Shell Scripting Challenge

This script will demonstrates practical use of comments, echo, variables, built-in variables, and wildcards in bash scripting.

#!/bin/bash

#Shell Scripting Challenge
#This script will demonstrates practical use of comments, echo, variables, built-in variables, and wildcards in bash scripting.

# 1. Comments
# Comments will help to undersatnd the scripts.
# There are two types of comments
# i> single line comments
# ii> multiline comments

# 2. Echo
# This command will help you to display message of your choice.
echo "Hello, Welcome to Shell Scripting Challenge"

# 3. variables
# It is used to store data of your choice like words,alphabets,and numbers etc.
# You can declare and assign data to variables.

name="Imran"
education="B.Tech"
echo "My name is $name, and i completed $education"

# Above the 'name' is variable and the value is 'Imran'
# To use variables need to use '$' and assign them into commands of your requirment

# 4. Using Variables
# Calculating sum of two numbers

num1=10 #First Number
num2=20 #Second Number
i=`expr $num1 + $num2` #Use the keyword 'expr' to perform arithmatic operations
echo "The sum of $num1 & $num2 is: $i" #Print the output

# Second method to calculate sum
sum=$((num1 + num2))
echo "The sum of $num1 & $num2 is: $i" #Print the output

# 5. Using Built-in Variables
# Bash provides several built-in variables that store useful information.

echo "The Current Working Directory is: $PWD" #Print the current working directory
echo "The Current logged in User ID is: $UID" #Print the User ID
echo "The Script file name is: $0" #Print the file name

# 6.Wildcards
# Wildcards are special characters used to perform pattern matching when working with files.

ls *.txt # List all the files who have .txt extension

Let’s breakdown the script:

Comments:

Comments begin with #. They are usefull to undarstand code or any script.

It is not executable by shell.
```
 # This is a comment.
```
Echo:

Echo print the text to terminal. You can print any text you want.
```
 echo "Hello, Welcome to Shell Scripting Challenge"
```
Variables:

Variables are used to store data.
```
 name="Imran"
 education="B.Tech"
```

Using Variables:

Performing arithmatic operations by using variables

 num1=10 #First Number
 num2=20 #Second Number

 i=`expr $num1 + $num2` #Use the keyword 'expr' to perform arithmatic operations

Output:

 echo "The sum of $num1 & $num2 is: $i"

Built-in Variables:

Bash provides several built-in variables that hold useful information.
- $0 holds the name of the script.
- $UID gives the current logged in User ID.
- $PWD holds the current working directory.

    echo "The Current Working Directory is: $PWD" #Print the current working directory
    echo "The Current logged in User ID is: $UID" #Print the User ID
    echo "The Script file name is: $0" #Print the file name

Wildcards:

Wildcards are special characters used to perform pattern matching when working with files.
```
 ls *.txt
```
This command lists all files that match the pattern *.txt (any file ending with .txt).

Happy Learning:)