Gain insights into the intricacies of the Bash shell, ideal for beginners. Delve into essential skills with interactive learning designed to ensure lasting knowledge without requiring prior experience.

dockerbash.tar.gz

tset

A course for anyone interested in understanding all aspects of the bash shell. Designed for use by beginners, it assumes as little knowledge as possible but teaches you all the intricacies of bash it took me decades to learn by trial and error. 

The interactive nature of the course instills the knowledge in a way you will not forget!

Master the Bash Shell

Now that you’ve learned about escapes and special characters you are in a position to understand how the bash **prompt** can be set up and controlled.

# How Important is this Lesson? 

This lesson is not essential, but most people find it interesting and
maybe fun to learn about.


# The `PS1` Variable

Type this:


bash
PS1='My super prompt>>>>   '
ls
exit

As you’ll remember, there are some *shell variables* that are set
within bash that are used for various purposes. One of these is `PS1`, which is
the prompt you see after each command is completed.

# The `PS2` Variable

bash
PS2='I am in the middle of something!>>>  '
cat > /dev/null << END
some text
END
exit

The PS2 variable is the ‘other’ prompt that the shell uses to indicate that you
are being prompted for input to a program that is running. By default, this is
set to `> `, which is why you see that as the prompt when you normally type the
`cat` command above in.

# `PS3`

`PS3` is used by the `select` looping structure. We don’t cover that in this
book as I've barely ever seen it used.

# `PS4`

`PS4` is the last one:

bash
PS4='> Value of PWD is: $PWD'
set -x
pwd
cd /tmp
ls $(pwd)
cd -
exit

In ‘trace’ mode `PS4` is echoed before each line of trace output. Do you remember
what trace mode is?

But why is the `>` in the output repeated? This indicates the _level_ of
indirection (ie subshells) in the trace. Every time the script goes one level
&lsquo;down&rsquo; a shell, the first character in the `PS4` value is repeated. Look at the
output after the `ls ＄(pwd)` command.

> Note: Things can get really confusing if you have commands in your prompt, or you have `PROMPT_COMMAND` set (see below section). If you don’t fully understand the output of the above, don’t panic!

# Pimp Your Prompt

For all the `PS` variables mentioned above, there are special escape values that
can be used to make your prompt display interesting information.

See if you can figure out what is going on here:

In this lesson, you will learn how to set up your main prompt, as well as other types of prompts and related shell variables.


Core Bash

Scripting Bash

Bash in Practice

Advanced Bash

The Prompt

How Important is this Lesson?

The `PS1` Variable

The `PS2` Variable

`PS3`

`PS4`