I don't have an answer but have you tried using tee  to split the output
streams?

Just don't cross them

Andy

On Wednesday, February 19, 2014, Mark J. Bailey <[email protected]> wrote:

> OK, the mystery shifts. If I don't setup the "real time" (sub-level child?)
> with the '-f' and just do a same level operation such as:
>
> tail -500 /var/log/pfsense | egrep -e '\.25\:' -e '\.465\:' -e '\.587\:'  |
> grep -v '192\.168\.0\.71'
>
> it works as desired!
>
> Something with the child process of the tail that is continuously reading
> the target(s) and feeding them to STDOUT in real time doesn't like that
> fork
> to the 2nd grep. I tried encapsulating the tail in '(' and ')' but no go.
>
> -----Original Message-----
> From: [email protected] <javascript:;> [mailto:
> [email protected] <javascript:;>] On
> Behalf Of Mark J. Bailey
> Sent: Wednesday, February 19, 2014 10:55 AM
> To: [email protected]
> Subject: RE: [nlug] Weird CentOS 6 Bash/Grep issue
>
> I actually already tried something like that. Like I said, I used multiple
> greps and what not before for decades now, so I was sitting there wondering
> why I was not seeing any output after a good bit of time, and that was when
> I discovered how it was behaving. The tail -f has to be feeding STDOUT, and
> what feeds out of egrep should be on STDOUT, so it stands to reason that
> the
> 2nd grep would be getting its feed on STDIN. Yet, I get no matches/output
> at
> all no matter what pattern I feed it. And, by the way, this is true for
> using egrep or fgrep as the 2nd filter. I wonder if there is some odd
> parent/child output stream scope or something being setup by the 'tail -f'
> that would be affecting this scenario. Not sure how one could tell.
>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Steven S. Critchfield
> Sent: Wednesday, February 19, 2014 10:32 AM
> To: [email protected]
> Subject: Re: [nlug] Weird CentOS 6 Bash/Grep issue
>
> > tail -f /var/log/pfsense | egrep -e '\.25\:' -e '\.465\:' -e '\.587\:'
> > | grep -v '192\.168\.0\.71'
>
> Just a thought, in the final grep, remove the back slashes, and add -F to
> the flags. -F should turn off the regex matching, therefore do simple
> string
> match and not interpret the periods as wild matches.
>
> Of course, the inverted grep you posted there matches every entry in your
> example.
> --
> Steven Critchfield [email protected]
>
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