# 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.

```bash
# 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:

```bash
# 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.