Shell Script Basics

This tutorial will guide you through the basic concepts of BASH shell scripting. It will include creating, writing, and executing scripts.

Beginner30 minutes

Step 1: Introduction to BASH

BASH (Bourne Again Shell) is a shell program in Unix. It's a command processor that allows you to type commands and get results.

Practice Exercise

Show Solution

Step 2: Creating a BASH Script

Let's start by creating a simple BASH script. In Unix, scripts start with a 'shebang' (#!) followed by the path to the interpreter.

#!/bin/bash

Practice Exercise

Create a new BASH script file named 'myscript.sh'.

Show Solution

Use the 'touch' command to create a new file: touch myscript.sh

Step 3: Writing a BASH Script

Now that we have our script file, we can write our first script. Let's print 'Hello, World!' to the console.

#!/bin/bash

 echo 'Hello, World!'

Practice Exercise

Edit 'myscript.sh' to print 'Hello, World!' to the console.

Show Solution

Use a text editor to add the following line to 'myscript.sh': echo 'Hello, World!'

Step 4: Executing a BASH Script

To run our script, we first need to make it executable with the 'chmod' command. Then, we can run it using the './' prefix.

chmod +x myscript.sh

 ./myscript.sh

Practice Exercise

Make 'myscript.sh' executable and run it.

Show Solution

Use the following commands: chmod +x myscript.sh; ./myscript.sh

Step 5: Using Variables in BASH Scripts

Variables allow us to store and manipulate data in our scripts. They are declared with the '=' operator and accessed with the '$' prefix.

name='John'

 echo "Hello, $name!"

Practice Exercise

Create a variable 'name' in 'myscript.sh' and print a greeting message using this variable.

Show Solution

Add the following lines to 'myscript.sh': name='John'; echo "Hello, $name!"

Step 6: Using Conditional Statements in BASH Scripts

Conditional statements allow us to perform different actions based on certain conditions. The 'if' statement is the most common conditional statement in BASH.

if [ $name == 'John' ]; then
 echo 'Hello, John!'
 else
 echo 'Hello, stranger!'
 fi

Practice Exercise

Modify 'myscript.sh' to print 'Hello, John!' if 'name' is 'John', and 'Hello, stranger!' otherwise.

Show Solution

Add the following lines to 'myscript.sh': if [ $name == 'John' ]; then echo 'Hello, John!'; else echo 'Hello, stranger!'; fi

Step 7: Using Loops in BASH Scripts

Loops allow us to execute a block of code multiple times. The 'for' loop is commonly used in BASH scripting.

for i in {1..5}; do
 echo $i
 done

Practice Exercise

Modify 'myscript.sh' to print the numbers from 1 to 5 using a for loop.

Show Solution

Add the following lines to 'myscript.sh': for i in {1..5}; do echo $i; done