Shell Scripting Tutorial in Linux

welcome to the video tutorial on shell scripting operating systems are made of many components but there are two prime components are kernel and shell the kernel is at the nucleus of a computer it makes the communication between the software and the hardware possible while the kernel is the innermost part of an operating system a shell is the outermost one a shell in a Linux operating system takes input from you in form of commands processes them and then gives an output it is the interface through which a user works on the program’s commands and scripts a shell is accessed by terminal which runs it when you run the terminal the shell issues a command prompt which is usually the dollar sign wherein you can type your input which is then executed when you hit the enter key so if we type in the PWD command and hit the enter key the output or the result is thereafter displayed on the terminal the shell wraps around the delegate interior of an operating system protecting it from accidental damage hence the name shell there are two main shells and Neelix the first one is the bourne shell the prompt for this shell is a dollar sign and its derivatives are the POSIX shell known as as H the conch shell also known as as H and the bourne-again shell also known as bash which is the most popular of them all second one is the C shell the prompt for this shell is a percentage sign and it’s subcategories are sea shell also known as CS h tops sea shell also known as TCS H will discuss bash shell base shell scripting in this tutorial so what is shell scripting and why do I need it writing a series of command for the shell to execute is called shell scripting it can combine lengthy and repetitive sequences of commands into a single and simple script which can be stored and execute it anytime this reduces the effort required by the end-user let us understand the steps in creating a shell script first create a file using a VI editor or any other text editor second nameless curve filed with an extension dot as H side the script with the hash sign followed by shriek followed by the been SH path write some code save the script file as file name dot as H for executing the script type bash followed by file name dot as H here the hash sign followed by shriek is an operator Khalsa Bank which directs the scripts to the interpretation location let’s create a small script using the VI editor will start with typing VI followed by the file name do not forget to enter the SH extension by pressing the i key on the keyboard will enter the insert mode of the VI editor let’s start with the script you need to start your script with shebang sign followed by the bin SH path every time you create a shell script let’s type in the command and quickly go ahead and save this file now in order to run the script we need to type in bash followed by the script name again do not forget to type in the SH extension upon hitting the enter key we will see that the command LS is executed commenting is important in any program in shell the syntax to add a comment as the hash sign followed by the comment that is understand this with an example so let us create another sample script now you’d again start with the bank sign followed by the bin as age path let us execute the command PWD now here we would like to add a comment which will tell us that the PWD command stands for present working directory let us quickly go ahead and save the script now upon running script 1.8 we will find that the PWD command was executed but the comment present working directory was ignored moving on to what I shall variables has discussed earlier variable stored data in form of characters and numbers similarly shell variables are used to store information and they can be read by the shell only for example this piece of script creates a shell variable and then prints end this is a small script which will create and it will use variables so let us start with creating the script we start the script as usual with the shebang followed by the bend as h path now let us start with writing the script as we have completed writing the script let us go ahead and save it now let us go ahead and run the script file for this we need to type in bash followed by the script name which is easy script dot s H in our case once we hit the enter key the script starts executing and it asks us what is your name we will type in the name guru nine nine upon hitting the enter again the script now tells us how do you do and it echoes our name let us put in good as you can see here the script repeats the remark that we have entered this is how we can create script based on bash shell now this is a simple script you can develop advanced scripts which contain conditional statements loops and functions shell scripting will make your life easy and Linux administration a breeze let us quickly recap what we learnt in this tutorial kernel is the nucleus of the operating systems and it communicates between hardware and software shell is a program which interprets user commands through CLI like terminal the bourne shell and the c shell are the most used shells in linux shell scripting is writing a series of commands for the shell to execute shell variables store the value of a strength or a number for the shell to read shell scripting can help you create complex programs containing conditional statements loops and functions thank you for watching this tutorial out see you in the next one