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anything i put after the grep command makes tshark show me a packet counter and nothing more.

TShark itself won't show you anything on the terminal, because its output is being piped to grep.

sort, however, cannot write anything until it reads an EOF - it might be the very last line it reads from the standard input that sorts first in its output. So it won't write anything to the uniq command until the grep exits, and grep won't exit until it reads an EOF, and that won't happen until TShark exits.

Therefore, nothing will be written to sniffer.log until TShark exits, and therefore the tail -f won't print anything until TShark exits.