tcpdump

Input Output
`-D`	List interfaces
`-i`	Input interface
`-r`	Read from file
`-r`	Read from file
`-w`	Write to file
`-c 5`	Exit after 5 packets

Display
`-xx`	Hex only
`-XX`	Hex + ascii
`-#`	Display frame number
`-e`	Display link header

Time
`-ttt`	delta between frames
`-tttt`	date
`-ttttt`	delta since frame 1

stdio
`-l`	Flush on end of line
`-U`	flush on end of packet
`-ttttt`	delta since frame 1

grep & awk
`tcpdump -i interface -l \| grep --line-buffered expr`
`tcpdump -i interface -l \| grep --line-buffered expr \| awk '{print $3}'`
`tcpdump -i interface -l \| grep --line-buffered expr \| awk '{print $3; fflush()}' \| python3 decode.py`