Lately I needed to run tcpdump on several servers for a given time, and then download the pcap fiels, all in a programmatic way.
So I got to know the useful timeout command, simple and straight-forward.
timeout 120s tcpdump -s 0 -A dst port 80
Remember that if you are not running as root and using sudo, you will need to put sudo before the timeout command, so it can actually send the SIGTERM without getting Permission denied.
sudo timeout 120s tcpdump -s 0 -A dst port 80
If you want to learn more about timeout:
https://explainshell.com/explain?cmd=timeout+120s+tcpdump+-s+0+-A+dst+port+80