quoted

Peter, do you agree that Linux appears to differ from POSIX here? (Not
sure if you tried my test program to verify...)

I did run the test program to validate that it's observed behavior is that
implemented by Linux, with which I'm very familiar.
I don't have a test setup for other *nixes.

I would be interested to know the results of

  ./noncanonical 0 5 3 0
  hello

Solaris 10:
read() completes when 5 bytes received.
OpenBSD 5.4
read() completes when 5 bytes received.

and

  ./noncanonical 0 5 3 2
   hel

Solaris
read blocks()
OpenBSD
read blocks


Plus my test case where Linux differs:

./noncanonical 100 5 3 0

Linux: read() returns after 3 bytes input

Solaris: read() returns only after 5 bytes input
OpenBSD: read() returns only after 5 bytes input

on other platforms.

With respect to POSIX compliance, it's hard to say. I'm not sure the
spec contemplates the degenerate case where max bytes < MIN. And

Well, given the way the other implementations behave, I think it does
contemplate it, because it carefull avoids talking about the number of
bytes requested by read() in that case.

specifically
with regard to terminal i/o behavior, POSIX is essentially ex post facto,
and is really documenting existing behavior.

Other than the degenerate case of max bytes < MIN, is there any other
variation between Solaris and Linux in non-canonical mode?

The only one I've seen is the one I noted. I haven't tested too
exhaustively though.

Cheers,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/