Pseudoterminal terminology (was Re: Rename "master" branch to "main"?)

[Zack Weinberg <zackw@panix.com>]

On Thu, Jul 2, 2020 at 4:58 PM Michael Kerrisk <mtk.manpages@gmail.com> wrote:
>
> > That said I think this is not as important as other, similar, changes
> > we could make. For instance, the term "master" is used _along with_
> > "slave" in manual/terminal.texi, and I fully intend to rewrite that
> > chapter to eliminate that terminology as soon as I find the time.
> > Anyone want to beat me to it?
>
> No, but please include me in the discussions. It would be good if libc
> and man-pages could find common terminology.
>
> But I agree also with Joseph that the scope is wider and we should
> think about what terminology POSIX might (be convinced to) switch to.
>
> Unlike Florian, I'm not excessively attached to the need to settle on
> a name that starts with 's'. I think it might be too easy to get into
> knots trying to find names that match 'm' and 's', and one should at
> least allow for the possibility of good names that don't fit with
> those letters; what would be best, IMO, is names that "feel right".

I agree.  In particular I think there is no reason to struggle with
coming up with terms that fit "ptmx" and "pts" because BSD ptys use
totally different device node names anyway (tty[pqrs...]NN and
pty[pqrs...]NN) and there's no hope of finding something that works
with both.

I don't want to commit to terminology until I've had a go at rewriting
the manual, because I think doing the rewrite will be the easiest way
to figure out whether the new terms are good, but what I'm currently
thinking is:

    "pty master device" -> "pty line-side device" or "outside device"
    "pty slave device"  -> "pty host-side device" or "inside device"
    /dev/ptmx stands for "pseudoterminal multiplexer"
    /dev/pts  stand for "pseudoterminals (directory of)"

Currently I like "line-side" and "host-side" because it seems like a
natural generalization from true terminal device nodes (which are
always host-side) to pseudoterminals (additionally have a line-side
device node).  And it can generalize to the relationship between
Linux's /dev/ttyNN and /dev/vcs(a)NN as well.

zw