Testing if a file is connected to a terminal

[Jakob Ovrum via Digitalmars-d-learn]

On Thursday, 17 December 2015 at 04:05:57 UTC, Adam D. Ruppe 
wrote:
> On Thursday, 17 December 2015 at 03:59:27 UTC, Jakob Ovrum 
> wrote:
>> There are some terminal libraries on Github (like consoled) 
>> but I have to say I think they're uninspiring in terms of 
>> quality and presentation.
>
> Can you be any more specific about that?

Where's the reference documentation?