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From: James Kuyper <jameskuyper@alumni.caltech.edu>
Newsgroups: comp.lang.c
Subject: Re: C90 fpeek
Date: Fri, 24 Jan 2025 09:24:35 -0500
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On 1/24/25 00:13, Keith Thompson wrote:
> "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.

A google search uncovered a stackoverflow question for which the answer was:

int fpeek(FILE *stream)
{
    int c;

    c = fgetc(stream);
    ungetc(c, stream);

    return c;
}

I don't see any reason why such a function is needed in the standard
library. However, if it were added, since fgetc() and ungetc() are
mandatory for hosted implementations, I also see no reason to allow for
it to be unsupported.