The Shell

The Shell#

reading

We will loosely follow the Software Carpentry lesson on The Unix Shell

The shell#

The shell is your interface to the operator system. It implements a REPL interface: Read, Execute, Print, Loop. This means it:

  • Reads the input (commands) you type

  • Executes the command

  • Prints the result of the command

  • Loops back to the start, waiting to read a new command

The power of the shell is that we can easily combine different tools together to create powerful commands to manipulate files on the computer.

To access the shell, we need to open a terminal on the computer. This will present us with the command prompt, which typically is a $ (although it can be customized)`.

Here’s a quick demonstration: the echo command simply prints anything following it to the terminal:

echo Hello, World

Which shell?#

There are a wide variety of shells that are used today. The default on many systems is BASH. Others that you might commonly encounter are zsh and fish.

We’ll focus on BASH, and most of what we learn here will apply directly to the other shells.

Some online shell documentation:

A basic “cheat sheet” is available here: Unix/Linux Command Reference.

Configuring Bash#

Every time we open a terminal, the shell reads a special file called .bashrc. This file contains commands that customize our shell in various ways.

As the semester goes on, we’ll add to this file to make our lives easier.

We can look at the current contents of our .bashrc file by doing:

cat ~/.bashrc
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