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From: jejones@mcrware.UUCP (James Jones)
Newsgroups: comp.sys.m6809
Subject: semantics of read()
Message-ID: <553@mcrware.UUCP>
Date: Wed, 11-Nov-87 13:27:00 EST
Article-I.D.: mcrware.553
Posted: Wed Nov 11 13:27:00 1987
Date-Received: Sat, 14-Nov-87 06:49:45 EST
Organization: Microware Systems Corp., Des Moines, Ia.
Lines: 17
Keywords: OS-9, Nuxi, read()

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A brief note to avoid confusion about the semantics of read():

The OS-9 read() call, like that of Nuxi, can return a count indicating that
fewer bytes than requested were read, the standard example being trying to
read more bytes than there are left in a disk file, or read past the end of
a tape.

That said, it is nonetheless still the case that read() puts the caller to
sleep until either enough bytes are ready or some error occurs while reading,
and for things such as terminal programs, file transfer programs, and the
like in OS-9, one can make profitable use of the SS_SIG and SS_RDY setstat
and getstat calls.  (I must admit to never having figured out why it is
that not having any data ready is thought to be an error (E$NRdy), but them's
the breaks.)  If you didn't grab Jim Omura's posting, you might want to.

		James Jones