Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Lew Pitcher <lew.pitcher@digitalfreehold.ca>
Newsgroups: comp.lang.c
Subject: Re: Question regarding fwrite() and fflush()
Date: Tue, 25 Jun 2024 21:28:24 -0000 (UTC)
Organization: A noiseless patient Spider
Lines: 32
Message-ID: <v5fcpo$1nt21$1@dont-email.me>
References: <v5f33f$1l548$3@dont-email.me> <86jziceo8c.fsf@linuxsc.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Injection-Date: Tue, 25 Jun 2024 23:28:24 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="378c0296351914fa8a558aaf0b11785d";
	logging-data="1832001"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1/U1MNy7UcByFRVaPgSeWjY7nD1kJQ2uDA="
User-Agent: Pan/0.139 (Sexual Chocolate; GIT bf56508
 git://git.gnome.org/pan2)
Cancel-Lock: sha1:sfycl1reMEhKPgkVgHs2tYYkL3o=
Bytes: 2058

On Tue, 25 Jun 2024 13:55:47 -0700, Tim Rentsch wrote:

> Lew Pitcher <lew.pitcher@digitalfreehold.ca> writes:
> 
>> In a recent reply here, I posted some code that used fwrite() to write
>> binary data to a file.  One version of this code used mmap() to access
>> this binary data in-situ, and I wonder if I should have called fflush()
>> before calling mmap().
>>
>> I understand the where to use fflush() on standard text formatted output
>> (where you use fprintf(), etc to externalize the output), but I don't see
>> anything my copies of either the ISO C or POSIX standards that say that
>> I /should/ use fflush(), but neither do I see anything that says I /need
>> not/ use fflush().
>>
>> So, wiser and more experienced minds, should I use fflush() in this case
>> or not?
> 
> Yes, do use fflush().

As I suspected.
Now, my code includes an fflush() after all the fwrite()s are complete.
 
> In the alternative, do a setbuf( file, 0 ) so that 'file' is
> unbuffered.



Thanks
-- 
Lew Pitcher
"In Skills We Trust"