Document process interaction with stdin, stout, stderr

Internals & Design
2

I’m not really sure what you’re saying here. The supported way to get all three streams as pipes is the following

julia> stdin, stdout, stderr = (Pipe() for _ in 1:3);

julia> spawn(`cat`, stdin, stdout, stderr) # or equivalently spawn(pipeline(`cat`, stdin=stdin, stdout=stdout, stderr=stderr))
Process(`cat`, ProcessRunning)

The readandwrite function is mostly a convenience API for the common case of needing only stdin/stderr.
Though, since we made processes readable/writable, we should probably change it to just return a process object.

Are you looking for better documentation?