From mboxrd@z Thu Jan  1 00:00:00 1970
From: norman@oclsc.org (Norman Wilson)
Date: Wed, 26 Apr 2017 21:04:37 -0400 (EDT)
Subject: [TUHS] 8th Edition Research Unix on SIMH
Message-ID: <20170427010437.AC0FC4422C@lignose.oclsc.org>

Tim Newsham:

  I'm not sure what fd 3 is intended to be, but its the telnet socket in p9p.

====

By the 10/e days, file descriptor 3 was /dev/tty.  There was
no more magic driver for /dev/tty; the special file still
existed, but it was a link to /dev/fd/3.

Similarly /dev/stdin stdout stderr were links to /dev/fd/0 1 2.

(I mean real links, not mere symbolic ones.)

I have a vague recollection that early on /dev/tty was fd/127
instead, but that changed somewhere in the middle 8/e era.

None of which says what Plan 9 did with that file descriptor,
though I suppose it could possibly have copied the /dev/tty
use.

And none of that excuses the hard-coded magic number file
descriptor, but hackers will be hackers.

Norman Wilson
Toronto ON