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To: Ken Brown <kbrown AT cornell DOT edu>, "cygwin AT cygwin DOT com" <cygwin AT cygwin DOT com>
Subject: RE: [EXTERNAL] Re: FIFO issues
Thread-Topic: [EXTERNAL] Re: FIFO issues
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Date: Tue, 20 Sep 2022 03:51:29 +0000
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From: "Lavrentiev, Anton \(NIH/NLM/NCBI\) \[C\] via Cygwin" <cygwin AT cygwin DOT com>
Reply-To: "Lavrentiev, Anton \(NIH/NLM/NCBI\) \[C\]" <lavr AT ncbi DOT nlm DOT nih DOT gov>
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Sender: "Cygwin" <cygwin-bounces+archive-cygwin=delorie DOT com AT cygwin DOT com>

> It seems that there's an exception: If no process has ever had the FIFO open for
> writing since it was opened for reading, then the FIFO is not considered to be
> at end-of-file.

IMO, when a virgin FIFO is read with a blocking read (of just one byte), it will block -- it will not return 0.
Meaning that such a FIFO was not ready for read (when the other end was not (yet) attached / written), and
also meaning that there was no EOF (which is obvious because a transaction has not even started).
select() should indicate just the same (and it does so on the discussed platforms) regardless of O_NONBLOCK.

Anton Lavrentiev
Contractor NIH/NLM/NCBI


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