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SubjectRe: strange disk activity [tail -f]
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___
To A Quick Young Fox:
Why jog exquisite bulk, fond crazy vamp,
Daft buxom jonquil, zephyr's gawky vice?
Guy fed by work, quiz Jove's xanthic lamp --
Zow! Qualms by deja vu gyp fox-kin thrice.
-- Lazy Dog


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