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StreamsEdit

A stream is an abstract interface implemented by various objects in Node. For example a request to an HTTP server is a stream, as is stdout. Streams are readable, writable, or both. All streams are instances of EventEmitter.

Readable StreamEdit

A Readable Stream has the following methods, members, and events.

Event: 'data'Edit

function (data) { }

The 'data' event emits either a Buffer (by default) or a string ifsetEncoding() was used.

Event: 'end'Edit

function () { }

Emitted when the stream has received an EOF (FIN in TCP terminology). Indicates that no more 'data' events will happen. If the stream is also writable, it may be possible to continue writing.

Event: 'error'Edit

function (exception) { }

Emitted if there was an error receiving data.

Event: 'close'Edit

function () { }

Emitted when the underlying file descriptor has been closed. Not all streams will emit this. (For example, an incoming HTTP request will not emit'close'.)

Event: 'fd'Edit

function (fd) { }

Emitted when a file descriptor is received on the stream. Only UNIX streams support this functionality; all others will simply never emit this event.

stream.readableEdit

A boolean that is true by default, but turns false after an 'error'occurred, the stream came to an 'end', or destroy() was called.

stream.setEncoding(encoding)Edit

Makes the data event emit a string instead of a Buffer. encoding can be'utf8', 'ascii', or 'base64'.

stream.pause()Edit

Pauses the incoming 'data' events.

stream.resume()Edit

Resumes the incoming 'data' events after a pause().

stream.destroy()Edit

Closes the underlying file descriptor. Stream will not emit any more events.

stream.destroySoon()Edit

After the write queue is drained, close the file descriptor.

stream.pipe(destination, [options])Edit

This is a Stream.prototype method available on all Streams.

Connects this read stream to destination WriteStream. Incoming data on this stream gets written to destination. The destination and source streams are kept in sync by pausing and resuming as necessary.

Emulating the Unix cat command:

process.stdin.resume();
process.stdin.pipe(process.stdout);

By default end() is called on the destination when the source stream emitsend, so that destination is no longer writable. Pass { end: false } asoptions to keep the destination stream open.

This keeps process.stdout open so that "Goodbye" can be written at the end.

process.stdin.resume();

process.stdin.pipe(process.stdout, { end: false });

process.stdin.on("end", function() {
  process.stdout.write("Goodbye\n");
});

NOTE: If the source stream does not support pause() and resume(), this function adds simple definitions which simply emit 'pause' and 'resume'events on the source stream.

Writable StreamEdit

A Writable Stream has the following methods, members, and events.

Event: 'drain'Edit

function () { }

Emitted after a write() method was called that returned false to indicate that it is safe to write again.

Event: 'error'Edit

function (exception) { }

Emitted on error with the exception exception.

Event: 'close'Edit

function () { }

Emitted when the underlying file descriptor has been closed.

Event: 'pipe'Edit

function (src) { }

Emitted when the stream is passed to a readable stream's pipe method.

stream.writableEdit

A boolean that is true by default, but turns false after an 'error'occurred or end() / destroy() was called.

stream.write(string, encoding='utf8', [fd])Edit

Writes string with the given encoding to the stream. Returns true if the string has been flushed to the kernel buffer. Returns false to indicate that the kernel buffer is full, and the data will be sent out in the future. The'drain' event will indicate when the kernel buffer is empty again. Theencoding defaults to 'utf8'.

If the optional fd parameter is specified, it is interpreted as an integral file descriptor to be sent over the stream. This is only supported for UNIX streams, and is silently ignored otherwise. When writing a file descriptor in this manner, closing the descriptor before the stream drains risks sending an invalid (closed) FD.

stream.write(buffer)Edit

Same as the above except with a raw buffer.

stream.end()Edit

Terminates the stream with EOF or FIN.

stream.end(string, encoding)Edit

Sends string with the given encoding and terminates the stream with EOF or FIN. This is useful to reduce the number of packets sent.

stream.end(buffer)Edit

Same as above but with a buffer.

stream.destroy()Edit

Closes the underlying file descriptor. Stream will not emit any more events.

stream.destroySoon()Edit

After the write queue is drained, close the file descriptor. destroySoon() can still destroy straight away, as long as there is no data left in the queue for writes.

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