UNIX01/Introduction To Processes

We have already seen processes under Linux with the ps command, but we will now look at them with a bit more in-depth.

Process Overview

Linux is a true multitasking system so there are numerous processes in various states at all times. In fact, many processes (called daemons) are started when the computer is first booted and continue to share CPU time until the computer is shut down. For example, Linux will store certain system information in logs and the system administrator can review those logs to look for problems. A program that monitors the system and writes logs would run as a daemon.

The who Command

In order to check on the processes running on your computer, one of the first things you would want to know is who is currently logged on (that way, you can tell who is running each process). You can do this with the who command. The following shows the output of who on my computer.

 [selfg@localhost selfg]$ who

 root     tty1         Jul 17 08:20         
 babbagec tty2         Jul 17 09:00         
 lovelace tty3         Jul 17 09:00         
 turinga  tty4         Jul 17 09:09         
 hopperg  tty5         Jul 17 09:17         
 selfg    :0           Jul 17 08:15

 [selfg@localhost selfg]$

On my computer, there were four users logged on, plus root. Who also returns information about where and what time each user logged on. For example, if turinga and hopperg were supposed to be to work at 9am, you see that they were actually late logging in.

(C) Copyright 2003 Samuel Hart

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