Different Users

On the Unix machine there can be multiple users, and because of the way that Unix is designed multiple users can be logged in at the same time. To see this we will use the following commands.

First we can run users, and this will show how many users are logged on. If a persons name shows up more than once it means they have more than one session open.

dave@[datadyne]:~/$ users
dave dave dave dave

As you can see I have 4 terminals open on this machine. Once you learn how to use a command line interface (which is what terminal is) it's hard to want to use anything else because of the level of increased productivity it allows.

dave@[datadyne]:~/$ w
18:08:22 up 14 days, 13:42,  4 users,  load average: 0.01, 0.03, 0.00
USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT
dave     pts/0     17:22   13:22   0.24s  0.24s -bash
dave     pts/1 22Sep10  2days  2:18   2:18  weechat-curses
dave     pts/2 22Sep10  2days  6.33s  6.07s python
dave     pts/3 23Sep10  0.00s  1.74s  0.01s w

This shows a lot more, this shows what program is running on all of the terminals. As you can see this particular machine has 4 users on (all me), and has been up for about 14 days. On the 4 terminals, I'm running bash in one, weechat-curses in another, python in another, and one ran 'w' to get the output that you are seeing. The programs I'm running are not important, what is important is that anyone on the machine can see what programs you are using with the w command.

Finally we are going to use cat to view the contents of the file. To use cat is simple, we will it like this.

dave@[datadyne]:~/$ cat /etc/passwd

cat will dump the contents of a file right on the terminal, so in this case it will dump the contents of /etc/passwd. This file in particular shows all of the users (along with more information) that exists on the computer.

For security purposes I will not show the output of this command, but hopefully this will teach you how to use the command.

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