The fuser Command Kills Processes on a Port

fuser identifies processes using files or sockets. Combined with -k, it kills whatever is holding a port open. Essential for freeing up ports when a dev server crashes without cleaning up.

# Kill whatever is on port 3000
fuser -k 3000/tcp
 
# Just identify the process (no kill)
fuser 3000/tcp
# Output: 3000/tcp:  12345
 
# Kill with a specific signal
fuser -k -SIGTERM 3000/tcp

Comparison with alternatives:

# lsof approach (more verbose, more info)
lsof -ti:3000 | xargs kill
 
# ss + grep approach (most portable)
ss -tlnp | grep :3000

fuser is part of psmisc on most Linux distributions. It is simpler than lsof for the common case of "kill whatever is on this port." The output format (PID/protocol) is also easier to parse in scripts.

On macOS, fuser exists but behaves differently. Use lsof -ti:PORT | xargs kill instead.