What is kernel

The kernel is a computer program at the core of a computer’s operating system that manages operations of computer and hardware.

What is shell scripting

Shell scripting is a series of Linux commands written in a file in sequence. It is a way to automate repetitive tasks, saving time and effort. Shell scripts are commonly used to manage systems, infrastructure, and handle batch processing.

What is shell

Shell is a program and command line interpreter. It is an interface between user and kernel.

Why Learn Shell Scripting?

1. To avoid repetitive work.

2. System admins use shell scripting for routine backups.

3. System monitoring

4. Adding new functionality to the shell etc.

   

Task:

1. Explain in your own words and with examples what Shell Scripting means for DevOps.

   Shell scripting in DevOps is a powerful tool for automating tasks, managing infrastructure, maintaining consistency, and integrating various tools and processes to achieve efficient and reliable software delivery.

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

   #!/bin/bash - #!/bin/bash in shell script is called shabang & its use to tell the system which interpreter/command to use to execute the commands written inside the scripts.

    #!/bin/bash 
    echo "Hello World!"
   

   

   #!/bin/sh - It is used to execute the file using sh, which is a Bourne

   shell, a compatible shell.

    #!/bin/sh
    echo "Hello World!"
   

   

   How to execute a shell script -

    # How to execute the shell script
    ./hello.sh
   

   

3. Write a Shell Script that prints I will complete #90DaysOfDevOps challenge.

#!/bin/bash --------> Shebang 
echo "I will complete 90daysofdevops challenge"

• 

4. Write a Shell Script that takes user input, input from arguments, and prints the variables.

#!/bin/bash
#Variables which takes input from users 

read -p "Please Enter your Name: " Name
read -p "Please Enter your Age: " Age

if [ $Age -gt 18 ]; then
        echo "Your Age is ${Age} and you are Eligible for voting. Happy Voting!!!"
fi

• 

  Before running scripts we need to ensure that we have executable permission for the shell file.

• As we can see in shell below, we only have read and write permission for input.sh file i.e, rw- , we have to make it rwx for executing.

•   $ ls -l Input.sh 
    -rw-rwxr-x 1 ubuntu ubuntu 243 Aug 21 05:31 Input.sh
  

• 

  To execute this file we need to give executable permission.

•   $chmod +x Input.sh
  

  

    $ls -l Input.sh 
    -rwxrwxr-x 1 ubuntu ubuntu 243 Aug 21 05:31 Input.sh
  

  

  

  As we see after giving permission script got executed and give output as it is.

• Input as an arguments -

•   #!/bin/bash
  
    Name=$1
    Age=$2
  
    echo "Your Name is ${Name}"
    echo "Your Age is ${Age}"
  
    if [ $Age -gt 18 ]; then
            echo "Your age is ${Age} and you are eligible for Vote."
            echo "Happy Voting!!!"
    else
            echo "Your age is ${Age} and you aren't eligible for Vote."
    fi
  

• 

  For arguments there is a different way to give input, in argument scripts we give input along with our script execution command. Like below:

•   $ ./arguments.sh Vibhuti 20
  

• 

5. Provide an example of an If-Else statement in Shell Scripting by comparing two numbers.

Number1=$1
Number2=$2

if [ $Number1 -gt $Number2 ]; then
        echo "${Number1} is greater than ${Number2} " 
elif [ $Number1 -lt $Number2 ]; then
        echo "${Number1} is less than ${Number2} "
else
        echo "${Number1} and ${Number2} are equal "
fi

•