System Activity

Basically a process is any program or command that is running on the computer. This includes any jobs belonging to you and everyone else as well as numerous applications which make up the entire OS, whatever is running and uses the CPU. We can list processes, kill them and view their current usage on the system.

The distinction between jobs and processes is very fine so expect them to be occassionally viewed as the same thing. In many cases many of the commands that act on jobs can also be used with processes and vice-versa.

There's a couple of basic commands to help out with processes, in their viewing, showing their usage and termination. First two are usually quite useful when it comes to the third. The first one we're going to deal with is top, which shows a list of what processes are currently being executed in order of what is using the CPU most by default, but it can be sorted by any one of the different items it shows.

We'll just cover what it displays and how to limit it to just your own processes or any users processes which is one of the most useful functions. Next ps and pstree which deal with displaying processes in general and finally kill which is used to terminate processes.

In this section

• Show usage with top
• List processes with ps
• Show process tree
• Killing processes