Re: Buffer contents well-defined after fgets() reaches EOF ?

From	Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups	comp.lang.c
Subject	Re: Buffer contents well-defined after fgets() reaches EOF ?
Date	2025-02-15 08:12 -0800
Organization	A noiseless patient Spider
Message-ID	<86cyfjyyoe.fsf@linuxsc.com> (permalink)
References	(1 earlier) <vo9hlo$g0to$1@dont-email.me> <vo9khf$ggd4$1@dont-email.me> <vobf3h$sefh$2@dont-email.me> <vobjdt$t5ka$1@dont-email.me> <vobkd5$t7np$1@dont-email.me>

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Andrey Tarasevich <noone@noone.net> writes:

> On Sun 2/9/2025 5:06 PM, Andrey Tarasevich wrote:
>
>> On Sun 2/9/2025 3:52 PM, Lawrence D'Oliveiro wrote:
>>
>>> On Sat, 8 Feb 2025 23:12:44 -0800, Andrey Tarasevich wrote:
>>>
>>>> If `fgets` reads nothing (instant end-of-file), the entire
>>>> buffer remains untouched.
>>>
>>> You mean, only a single null byte gets written.
>>
>> No.  The buffer is not changed at all in such case.
>
> ... which actually raises an interesting quiz/puzzle/question:
>
>   Under what circumstances `fgets` is expected to return an empty
> string?  (I.e. set the [0] entry of the buffer to '\0' and return
> non-null)?
>
> The only answer I can see right away is:
>
>   When one calls it as `fgets(buffer, 1, file)`, i.e. asks it to
> read 0 characters.
>
> This is under assumption that asking `fgets` to read 0 characters
> is supposed to prevent it from detecting end-of-file condition or
> I/O error condition.  One can probably do some nitpicking at the
> current wording... but I believe the above is the intent.

Clearly there are more than a few C implementors who agree with that.

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Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-09 06:59 +0100
  Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-09 06:23 +0000
  Re: Buffer contents well-defined after fgets() reaches EOF ? Andrey Tarasevich <noone@noone.net> - 2025-02-08 22:23 -0800
    Re: Buffer contents well-defined after fgets() reaches EOF ? Andrey Tarasevich <noone@noone.net> - 2025-02-08 23:12 -0800
      Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-09 23:52 +0000
        Re: Buffer contents well-defined after fgets() reaches EOF ? Andrey Tarasevich <noone@noone.net> - 2025-02-09 17:06 -0800
          Re: Buffer contents well-defined after fgets() reaches EOF ? Andrey Tarasevich <noone@noone.net> - 2025-02-09 17:22 -0800
            Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-10 12:49 +0200
              Re: Buffer contents well-defined after fgets() reaches EOF ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-02-13 07:14 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-14 16:51 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? scott@slp53.sl.home (Scott Lurndal) - 2025-02-14 15:10 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-14 17:23 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? scott@slp53.sl.home (Scott Lurndal) - 2025-02-14 16:46 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-14 17:28 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-14 17:22 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-02-14 11:03 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-14 19:34 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-15 20:06 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? scott@slp53.sl.home (Scott Lurndal) - 2025-02-14 20:01 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-14 20:51 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-15 19:02 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-15 19:29 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-16 04:29 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-02-16 01:04 -0500
                Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-16 07:37 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-16 18:59 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-16 10:48 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-16 19:14 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-17 11:54 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-16 07:32 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-16 11:05 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-16 19:25 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-16 19:21 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? scott@slp53.sl.home (Scott Lurndal) - 2025-02-16 20:26 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-15 19:41 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-15 20:29 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-16 04:33 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-14 20:23 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-02-14 14:38 -0500
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-14 21:02 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-15 19:53 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-16 04:48 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-02-15 08:37 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-15 20:08 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-02-18 20:17 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-21 05:58 +0000
            Re: Buffer contents well-defined after fgets() reaches EOF ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-02-15 08:12 -0800
          Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-10 02:44 +0100
          Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-10 03:28 +0000
            Re: Buffer contents well-defined after fgets() reaches EOF ? Andrey Tarasevich <noone@noone.net> - 2025-02-09 20:11 -0800
              Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-10 07:21 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? scott@slp53.sl.home (Scott Lurndal) - 2025-02-10 16:39 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-02-10 13:58 -0500
                Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-11 01:03 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-02-10 22:33 -0500
                Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-11 03:42 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-11 04:54 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-02-11 13:07 -0500
                Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-11 21:47 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-02-11 17:44 -0500
                Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-12 06:16 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-02-11 13:59 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-02-11 17:58 -0500
                Re: Buffer contents well-defined after fgets() reaches EOF ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-02-11 15:40 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-02-17 21:11 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Andrey Tarasevich <noone@noone.net> - 2025-02-10 22:32 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Andrey Tarasevich <noone@noone.net> - 2025-02-10 22:38 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-11 12:04 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-02-13 07:29 -0800
    Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-09 08:13 +0100
      Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-09 12:50 +0200
        Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-09 18:29 +0100
          Re: Buffer contents well-defined after fgets() reaches EOF ? Mark Bourne <nntp.mbourne@spamgourmet.com> - 2025-02-10 21:57 +0000
      Re: Buffer contents well-defined after fgets() reaches EOF ? Andrey Tarasevich <noone@noone.net> - 2025-02-09 07:27 -0800
        Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-09 18:34 +0100
          Re: Buffer contents well-defined after fgets() reaches EOF ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-02-09 16:57 -0800
            Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-10 02:35 +0100
              Re: Buffer contents well-defined after fgets() reaches EOF ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-02-09 20:37 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-10 07:08 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-02-09 22:41 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-10 07:54 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Mark Bourne <nntp.mbourne@spamgourmet.com> - 2025-02-10 23:22 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-11 00:59 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-17 02:50 +0000
      Re: Buffer contents well-defined after fgets() reaches EOF ? Mark Bourne <nntp.mbourne@spamgourmet.com> - 2025-02-10 22:57 +0000
        Re: Buffer contents well-defined after fgets() reaches EOF ? Mark Bourne <nntp.mbourne@spamgourmet.com> - 2025-02-10 23:24 +0000
  Re: Buffer contents well-defined after fgets() reaches EOF ? Ben Bacarisse <ben@bsb.me.uk> - 2025-02-10 01:32 +0000
    Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-10 02:40 +0100

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