Sometimes during day to day development I get a Port already in use error (or a variant of it), and I quickly want to see which process I forgot to terminate.

We can get the PID of the process occupying a port (e.g. 8888) with:

$ lsof -ti:8888

In order to quickly kill it, we can just pipe the output into the kill command

$ lsof -ti:8888 | kill -9