27 Apr
2017
27 Apr
'17
7:04 a.m.
Tim Newsham:
I'm not sure what fd 3 is intended to be, but its the telnet socket in p9p.
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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