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From: Jason Mills <jmills AT cs DOT mun DOT ca>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: fstream and fflush
Date: Fri, 22 Oct 2004 07:58:06 -0230
Organization: Memorial University of Newfoundland
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Hans-Bernhard Broeker wrote:

> Jason Mills <jmills AT cs DOT mun DOT ca> wrote:
> 
> 
>>After more tests, I discovered that fstream::flush() and
>>fflush(NULL) both will not flush the stream if I am writing rapidly
>>to the stream.  If I sleep(), (maybe if I a do other work, I have
>>not checked) the stream is eventually flushed. Can someone explain?
> 
> 
> What exactly do you expect flush() to do for you,  if you keep writing
> stuff to the file afterward

Two things:
1. It is a log file, so I wanted to make sure a log record is written
to the disk as soon as possible so no records are lost, on a crash
for example.
2. Perhaps unwisely, I was using stat() to query the file size
periodically in order to rotate the log file based on file size. (I
have since changed this design.)

 >
 > i.e. how do you define that it did "not
 > flush the stream"?
 >

For example, I had the logger configured to create 1M log files. But
because flush did not dump any records to the file, stat() always
reported a file size of 0M. Hence (e.g.) my log file reached a size
of 19M when I finally killed the program.

When I killed the program, the data was written. But will this happen
if the power to the machine is cut? If not I lose log records.

Jason