tethereal oddness. Can't handle output to a pipe?

[Naoki]

Ok, it was my birthday yesterday so I'm hung over in a supreme way which
may be the cause of this but..

# tethereal -i eth0 'port 80' > zzz
Capturing on eth0
96465
8126 packets dropped

This works and puts the data in to the file 'zzz' as one would expect.
If I then run "grep jpg zzz" I see a load of requests, again as one
would expect.

And then ..

# tethereal -i eth0 'port 80' | grep 'jpg' 
Capturing on eth0
24685
1132 packets dropped

Prints out the requests with 'jpg' in them. Nothing tricky there.

However, here it becomes a little more interesting..

# tethereal -i eth0 'port 80' | grep 'jpg' > zzz
Capturing on eth0
24685
1132 packets dropped

Leaves me with a zero byte file and a sense of stupidity.

So, the output is not on stderr, but it seems by throwing a
pipe->grep->redirect into the mix my data goes into /dev/null.

To ensure I wasn't going mad and prove ethereal is doing something odd I
tested this :
# echo '/blah.jpg' | grep 'jpg' > yoyoy
# cat yoyoy
/blah.jpg

Yep, good only pipe, grep, redirect is still working as I expected.

I'm using tethereal 0.10.14

Compiled with GLib 2.6.6, with libpcap 0.8.3, with libz 1.2.2.2,
with libpcre 5.0, with Net-SNMP 5.2.1.2, without ADNS.

Running with libpcap version 0.8.3 on Linux 2.6.14-1.1653_FC4smp.


Anybody care to point out the stupid thing I'm missing?