tail -f and pipes with bash shell

[Peter Ekberg]

Hello!

What is going on here?

~$ ps -f | grep $$
    peda    2316       1 con  20:21:51 /usr/bin/bash
    peda    3180    2316 con  21:51:47 /usr/bin/ps
    peda    3164    2316 con  21:51:47 /usr/bin/grep

  [I use bash, if that matters]

~$ tail -f frame.log | grep Antenna
2005-05-11,21:51:07: Antenna DAC 0
2005-05-11,21:51:17: Antenna DAC 0
2005-05-11,21:51:26: Antenna DAC 0
2005-05-11,21:51:36: Antenna DAC 0
2005-05-11,21:51:46: Antenna DAC 0
2005-05-11,21:52:06: Antenna DAC 0

  [Fine, that works, I get bored and press ^C]

~$ tail frame.log | grep Antenna | cat
2005-05-11,21:51:17: Antenna DAC 0
2005-05-11,21:51:26: Antenna DAC 0
2005-05-11,21:51:36: Antenna DAC 0
2005-05-11,21:51:46: Antenna DAC 0
2005-05-11,21:52:06: Antenna DAC 0

  [Fine, that works...]

~$ tail -f frame.log | grep Antenna | cat

  [No output!? I'm puzzled and press ^C]

Every other line in frame.log is an "Antenna"-
line, so I really think there should be output
from the last command as well.

(For the real task I'm doing I want to do more
 than 'cat' at the end of the pipe, this is just
 a trimmed down example.)

Can anyone please provide any hints?

Cheers,
Peter
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