Re: tail and grep
On Wed, Jul 08, 1998 at 01:09:27PM -0700, Patrick Olson wrote:
> > > tail -f /var/log/messages | grep "local IP" > /home/pppusers/dynamic.IP
> > >
> > > it does nothing but create a 0 byte file.
> >
> > "tail -f" will run forever; output to the file won't be flushed until you've
> > written a certain amount to the file -- one line obviously isn't enough.
> > The screen on the other hand is flushed immediately. I suspect you don't
> > really need the -f for tail, especially if you are just running this
> > from the ip-up script or something.
>
> If I ran tail from the script without the -f, it would terminate
> immediately. Since tail would terminate before the chat part of the
> script has even finished, it would never see the string I'm looking for.
>
> Am I making any sense here?
I think you need to somehow ensure that tail isn't used until
that line isn't written in the log; -f will get it to wait, but will
never get you any output in the dynamic.IP file.
Hamish
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Hamish Moffatt, hamish@debian.org, hamish@rising.com.au, hmoffatt@mail.com
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