tcpdump & tee

This is something I always forget how to do: run a tcpdump while both looking at the packets AND writing them to a file at the same time.  I always remember it involves 'tee', but never the exact syntax.  So, here is the command:

tcpdump -i eth1 -U -w - | tee dump.pcap | tcpdump -n -r -

This will listen:

• listen on eth1 (-i eth1)
• Don't wait until the output buffer fills before writing packets (-U)
• Write packets to STDOUT (-w -)
• Read from STDIN write to file and write to STDOUT (
  tee dump.pcap)
• Read packets from STDIN (and don't resolve names) (tcpdump -n -r -)