shell-scripting-tutorial

1. Introduction to Bash Scripting

What is Bash? Bash (Bourne Again SHell) is a shell and programming language for the GNU Operating System. It's widely used on various UNIX-like systems and is the default shell on most Linux distributions and macOS.

Creating a Bash Script To start writing a Bash script, create a new text file and start with the shebang line, which tells the system which interpreter to use:

#!/bin/bash

Make the script executable:

chmod +x script_name.sh

Run the script:

./script_name.sh

2. Basic Commands and Syntax

Echo Command Used to display a line of text/string:

echo "Hello, World!"

Variables Creating and using variables:

name="Alice"
echo "Hello, $name!"

Reading Input Reading input from the user:

read -p "Enter your name: " name
echo "Hello, $name!"

3. Conditional Statements

If-Else Statement Simple if-else example:

read -p "Enter a number: " num
if [[ $num -gt 10 ]]
then
    echo "The number is greater than 10."
else
    echo "The number is 10 or less."
fi

4. Loops

For Loop Loop through a list of numbers:

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

While Loop Condition-based looping:

count=1
while [[ $count -le 5 ]]
do
    echo "Count $count"
    ((count++))
done

5. Case Statements

Handling multiple conditions using a case statement:

read -p "Enter your choice: " choice
case $choice in
    1) echo "You chose option 1";;
    2) echo "You chose option 2";;
    *) echo "Invalid option";;
esac

6. Functions

Creating Functions A simple function to display a greeting:

function greet {
    echo "Hello, $1!"
}
greet "Alice"

Return Values Using output from a function:

function add {
    local sum=$(( $1 + $2 ))
    echo $sum
}

result=$(add 5 3)
echo "The sum is $result"

7. Advanced Topics

Debugging Turn on debugging:

set -x

Turn off debugging:

set +x

Arrays and Substrings Working with arrays and manipulating their content:

arr=(apple banana cherry)
echo "${arr[1]}"          # Outputs banana
echo "${arr[@]:1:2}"      # Outputs banana cherry

8. Practical Examples

Script with Arguments Using positional parameters:

#!/bin/bash
echo "Script Name: $0"
echo "First Argument: $1"
echo "Second Argument: $2"

Run this script with two arguments to see how it handles input parameters.

This tutorial covers the basics and some advanced aspects of Bash scripting. With practice, you'll get more comfortable and discover even more functionalities of Bash.