What is "the shell"?
Simply put, the shell is a program that takes your
commands from the keyboard and gives them to the operating system to
perform. In the old days, it was the only user interface available on a
Unix computer. Nowadays, we have graphical user interfaces (GUIs)
in addition to command line interfaces (CLIs) such as the
On most Linux systems a program called bash
(which stands for Bourne Again SHell, an enhanced version of the
original Bourne shell program, sh, written by Steve Bourne) acts as the
shell program. There are several additional shell programs available on
a typical Linux system. These include: ksh, tcsh and zsh.
These are called "terminal emulators." They are
programs that put a window up and let you interact with the shell.
There are a bunch of different terminal emulators you can use. Most
Linux distributions supply several, such as: xterm, rxvt,
konsole, kvt, gnome-terminal, nxterm, and eterm.
Your window manager probably has a way to launch
programs from a menu. Look through the list of programs to see if
anything looks like a terminal emulator program. In KDE, you can find
"konsole" and "terminal" on the Utilities menu. In Gnome, you can find
"color xterm," "regular xterm," and "gnome-terminal" on the Utilities
menu. You can start up as many of these as you want and play with them.
While there are a number of different terminal emulators, they all do
the same thing. They give you access to a shell session. You will
probably develop a preference for one, based on the different bells and
whistles each one provides.
Ok, let's try some typing. Bring up a terminal
window. You should see a shell prompt that contains your user name and
the name of the machine followed by a dollar sign. Something like this:
Excellent! Now type some nonsense characters and
press the enter key.
[me@linuxbox me]$ kdkjflajfks
If all went well, you should have gotten an error
message complaining that it cannot understand you:
[me@linuxbox me]$ kdkjflajfks
bash: kdkjflajfks: command not found
Wonderful! Now press the up-arrow key. Watch how
our previous command "kdkjflajfks" returns. Yes, we have command
history. Press the down-arrow and we get the blank line again.
Recall the "kdkjflajfks" command using the
up-arrow key if needed. Now, try the left and right-arrow keys. You can
position the text cursor anywhere in the command line. This allows you
to easily correct mistakes.
You're not logged in as root, are you?
Don't operate the computer as the superuser. You
should only become the superuser when absolutely necessary. Doing
otherwise is dangerous, stupid, and in poor taste. Create a user
account for yourself now!
Even though the shell is a command line interface,
you can still use the mouse for several things. That is, if you have a
3-button mouse; and you should have a 3-button mouse if you want to use
First, you can use the mouse to scroll backwards
and forwards through the output of the terminal window. To demonstrate,
hold down the enter key until it scrolls off the window. Now, with your
mouse, you can use the scroll bar at the side of the terminal window to
move the window contents up and down. If you are using xterm, you may
find this difficult, since the middle button is required for this
operation. If you have a 2-button mouse, it may have been configured to
emulate a 3-button mouse. This means the middle button can be simulated
by pressing down both the left and right buttons at the same time.
Next, you can copy text with the mouse. Drag your
mouse over some text (for example, "kdkjflajfks" right here on the
browser window) while holding down the left button. The text should
highlight. Now move your mouse pointer to the terminal window and press
the middle mouse button. The text you highlighted in the browser window
should be copied into the command line. Did I mention that you will
need a 3-button mouse?
A few words about focus...
When you installed your Linux system and its
window manager (most likely Gnome or KDE), it was configured to behave
in some ways like that legacy operating system.
In particular, it probably has its focus
policy set to "click to focus." This means that in order for a
window to gain focus (become active) you have to click in the window.
This is contrary to traditional X windows behavior. If you take my
advice and get a 3-button mouse, you will want to set the focus policy
to "focus follows mouse". This will make using the text copying feature
of X windows much easier to use. You may find it strange at first that
windows don't raise to the front when they get focus (you have to click
on the title bar to do that), but you will enjoy being able to work on
more than one window at once without having the active window obscuring
the the other. Try it and give it a fair trial; I think you will like
it. You can find this setting in the configuration tools for your