Re: strange disk activity [tail -f]

Kevin M Bealer (kmb203@psu.edu)
Tue, 2 Apr 1996 00:40:28 -0500 (EST)


On Mon, 1 Apr 1996, Zefram wrote:

> >yep, "tail -f" reads (polls) the file every second, this in turn changes
> >the atime field, and bdflush updates the inode and the superblock.
>
> There's a voice in my head saying "that should happen on open(2), not
> read(2)". Am I just hallucinating? More to the point, why do we get
> this repeated (and annoying) disk activity under 1.3.~80 but not
> 1.2.x? Can the new bdflush be tuned to wait longer before flushing,
> and if so, how?
>
> >might be a stupid question, but is there no way doing event based reads
> >on files [selects and/or blocking reads at the end of the file] ?
>
> Not under Unix.
>
> -zefram

But couldn't you kludge it by

(use a script of course but pseudo C is easy to read :)

touch(/tmp/tempfile);
while(1)
{
while(mod_date(/tmp/tempfile) < mod_date(/file/in/question))
{
sleep(1);
}
clear();
touch(/tmp/tempfile);
tail(/file/in/question);
}

Or was the goal more frequent updates?

__kmb203@psu.edu_____________________________Debian/GNU__Linux__1.3.77___
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