What is 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 user and converts them into something that the kernel can understand. It is a command language interpreter that executes commands read from input devices such as keyboards or from files. The shell gets started when the user logs in or starts the terminal.

What is Kernel?

The kernel is a computer program that is the core of a computer’s operating system, with complete control over everything in the system.

What is shell scripting?

Shell scripting in Linux involves writing scripts or programs using shell commands and scripting constructs. The shell is a command-line interface to the operating system, and it allows you to automate tasks and perform system administration. Bash (Bourne Again Shell) is one of the most commonly used shells for scripting in Linux. Here are the key components and concepts of shell scripting:

1. Shebang: The shebang is the first line of a shell script that specifies the interpreter to be used to execute the script. For Bash scripts, the shebang line is typically #!/bin/bash.

2. Variables: You can declare and use variables in shell scripts. Variables can store values, and you can access them using the $ symbol. For example:

   name="John"

   echo "Hello, $name"

3. User Input: You can read user input using the read command:

   echo "What is your name?"

   read name echo

   "Hello, $name"

4. Conditional Statements: You can use conditional statements to make decisions in your script. Common constructs include if, elif, and else. For example:

   if [ "$age" -lt 18 ]; then

   echo "You are a minor."

   else

   echo "You are an adult."

   fi

5. Loops: Shell scripts support various types of loops, including for and while. Here's an example of a for loop:

   for i in {1..5}

   do

   echo "Iteration $i"

   done

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Difference b/w Shell Scripting and Programming?

• Interpreted vs compiled:

  Shell scripts are interpreted, which means that the code is executed line by line, rather than compiled into machine code and run as an executable file. Programming languages are typically compiled, which means that the code is converted into machine code before it is executed.

• Purpose:

  Shell scripts are typically used to automate tasks on a Unix-like operating system. Programming languages are used to develop software applications.

• Complexity:

  Shell scripts can be relatively simple, but they can also be complex and difficult to read. Programming languages are typically more complex than shell scripts.

• Power:

  Shell scripts can be used to do a variety of tasks, including launching programs, managing files, and controlling processes. Programming languages can be used to do even more complex tasks, such as creating databases, developing user interfaces, and writing web applications.

• Ease of use:

  Shell scripts can be easier to learn than programming languages, but they can also be less powerful and flexible. Programming languages are typically more difficult to learn, but they are also more powerful and flexible.

In general, shell scripts are a good choice for simple tasks that need to be automated on a Unix-like operating system. Programming languages are a good choice for more complex tasks, such as developing software applications.