Why is process stdin/stdout/stderr a stream.Duplex?

[killmag10]

Hi,

why is process stdin/stdout/stderr a stream.Duplex?

On the doc's stdin is a stream.Readable and stdout/stderr is a stream.Writable.

Tested on 0.10.29:

$ node
> process.stdin instanceof require('stream').Readable;
true
> process.stdin instanceof require('stream').Writable;
false
> process.stdin instanceof require('stream').Duplex;
true
> process.stdout instanceof require('stream').Readable;
true
> process.stdout instanceof require('stream').Writable;
false
> process.stdout instanceof require('stream').Duplex;
true
> process.stderr instanceof require('stream').Readable;
true
> process.stderr instanceof require('stream').Writable;
false
> process.stderr instanceof require('stream').Duplex;
true

Is this correct?

[chrisdickinson]

std{in,out,err} all inherit from net.Socket, which is a stream.Duplex. For all intents and purposes, stdin should be thought of as a Readable, and std{out,err} as Writable's.

[TooTallNate]

What @chrisdickinson said: it's an implementation detail. Don't rely on it.

For example, if you redirect stdout to a file, then it will be a fs.WriteStream instance instead of a net.Socket.

[killmag10]

OK, thank for your response. :)

I write a nodejs compatibility layer for java, so i'm interested on implementation details. ;)