'` has been emitted.
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composecljs

(compose read-stream stream)
(compose read-stream stream options)

Parameters:

  • stream: T | ComposeFnParam | Iterable<T> | AsyncIterable<T>
  • options: { signal: AbortSignal; } | undefined

Returns: T

**Parameters:**
- `stream`: `T | ComposeFnParam | Iterable<T> | AsyncIterable<T>`
- `options`: `{ signal: AbortSignal; } | undefined`

**Returns:** `T`
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destroycljs

(destroy read-stream)
(destroy read-stream error)

Destroy the stream. Optionally emit an 'error' event, and emit a 'close' event (unless emitClose is set to false). After this call, the readable stream will release any internal resources and subsequent calls to push() will be ignored.

Once destroy() has been called any further calls will be a no-op and no further errors except from _destroy() may be emitted as 'error'.

Implementors should not override this method, but instead implement readable._destroy().

Parameters:

  • error: Error | undefined - Error which will be passed as payload in 'error' event

Returns: ReadStream

Destroy the stream. Optionally emit an `'error'` event, and emit a `'close'` event (unless `emitClose` is set to `false`). After this call, the readable
stream will release any internal resources and subsequent calls to `push()` will be ignored.

Once `destroy()` has been called any further calls will be a no-op and no
further errors except from `_destroy()` may be emitted as `'error'`.

Implementors should not override this method, but instead implement `readable._destroy()`.

**Parameters:**
- `error`: `Error | undefined` - Error which will be passed as payload in `'error'` event

**Returns:** `ReadStream`
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destroyed?cljs

(destroyed? read-stream)

Is true after readable.destroy() has been called.

Is `true` after `readable.destroy()` has been called.
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dropcljs

(drop read-stream limit)
(drop read-stream limit options)

This method returns a new stream with the first limit chunks dropped from the start.

Parameters:

  • limit: number - the number of chunks to drop from the readable.
  • options: Pick<ArrayOptions, "signal"> | undefined

Returns: Readable - a stream with limit chunks dropped from the start.

This method returns a new stream with the first *limit* chunks dropped from the start.

**Parameters:**
- `limit`: `number` - the number of chunks to drop from the readable.
- `options`: `Pick<ArrayOptions, "signal"> | undefined`

**Returns:** `Readable` - a stream with *limit* chunks dropped from the start.
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emit?cljs

(emit? read-stream & event)
(emit? read-stream event chunk)
(emit? read-stream event err)
(emit? read-stream event & args)

Parameters:

  • event: string | symbol
  • args: any[]
  • chunk: any
  • err: Error

Returns: boolean

**Parameters:**
- `event`: `string | symbol`
- `args`: `any[]`
- `chunk`: `any`
- `err`: `Error`

**Returns:** `boolean`
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erroredcljs

(errored read-stream)

Returns error if the stream has been destroyed with an error.

Returns error if the stream has been destroyed with an error.
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event-namescljs

(event-names read-stream)

Returns an array listing the events for which the emitter has registered listeners. The values in the array are strings or Symbols.

import { EventEmitter } from 'node:events';

const myEE = new EventEmitter();
myEE.on('foo', () => {});
myEE.on('bar', () => {});

const sym = Symbol('symbol');
myEE.on(sym, () => {});

console.log(myEE.eventNames());
// Prints: [ 'foo', 'bar', Symbol(symbol) ]

Returns: (string | symbol)[]

Returns an array listing the events for which the emitter has registered
listeners. The values in the array are strings or `Symbol`s.

```js
import { EventEmitter } from 'node:events';

const myEE = new EventEmitter();
myEE.on('foo', () => {});
myEE.on('bar', () => {});

const sym = Symbol('symbol');
myEE.on(sym, () => {});

console.log(myEE.eventNames());
// Prints: [ 'foo', 'bar', Symbol(symbol) ]
```

**Returns:** `(string | symbol)[]`
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everycljs

(every read-stream fn)
(every read-stream fn options)

This method is similar to Array.prototype.every and calls fn on each chunk in the stream to check if all awaited return values are truthy value for fn. Once an fn call on a chunk awaited return value is falsy, the stream is destroyed and the promise is fulfilled with false. If all of the fn calls on the chunks return a truthy value, the promise is fulfilled with true.

Parameters:

  • fn: (data: any, options?: Pick<ArrayOptions, "signal"> | undefined) => boolean | Promise<boolean> - a function to call on each chunk of the stream. Async or not.
  • options: ArrayOptions | undefined

Returns: Promise<boolean> - a promise evaluating to true if fn returned a truthy value for every one of the chunks.

This method is similar to `Array.prototype.every` and calls *fn* on each chunk in the stream
to check if all awaited return values are truthy value for *fn*. Once an *fn* call on a chunk
`await`ed return value is falsy, the stream is destroyed and the promise is fulfilled with `false`.
If all of the *fn* calls on the chunks return a truthy value, the promise is fulfilled with `true`.

**Parameters:**
- `fn`: `(data: any, options?: Pick<ArrayOptions, "signal"> | undefined) => boolean | Promise<boolean>` - a function to call on each chunk of the stream. Async or not.
- `options`: `ArrayOptions | undefined`

**Returns:** `Promise<boolean>` - a promise evaluating to `true` if *fn* returned a truthy value for every one of the chunks.
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filtercljs

(filter read-stream fn)
(filter read-stream fn options)

This method allows filtering the stream. For each chunk in the stream the fn function will be called and if it returns a truthy value, the chunk will be passed to the result stream. If the fn function returns a promise - that promise will be awaited.

Parameters:

  • fn: (data: any, options?: Pick<ArrayOptions, "signal"> | undefined) => boolean | Promise<boolean> - a function to filter chunks from the stream. Async or not.
  • options: ArrayOptions | undefined

Returns: Readable - a stream filtered with the predicate fn.

This method allows filtering the stream. For each chunk in the stream the *fn* function will be called
and if it returns a truthy value, the chunk will be passed to the result stream.
If the *fn* function returns a promise - that promise will be `await`ed.

**Parameters:**
- `fn`: `(data: any, options?: Pick<ArrayOptions, "signal"> | undefined) => boolean | Promise<boolean>` - a function to filter chunks from the stream. Async or not.
- `options`: `ArrayOptions | undefined`

**Returns:** `Readable` - a stream filtered with the predicate *fn*.
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findcljs

(find read-stream fn)
(find read-stream fn options)

This method is similar to Array.prototype.find and calls fn on each chunk in the stream to find a chunk with a truthy value for fn. Once an fn call's awaited return value is truthy, the stream is destroyed and the promise is fulfilled with value for which fn returned a truthy value. If all of the fn calls on the chunks return a falsy value, the promise is fulfilled with undefined.

Parameters:

  • fn: (data: any, options?: Pick<ArrayOptions, "signal"> | undefined) => boolean | Promise<boolean>
  • options: ArrayOptions | undefined

Returns: Promise<any> - a promise evaluating to the first chunk for which fn evaluated with a truthy value, or undefined if no element was found.

This method is similar to `Array.prototype.find` and calls *fn* on each chunk in the stream
to find a chunk with a truthy value for *fn*. Once an *fn* call's awaited return value is truthy,
the stream is destroyed and the promise is fulfilled with value for which *fn* returned a truthy value.
If all of the *fn* calls on the chunks return a falsy value, the promise is fulfilled with `undefined`.

**Parameters:**
- `fn`: `(data: any, options?: Pick<ArrayOptions, "signal"> | undefined) => boolean | Promise<boolean>`
- `options`: `ArrayOptions | undefined`

**Returns:** `Promise<any>` - a promise evaluating to the first chunk for which *fn* evaluated with a truthy value,
or `undefined` if no element was found.
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flat-mapcljs

(flat-map read-stream fn)
(flat-map read-stream fn options)

This method returns a new stream by applying the given callback to each chunk of the stream and then flattening the result.

It is possible to return a stream or another iterable or async iterable from fn and the result streams will be merged (flattened) into the returned stream.

Parameters:

  • fn: (data: any, options?: Pick<ArrayOptions, "signal"> | undefined) => any - a function to map over every chunk in the stream. May be async. May be a stream or generator.
  • options: ArrayOptions | undefined

Returns: Readable - a stream flat-mapped with the function fn.

This method returns a new stream by applying the given callback to each chunk of the stream
and then flattening the result.

It is possible to return a stream or another iterable or async iterable from *fn* and the result streams
will be merged (flattened) into the returned stream.

**Parameters:**
- `fn`: `(data: any, options?: Pick<ArrayOptions, "signal"> | undefined) => any` - a function to map over every chunk in the stream. May be async. May be a stream or generator.
- `options`: `ArrayOptions | undefined`

**Returns:** `Readable` - a stream flat-mapped with the function *fn*.
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for-eachcljs

(for-each read-stream fn)
(for-each read-stream fn options)

This method allows iterating a stream. For each chunk in the stream the fn function will be called. If the fn function returns a promise - that promise will be awaited.

This method is different from for await...of loops in that it can optionally process chunks concurrently. In addition, a forEach iteration can only be stopped by having passed a signal option and aborting the related AbortController while for await...of can be stopped with break or return. In either case the stream will be destroyed.

This method is different from listening to the 'data' event in that it uses the readable event in the underlying machinary and can limit the number of concurrent fn calls.

Parameters:

  • fn: (data: any, options?: Pick<ArrayOptions, "signal"> | undefined) => void | Promise<void> - a function to call on each chunk of the stream. Async or not.
  • options: ArrayOptions | undefined

Returns: Promise<void> - a promise for when the stream has finished.

This method allows iterating a stream. For each chunk in the stream the *fn* function will be called.
If the *fn* function returns a promise - that promise will be `await`ed.

This method is different from `for await...of` loops in that it can optionally process chunks concurrently.
In addition, a `forEach` iteration can only be stopped by having passed a `signal` option
and aborting the related AbortController while `for await...of` can be stopped with `break` or `return`.
In either case the stream will be destroyed.

This method is different from listening to the `'data'` event in that it uses the `readable` event
in the underlying machinary and can limit the number of concurrent *fn* calls.

**Parameters:**
- `fn`: `(data: any, options?: Pick<ArrayOptions, "signal"> | undefined) => void | Promise<void>` - a function to call on each chunk of the stream. Async or not.
- `options`: `ArrayOptions | undefined`

**Returns:** `Promise<void>` - a promise for when the stream has finished.
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iteratorcljs

(iterator read-stream)
(iterator read-stream options)

The iterator created by this method gives users the option to cancel the destruction of the stream if the for await...of loop is exited by return, break, or throw, or if the iterator should destroy the stream if the stream emitted an error during iteration.

Parameters:

  • options: { destroyOnReturn?: boolean | undefined; } | undefined

Returns: AsyncIterableIterator<any>

The iterator created by this method gives users the option to cancel the destruction
of the stream if the `for await...of` loop is exited by `return`, `break`, or `throw`,
or if the iterator should destroy the stream if the stream emitted an error during iteration.

**Parameters:**
- `options`: `{ destroyOnReturn?: boolean | undefined; } | undefined`

**Returns:** `AsyncIterableIterator<any>`
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listener-countcljs

(listener-count read-stream event-name)
(listener-count read-stream event-name listener)

Returns the number of listeners listening for the event named eventName. If listener is provided, it will return how many times the listener is found in the list of the listeners of the event.

Parameters:

  • event-name: string | symbol - The name of the event being listened for
  • listener: Function | undefined - The event handler function

Returns: number

Returns the number of listeners listening for the event named `eventName`.
If `listener` is provided, it will return how many times the listener is found
in the list of the listeners of the event.

**Parameters:**
- `event-name`: `string | symbol` - The name of the event being listened for
- `listener`: `Function | undefined` - The event handler function

**Returns:** `number`
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listenerscljs

(listeners read-stream event-name)

Returns a copy of the array of listeners for the event named eventName.

server.on('connection', (stream) => {
  console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection')));
// Prints: [ [Function] ]

Parameters:

  • event-name: string | symbol

Returns: Function[]

Returns a copy of the array of listeners for the event named `eventName`.

```js
server.on('connection', (stream) => {
  console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection')));
// Prints: [ [Function] ]
```

**Parameters:**
- `event-name`: `string | symbol`

**Returns:** `Function[]`
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mapcljs

(map read-stream fn)
(map read-stream fn options)

This method allows mapping over the stream. The fn function will be called for every chunk in the stream. If the fn function returns a promise - that promise will be awaited before being passed to the result stream.

Parameters:

  • fn: (data: any, options?: Pick<ArrayOptions, "signal"> | undefined) => any - a function to map over every chunk in the stream. Async or not.
  • options: ArrayOptions | undefined

Returns: Readable - a stream mapped with the function fn.

This method allows mapping over the stream. The *fn* function will be called for every chunk in the stream.
If the *fn* function returns a promise - that promise will be `await`ed before being passed to the result stream.

**Parameters:**
- `fn`: `(data: any, options?: Pick<ArrayOptions, "signal"> | undefined) => any` - a function to map over every chunk in the stream. Async or not.
- `options`: `ArrayOptions | undefined`

**Returns:** `Readable` - a stream mapped with the function *fn*.
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max-listenerscljs

(max-listeners read-stream)

Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to {@link defaultMaxListeners }.

Returns: number

Returns the current max listener value for the `EventEmitter` which is either
set by `emitter.setMaxListeners(n)` or defaults to {@link defaultMaxListeners }.

**Returns:** `number`
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offcljs

(off read-stream event-name listener)

Alias for emitter.removeListener().

Parameters:

  • event-name: string | symbol
  • listener: (...args: any[]) => void

Returns: ReadStream

Alias for `emitter.removeListener()`.

**Parameters:**
- `event-name`: `string | symbol`
- `listener`: `(...args: any[]) => void`

**Returns:** `ReadStream`
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oncljs

(on read-stream event listener)

Parameters:

  • event: string | symbol
  • listener: (...args: any[]) => void

Returns: ReadStream

**Parameters:**
- `event`: `string | symbol`
- `listener`: `(...args: any[]) => void`

**Returns:** `ReadStream`
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oncecljs

(once read-stream event listener)

Parameters:

  • event: string | symbol
  • listener: (...args: any[]) => void

Returns: ReadStream

**Parameters:**
- `event`: `string | symbol`
- `listener`: `(...args: any[]) => void`

**Returns:** `ReadStream`
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pathcljs

(path read-stream)

The path to the file the stream is reading from as specified in the first argument to fs.createReadStream(). If path is passed as a string, thenreadStream.path will be a string. If path is passed as a Buffer, thenreadStream.path will be a Buffer. If fd is specified, thenreadStream.path will be undefined.

The path to the file the stream is reading from as specified in the first
argument to `fs.createReadStream()`. If `path` is passed as a string, then`readStream.path` will be a string. If `path` is passed as a `Buffer`, then`readStream.path` will be a
`Buffer`. If `fd` is specified, then`readStream.path` will be `undefined`.
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pausecljs

(pause read-stream)

The readable.pause() method will cause a stream in flowing mode to stop emitting 'data' events, switching out of flowing mode. Any data that becomes available will remain in the internal buffer.

const readable = getReadableStreamSomehow();
readable.on('data', (chunk) => {
  console.log(`Received ${chunk.length} bytes of data.`);
  readable.pause();
  console.log('There will be no additional data for 1 second.');
  setTimeout(() => {
    console.log('Now data will start flowing again.');
    readable.resume();
  }, 1000);
});

The readable.pause() method has no effect if there is a 'readable' event listener.

Returns: ReadStream

The `readable.pause()` method will cause a stream in flowing mode to stop
emitting `'data'` events, switching out of flowing mode. Any data that
becomes available will remain in the internal buffer.

```js
const readable = getReadableStreamSomehow();
readable.on('data', (chunk) => {
  console.log(`Received ${chunk.length} bytes of data.`);
  readable.pause();
  console.log('There will be no additional data for 1 second.');
  setTimeout(() => {
    console.log('Now data will start flowing again.');
    readable.resume();
  }, 1000);
});
```

The `readable.pause()` method has no effect if there is a `'readable'` event listener.

**Returns:** `ReadStream`
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paused?cljs

(paused? read-stream)

The readable.isPaused() method returns the current operating state of the Readable. This is used primarily by the mechanism that underlies the readable.pipe() method. In most typical cases, there will be no reason to use this method directly.

const readable = new stream.Readable();

readable.isPaused(); // === false
readable.pause();
readable.isPaused(); // === true
readable.resume();
readable.isPaused(); // === false

Returns: boolean

The `readable.isPaused()` method returns the current operating state of the `Readable`. This is
used primarily by the mechanism that underlies the `readable.pipe()` method. In most typical cases,
there will be no reason to use this method directly.

```js
const readable = new stream.Readable();

readable.isPaused(); // === false
readable.pause();
readable.isPaused(); // === true
readable.resume();
readable.isPaused(); // === false
```

**Returns:** `boolean`
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pending?cljs

(pending? read-stream)

This property is true if the underlying file has not been opened yet, i.e. before the 'ready' event is emitted.

This property is `true` if the underlying file has not been opened yet,
i.e. before the `'ready'` event is emitted.
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pipecljs

(pipe read-stream destination)
(pipe read-stream destination options)

Parameters:

  • destination: T
  • options: { end?: boolean | undefined; } | undefined

Returns: T

**Parameters:**
- `destination`: `T`
- `options`: `{ end?: boolean | undefined; } | undefined`

**Returns:** `T`
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prepend-listenercljs

(prepend-listener read-stream event listener)

Parameters:

  • event: string | symbol
  • listener: (...args: any[]) => void

Returns: ReadStream

**Parameters:**
- `event`: `string | symbol`
- `listener`: `(...args: any[]) => void`

**Returns:** `ReadStream`
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prepend-once-listenercljs

(prepend-once-listener read-stream event listener)

Parameters:

  • event: string | symbol
  • listener: (...args: any[]) => void

Returns: ReadStream

**Parameters:**
- `event`: `string | symbol`
- `listener`: `(...args: any[]) => void`

**Returns:** `ReadStream`
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push?cljs

(push? read-stream chunk)
(push? read-stream chunk encoding)

Parameters:

  • chunk: any
  • encoding: BufferEncoding | undefined

Returns: boolean

**Parameters:**
- `chunk`: `any`
- `encoding`: `BufferEncoding | undefined`

**Returns:** `boolean`
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raw-listenerscljs

(raw-listeners read-stream event-name)

Returns a copy of the array of listeners for the event named eventName, including any wrappers (such as those created by .once()).

import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.once('log', () => console.log('log once'));

// Returns a new Array with a function `onceWrapper` which has a property
// `listener` which contains the original listener bound above
const listeners = emitter.rawListeners('log');
const logFnWrapper = listeners[0];

// Logs "log once" to the console and does not unbind the `once` event
logFnWrapper.listener();

// Logs "log once" to the console and removes the listener
logFnWrapper();

emitter.on('log', () => console.log('log persistently'));
// Will return a new Array with a single function bound by `.on()` above
const newListeners = emitter.rawListeners('log');

// Logs "log persistently" twice
newListeners[0]();
emitter.emit('log');

Parameters:

  • event-name: string | symbol

Returns: Function[]

Returns a copy of the array of listeners for the event named `eventName`,
including any wrappers (such as those created by `.once()`).

```js
import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.once('log', () => console.log('log once'));

// Returns a new Array with a function `onceWrapper` which has a property
// `listener` which contains the original listener bound above
const listeners = emitter.rawListeners('log');
const logFnWrapper = listeners[0];

// Logs "log once" to the console and does not unbind the `once` event
logFnWrapper.listener();

// Logs "log once" to the console and removes the listener
logFnWrapper();

emitter.on('log', () => console.log('log persistently'));
// Will return a new Array with a single function bound by `.on()` above
const newListeners = emitter.rawListeners('log');

// Logs "log persistently" twice
newListeners[0]();
emitter.emit('log');
```

**Parameters:**
- `event-name`: `string | symbol`

**Returns:** `Function[]`
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readcljs

(read read-stream)
(read read-stream size)

The readable.read() method reads data out of the internal buffer and returns it. If no data is available to be read, null is returned. By default, the data is returned as a Buffer object unless an encoding has been specified using the readable.setEncoding() method or the stream is operating in object mode.

The optional size argument specifies a specific number of bytes to read. If size bytes are not available to be read, null will be returned unless the stream has ended, in which case all of the data remaining in the internal buffer will be returned.

If the size argument is not specified, all of the data contained in the internal buffer will be returned.

The size argument must be less than or equal to 1 GiB.

The readable.read() method should only be called on Readable streams operating in paused mode. In flowing mode, readable.read() is called automatically until the internal buffer is fully drained.

const readable = getReadableStreamSomehow();

// 'readable' may be triggered multiple times as data is buffered in
readable.on('readable', () => {
  let chunk;
  console.log('Stream is readable (new data received in buffer)');
  // Use a loop to make sure we read all currently available data
  while (null !== (chunk = readable.read())) {
    console.log(`Read ${chunk.length} bytes of data...`);
  }
});

// 'end' will be triggered once when there is no more data available
readable.on('end', () => {
  console.log('Reached end of stream.');
});

Each call to readable.read() returns a chunk of data, or null. The chunks are not concatenated. A while loop is necessary to consume all data currently in the buffer. When reading a large file .read() may return null, having consumed all buffered content so far, but there is still more data to come not yet buffered. In this case a new 'readable' event will be emitted when there is more data in the buffer. Finally the 'end' event will be emitted when there is no more data to come.

Therefore to read a file's whole contents from a readable, it is necessary to collect chunks across multiple 'readable' events:

const chunks = [];

readable.on('readable', () => {
  let chunk;
  while (null !== (chunk = readable.read())) {
    chunks.push(chunk);
  }
});

readable.on('end', () => {
  const content = chunks.join('');
});

A Readable stream in object mode will always return a single item from a call to readable.read(size), regardless of the value of the size argument.

If the readable.read() method returns a chunk of data, a 'data' event will also be emitted.

Calling {@link read } after the 'end' event has been emitted will return null. No runtime error will be raised.

Parameters:

  • size: number | undefined - Optional argument to specify how much data to read.

Returns: any

The `readable.read()` method reads data out of the internal buffer and
returns it. If no data is available to be read, `null` is returned. By default,
the data is returned as a `Buffer` object unless an encoding has been
specified using the `readable.setEncoding()` method or the stream is operating
in object mode.

The optional `size` argument specifies a specific number of bytes to read. If
`size` bytes are not available to be read, `null` will be returned _unless_ the
stream has ended, in which case all of the data remaining in the internal buffer
will be returned.

If the `size` argument is not specified, all of the data contained in the
internal buffer will be returned.

The `size` argument must be less than or equal to 1 GiB.

The `readable.read()` method should only be called on `Readable` streams
operating in paused mode. In flowing mode, `readable.read()` is called
automatically until the internal buffer is fully drained.

```js
const readable = getReadableStreamSomehow();

// 'readable' may be triggered multiple times as data is buffered in
readable.on('readable', () => {
  let chunk;
  console.log('Stream is readable (new data received in buffer)');
  // Use a loop to make sure we read all currently available data
  while (null !== (chunk = readable.read())) {
    console.log(`Read ${chunk.length} bytes of data...`);
  }
});

// 'end' will be triggered once when there is no more data available
readable.on('end', () => {
  console.log('Reached end of stream.');
});
```

Each call to `readable.read()` returns a chunk of data, or `null`. The chunks
are not concatenated. A `while` loop is necessary to consume all data
currently in the buffer. When reading a large file `.read()` may return `null`,
having consumed all buffered content so far, but there is still more data to
come not yet buffered. In this case a new `'readable'` event will be emitted
when there is more data in the buffer. Finally the `'end'` event will be
emitted when there is no more data to come.

Therefore to read a file's whole contents from a `readable`, it is necessary
to collect chunks across multiple `'readable'` events:

```js
const chunks = [];

readable.on('readable', () => {
  let chunk;
  while (null !== (chunk = readable.read())) {
    chunks.push(chunk);
  }
});

readable.on('end', () => {
  const content = chunks.join('');
});
```

A `Readable` stream in object mode will always return a single item from
a call to `readable.read(size)`, regardless of the value of the `size` argument.

If the `readable.read()` method returns a chunk of data, a `'data'` event will
also be emitted.

Calling {@link read } after the `'end'` event has
been emitted will return `null`. No runtime error will be raised.

**Parameters:**
- `size`: `number | undefined` - Optional argument to specify how much data to read.

**Returns:** `any`
sourceraw docstring

readable-aborted?cljs

(readable-aborted? read-stream)

Returns whether the stream was destroyed or errored before emitting 'end'.

Returns whether the stream was destroyed or errored before emitting `'end'`.
sourceraw docstring

readable-did-read?cljs

(readable-did-read? read-stream)

Returns whether 'data' has been emitted.

Returns whether `'data'` has been emitted.
sourceraw docstring

readable-encodingcljs

(readable-encoding read-stream)

Getter for the property encoding of a given Readable stream. The encoding property can be set using the {@link setEncoding } method.

Getter for the property `encoding` of a given `Readable` stream. The `encoding` property can be set using the {@link setEncoding } method.
sourceraw docstring

readable-ended?cljs

(readable-ended? read-stream)

Becomes true when 'end' event is emitted.

Becomes `true` when [`'end'`](https://nodejs.org/docs/latest-v20.x/api/stream.html#event-end) event is emitted.
sourceraw docstring

readable-flowing?cljs

(readable-flowing? read-stream)

This property reflects the current state of a Readable stream as described in the Three states section.

This property reflects the current state of a `Readable` stream as described
in the [Three states](https://nodejs.org/docs/latest-v20.x/api/stream.html#three-states) section.
sourceraw docstring

readable-high-water-markcljs

(readable-high-water-mark read-stream)

Returns the value of highWaterMark passed when creating this Readable.

Returns the value of `highWaterMark` passed when creating this `Readable`.
sourceraw docstring

readable-lengthcljs

(readable-length read-stream)

This property contains the number of bytes (or objects) in the queue ready to be read. The value provides introspection data regarding the status of the highWaterMark.

This property contains the number of bytes (or objects) in the queue
ready to be read. The value provides introspection data regarding
the status of the `highWaterMark`.
sourceraw docstring

readable-object-mode?cljs

(readable-object-mode? read-stream)

Getter for the property objectMode of a given Readable stream.

Getter for the property `objectMode` of a given `Readable` stream.
sourceraw docstring

readable?cljs

(readable? read-stream)

Is true if it is safe to call {@link read }, which means the stream has not been destroyed or emitted 'error' or 'end'.

Is `true` if it is safe to call {@link read }, which means
the stream has not been destroyed or emitted `'error'` or `'end'`.
sourceraw docstring

reducecljs

(reduce read-stream fn)
(reduce read-stream fn initial)
(reduce read-stream fn initial options)

This method calls fn on each chunk of the stream in order, passing it the result from the calculation on the previous element. It returns a promise for the final value of the reduction.

If no initial value is supplied the first chunk of the stream is used as the initial value. If the stream is empty, the promise is rejected with a TypeError with the ERR_INVALID_ARGS code property.

The reducer function iterates the stream element-by-element which means that there is no concurrency parameter or parallelism. To perform a reduce concurrently, you can extract the async function to readable.map method.

Parameters:

  • fn: (previous: T, data: any, options?: Pick<ArrayOptions, "signal"> | undefined) => T
  • initial: T
  • options: Pick<ArrayOptions, "signal"> | undefined

Returns: Promise<T> - a promise for the final value of the reduction.

This method calls *fn* on each chunk of the stream in order, passing it the result from the calculation
on the previous element. It returns a promise for the final value of the reduction.

If no *initial* value is supplied the first chunk of the stream is used as the initial value.
If the stream is empty, the promise is rejected with a `TypeError` with the `ERR_INVALID_ARGS` code property.

The reducer function iterates the stream element-by-element which means that there is no *concurrency* parameter
or parallelism. To perform a reduce concurrently, you can extract the async function to `readable.map` method.

**Parameters:**
- `fn`: `(previous: T, data: any, options?: Pick<ArrayOptions, "signal"> | undefined) => T`
- `initial`: `T`
- `options`: `Pick<ArrayOptions, "signal"> | undefined`

**Returns:** `Promise<T>` - a promise for the final value of the reduction.
sourceraw docstring

remove-all-listenerscljs

(remove-all-listeners read-stream)
(remove-all-listeners read-stream event-name)

Removes all listeners, or those of the specified eventName.

It is bad practice to remove listeners added elsewhere in the code, particularly when the EventEmitter instance was created by some other component or module (e.g. sockets or file streams).

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters:

  • event-name: string | symbol | undefined

Returns: ReadStream

Removes all listeners, or those of the specified `eventName`.

It is bad practice to remove listeners added elsewhere in the code,
particularly when the `EventEmitter` instance was created by some other
component or module (e.g. sockets or file streams).

Returns a reference to the `EventEmitter`, so that calls can be chained.

**Parameters:**
- `event-name`: `string | symbol | undefined`

**Returns:** `ReadStream`
sourceraw docstring

remove-listenercljs

(remove-listener read-stream event listener)

Parameters:

  • event: string | symbol
  • listener: (...args: any[]) => void

Returns: ReadStream

**Parameters:**
- `event`: `string | symbol`
- `listener`: `(...args: any[]) => void`

**Returns:** `ReadStream`
sourceraw docstring

resumecljs

(resume read-stream)

The readable.resume() method causes an explicitly paused Readable stream to resume emitting 'data' events, switching the stream into flowing mode.

The readable.resume() method can be used to fully consume the data from a stream without actually processing any of that data:

getReadableStreamSomehow()
  .resume()
  .on('end', () => {
    console.log('Reached the end, but did not read anything.');
  });

The readable.resume() method has no effect if there is a 'readable'event listener.

Returns: ReadStream

The `readable.resume()` method causes an explicitly paused `Readable` stream to
resume emitting `'data'` events, switching the stream into flowing mode.

The `readable.resume()` method can be used to fully consume the data from a
stream without actually processing any of that data:

```js
getReadableStreamSomehow()
  .resume()
  .on('end', () => {
    console.log('Reached the end, but did not read anything.');
  });
```

The `readable.resume()` method has no effect if there is a `'readable'`event listener.

**Returns:** `ReadStream`
sourceraw docstring

set-bytes-read!cljs

(set-bytes-read! read-stream value)

The number of bytes that have been read so far.

The number of bytes that have been read so far.
sourceraw docstring

set-destroyed!cljs

(set-destroyed! read-stream value)

Is true after readable.destroy() has been called.

Is `true` after `readable.destroy()` has been called.
sourceraw docstring

set-encodingcljs

(set-encoding read-stream encoding)

The readable.setEncoding() method sets the character encoding for data read from the Readable stream.

By default, no encoding is assigned and stream data will be returned as Buffer objects. Setting an encoding causes the stream data to be returned as strings of the specified encoding rather than as Buffer objects. For instance, calling readable.setEncoding('utf8') will cause the output data to be interpreted as UTF-8 data, and passed as strings. Calling readable.setEncoding('hex') will cause the data to be encoded in hexadecimal string format.

The Readable stream will properly handle multi-byte characters delivered through the stream that would otherwise become improperly decoded if simply pulled from the stream as Buffer objects.

const readable = getReadableStreamSomehow();
readable.setEncoding('utf8');
readable.on('data', (chunk) => {
  assert.equal(typeof chunk, 'string');
  console.log('Got %d characters of string data:', chunk.length);
});

Parameters:

  • encoding: BufferEncoding - The encoding to use.

Returns: ReadStream

The `readable.setEncoding()` method sets the character encoding for
data read from the `Readable` stream.

By default, no encoding is assigned and stream data will be returned as `Buffer` objects. Setting an encoding causes the stream data
to be returned as strings of the specified encoding rather than as `Buffer` objects. For instance, calling `readable.setEncoding('utf8')` will cause the
output data to be interpreted as UTF-8 data, and passed as strings. Calling `readable.setEncoding('hex')` will cause the data to be encoded in hexadecimal
string format.

The `Readable` stream will properly handle multi-byte characters delivered
through the stream that would otherwise become improperly decoded if simply
pulled from the stream as `Buffer` objects.

```js
const readable = getReadableStreamSomehow();
readable.setEncoding('utf8');
readable.on('data', (chunk) => {
  assert.equal(typeof chunk, 'string');
  console.log('Got %d characters of string data:', chunk.length);
});
```

**Parameters:**
- `encoding`: `BufferEncoding` - The encoding to use.

**Returns:** `ReadStream`
sourceraw docstring

set-max-listenerscljs

(set-max-listeners read-stream n)

By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default that helps finding memory leaks. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set to Infinity (or 0) to indicate an unlimited number of listeners.

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters:

  • n: number

Returns: ReadStream

By default `EventEmitter`s will print a warning if more than `10` listeners are
added for a particular event. This is a useful default that helps finding
memory leaks. The `emitter.setMaxListeners()` method allows the limit to be
modified for this specific `EventEmitter` instance. The value can be set to `Infinity` (or `0`) to indicate an unlimited number of listeners.

Returns a reference to the `EventEmitter`, so that calls can be chained.

**Parameters:**
- `n`: `number`

**Returns:** `ReadStream`
sourceraw docstring

set-path!cljs

(set-path! read-stream value)

The path to the file the stream is reading from as specified in the first argument to fs.createReadStream(). If path is passed as a string, thenreadStream.path will be a string. If path is passed as a Buffer, thenreadStream.path will be a Buffer. If fd is specified, thenreadStream.path will be undefined.

The path to the file the stream is reading from as specified in the first
argument to `fs.createReadStream()`. If `path` is passed as a string, then`readStream.path` will be a string. If `path` is passed as a `Buffer`, then`readStream.path` will be a
`Buffer`. If `fd` is specified, then`readStream.path` will be `undefined`.
sourceraw docstring

set-pending!cljs

(set-pending! read-stream value)

This property is true if the underlying file has not been opened yet, i.e. before the 'ready' event is emitted.

This property is `true` if the underlying file has not been opened yet,
i.e. before the `'ready'` event is emitted.
sourceraw docstring

set-readable!cljs

(set-readable! read-stream value)

Is true if it is safe to call {@link read }, which means the stream has not been destroyed or emitted 'error' or 'end'.

Is `true` if it is safe to call {@link read }, which means
the stream has not been destroyed or emitted `'error'` or `'end'`.
sourceraw docstring

somecljs

(some read-stream fn)
(some read-stream fn options)

This method is similar to Array.prototype.some and calls fn on each chunk in the stream until the awaited return value is true (or any truthy value). Once an fn call on a chunk awaited return value is truthy, the stream is destroyed and the promise is fulfilled with true. If none of the fn calls on the chunks return a truthy value, the promise is fulfilled with false.

Parameters:

  • fn: (data: any, options?: Pick<ArrayOptions, "signal"> | undefined) => boolean | Promise<boolean> - a function to call on each chunk of the stream. Async or not.
  • options: ArrayOptions | undefined

Returns: Promise<boolean> - a promise evaluating to true if fn returned a truthy value for at least one of the chunks.

This method is similar to `Array.prototype.some` and calls *fn* on each chunk in the stream
until the awaited return value is `true` (or any truthy value). Once an *fn* call on a chunk
`await`ed return value is truthy, the stream is destroyed and the promise is fulfilled with `true`.
If none of the *fn* calls on the chunks return a truthy value, the promise is fulfilled with `false`.

**Parameters:**
- `fn`: `(data: any, options?: Pick<ArrayOptions, "signal"> | undefined) => boolean | Promise<boolean>` - a function to call on each chunk of the stream. Async or not.
- `options`: `ArrayOptions | undefined`

**Returns:** `Promise<boolean>` - a promise evaluating to `true` if *fn* returned a truthy value for at least one of the chunks.
sourceraw docstring

takecljs

(take read-stream limit)
(take read-stream limit options)

This method returns a new stream with the first limit chunks.

Parameters:

  • limit: number - the number of chunks to take from the readable.
  • options: Pick<ArrayOptions, "signal"> | undefined

Returns: Readable - a stream with limit chunks taken.

This method returns a new stream with the first *limit* chunks.

**Parameters:**
- `limit`: `number` - the number of chunks to take from the readable.
- `options`: `Pick<ArrayOptions, "signal"> | undefined`

**Returns:** `Readable` - a stream with *limit* chunks taken.
sourceraw docstring

to-arraycljs

(to-array read-stream)
(to-array read-stream options)

This method allows easily obtaining the contents of a stream.

As this method reads the entire stream into memory, it negates the benefits of streams. It's intended for interoperability and convenience, not as the primary way to consume streams.

Parameters:

  • options: Pick<ArrayOptions, "signal"> | undefined

Returns: Promise<any[]> - a promise containing an array with the contents of the stream.

This method allows easily obtaining the contents of a stream.

As this method reads the entire stream into memory, it negates the benefits of streams. It's intended
for interoperability and convenience, not as the primary way to consume streams.

**Parameters:**
- `options`: `Pick<ArrayOptions, "signal"> | undefined`

**Returns:** `Promise<any[]>` - a promise containing an array with the contents of the stream.
sourceraw docstring

unpipecljs

(unpipe read-stream)
(unpipe read-stream destination)

The readable.unpipe() method detaches a Writable stream previously attached using the {@link pipe } method.

If the destination is not specified, then all pipes are detached.

If the destination is specified, but no pipe is set up for it, then the method does nothing.

const fs = require('node:fs');
const readable = getReadableStreamSomehow();
const writable = fs.createWriteStream('file.txt');
// All the data from readable goes into 'file.txt',
// but only for the first second.
readable.pipe(writable);
setTimeout(() => {
  console.log('Stop writing to file.txt.');
  readable.unpipe(writable);
  console.log('Manually close the file stream.');
  writable.end();
}, 1000);

Parameters:

  • destination: WritableStream | undefined - Optional specific stream to unpipe

Returns: ReadStream

The `readable.unpipe()` method detaches a `Writable` stream previously attached
using the {@link pipe } method.

If the `destination` is not specified, then _all_ pipes are detached.

If the `destination` is specified, but no pipe is set up for it, then
the method does nothing.

```js
const fs = require('node:fs');
const readable = getReadableStreamSomehow();
const writable = fs.createWriteStream('file.txt');
// All the data from readable goes into 'file.txt',
// but only for the first second.
readable.pipe(writable);
setTimeout(() => {
  console.log('Stop writing to file.txt.');
  readable.unpipe(writable);
  console.log('Manually close the file stream.');
  writable.end();
}, 1000);
```

**Parameters:**
- `destination`: `WritableStream | undefined` - Optional specific stream to unpipe

**Returns:** `ReadStream`
sourceraw docstring

unshiftcljs

(unshift read-stream chunk)
(unshift read-stream chunk encoding)

Passing chunk as null signals the end of the stream (EOF) and behaves the same as readable.push(null), after which no more data can be written. The EOF signal is put at the end of the buffer and any buffered data will still be flushed.

The readable.unshift() method pushes a chunk of data back into the internal buffer. This is useful in certain situations where a stream is being consumed by code that needs to "un-consume" some amount of data that it has optimistically pulled out of the source, so that the data can be passed on to some other party.

The stream.unshift(chunk) method cannot be called after the 'end' event has been emitted or a runtime error will be thrown.

Developers using stream.unshift() often should consider switching to use of a Transform stream instead. See the API for stream implementers section for more information.

// Pull off a header delimited by \n\n.
// Use unshift() if we get too much.
// Call the callback with (error, header, stream).
const { StringDecoder } = require('node:string_decoder');
function parseHeader(stream, callback) {
  stream.on('error', callback);
  stream.on('readable', onReadable);
  const decoder = new StringDecoder('utf8');
  let header = '';
  function onReadable() {
    let chunk;
    while (null !== (chunk = stream.read())) {
      const str = decoder.write(chunk);
      if (str.includes('\n\n')) {
        // Found the header boundary.
        const split = str.split(/\n\n/);
        header += split.shift();
        const remaining = split.join('\n\n');
        const buf = Buffer.from(remaining, 'utf8');
        stream.removeListener('error', callback);
        // Remove the 'readable' listener before unshifting.
        stream.removeListener('readable', onReadable);
        if (buf.length)
          stream.unshift(buf);
        // Now the body of the message can be read from the stream.
        callback(null, header, stream);
        return;
      }
      // Still reading the header.
      header += str;
    }
  }
}

Unlike {@link push }, stream.unshift(chunk) will not end the reading process by resetting the internal reading state of the stream. This can cause unexpected results if readable.unshift() is called during a read (i.e. from within a {@link _read } implementation on a custom stream). Following the call to readable.unshift() with an immediate {@link push } will reset the reading state appropriately, however it is best to simply avoid calling readable.unshift() while in the process of performing a read.

Parameters:

  • chunk: any - Chunk of data to unshift onto the read queue. For streams not operating in object mode, chunk must be a string, Buffer, Uint8Array, or null. For object mode streams, chunk may be any JavaScript value.
  • encoding: BufferEncoding | undefined - Encoding of string chunks. Must be a valid Buffer encoding, such as 'utf8' or 'ascii'.

Returns: void

Passing `chunk` as `null` signals the end of the stream (EOF) and behaves the
same as `readable.push(null)`, after which no more data can be written. The EOF
signal is put at the end of the buffer and any buffered data will still be
flushed.

The `readable.unshift()` method pushes a chunk of data back into the internal
buffer. This is useful in certain situations where a stream is being consumed by
code that needs to "un-consume" some amount of data that it has optimistically
pulled out of the source, so that the data can be passed on to some other party.

The `stream.unshift(chunk)` method cannot be called after the `'end'` event
has been emitted or a runtime error will be thrown.

Developers using `stream.unshift()` often should consider switching to
use of a `Transform` stream instead. See the `API for stream implementers` section for more information.

```js
// Pull off a header delimited by \n\n.
// Use unshift() if we get too much.
// Call the callback with (error, header, stream).
const { StringDecoder } = require('node:string_decoder');
function parseHeader(stream, callback) {
  stream.on('error', callback);
  stream.on('readable', onReadable);
  const decoder = new StringDecoder('utf8');
  let header = '';
  function onReadable() {
    let chunk;
    while (null !== (chunk = stream.read())) {
      const str = decoder.write(chunk);
      if (str.includes('\n\n')) {
        // Found the header boundary.
        const split = str.split(/\n\n/);
        header += split.shift();
        const remaining = split.join('\n\n');
        const buf = Buffer.from(remaining, 'utf8');
        stream.removeListener('error', callback);
        // Remove the 'readable' listener before unshifting.
        stream.removeListener('readable', onReadable);
        if (buf.length)
          stream.unshift(buf);
        // Now the body of the message can be read from the stream.
        callback(null, header, stream);
        return;
      }
      // Still reading the header.
      header += str;
    }
  }
}
```

Unlike {@link push }, `stream.unshift(chunk)` will not
end the reading process by resetting the internal reading state of the stream.
This can cause unexpected results if `readable.unshift()` is called during a
read (i.e. from within a {@link _read } implementation on a
custom stream). Following the call to `readable.unshift()` with an immediate {@link push } will reset the reading state appropriately,
however it is best to simply avoid calling `readable.unshift()` while in the
process of performing a read.

**Parameters:**
- `chunk`: `any` - Chunk of data to unshift onto the read queue. For streams not operating in object mode, `chunk` must be a string, `Buffer`, `Uint8Array`, or `null`. For object mode
streams, `chunk` may be any JavaScript value.
- `encoding`: `BufferEncoding | undefined` - Encoding of string chunks. Must be a valid `Buffer` encoding, such as `'utf8'` or `'ascii'`.

**Returns:** `void`
sourceraw docstring

wrapcljs

(wrap read-stream stream)

Prior to Node.js 0.10, streams did not implement the entire node:stream module API as it is currently defined. (See Compatibility for more information.)

When using an older Node.js library that emits 'data' events and has a {@link pause } method that is advisory only, the readable.wrap() method can be used to create a Readable stream that uses the old stream as its data source.

It will rarely be necessary to use readable.wrap() but the method has been provided as a convenience for interacting with older Node.js applications and libraries.

const { OldReader } = require('./old-api-module.js');
const { Readable } = require('node:stream');
const oreader = new OldReader();
const myReader = new Readable().wrap(oreader);

myReader.on('readable', () => {
  myReader.read(); // etc.
});

Parameters:

  • stream: ReadableStream - An "old style" readable stream

Returns: ReadStream

Prior to Node.js 0.10, streams did not implement the entire `node:stream` module API as it is currently defined. (See `Compatibility` for more
information.)

When using an older Node.js library that emits `'data'` events and has a {@link pause } method that is advisory only, the `readable.wrap()` method can be used to create a `Readable`
stream that uses
the old stream as its data source.

It will rarely be necessary to use `readable.wrap()` but the method has been
provided as a convenience for interacting with older Node.js applications and
libraries.

```js
const { OldReader } = require('./old-api-module.js');
const { Readable } = require('node:stream');
const oreader = new OldReader();
const myReader = new Readable().wrap(oreader);

myReader.on('readable', () => {
  myReader.read(); // etc.
});
```

**Parameters:**
- `stream`: `ReadableStream` - An "old style" readable stream

**Returns:** `ReadStream`
sourceraw docstring

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