You know.. a couple of handy examples of how to use lsof...

lsof examples.sh

# Find what's using a volume on macOS
lsof | grep /Volumes/

# Check what processes are listening on port
lsof -iTCP -sTCP:LISTEN -P -n

# Kills a process using PID
#
# awk grabs the PIDs.
# tail gets rid of the pesky first entry: "PID".
# xargs executes kill -9 on the PIDs.
# The -r / --no-run-if-empty, prevents kill command failure, in case lsof did not return any PID.
lsof +D ./ | awk '{print $2}' | tail -n +2 | xargs -r kill -9


# Kills the process running on a port
lsof -t -t:port | xargs kill

# Determines which app is opening too many files
lsof -n | awk '{print $1}' | uniq -c | sort -rn | head -n $LINES