Basic of Linux

If you are using Ubuntu then you must know about the following terms:-

1. Kernel

2. shell

Kernel:-

is a central component of an operating system that manages the operations of computers and hardware.

It manages operations of memory and CPU time. It is a core component of an operating system.

Kernel acts as a bridge between applications and data processing performed at the hardware level using inter-process communication and system calls.

Shell:-

A shell is a special user program that provides an interface for the user to use operating system services. Shell accepts human-readable commands from users and converts them into something which the kernel can understand.

Shell Scripting:-

As a shell can also take commands as input from the file we can write these commands in a file and can execute them in the shell to avoid this repetitive work. These files are called Shell Scripts or Shell Programs.

A shell script comprises the following elements –

• Shell Keywords – if, else, break etc.

• Shell commands – cd, ls, echo, pwd, touch etc.

• Control flow – if..then..else, case and shell loops etc.

Why do we need shell scripts

• To avoid repetitive work and automation

• System admins use shell scripting for routine backups

• System monitoring

• Adding new functionality to the shell etc.

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

Bash:- It simplifies certain operations that are hard to accomplish efficiently with a GUI.

#!/bin/bash:- This is the first line of the shell path. It tells the shell to execute it via bash shell.

/bin/bash vs /bin/sh:- bash is a newer and improved version of the shell. The features offered and the advantages of Bash over Shell are very heavy. So bash is better.

Write a Shell Script that prints I will complete the #90DaysOofDevOps challenge

According to the above image, nano is like a notepad devops_first.sh is the filename. After entering that nano devops_first.sh text editor will open and it shows like below diagram.

According to this image #!/bin/bash This is the first line of the shell path.
echo keyword is used to write the statement whatever we want.

Write a Shell Script to take user input and print the variables.

Shell Script: - following is the script as input

Output:-

• Write an Example of If else in Shell Scripting by comparing 2 numbers

  Shell Script:-

Output:-