Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: "Paul Edwards" <mutazilah@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: C90 fpeek
Date: Fri, 24 Jan 2025 16:41:39 +1100
Organization: A noiseless patient Spider
Lines: 38
Message-ID: <vmv96o$23d5m$1@dont-email.me>
References: <vmv082$1u6pm$1@dont-email.me> <87plkc6bgm.fsf@nosuchdomain.example.com>
Injection-Date: Fri, 24 Jan 2025 06:41:45 +0100 (CET)
Injection-Info: dont-email.me; posting-host="fda4a84c3bda6e185fc69fc9e52e89a8";
	logging-data="2208950"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1/Yk8sUYkE9ivJ6GzTAzPfaT2HJEk3rRcw="
Cancel-Lock: sha1:TX3s1U/Ns34Cc2mNEr0sQg2D6XQ=
X-MSMail-Priority: Normal
X-Priority: 3
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106
Bytes: 2376

"Keith Thompson" <Keith.S.Thompson+u@gmail.com> wrote in message
news:87plkc6bgm.fsf@nosuchdomain.example.com...
> "Paul Edwards" <mutazilah@gmail.com> writes:
> [...]
> > With the benefit of hindsight, is there any reason why fpeek
> > couldn't have been added to C90, with implementations
> > being allowed with just a macro that returns some sort of
> > "unsupported"?
> >
> > If fpeek (or similar) makes sense, can someone suggest an
> > appropriate interface?
> [...]
>
> It would help to know what "fpeek" is supposed to do.  There no such
> function in any edition of the C standard or in any implementation
> that I'm aware of.

fpeek would tell you whether there are any characters available
to be read, on a bidirectional data stream, opened with r+b or
whatever.

For an ordinary disk file, it wouldn't necessarily do anything,
and just return with "unknown" or whatever, for the application
to decide what to do.

But for a serial port/modem connected to a BBS, the infrastructure
would likely already know if there are characters sitting at the COM
port (or some corresponding buffer), so it would be in a position to
confirm/deny the presence of pending characters to be read.

It also occurred to me that games could use this, fpeek of stdin to
see if a key has been pressed.

Apologies for not making this clearer in the original post.

BFN. Paul.