Processes

ps aux lists every running process. top shows a live, auto-refreshing view of what's using CPU and memory right now.

Example: finding and stopping a specific process

$ ps aux | grep python
$ kill 4821

The grep filters ps's full output down to just lines mentioning "python" — piping is covered properly in the next lesson, but this is one of its most common real uses: a command produces too much output, and a second command narrows it down to what you actually care about. Once you've found the right process id (PID) — 4821 here — kill stops it. Add -9 (kill -9 4821) to force-kill a process that isn't responding to the normal, more polite request to stop.