Command Line Course

The Shell

Simply put, the shell is a program that takes 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-like system such as Linux. Nowadays, we have graphical user interfaces (GUIs) in addition to command line interfaces (CLIs) such as the shell.

On most Linux systems a program called bash (which stands for Bourne Again SHell, an enhanced version of the original Unix shell program, sh, written by Steve Bourne) acts as the shell program. Besides bash, there are other shell programs available for Linux systems. These include: ksh, tcsh and zsh.

Terminal

It’s a program called a terminal emulator. This is a program that opens a window and lets you interact with the shell. There are a bunch of different terminal emulators we can use. Some Linux distributions install several. These might include gnome-terminal, konsole, xterm, rxvt, kvt, nxterm, and eterm.

Let’s try some typing. Bring up a terminal window. The first thing we should see is a shell prompt that contains our user name and the name of the machine followed by a dollar sign. Something like this:

[me@linuxbox_me]$

sudo

A widely used command in the Linux command line, sudo stands for “SuperUser Do”. So, if you want any command to be done with administrative or root privileges, you can use the sudo command.

For example, if you want to edit a file like viz. alsa-base.conf, which needs root permissions, you can use the command – sudo nano alsa-base.conf.

You can enter the root command line using the command sudo bash, then type in your user password. You can also use the command su to do this, but you need to set a root password before that. For that, you can use the command sudo passwd. Then type in the new root password