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Basic Linux Shell Scripting for DevOps .

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Adfar Banday
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What is the Kernel?

Imagine the kernel as the conductor of an orchestra. It's the core program of an operating system, responsible for managing hardware resources, memory allocation, and communication with various devices. It has complete control over the system, ensuring everything runs smoothly behind the scenes.

What is a Shell?

Think of the shell as an interpreter. It acts as a bridge between you and the kernel, allowing you to interact with the system using commands. It translates human-readable commands into a language the kernel understands, making it possible to control various aspects of your system.

What is Linux Shell Scripting?

Shell scripting involves creating a series of commands saved in a file, called a script. These scripts are then executed by the shell, automating repetitive tasks or complex workflows. Shell scripting is a powerful tool for DevOps engineers as it enables them to:

  • Automate repetitive tasks: Save time and effort by automating tasks you frequently perform manually.

  • Manage infrastructure: Automate tasks like provisioning and configuring servers, simplifying infrastructure management.

  • Improve consistency: Ensure tasks are performed consistently and accurately, reducing the risk of errors.

  • Increase efficiency: Streamline your workflow by automating tedious processes.

Examples of Shell Scripting in DevOps:

  • Deploying applications: Write a script to automate the process of deploying an application to multiple servers.

  • Provisioning servers: Create a script to automatically set up a new server with the required software and configurations.

  • Monitoring system health: Develop a script to monitor system resources and send alerts if any issues arise.

#!/bin/bash vs. #!/bin/sh

The line #!/bin/bash at the beginning of a script is called the shebang. It tells the system which interpreter to use to execute the script. In this case, /bin/bash specifies the Bash shell.

While you can use #!/bin/sh as well, it's generally recommended to use #!/bin/bash for better portability. This is because sh is a symbolic link that might point to different shells on different systems. Using bash explicitly ensures your script uses the intended interpreter regardless of the system configuration.

Shell Script Examples:

1. Print a message:

Bash

#!/bin/bash
echo "I will complete the #90DaysOfDevOps challenge!"

2. User Input:

Bash

#!/bin/bash
read -p "Enter your name: " name
echo "Hello, $name!"

3. Arguments and Variables:

Bash

#!/bin/bash
name=$1
age=$2
echo "Hello, $name. You are $age years old."

4. If-else statement:

Bash

#!/bin/bash
read -p "Enter a number: " num1
read -p "Enter another number: " num2

if [ $num1 -gt $num2 ]; then
  echo "$num1 is greater than $num2."
else
  echo "$num2 is greater than or equal to $num1."
fi

This is just a basic introduction to shell scripting. As you delve deeper, you'll discover its immense potential for simplifying your DevOps tasks and empowering you to automate your way to success

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