On Thu, Nov 23, 2006 at 03:28:24PM +1100, Zhasper wrote:
> On 11/23/06, Matthew Hannigan <[EMAIL PROTECTED]> wrote:
> >On Thu, Nov 23, 2006 at 01:30:50PM +1100, Penedo wrote:
> >> On 23/11/06, Matthew Hannigan <[EMAIL PROTECTED]> wrote:
> >> >On Thu, Nov 23, 2006 at 08:23:37AM +1100, Penedo wrote:
> >> >> On 23/11/06, Howard Lowndes <[EMAIL PROTECTED]> wrote:
> >> >> >I want to tail -f the syslog file but I only want to see what I want
> >to
> >> >> >see and I don't want to see what I don't what to see. The idea is to
> >> >> >tail follow through a filter. Is that possible.
> >> >>
> >> >> What's wrong with "tail -f syslog | grep ..."?
> >> >
> >> >Buffering
> >>
> >> Can you elaborate? It works for me (I mean - I get the output through
> >> grep as soon as tail wakes up and reads the line).
> >
> >Yeah, I was a little terse/inaccurate.
> >One grep is fine, two greps ain't so good.
> >(tail -f blah | grep wanted | grep -v notwanted)
>
> Could you expand on what makes this "not so good"?
You don't get the output in as timely a fashion;
it comes with spurts as the buffer is filled up
then written out.
Try this out:
while true ; do s=$RANDOM; echo $s; usleep $s; done >crap &
tail -f crap |grep 3
vs
tail -f crap | grep 3 | grep -v 8
Matt
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