How to run Wireshark in the background without the GUI?
As initially seen here:

As far as I remember TShark comes with all distributions of Wireshark. This runs from the command line. The documentation for it is here: http://www.wireshark.org/docs/man-pages/tshark.html
And there's some examples on how to use it here: http://www.codealias.info/technotes/the_tshark_capture_and_filter_example_page

— David Hewitt