Re: Teaching emacsclient to act as a pager, and more

[sbaugh@catern.com]

Eli Zaretskii <eliz@gnu.org> writes:
>> From: sbaugh@catern.com
>> Date: Fri, 09 Sep 2016 10:14:33 -0400
>> 
>> >From c2ff58ce764801101fb4c37fd3963f99cb8652a2 Mon Sep 17 00:00:00 2001
>> From: Spencer Baugh <sbaugh@catern.com>
>> Date: Sun, 5 Jun 2016 00:40:28 -0400
>> Subject: [PATCH 1/5] process: add features for direct use of FDs
>> 
>> - A new keyword argument for make-network-process, :ancillary. When
>> non-nil, Emacs will check for ancillary data when reading from the
>> network process. If any is found, it is passed as an additional argument
>> to the process filter function. At the moment, this only supports
>> reading passed file descriptors out of ancillary data.
>> This is inherited by the children of server processes.
>> 
>> - A new Lisp function make-fd-process, which accepts keyword arguments
>> exactly like make-pipe-process, but also accepts :infd and :outfd, which
>> take Lisp integers which should be file descriptors that can be read
>> from and written to, respectively.
>
> Cannot this be handled by the existing make-pipe-process?  If not, why
> not?
>
> Thanks.

First off, make-fd-process is only an exact clone of make-pipe-process
at the moment because that was the fastest way to get something
working. Still, they are quite similar.

But make-pipe-process makes a process object backed by a
pipe. make-fd-process makes a process object backed by arbitrary file
descriptors.

I don't think it would be a good API to add :infd and :outfd arguments
to make-pipe-process. That would cause make-pipe-process to make process
objects backed by arbitrary file descriptors and not just pipes. For
one, the name would become confusing.

If there was a file-descriptor Elisp type, then one solution would be to
add a make-pipe Elisp function that is just a thin wrapper around the
pipe system call, returning two FD objects. Then make-pipe-process can
just call make-pipe followed by make-fd-process.