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From: ford@crash.CTS.COM (Michael Ditto)
Newsgroups: comp.bugs.4bsd
Subject: Re: read() from tty has fencepost error
Message-ID: <1325@crash.CTS.COM>
Date: Fri, 3-Jul-87 07:27:42 EDT
Article-I.D.: crash.1325
Posted: Fri Jul  3 07:27:42 1987
Date-Received: Sat, 4-Jul-87 13:22:34 EDT
References: <648@haddock.UUCP> <6040@brl-smoke.ARPA> <13048@topaz.rutgers.edu>
Reply-To: ford@crash.CTS.COM (Michael Ditto)
Organization: Crash TS, El Cajon, CA
Lines: 47

In article <13048@topaz.rutgers.edu> ron@topaz.rutgers.edu (Ron Natalie) writes:
>Excuse me System V breath, if you look on your own beloved operating system
>you will see that EOT works the opposite way that it does on system V, that
>is, the following code
>
>    main()  {
>	int count;
>	char buf[10];
>
>	do {
>	    count = read(0, buf, 5);
>	    printf("\ncount = %d\n", count);
>	} while(count);
>    }
>
> [...]
>
>    % a.out
>    a<NL>
>
>    count = 2
>    abcde<EOT>
>    count = 5
>
>...at this point it waits for you to type more input...
>
>I guess System V is wrong for once :-)
>

No, this is the spec for EOF in termio(7) (SysV's equivalent to tty(4)):

	[When EOF is received] all the characters waiting to be read are
	immediately passed to the program, without waiting for a new-line,
	and the EOF is descarded.  Thus, if there are no characters waiting,
	which is to say the EOF occurred at the beginning of a line, zero
	characters will be passed back [...]

This is the way UNIX has always worked, except for Berkeley's versions, and
AT&T still does it this way.

(The above quote from termio(7) is copyright by AT&T, but you can see it on
your SysV system with "man 7 termio".  [Lame attempt at disclaimer]).
-- 

Michael "Ford" Ditto				-=] Ford [=-
P.O. Box 1721					ford@crash.CTS.COM
Bonita, CA 92002				ford%oz@prep.mit.ai.edu