trouble with multiple pipes

[Dominik Vogt <dominik_vogt@xxxxxx>]

I am using zsh 3.0.5 on a 2.2.5 Linux kernel. I encountered a problem
when trying to use multiple pipes with and a command that does not
finish:

E.g. I have a file foo:

  # cat foo
  1
  2
  3
  4
  5

Now I want to view that file with "tail -f" so that I get all lines
that are written to the file too:

  # tail -f foo
  1
  2
  3
  4
  5
  (pressed ^C to stop tail)

Now I don't want to see all lines with a '5':

  # tail -f foo | grep -v 5
  1
  2
  3
  4
  (pressed ^C to stop tail)

And now I want to remove '4' from the output too:

  # tail -f foo | grep -v 5 | grep -v 4
  (no output generated, pressed ^C)

But when I terminate 'tail'
  # killall tail
  1
  2
  3
  zsh: terminated  tail -f foo | 
  zsh: done        grep -v 5 | grep -v 4

Why doesn't get the output of the first pipe get through to
the second one? Any ideas how to circumvent this problem?
Unfortunately I need to filter the output from a running
daemon in this way, but I'm out of ideas.

The same behaviour occurs on HP-UX 10.20 (not that I think the
OS matters) or with ksh or bash.

Please respond to me personally, I'm not on the list.

Bye

Dominik ^_^

-- 
Dominik Vogt, Hewlett-Packard GmbH, Dept. BVS
Herrenberger Str.130, 71034 Boeblingen, Germany
phone: 07031/14-4596, fax: 07031/14-3883, dominik_vogt@xxxxxx