Introduction

It is a free software written by Brian Fox and released in 1989 as a replacement for Sh (Bourne Shell). Bash is used by developers, data scientists, system administrators, Network Engineers, and any other person heavily relying on Unix/Linux operating systems.

Each Bash based Linux script starts by the line #!/bin/bash

! Where #! is referred to as the shebang and rest of the line is the path to the interpreter specifying the location of bash shell in our operating system.

Who developed the bash shell ?

john kets Brian Fox Kot valley None of the above

hello world

Let's kick things off by creating a simple program that displays the text "Hello world!".

In Bash, we use the echo command to output text.

to generate our message, the code would look like this:

echo "Hello World !"

Tap   to   try    |

Wow great! You’ve just written your first Bash program.

! The text should be in single or double quotation marks.

Fill in the blanks to output "Bash is Awesome!" ?

"Bash is Awesome!"

comments

Bash script provides support for two types of comments, just like the other programming language.

single line comment
multi line comment

single line comment

To write single line comment in bash, we have to use hash (#) symbol at the starting of the comment.

echo "Hello I'm Somya !"

# This is a single line comment

echo "I'm Learning Bash"

multi line comment

There are two ways to insert multi-line comments in bash scripts:

By enclosing the comments between <<COMMENT and COMMENT
By enclosing the comments between (: ') and single quote (')

echo "Introducing multiline comment !"

<<COMMENT
This is a multi line comment there is another way of making multiline comments
COMMENT

: ' This is also multi line comment
remember both formats to use multiline comments '

Tap   to   try    |

! There is a space between : '

What is the output of this code ?

: ' is great'
echo "bash"
# bash is great !

bash variables

Variables are the containers which store data or a useful piece of information as the value inside them.
is the syntax for a variable:

variable_name = value
# how to print variable // using dollar sign

echo $variable_name

Rules for bash variables

There are same rule applicable for other language variables.
Variables names only starts with underscore or alphabets only.

! There should be no space between either side of (=) sign

What is the output of this code ?

num = 12
num =14
num=8
echo $num

how to read input

In this topic we will learn how to read user input in bash command.

To read the Bash user input, we use the built-in Bash command called read. It takes input from the user and assigns it to the variable. It reads only a single line from the Bash shell.

Below is the syntax for its implementation.

read variable_name

echo $variable_name

Tap   to   try    |

how to read multiple value

This can be also possible to read miltiple values from the user and store these values in diffrent variables

read variable1 variable2 variable3 .... variableN

echo $variable1 $variable2 $variable3 .... $variableN

Tap   to   try    |

! If we don't pass any variable to read command than simply use built-in variable REPLY with dollar sign.

What is the output of this code ? if the user input the value 78

num=22
read echo $REPLY

Lesson Completed!

You've just learnt introduction. Don't forget to test your knowledege with practice!

Your reward:
+10 💎

➡️ BASH Tutorial 👆