Re: Using file descriptors in Emacs

[Eli Zaretskii]

> From: address@hidden
> Date: Sat, 10 Sep 2016 10:28:44 -0400
> 
> > Please elaborate: how are file descriptors required for that?  A shell
> > needs to pass file descriptors to the subprocesses it invokes, which
> > AFAIK we already do in the primitives that invoke subprocesses.  What
> > else is needed, and how does the feature you propose fit into that?
> 
> Two features that I would like to add to eshell (or some shell in Emacs)
> that I believe will require the ability to directly manipulate file
> descriptors:
> 
> - Piping data to and from processes without that data round-tripping through
> Emacs, which is necessary if I want to write a pipeline processing any
> significant amount of data (which I frequently do in even casual shell
> use)
> - Redirecting higher file descriptors than 0/1/2 (that is, when creating
> a process, before forking, use dup2 to rearrange what file descriptors are
> in what slots)
> 
> Of the two, the first is more important, but I think the second is also
> necessary.

It sounds like none of these two features need file descriptors to be
exposed to Lisp.  Both of these sound like extensions of
start-process, and the descriptors could be dealt with entirely on the
C level, as applications shouldn't care about them.  Am I missing
something?