You could argue that the most direct descendant is the one in which all resources are presented and accessed via open/read/write/close.

If your kernel has separate system calls for reading directories, or setting up network connections, or debugging processes, then you may not be a direct descendant, at least philosophically (and, yes, I know about ptrace ...)

But your kernel might be Plan 9, which at least to me, is the direct descendant. :-)

On Wed, Jun 5, 2024 at 10:51 AM Will Senn <will.senn@gmail.com> wrote:

On 6/5/24 12:34 PM, segaloco via TUHS wrote:
> On Wednesday, June 5th, 2024 at 3:17 AM, Andrew Lynch via TUHS <tuhs@tuhs.org> wrote:
>
>> Hi
>>
>> Out of curiosity, what would be considered the most direct descendent of Unix available today?
>>
>> ...
>>
>> Thanks, Andrew Lynch
> snip
> Given this, my humble opinion (which again this sort of thing I believe is largely a philosophical matter of opinion...) is that the BSD line captures the spirit of Research UNIX much more than System V does, while System V retains much more of the source code lineage of what most folks would consider a "pure" UNIX. Of course all of this too is predicated on treating V7 (really 32V...) as that central point of divergence.
When I saw this thread appear, I was of two minds about it, but this
lines up with where my thoughts were headed. I've done a lot of delving
into the v6/v7 environments over the last 10 years or so and it feels
much closer in kinship to BSD derivatives than to SysV... source code
lineages aside. Also, I get more mileage out of my BSD books and docs
than those treating SysV. I'd vote for *BSD as sticking closest to the
unix way, if there is still such a thing... I say this as I just typed
'kldload linux64' into freebsd's terminal so I could run sublime
alongside nvi... sometimes I wish I was a purist, but I'm way too fond
of experimentation :).

Will