Shell Scripting Full Course 2026 [FREE] | Shell Scripting Tutorial For Beginners | Simplilearn

Key Takeaways

[music] If you've ever wondered how people automate tasks on a computer, manage files faster, or make the system do repetitive work on its own, this is where the journey begins. Shell scripting is simply a way to talk to your computer using simple commands, put those commands into a file, and let the computer do the work for you. No heavy programming is needed. If you can understand basic instructions, you're already qualified to start. So in this course we'll move slowly, clearly and practically. We'll start from the absolute basics what the shell even is and step by step we'll build scripts that actually solve real world problems. By the end you will not just understand what shell scripts are, you'll be the one to write useful ones with confidence. So here's what we will cover in this course. What a shell is and why people use shell scripts. A quick refresher on basic Linux commands. Writing and running your very first shell script. Using variables and taking input from users. Making decisions using conditions. Repeating tasks using loops. Organizing code with functions. Working with files, text, and logs. Handling errors and understanding what went wrong. Using advanced features like arrays and menus. Automating tasks like backups and reports. Making scripts interactive and userfriendly. Building real world projects that you can actually use. Understanding where shell scripting fits in real jobs. Before we dive into the technical details, let me share something exciting that can help you take your cyber security skills to the next level and truly accelerate your career. The cyber security expert masters program by simply learn is a comprehensive hands-on learning experience designed for professionals who want to become end toend cyber security experts and get certified in some of the most in- demand credentials globally. So this is including C, AI, CompTIA security and CISSP. 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B, a file that contains instructions of a computer. C, a type of hardware, or D, a text editor. Have you ever found yourself doing the same repetitive task on your computer, whether it's organizing files, renaming them, or performing maintenance work? What if I told you that there's a way to automate all of that? Maybe something as simple as renaming files, organizing your photos, or managing a bunch of servers. Well, today we're going to learn a powerful way to automate those repetitive tasks. Shell scripting. So, what exactly is Shell? Imagine you're trying to give instructions to a robot in your house. Instead of telling the robot each task individually, you give it a list of tasks and it does them for you. That's exactly what Shell is for your computer. It's a way to communicate directly with your operating system using commands. Shell is a command line interface where you type commands into a terminal and the computer follows those commands to execute tasks. It's like sending your computer a series of secret codes that it understands and in return it carries out the tasks you have asked it to. Think of it as a translator between you and the operating system. Here's why you should learn shell scripting. Now, you may be wondering, why should I learn shell scripting? Imagine you're a chef in a busy kitchen and have to chop vegetables, boil water, and stir the sauce over and over again. Wouldn't it be great if someone automated some of that for you? Imagine if your oven, for example, imagine if your oven could start itself or your vegetables could chop themselves. Shell scripting is like having that automation in your digital kitchen. It allows you to automate tasks on your computer, saving you time and effort, just like having a robot assistant in the kitchen. Learning shell scripting can help you automate repetitive tasks, manage files, run programs, and control systems more effectively. It opens up career options in areas like DevOps and IT system management where automation is key to saving time and resources. Now, let's talk about how you can set up a Linux environment. Think of this like setting up a kitchen to cook your automated meals. You need the right tools and space to do it efficiently. In the world of shell scripting, that space is your Linux environment. You can set up a Linux environment in several ways. If you're on Windows, you can use WSL, which allows you to run a full Linux environment within your Windows machine. It's like creating a mini Linux kitchen inside your home. Alternatively, you can use a virtual machine or set up a cloud-based environment like AWS or Azure. No matter which option you choose, having access to a Linux environment is essential because it's where you will practice shell scripting. Linux is a go-to operating system for scripting and server management. We shall now speak about code reusability and maintenance. Imagine you're baking cookies. Every time you bake, you reuse the same recipe over and over again. That's exactly how code reusability works. Once you write a script, you can reuse it for different tasks, reducing the effort required each time. But just like a baker keeps the kitchen clean and organized, you also need to maintain your scripts. This means updating them when new tasks come up, adding comments to explain what's going on, and fixing any issues that arise. Maintaining your scripts ensure that they remain efficient and adaptable as your needs change. Reusability and maintenance saves your time and makes your scripts more robust. We shall now move on to common mistakes that you should avoid. Have you ever followed a recipe and forgotten an ingredient? It can ruin the whole dish. In scripting, one of the most common mistakes is hard coding values. This is like saying, "My recipe always needs exactly 1 cup of sugar without being able to adjust it." Instead, you should use variables which act like adjustable ingredients so you can change them as needed. Another mistake is not validating user input. Imagine a dinner guest asking for something that they don't like. If you don't check, you might end up with a bad meal. Similarly, in scripting, if you don't check the inputs your script receives, it could break unexpectedly. Always validate inputs to prevent errors. And don't forget debugging. This is like checking your ingredients before cooking. By anticipating potential problems, you can prevent your scripts from crashing. Let's move on to learning resources and practice platforms. So, now that you're all set to start scripting, where do you go to practice? Learning to script is like learning to bake. You start with simple recipes and build your skills over time. There are plenty of online platforms where you can learn shell scripting like Code Academy, Free Code Camp, and Udemy. These platforms offer interactive tutorials where you can practice and experiment with real world problems. Once you're comfortable with basics, you can turn to GitHub and Stack Overflow to connect with other developers and find open-source projects where you can contribute. These platforms are great places to practice and interact with other learners so you can keep improving your skills. So, as we wrap up, let's talk about what's next for you in shell scripting. Remember, just like learning to cook, shell scripting is a skill that improves the more you practice. Start by writing simple scripts to automate basic tasks. As you get more comfortable, you can move on to advanced topics like file permissions, process management, and even integrating your scripts with other tools. The skills you develop through shell scripting will help you manage systems, automate workflows, and make your digital life much more efficient. As you continue learning, explore advanced automation frameworks and cloudnating scripting to further enhance your skills and open up more career opportunities in fields like DevOps and system administration. So, let's start by understanding how to navigate around the Linux file system. Think of it like exploring a large city where every directory is a building and every file is a room inside that building. So, to get around, you need to know where you are and how to move from one place to another. Let's start off with the first command, which is the ls command. So this command lists the files and the directories in your current location. Imagine it as the city map. It shows all the buildings around you. So you can even customize it to show details like file sizes or modification dates. For example, when you type, so I will be typing the first command here, ls, you'll get a simple list of everything in your current directory. So to see more details, use the l flag for long listings. So this shows you the file permissions, ownership, size, and more. So, I'll just show you how it's done. So, as you can see, it shows you the file permissions, ownership, and size. We shall now move on to the next command, which is the CD command. So, it's short for change directory. And this command helps you navigate to a new directory. Think of it like taking a shortcut to the next building on your city map. So, for example, I'll show you one second. So, I shall type change directory and downloads. So, this command takes you to the downloads folder inside your current directory. So to go back to the previous directory you can use so by using cd followed by two dots it moves you up one level in the file system like going back to the main street from a side alley. Next we shall talk about the pwd command. So this command tells you your current location in the file system. It's like looking at your GPS to see exactly where you are on the map. So to check your location just type. So this will print the full path of your current directory as it has been shown over here. Next we shall move on to file operations. Now that we know how to get around, let's talk about some essential file operations. So these are the tools that you will use to create, move, copy and delete files in your file system. Now we shall speak about the CP command. So the CP command is used to copy files or directories. So think of it like making a photocopy of a document. You're creating a duplicate while the original remains intact. So before showing you how to execute the CP command, I will first create two different files. I will use the touch keyword to create two different files. So file 1.xt and then I will also create the second file which is file 2 txt. So as you can see two files have been created in the directory. So now we shall move ahead and copy the first file into the second file. We shall now copy the first file into the second file. On using this particular command you can copy the contents in file one to the file two. Now let's talk about the move command. So the MV command moves files or directories or it can rename them. So it's like picking up a document and placing it in a new location or even renaming them. So in order to rename an old file, this is the command you use. So as you can see the file has been renamed from file 1.xt to file txt. So in order to move a file to a new directory, here's what you're supposed to do. So I have moved the file.txt to a different location. Now we shall speak about the remove command. So the rm command is used to delete files. It's like throwing away a document. But be careful though. Once it's gone, it's really hard to get it back. So, I'll show you how to execute that. So, as you can see, the file has been deleted from the directory. So, if you want to delete an entire directory and its contents, use the R flag. So, in order to show you how to delete a file, I shall first create a file. So, if you want to delete a directory, I'll first go ahead and create a directory. So, I shall go ahead and remove the directory using the r command. And I will be deleting the directory called my folder. So as you can see the directory has been removed. Now we shall move on to the make directory. So this command creates a new directory. Think of it like building a new folder to store your files. So you can even create multiple directories at once. I will show you how to do it. I shall use the command name. Then I shall add some folders here. So as you can see multiple folders have been created. Next, we shall move on to viewing file content. Sometimes you just need to peek inside a file without opening it fully. So, Linux gives you several commands for viewing file content. So, let's explore them. Firstly, the CAD command. So, the CAT command displays the entire content of a file. It's like opening up a book and reading it from cover to cover. So, I shall show you how to implement this. Before that, I'll go ahead and create an empty file using the touch command. Um so now that a file has been created I will go ahead and open this file using the cat command. So in order to copy some content into the file here's what we will do. I shall use the echo command within brackets I will paste the content which I want. So let me go ahead and do that. Then we shall follow up that by the file name in which we are going to copy the content into. So let's move ahead and view the file again using the cat command. So this will show you the entire content of the file 1.txt in the terminal. As you can see here, we shall now move on to the next command which is the less command. Sometimes a file is just too large to read it all at once. So in those cases, less is your friend. So it allows you to scroll through the file similar to flipping through a textbook. So I'll go ahead and show you how to implement less. So we use the less command followed by the name of the file. So with less you can scroll up and down through the content using arrow keys or spacebar to go down a page. About the head command. So if you want to see the first few lines of a file use head. So it shows you at the top of the file like reading the introduction of a book. So as you can see I've used the head command followed by the file name. So by default head shows you the first 10 lines of a file. So if you want to change that number you can use the n option. So I'll go ahead and show you how it's done. So since I've attached a paragraph here, it doesn't really execute the command. So I will go ahead and add some new content into the file. So I will do that as follows. So now let's go ahead and try executing it with a command. So I shall be using the first five lines and then yeah. So as you can see you can see the first five lines. Now let's move on to the next command. Just like head but for the last few lines of a file. So this is useful if you want to see the most recent content in a log file or a document. So I'll use the tail command followed by the name of [clears throat] the file. So as you can see you can see the last few lines in the file. So you can also use the f option to follow a file in real time. So this is especially useful for logs. Now we shall move on to permissions and ownership. So is built with strong security features and one of the most important aspects is controlling who can access and modify. So this is where file permissions and ownerships come into play. This is the chod command. So this command changes the permissions of a file or directory. So it's like deciding who can read, write or execute a file. On using this command on the file, it gives the owner full access which is read, write and execute as well as read, execute access to everybody else. You can also use symbolic notation instead of numbers. I'll go ahead and show you that plus x i. Let's move on to the next command which is chon. So the ch on command changes the owner and the group of a file. So it's like transferring ownership of a document to somebody else. So I'll go ahead and show you an example. So I'll use the ch own command followed by the user and the group and the name of the file. So this changes the owner of the file to the user and group. Now let's move on to getting started with shell scripts. So imagine you want your computer to do something for you like sending an email, backing up files, or even checking the weather. So instead of manually doing each task every time, we can write a shell script to automate it. So a shell script is simply a file that contains a series of commands that the shell can execute. So let's start by creating your first shell script, a simple one that greets you. So for that, you will have to open your terminal and use the touch command to create a new file called greeting.sh. So I'll go ahead and do that using the touch command. And the name of the file will be greeting.sh. So as you can see a file has been created. Now let's learn to open the file. So use a text editor like nano or vim to open the script file. Let's use nano for simplicity. So I'll go ahead and show that to you. nano followed by greeting.sh. So as you can see we are inside the editor. Now if you want to exit from the file you can just do ctrl x. That has been done. Now let's write our first script inside the file. So you will have to go ahead and type the following. So now that this has been typed into the editor, you will finally press enter. So before that we will have to save the file. After you type Ctrl X, you will get an option here where they're asking you to save modified buffer. You will go ahead and press Y. Now in order to escape the editor, type Ctrl X. So the bin bash part of the top file is known as the shebang. So it tells the system to use the bash shell to execute the script. So echo is a command that prints the text inside the quotation marks to the terminal. So regarding saving and closing the file, once you've written the script, save and close the editor. So in nano you're supposed to presstrl + x and then press y to confirm saving and finally press enter. This has been shown to you already. We shall now learn about executing bash scripts. So you've just written a simple script, but now you need to run it. So in order to do so, you need to tell your computer to execute the script. So before running the script, you need to give it permissions to execute. So you can do this with the help of the chmod command. So I'll go ahead and do that now. ch + x followed by the name of the file. So now that your script is executable, it's time to run it. So to execute it, use the following command, which is dot / followed by the name of the file. So when you run this your terminal will display hello welcome to shell scripting as it's shown here. So if the terminal says permission denied ensure that you've executed the permissions with the chod plus x. I shall now brief you on the role of shebang. So the shebang is a critical part of every shell script. So it's a special line that tells your system how to interpret the script. So let's break it down. So now the hash part along with the exclamation mark is called the shebang. So it's a special character sequence that indicates that the path to the interpreter is used to run the script. Specifies that the script should be executed using the bash shell. So bash is a popular shell in the Linux system and it's used to run most of the shell scripts. So the shebang is necessary because it allows you to run your script by simply typing dot and slash and there is no need to specify the interpreter each time. In programming, comments are a way to add notes or explanations in your code without affecting its execution. So comments are like little reminders you leave for yourself in your code, making it easier for you to understand it later. In bash, comments start with the hash symbol. Anything written after hash is going to be ignored by the system when executing the script. So it's just for humans to read. Speaking about single line comments, any line starting with a hash is a comment. So why should you be using comments? If someone else is reading your script or even if you're months later, comments can help you explain what each part of the script does. It also helps with debugging. So you can comment out parts of the script to temporarily disable them while testing other sections. Organizing your code. Large scripts can become messy. So use comments to divide the script into sections making it more readable. With these basics, you're now ready to start writing and executing simple shell scripts that can automate tasks on your system. We shall now learn to define and use variables. So in programming, variables are like containers that hold information. So in shell scripting variables store values that can be used throughout the script. For instance, imagine you have a box labeled name and inside that box you place your actual name. So that's essentially what variables do. They store data that you can use whenever needed in bash. Defining a variable is simple. So I will show you how to do it. You type name followed by the name that you want to enter. I shall use John over here. Make sure that there is no space in between the equal to sign and the double quotes. So here name is the variable and John is the value stored in that variable. Now we shall move on to how to use a variable. So in order to access the value stored in the variable, use the dollar symbol before the variable name. So I shall go ahead and show you how to do it. For doing that you will have to use the echo keyword followed by hello dollar sign and the name. So as you can see we've got hello John as the output. So as I said when you run the script the shell replaces dollar name with the actual value which is John. So you see the greeting hello John printed on the terminal. We shall now learn changing the value of a variable. So variables can be updated just like changing the contents of a box. You can reassign a new value to the same variable. So I shall go ahead and replace the name with the name Alice. Make sure that there's no space between the double quotations as well as following the name. Shall use the echo command again followed by hello. So as you can see the output has been updated to hello Alice. So this flexibility is useful for handling dynamic data during script execution. Like I said you should make sure that there are no spaces around the equal to sign. So when defining a variable in bash ensure that there are no spaces around the equal to sign. For example, this will throw an error. So let me go ahead and leave a space between the equal to sign. Yeah. So as you can see it says command name not found. We shall now move on to reading input from users. So sometimes you want your script to interact with the user asking for input and using that input in real time. So this is where the read command comes in handy. The read command allows you to capture user input and store it in a variable. So I shall now show you how to use read in order to get an input. So go ahead and use the echo command. and within the brackets what what is your we shall now type read name followed by the echo command hello dollar sign the name yeah so in this example the script will prompt the user with what is your name and wait for their input so once the user enters their name it stores it in the name variable and greets them with their name so I will go ahead and show it to you so what is your name I shall go ahead and type Alice it stores the name in the variable and greets them with the name Alice. We shall now move on to multiple inputs. You can read multiple values at once and assign them to different variables. So as you can see I have used the echo command followed by enter your first name and your last name. Then I use the read command followed by the first name last name. So for example if the user types John do it assigns John to the first name and do to the last name. So I'll go ahead and show you this. So here it's asking me to enter the first and the last name. So I shall go ahead and type John. So as you can see I've received the output as hello followed by the first name along with the last name. You can also give a variable default value if the user doesn't input anything. So I've shown the code here as follows. So here you can see the output. The code asks you to enter your favorite color. So I'll go ahead and type blue. And then I can see the output. Your favorite color is blue. Let's move on to environment versus userdefined variables. Now let's differentiate between two types of variables that you will encounter in shell scripting. They are userdefined variables and environment variables. Here's what is userdefined variables. So these are variables that you can create in your script to store specific values. They are used within the script and do not persist once the script finishes running. So I'll go ahead and show you an example. I shall type user is equal to John. also have to make sure that there's no space between the equal to. Then use the echo command and type hello followed by dollar sign and the user. So in this case user is a userdefined variable. It only exists during the scripts execution. We shall now move on to environment variable. So these are systemwide variables that are set by the system or by the user to control the behavior of the shell or operating system. So environment variables are used for systemwide settings like the location of important files or directories. I'll go ahead and show you an example. For example, the home [snorts] directory. So home indicates the home directory of the current user. Then we have path. So path is a list of directories where executable programs are located. So in order to see all of the environment variables in your system, use the print end command. So I'll go ahead and show you that. Print n. So as I said you can see all of the environment variables in the system. We shall now move on to setting environment variables. So you can create environment variables temporarily for the duration of the session by using the export command. For example, user to. So this sets the variable user as an environment variable making it easily accessible to other processes. So here are the differences between an environment and a userdefined variable. So userdefined variables are only available within the script or a session while environment variables can be accessed by any process running on your system. Environment variables can be persistent across different sessions if set in specific files while userdefined variables disappear after the script finishes. You can access environment variables just like userdefined variables by using the dollar symbol. I'll go ahead and show that to you. So we use the echo command again followed by your home. So this prints the current user's home directory like home followed by the user. You can modify an environment variable within your script by making the export command. But to make permanent changes, you would need to add the export command to configuration files like dobash rc or bash profile. You have learned to use variables to store and manipulate data in your scripts, interact with users for inputs and distinguish between userdefined and environment variables. So these foundational concepts are crucial as we move into more complex shell scripting tasks. We shall now move on to conditions and decision-m. Conditions allow your script to make decisions based on certain criteria just like how you make decisions in real life. For example, if it is raining, you might take an umbrella. Conditions allow your script to make decisions based on certain criteria just like how you make decisions in real life. For example, if it's raining, you might take an umbrella. Otherwise, you would leave it at home. Shell scripting uses if else statements to make similar decisions. An if statement checks a condition and based on whether it's true or false, it executes different code. I'll go ahead and show you an if else syntax. So, as you can see, I've typed out the code here. I shall now tell you how this works. So, the condition dollar weather is equal to equal to rain checks if the value of the variable weather is equal to rain. So, if this condition is true, the script will output take an umbrella. So if the condition is false, the script will output no umbrella needed. So as you can see the output here is no umbrella needed. We shall now move on to conditions and decision making. Starting off with we have if else statements. So conditions allow your script to make decisions based on certain criteria. Just like how you make decisions in real life. So for example, if it's raining, you might take an umbrella otherwise you will leave it at home. So shell scripting uses if else statements to make similar decisions. And if statement checks a condition and based on whether it's true or false, it executes different code. So I'll go ahead and show you a basic if else syntax. So this is the code for the same. I shall now tell you how this works. So the condition weather is equal to rain checks if the value of the variable weather is equal to rain. So if the condition is true, the script will output take an umbrella. And if the condition is false, the script will output no umbrella needed. So we'll move on to an example with user input. So let's say we want to ask a user for their age and check if they are eligible to vote. So I'll go ahead and type the code for that. So as you can see I've typed this code over here. The condition age g 18 checks if the user's age is greater than or equal to 18. So the GE here stands for greater than or equal. So based on the user's input, the script can either print you can vote or sorry you can't vote yet. So let's go ahead and execute this. Let's just say I enter my age as 23. It gives us the output of you can vote. So let's go ahead and execute the same code again. [snorts] So if I enter my age as let's say 16 here the output is sorry you can't vote yet. We shall now move on to l if ladder. So when you have multiple conditions to check instead of stacking multiple if else statements you can use l if which stands for else if. So this lets you check several conditions one after another. So I'll go ahead and show you a basic LF syntax. So I'll go ahead and type in the code as follows. So this example checks three conditions. Firstly, if the age is 18 or more, it prints you are an adult. So if the age is between 13 and 17, it prints you're a teenager. Finally, if the age is less than 13, it prints you are a child. So here's how LF works. So it lets you check multiple conditions one by one and it stops once a true condition is found. If none of the conditions are true, then the else block is executed. So I'll go ahead and execute that for you. We shall now move on to test and syntax. Test command is used in shell scripting to evaluate conditions. So it's often written as within square brackets condition which is shorthand for test condition. This command helps you compare values and check for various conditions like file existence, strings and numbers. Using test for conditions is as follows. So here f checks if the file.txt txt is a regular file. If it exists, it prints file exists. So here, as you can see, the output is file does not exist. We shall now move on to checking for directories. You can also check for directories using the d command. The code is as follows here. And here the output is directory does not exist. Moving on, we have comparison operators which are strings, integers, and files. To make effective decisions in your scripts, you will often need to compare values. Bash provides several operators for comparing strings, integers and files. So we shall now talk about string comparison. Firstly we have equality. It checks if two strings are equal. Secondly we have inequality. So it checks if two strings are not equal. So I'll show you a small example. So we shall go ahead and type name is equal to Alice followed by an if statement where if dollar name is equal to equal to. So as you can see the output is hello Alice greater than or equal to less than or equal to. So I'll go ahead and show you an example for the same. So here the output is 10 is less than 20. We can also do file comparison. You can also test file properties. For example, there's existence where E checks if the file exists. Then there's regular file where F checks if it's a regular file. Then we have directory where D checks if it's a directory. We have writable where W checks if the file is writable. So I will show you an example which uses all of the above commands. So I've gone ahead and executed the code here. So I'll give you a small summary of the file operators we used. So E stands for exists where F stands for regular file, D stands for directory, R stands for readable and W stands for writable. Lastly X stands for executable. So this particular chapter covered the key conditional and comparison commands in shell scripting. So these tools allow you to control the flow of your scripts and make decisions based on dynamic outputs, file states and conditions that you define. We shall now move on to the next chapter which is on loops in shell scripting. This includes for, while and until loops. So in shell scripting loops help automate repetitive tasks, save time and effort. So let's explore three types of loops for, while and until. Firstly, we have the for loop. So the for loop is one of the most commonly used loops. So it helps you repeat a set of commands for a specific number of times or over a list of items. So the simplest way to use a for loop is by specifying a range of values. So I'll go ahead and show you an example for the same. Gone ahead and executed the code. So as you can see the loop printed numbers from 1 to 5. So it's like telling the script repeat the following command five times once for each number from 1 to 5. We shall now move on to looping over directories. So you can use a for loop to process files in a directory. So I'll show you an example for the same. So for file in star txt along with the do command. So this will loop through all of the text files in the current directory and print their names as shown in the output. We shall now move on to the y loop. So the y loop is used when you want to repeat a set of commands as long as a specific condition is true. So it continues executing as long as the condition evaluates to be true. So let's say we want to print numbers till we reach the number five. Let me go ahead and show you the code for the same. So here we've used count as well as while. So the loop keeps running until the count reaches five. So it starts at one, prints it and then increments it by one each time. So you can see the same in the output. We shall now move on to until loop. So an until loop works similarly to a while loop, but it continues until a condition becomes true rather than while a condition is true. So in other words, it's the opposite of a while loop. So let's use until to print the numbers from 1 to 5. So the code here, it's as follows. So this is a simple example which uses the loop. So as you can see the loop will continue running until the count is greater than five. So the key difference between while and until is how the condition is evaluated. So the until loop runs as long as a condition is false. We shall now move on to looping through arrays and strings. So sometimes you might need to loop through a list of items or the elements in an array. So in bash arrays can hold multiple values and looping through them allows you to process them individually. So you can use the for loop to iterate through each element of an array. So I'll go ahead and show you a simple example. So here we have three fruits which is apple, banana and cherry. So as you can see in this example, fruits is an array containing three items. So the for loop iterates over each item in the array and prints it. So as you can see the final output is I like apples, I like bananas and I like cherries. We shall now move on to looping through a string. So you can loop through a string character by character like scanning a sentence for specific words. for example. So as you can see the fold w1 command breaks the word into individual characters and the for loop prints each letter in a new line. So as you can see in this example the characters in the word hello have been printed in five different lines. So H is printed in one line, E is printed in the second line, L in the third, the other L in the fourth and O in the fifth. So we shall now move on to break and continue statements. Why loops allow us to repeat tasks? Sometimes we need to break out of the loop or skip certain iterations. So this is where the break and continue commands come in. The command is used to exit a loop prematurely no matter where you are in the iteration. So I'll prove it to you with the help of an example loop. The script will print numbers from 1 to 4. So when it reaches five, it will print breaking the loop at five and then exit the loop immediately. Moving on to the continue statement. The continue command is used to skip the current iteration of the loop and move to the next one. So here when the i equals 3 the script will print skipping number three and move on to the next iteration skipping the echo for three. So this is seen in the example as shown. So let's move on to a real world looping scenario. Let's take a real world example where you need to check if files are backed up correctly. So you want to loop through a list of files check their size and if any file is too large let's say above 100 MB you will log it. So here's an example scenario. So over here stat c and dollar file retrieves the size of each file in the bytes. So if the file size is greater than 100 MB it logs a warning in large files.log. So if the file is within the size limit it prints a confirmation. We shall now move on to the next chapter which is functions and modular scripting. So in shell scripting functions are like small reusable blocks of code that perform a specific task. You can write a function once and then call it multiple times in your script, making your code more organized and easier to manage. To define a function in bash, we use the following syntax. So as you can see on my screen, this is the syntax you use to define a function in bash. So I'll go ahead and execute an example for the same. So this is a function that prints a greeting. Next, we will move on to calling the function. So after defining the function, you can call it by simply writing its name followed by parenthesis. So as you can see here the output is hello welcome to shell scripting. Now we shall speak about functions which are great for avoiding repetition. For example, if you wanted to print a greeting message multiple times in different places, you could call the greet function instead of repeating the echo command. Next we shall move on to function parameters and return values. In additions to performing tasks, functions can accept input and return values making them even more powerful. So this is like giving the function some data to work with and getting the result back. Now speaking about function parameters, when calling a function, you can pass data into it as parameters. So inside the function, you can access these parameters using special variables like dollars one, dollars 2 and so on where dollars one is the first argument and dollar two is the second and so on. So I'll show you a small example for the same. So as you can see the output here is hello Alice. So in this case Alice is passed as the first argument to the greet function. So the dollar one inside the function represents Alice. So the output is hello Alice. Now we shall talk about using multiple parameters. So you can pass multiple arguments into a function and then access them using dollar one and dollar two. So I'll go ahead and show you an example. So I have picked two names for the same which is Alice and Johnson. Let me go and execute this. Yeah. So as you can see we've received the output as hello Alice Johnson. Moving on to returning values from functions. So in bash functions don't return values like other programming languages. However, you can use echo to output a result and capture it when calling the function. So in this example, the add function calculates the sum of two numbers and outputs the result. So we capture this result in the variable result using dollars and parenthesis and then print it using source and external script files. So as your scripts grow, you will want to break them into smaller, more manageable pieces. So this is where source and external scripting files come into play. Instead of writing all of your functions and code into a single file, you can organize them into separate files and source them into your main script. I shall now show you how to use source to include external files. So the source command allows you to include and execute code from an external file. This is useful for reusing functions and variables across different scripts. For example, first you create a separate file called functions.sh with some functions. Now that that's done in your main script, use source to include the functions.sh file. So as you can see, we've gotten the output as hello Alice. When you run main script.sh, it will source functions.sh and execute the gin. So why do you have to use source? You use it for code reusability where you can write common functions in one file and source them in multiple scripts. It helps to organize your code into smaller files making it easier to maintain. External script execution. You can also execute an external script as a standalone program. To do this, ensure that the script is executable and run it like this. So, as you can see, this has been executed. Next, we will move on to file handling and text processing. So, in shell scripting, redirects are used to control where the output of a command goes and where the input comes from. Think of them as pipelines that direct the flow of data between commands and files. So, let's speak about redirecting output. So the less than symbol is used to redirect the output of a command to a file overriding any existing content. So for example, this particular symbol displayed on my screen, the output to an existing file without overwriting its content. So I'll show you a small example for the same. As you can see, I've executed the code. So this will add welcome back to the end of the greeting.txt leaving the previous content intact. We shall now speak about redirecting input. So the greater than symbol is used to rewrite input from a file to a command like feeding a file into a program. So for example, so it says that there's no such file or directory. So let me go ahead and just create a new file called as names. So I think this should do the job. Yeah. So this will read the contents of names.txt and feed it into the sort command to display the sorted contents. Now speaking about redirecting error outputs. So errors are typically displayed in the terminal but with this command you can redirect error messages to a file. So I'll show you this with an example. So if the ls command fails because the directory doesn't exist the error will be written to an error log instead of being shown in the terminal. Let's move ahead and speak about pipes and chaining commands. So pipes allow you to send the output of one command directly into the input of another command. So this is extremely useful when you want to combine multiple commands into a single workflow. A pipe connects the output of one command into the input of an other like linking two pipes together. So here's a small example for the same. Yeah. So this will list the files in a long format and then use gre to filter and show only the files containing txt in their names. Let's now speak about chaining multiple commands. You can chain multiple commands together using pipes them and then view the top five with head. These are the files which have been displayed. The part here lists the files. here sorts the list of the files and shows the first five files in the sorted list. So I shall now show you how to use these two commands is used to run the second command only if the first one succeeds. Used to run the second command only if the first one fails. In other words, it returns false. After executing this command, the attempt was made to create a folder and depending on whether it succeeds or fails, it will print the corresponding message. So this was created successfully. So there are no issues. We shall now speak about some basics which are GP, set and AWK. So these are powerful tools for searching, modifying and processing text and files. So let's break them down. Let's talk about the GP command which is also the global regular expression print. So GP is used to search for patterns within text. Think of it like a search function for your files. So it says that there is no filet txt. So I'll go ahead and create one. Now let's go ahead and create one. call file txt. Yeah. Now we shall go and execute the correct command. Yeah. So this will search for the word hello in the file.txt and print all the lines that contain it. So let's go and add some content within the file.xt. So let's just add hello to shell scripting. And this is contained in file. Yeah. So this has been done. Let's now go ahead and execute the GP command. I'm assuming that the lines contained in file.txt is a single line. So that's the reason why it's not able to print all the lines which contain the word hello. So we shall now move on to case insensitive search. So on executing the command, this is the output we get. So it will match hello in all smalls or even if it's in all caps. So this will search for the word error in all of the log files in the current directory. So let me try and show that. So echo error. I'll just go ahead and change the sentence within the file of file. Yeah. So let's go ahead and execute this command again. Yeah. So as you can see when the command was executed it searched for the word error in all of the log files in the correct directory. So this is inclusive of the text file. We shall now move on to the set command which is also called as the stream editor. So set is used to perform basic text transformations on an input stream which is a file or an input provided by a pipeline. For example, you can replace text. I'll go ahead and show it to you. File. So as you can see new text in each line. Let's move on to in place editing which modifies the file directly. Now we shall learn to delete lines. So this particular command here is supposed to delete the second line from file.xt. So as you can see the second line has been deleted and we're left with hello welcome to shell scripting. Then we have AWK which is pattern scanning and processing language. So AWK is a powerful tool for text processing especially useful when dealing with columns of data. So for example if you want to print specific columns this is the line of code that you're supposed to be executing. Yeah. So as you can see it prints the first and third columns of each line in file.txt. So as you can see the word hello is printed and the word is has been printed at the bottom. Now speaking of values in a column so it sums up the values in the second column of file.txt. So as you can see you have obtained the sum of the values in the second column of file.tx. Now we shall speak about filter based on condition. So this is the code which we're executing for filter based on condition. So as you can see this prints the first and the second columns but only if the value in the second column is greater than 100. Let's now move on to logging and appending to logs. So log files are crucial for tracking events especially for troubleshooting and monitoring processes. So bash scripts often include logging mechanisms to capture the scripts activity and potential errors. If you want to redirect output to a log file, you can log the output of a script to a file using redirection. So this is the line of code for the same script.log. Yeah. So let me go ahead and run this. So this will create a file called script.log with the text script started. Now if you want to append to log files to keep adding new log entries without