# Day 4 Task: Basic Linux Shell Scripting for DevOps Engineers.

## **What is Shell Scripting?**

* A shell script is **a text file that contains a sequence of commands for a UNIX-based operating system**. It is called a shell script because it combines a sequence of commands, that would otherwise have to be typed into the keyboard one at a time, into a single script.
    
* It's a way to automate repetitive tasks, making your life easier and more productive.
    

## Why is Shell Scripting important in DevOps?

* In the realm of DevOps, where speed and efficiency are key, shell scripting is the secret weapon!
    
* Shell scripting for DevOps **enables automation of deployment, configuration management, CI/CD pipelines, monitoring, logging, and performance optimization tasks**. Shell scripting languages, such as Bash, are used for automating tasks in DevOps workflows.
    
* With shell scripting, you can save time, reduce errors, and focus on the truly important tasks at hand!
    

## What is #!/bin/bash? Can we write #!/bin/sh as well?

* The line "#!/bin/bash" is like the enchanting spell that tells the computer to use the Bash interpreter, unlocking a world of powerful features for shell scripting!
    
* Yes, We can also write "#!/bin/sh" to use the default shell interpreter available on Unix-based systems.
    
* However, keep in mind that it might limit access to some advanced features. So, if you want the full magical experience, go for "#!/bin/bash" and unlock the true potential of shell scripting!
    

### **Write a Shell Script which prints**

### `I will complete #90DaysOofDevOps challenge.`

create a file with extension .sh like 90days.sh

open file with any editor and write their

```plaintext
#!/bin/bash

echo "I will complete the #90DaysOfDevOps challenge!"
```

Save the file, open your terminal, and execute the following command to make the script executable

```plaintext
chmod +x 90days.sh
```

🔮 Finally, run the script using:

```plaintext
./90days.sh
```

### **Write a Shell Script to take user input, input from arguments and print the variables.**

Create a new file called `user_input.sh` and add the following captivating script:

```plaintext
#!/bin/bash

echo "Enter your name:"
read name

echo "Your name is: $name"

echo "Arguments provided: $@"
```

This script uses its magic to prompt you to enter your name, reads the input, and then prints it along with any command-line arguments you provide. Here's how you can cast the spell:

```plaintext
./user_input.sh lokesh kumar hello
```

The output will mesmerize you:

```plaintext
Your name is: lokesh kumar
Arguments provided: hello
```

## **Using If-Else Statements in Shell Scripting**

Conditional statements, such as if-else, give your script the power to make decisions. Let's compare two numbers and conjure a message based on the comparison:

Create a new file called `number_comparison.sh` and add the following spellbinding script:

```plaintext
#!/bin/bash
number1=10
number2=20

if [ $number1 -gt $number2 ]
then
  echo "Number 1 is greater than Number 2"
elif [ $number1 -lt $number2 ]
then
  echo "Number 1 is less than Number 2"
else
  echo "Number 1 is equal to Number 2"
fi
```

In this enchanting script, we compare two numbers and conjure a message based on the result. Cast the spell by running:

```plaintext
./number_comparison.sh
```

The output will mesmerize you:

```plaintext
Number 1 is less than Number 2
```

With if-else statements, your script becomes a magical oracle that makes decisions based on the conditions you set!