Linux Full Course - 10 Hours [2026] | Linux Tutorial For Beginners | Linux Training | Edureka Live

Key Takeaways

Hello everyone and welcome to the Linux full course. In this course, you will start with the fundamentals of Linux exploring the different shells and learning how to set up Linux using virtual box. We will then move into hands-on commands on Ubuntu and understand how Linux is used in DevOps workflows. We will cover the Linux file system, package management, and even dive into administration tasks like configuring a DNS server. You will also learn shell scripting and discover tools like shell GPT to enhance productivity. So before wrapping up, we will cover Linux interview question and answers to help you prepare for real world opportunities. So before we begin, please like, share and subscribe to Edureka's YouTube channel and hit the bell icon to stay updated on the latest content from Edureka. Also do check out Edureka's DevOps certification training course with Genai designed to equip learners with the skills to master AI integrated DevOps across the entire software delivery life cycle. And through hands-on learning, you will gain expertise in building intelligent, automated, and secure CI/CD pipelines. This comprehensive course covers essential tools like Git, Genkins, Terraform, Enible, Docker, Kubernetes and monitoring frameworks while also integrating AIdriven solutions for code generation, testing and analytics. So do check out the course link given in the description box below. And now let us get started with our first topic that is fundamentals of Linux. >> Why did Linux become popular? Well uh before I talk about uh you know why they became popular let's look at the birth of Linux how things started off okay so back in 1969 there was this person called uh you know in fact there were two people Dennis and Ken Thompson right so they were working in the AT&T Bell Labs and what they did was they created this C programming right so we're all aware of programming right so we're all aware of these basic programming languages right so C is one of the most basic and one of the most effective and the root of all the other programming languages so that was C and it was them that developed C and the Unix operating system. So that was what happened in 1969. Okay. And then in the decade that followed. Okay. So basically in the 1970s people started developing or contributing to the development of these two things. Okay. So they started contributing to the development of the C programming language and the Unix operating system. So in our session we'll discuss more on Unix operating system and uh since it's about Linux, right? So Unix is basically the mother of Linux because uh Linux is based on the Unix operating system. Okay, I'll tell you how that's the case uh in some more time but that's why we are starting off with Unix operating system. Okay, so I'm not going to cover about uh C and getting back to our slides. So it says growth of Unix because of open-source collaboration and there was commercial sale of Unix. Now what this meant is that you know the product that Dennis Richie and Ken Thompson created right that those were you know something really attractive there were some amazing software and operating systems that would you know power machines and computers. Now what this meant was uh you know they had to be developed to become even better right. So they made it open source. It was uh when we say open source it means that it was freely available to use uh by anyone. So anybody any person any scientist or uh any engineer or anybody could just get access to the source code and start improving that source code and if they feel that they have improved the software in any way then they can just uh you know give that code back to uh the developers. So basically it was all about collaborated development. So that's what happened with Unix operating systems in the 70s. Many hippies, scientists, they all collaborated together, wrote their own code, their own version of Unix operating system and contributed to the development of Unix operating system. And uh since AT&T, they were the uh ones who built Unix or the ones that were responsible for founding Unix. They were the ones that gained a lot of benefit. They got help from other people for uh you know developing the operating system. And what they did in turn was they made it a business, right? So they made money out of that by you know starting commercial sale of Unix and uh this was something that did not go down well with many people and this did not go down well with the other developers and scientists because uh it was their effort which contributed to the growth of Unix but however they are not getting any benefits of you know Unix because AD&T that was making money out of somebody else's work so that's what happened in the 1970s okay and then came the 1980s which was a little more different so instead of you know buying you know Unix from AT&T and uh you know having two different versions of Unix. One was a free BSD and the other one was the paid AT&T version of Unix. So instead of going to go for them, companies started developing their own Unix. So IBM came up with their own uh Unix version called the AIX. Solaris came up with their own version called the Sun operating system and HP came up with their own version of Unix called HPUX. So there are other versions also like POSX and all these things. Now since there were many versions right many flavors and many dialects of the same Unix operating system it was becoming a little problematic because each of the dialects would be a little different. So the IBM's Unix would be different from HP's Unix and Solaris's Unix or it would be different from POSIX. Okay. So each of them would be different but however they're all based on the same thing. So it was unnecessary you know confusion there with so many versions of Unix. So that is when this person called Richard Stallman came up with something called as the GNU project. Okay. So I told you earlier that uh Linux is just a kernel and not an operating system on its own. So what this person did was you know he came up with something called as a free software movement. So he wanted something like you know back in the 70s when everyone could collaborate and work on the same one single operating system like that. He tried to bring back that era and this free software movement of his idea led to the GNU project. So the GNU project was all about people being able to access an operating system for free and you know developing that operating system. So that's what uh this led to and uh that's what we call even today right so GNU is basically the operating system and the uh Linux is the kernel that powers the operating system. So a combination of these two is what results in one of the distributions of Linux. So we have multiple distributions like Ubuntu CentOS Redat Debian Fedora all these things. So all these things are a flavors a combination of one of the operating systems and the uh you know Linux kernel. Okay. So that's what they are. So this is what happened in the 1980s and then you know mid to late 1980s was when Richard Stallman came into the picture and he came up with the GU project where people could develop uh you know and use free operating system. So that's what happened here and the event that happened after this is what is a result of today's world. Okay. So after that then in the 1990s so probably 1991 or 1992 that was when this person called Lenn Star Tarz who was still back in college at that time he put the Linux kernel source code online so he was trying to use the postix version with one hardware called 386 and he thought that it's compatible only with that hardware and so he put the source code online for anyone to use and later they found out that it could be used with the GNU and that's when the whole uh thing gained popularity so that's when we uh you know came up with something called as the Linux plus GNU this whole term of having a kernel plus this operating system and getting them to work together. So that's what happened here. All right. So guys uh that's how Linux was born. Okay. Now without wasting any more time let me go to the next slide and talk about the various distributions of Linux. So I told you that there are many versions like Ubuntu CentOS and all. So let's talk about those. And uh when we talk about distributions, the most important and the most famous ones are those of Red Hat Enterprise, Linux, Fedora and Debian. Okay. So these three are primarily different companies and enterprises. Well, Debian is basically not one company. It's kind of you know, let's say a group of developers developing this uh version of Linux. Okay, this version of Linux and the Ubuntu version. So that is what Debian is. And the Red Hat is basically an enterprise. It's a company that is commercially selling the Linux distribution. Okay. And it's probably the most used and the most popular of them all. Uh why? Because they are very stable. They are very reliable. And as it's written here, servers and workstations, right? So it's the preferred Linux distribution for servers and workstations. The Red Hat Enterprise Linux. So they have a free version. So that's called the uh CentOS. And uh today's demonstration, I'll be showing it to you on CentOS only. Okay. So they have that and they have various other distributions. In fact, even Fedora, right, that which we are going to talk about next. Even Fedora is a company that's funded by Red Hat itself. So it's again one of the variations of Red Hat and Fedora has its own set of you know distributions under it and that's about the Federa distribution. Then comes the Debian. So this again I spoke about Debian. So Debian is you know the Linux distribution that is developed with the help of many developers. So this is not developed for commercial purpose. It's basically free and open source software and anybody with the skills can start contributing to this software. And you have many other distributions. Okay. So these are among the important and the commercial ones. And if you're talking about some of the free distributions which people can use then they are Ubuntu, Linux Mint, CentOS, OpenS Gen 2 and many more. Okay. So there are almost 100 Linux distributions today and you can use any of them. you know if you're getting started with Linux then I would suggest you to either start off with Ubuntu or CentOS because uh CentOS is you know something that's really reliable and that's really fast okay and Ubuntu is the most popular Linux distribution out there okay so I read somewhere that Ubuntu is the third most used operating system okay so that's what Ubuntu is all about of course it's not as fast as CentOS but still Ubuntu is you know a very popular and very handy tool and Linux Mint is the other distribution which can be used for playing movies and listening to music because this gives you more of a windows like interface. So that's what Linux Mint is. So we have various distributions like this. You can start off with one of these distributions mentioned here. You can either go for the Red Hat Enterprise Linux or the Fedora or the Debian or the other operating systems which are based on them. Okay. So the CentOS here it is based on Red Hat Enterprise Linux. Okay. So uh the RE right we call them RE. So they have the free version that you know they provide for enterprise users are is that of CentOS and Fedora again for that matter of fact you know they have multiple distributions under them under their name and Debian are the people who are the founders of Ubuntu. Okay so Ubuntu is a distribution that is based on Debian and since Ubuntu is so popular there are different versions of Ubuntu itself right there are other distributions like X Ubuntu or Ed Ubuntu all these things and they are the other you know versions of Ubuntu. So that's about the uh different Linux distributions and you guys can probably you know if you're newcomers then I would suggest you to go for either Ubuntu or CentOS like I said earlier. All right great. So let me go to the next slide then. Okay so now we are in this slide and uh let's talk about the features of Linux here. So the Linux features you know when we say features it's basically those compared to the other operating systems compared to Windows and compared to Mac. Okay. Okay, so compared to them how does Linux perform and you know what are the benefits with Linux and uh first of all we have uh this feature of uh you know the updates being very easy to be performed. If you have any software in your operating system or if it's the operating system itself which you want to update then it's really easy with Linux it's uh just going to be one command that you need to run and you know you can run that command from the terminal. Okay, for those guys who don't know what a terminal is. So let me just open my uh Linux version and show you what a terminal is. Okay. So this is my uh CentOS version of Linux. All right. And then you have different options here. Right. So the terminal that you see here, this is what I was talking about. So when you open the terminal, there's another window that opens. Okay. Now this is the command line interface. So when I say command line interface, this is where I can uh put in my commands and I can get my uh you know software or my kernel to listen to those commands and perform actions by creating a process for uh those commands. So the whole benefit of Linux is this CLI because the CLI is really helpful. If you're going for Windows or something, you have a very good GUI. All right. So even in Linux, you have a GUI. So let me show you the GUI aspect. So similar to Windows, you can just go to the computer and you can go to file system. You can open various other folders and directories. So you have multiple directories and folders here, right? So I mean directories are basically folders. Folders is what you call in Windows and here you call them directories. So I can go into any of these uh you know directories and I can close them like this. I can access any of these directories. I can access any software or anything that's installed anywhere. So Linux basically provides a GUI too. Okay. But the thing with Linux is that you also have a terminal right. This terminal is basically a command line interface where you can you know put in your uh commands and you can get the software to behave the way you want to. you can run certain commands, you can install software, you can run uh programs, you can run codes. So that's what the advantage with the uh CLI is and this is basically the reason why uh it's very popular among all these software developers. Okay, so I told you earlier that software developers favorite tool, right? Linux. So that's because Linux is the free version of Unix and it's also you know possible to develop and create so many programs. So that's the thing with Linux. So that's why it's so popular. So back in the slides I told you that it was very easy to perform updates right. So those updates can be you know easily performed by just running a few commands here. You know by uh writing one single command I can update a particular software. Supposing I have Java installed in my uh system then I can just write a command for updating that. I can just say sudo yum update and the uh package name. If it's Java I can just put the Java version. if it's uh any other language or if it's any other software then I can put that software name over here and update the uh application. So that's how simple and that's how easy uh you know it is to update softwares over here. So I was talking about uh this aspect. So let me go back to the slides and talk about the other features. Okay. So that was how updates can be easily performed. And then another feature is that the software is free. You don't have to pay for uh Linux. So because Windows of course you all know that Windows is paid. you can't, you know, have a pirated version. If you're caught having a pirated version, you'll be fined. Of course, home, you know, desktop users and home users don't really have that problem because there are no routine checks. But companies cannot use uh the pirated version of Windows because if there are audits, they can come and seize the computers and put a heavy fine on the company. So that's what we say when the free software licensing is there in Linux because you don't have to have any license. You can just uh you know get all the folks in your company to work on Linux for free. So that's the free software licensing aspect and then you have the access to source code right so when we say access to source code I told you that back in the 700s people could just collaborate together and develop the operating system so that is what I'm talking about here so the entire the source code for uh running this OS the basically the Ubuntu or the CentOS source code is available to you and you can customize it and you can uh you know change it the way you want you can make it behave the way you want to and uh if it's a really good visual that you've added Then you can also share your discoveries and your uh you know features with other people with other fellow developers. You can do all these things. So you have complete uh you know access to the source code and you have complete freedom with what your OS can do and how it behaves. But the same thing cannot be set for Windows right. So Windows you cannot change it completely. you don't get access to the source code at all and you can't change all the features the way you want to because that's proprietary tool and it's programmed to behave in one way and if you try changing too many things then your uh you know windows will uh report so that's what is going to happen so that's about the uh access to source code feature and then we have another feature that is multiple distributions so I spoke about the different distributions in the previous slide so the basic distributions are those of Red Hat Debian or Fedora Right. So you have various versions of them itself. You have different flavors in the Red Hat and you have different ones in the Debian and again Federra has a lot of other distributions further. Many distributions are based on them. So you have so many options and if you don't like one of the distributions then you can work on another distribution right. So if you don't like CentOS is because uh you know you don't get support for everything then you can use Ubuntu. Okay. It is the most popular operating system and it has support for almost every application and every software. So you can use that but if you're unhappy with the speed of Ubuntu then you can probably switch to CentOS. So you have all that flexibility and all this flexibility without any cost. Okay. Uh no cost with respect to uh energy or having to learn something new because all these are Linux. At the end of the day the commands will be the same almost 98% of commands will be the same. There are just going to be minor differences in the commands that will be executed in uh the different uh distributions. But yeah 98% of them would be the same. You won't have a tough transition time also. you'll have uh you know you can gain so many benefits by using Linux and the last but not the least right so this feature is probably the highlight of Linux so it says better malware protection so when we say better malware protection we say that it's the ultimate okay in Windows if you people would have noticed that you need an antivirus because uh it's prone to viruses and attacks and bugs and all these things so people can easily hack into your system right so the same thing cannot uh you know happen With Linux, you don't need an antivirus at all. Linux is completely antivirus free. Okay, 100% you don't need an antivirus. And in fact, you don't even have an antivirus. But of course, it doesn't mean that, you know, it's completely secure. Also, uh security is something that's really good, but it's still developing in Linux, but it's definitely better than Windows, right? So, you can be sure that no one's going to hack your system so easily. So, that's what uh Linux is all about. So, guys, that brings us to the end of this slide of Linux features, okay? And if you guys have uh you know any doubts even now about Linux and how good Linux is then um that should have been clarified and put to rest by now. Okay. So moving on. So uh enough with the theory now let's straight away get started with our hands-on. Okay. So I'm going to show you how to run commands and how to do various other things with the CentOS operating system. Okay. So the first of all the first part of this hands-on session is going to be about you know an introduction to the terminal and the various commands and the basic commands and how to browse through the uh different uh directories. Okay. So we use commands like pwd clear ls and cd commands. Okay. Now let me go to my cents. Okay. In case I uh forgot to mention it earlier then guys I'm using a VM here. Okay. So I'm running my Windows operating system on my uh laptop and I have a virtual box installed and in the virtual box I've instantiated my uh Linux virtual machine. Okay. So my Linux distribution here is CentOS. Let me just show you another thing. Okay. So this is the virtual box that I was talking about. This is what I'm running in my Windows and I have uh you know multiple options. So I can choose any VM that I want to. So this is the virtual box and all these are the different VMs that we have in my virtual box. So currently I'm running this VM called master. Okay. And later on I'll be turning on even this VM called slave. Now I'll be doing these two for uh showing you how SSH works. So I told you in the agenda slide that I'll you know get two remote machines to access each other right. So for that purpose I need these two VMs and of course both are CentOS and uh yeah as you can see the information it says that 32-bit system I've called it or named it master and this one is named it as slave. So similarly I have the Ubuntu also. So the Ubuntu 64-bit is uh this. So let me just uh turn on the Ubuntu and show you how Ubuntu looks like. Okay. So let's just wait for some time. Okay. So let me just enter the password for the user. And here we are. This is my Ubuntu uh OS, right? So even this is being hosted on the same virtual box. So I am kind of running two different virtual machines at the same time. Okay. So we have options uh to browse the internet and I can open the terminal here. The terminal option is right here in my Ubuntu operating system. Okay. So I just want to show you the uh Ubuntu operating system. So let me just quickly turn it off and uh go back to my uh CentOS and start running a couple of commands. Okay. So I was uh showing you the uh CentOS, right? So login. Okay. So this is my uh terminal and uh first of all the main difference that you people need to understand between Windows and Linux is that in Windows it was you know the storing uh files or folders it was all in drives. Okay. So we had a C drive, we had a D drive, we had uh many more drives like that and we could store ouruh documents all in those folders. Okay. But in Linux it's a little different from how uh Windows works. In Linux we have something called as the root directory. Okay. So we have file system here right. So basically whatever folders or documents or directories you have everything can be accessed from the file system. When I clicked on file system then you would have noticed that I got a forward slasher. Okay so this forward slash basically means root. Okay this means I'm in the root directory and in the root directory every document and every folder is present in this root directory. Okay. Now whether it is uh me storing some kind of uh you know important files or uh MP3s or videos then everything can be accessed from the root. So you can think of this something like a tree hierarchal structure. Okay. So you have one root and all the other branches and all the uh leaves and all those things you can consider them to be the different directories and the files inside. So they can all be accessed from the root. And if you want me to show you where uh one minute. Okay. So now this is your desktop right? So you have the different icons here and each of these icons are for different operation. So you have home and then you have a terminal and you have an LMS. So this is a folder and this is a document. Okay. So read me is a document. So uh what I'm going to do is I'm going to browse to the desktop folder. So from uh root directory if you go to this folder called home right. So under home directory you have other option. You have Edrica and Uzi. Okay. So now if I go to the edurea directory then you have other options of desktop documents downloads uh music and all these things. So if I go to desktop then in this directory you have the files and the different things that are present on my desktop. So LMS was a folder that was present readme this was a file that was present the terminal was present on my desktop so that is available here. So Eclipse IDE is present here. So all this was present on my desktop. So I get the same thing accessed from here. And similarly if you're downloading something from the internet then that will get downloaded to uh this folder the downloads folder right so you have a documents folder similarly you have a videos folder music folder so all these files or folders will be stored in some place right so they will be stored in your uh /home/reka okay if you're downloading them and uh you know if not if it's going to be softares which you're going to install then you can install them in any other uh directory here in fact most of the softwares that you install they'll be by default they'll get installed in this directory in the bin directory right so You have the bin directory. You have the lib directory which will have a list of all the different libraries that the OS would use. And then you have the sbin. You have all these things, right? So they can all be accessed from here. And uh that's about accessing them from the GUI aspect. Okay. And the same thing can be done through the terminal. Okay. Now uh let me go to my terminal and show you how that is done. So this is my uh terminal. Okay. This is the command line interface where I can uh put in my commands and when those commands are executed by the uh kernel or by the shell then uh program will get activated and some kind of uh features will run. All right. Okay guys uh so before I get started let me go back to my slides and show you what are the different basic commands that I want to run first of all. Okay. So as you can see it says L provides a CLA to communicate with the operating system. Right. So that was a terminal that I showed you. The CLI is called the terminal and the CLI is basically it's better for tasks which cannot be performed with the GUI. You know uh I showed you the concept of going to different directories and different folders, right? So it was a little tough. I had to go to go through multiple directories. So through the GUI that's one kind of you know drawback. You'll have to spend a lot of time navigating. But with the uh CLI it's easier. It's just one command and you can access the directory that you want to. That's the advantage with the CLI. Okay. And this is just one basic example that I'm giving you. There are many more advanced concepts and topics which is not very easy to perform with the help of a GUI. So in those places you can just use the CLI to perform those tasks. And the CLA is also much faster in quite a few ways. Okay. So that's the advantage with the CLI and running the commands. Basically the first and foremost you have the pwd. Okay. Now this stands for print working directory. Okay. And what it does is it displays the current working directory of the terminal. Okay. Then there's this forward slash and I told you that the forward slash represents the root directory. Okay. Now let me go to the terminal and show you these two things. So uh right now we are in the home directory. Okay. Now let me just type it down. Let me just put pwd. And when I put pwd it prints the current working directory. Okay. The presently working directory. So that is home/reka. Now uh if I go to the uh computer and file system and home and inside this eda then what you see here right so this is the folder that I'm accessing through my terminal because the present working directory is set to this folder okay now if I want to you know say I want to change the directory it means I want to change from this particular folder to a different folder so there are other options like desktop folder and documents folder right if I want to move to one of these folders then how will I do it using the terminal so I'm just going to show you how That is done. I just want to minimize this a little bit. Yeah, the command for that is cd space the name of the folder. Supposing I want to go to the desktop folder. Then I can just put dsk t o p. All right. And when I put enter, then I'm inside this folder. So earlier you had you saw this option, right? So this represents the directory I'm in. Okay, I was in fact in the home directory and right now I'm in the desktop directory. So desktop is uh the directory inside. And if I want to you know list down the contents in the uh desktop then I can run the ls command. Okay. So when I put ls it basically lists down the different folders and the different files that are present in that directory. Okay. So we have the eclipse we have lms which is a folder. We have readme which is another file. We have all these things. Okay. So let me just go to the desktop folder and show you the same. Okay. We have the terminal. We have the lms which is a folder. And similarly going back to the terminal if I want to enter this Linux folder then I can again uh you know just say cd and space lms. Okay when I do this I'm inside this folder. Okay now if I put ls then I have the list of the folders or documents are present in this lms folder. Okay so uh ls is basically the command to list down the folders or files in that directory and yeah cd space the file name or the directory name would move you to that particular directory. Now that is the same thing that I've discussed in uh this slide here also. Okay. So I spoke about the present working directory which displays the current uh directory that your terminal is uh in and then you have the root directory from where all your directories or folders are marked right. So everything can be accessed from the root directory. So that is this and then you have something called as the echo command. You have the su and the pseudo commands. Okay. Uh these are something a little advanced. So before I show this let me show you the uh clear command. Let me explain the clear command. Okay. Now getting back to my u terminal. When I type clear, the whole uh CLI is cleared, right? My terminal is cleared. So whatever commands I ran previously, those are not present anymore. But what happens is those commands, they don't get deleted or something. They are just scrolled down. So as you can see, they are still present here. So when I scroll down, what happens is, you know, it just makes sure that the other documents or the other commands that I specified earlier, those are all hidden and I'm showed something new. So that's what happens here. Okay. So that is this. Now I told you that you know by giving CD you can go to the directory or the folder that's in the present working directory. Right. But how about going back to the previous directory. So basically from EDA folder to go to desktop we clicked on this and then we entered this folder. Right? So from this directory by clicking on LMS you go to a different directory. Right? So you go in here but using the GUI you can just click on the uh cross mark here and you can exit that directory. But how about you're doing that with the help of the terminal. How will you do it here? So to do that we have the option called CD space two period marks period marks or full stop. So that's what we call right dot. So if you have two dots after CD this means you want to navigate to the previous directory. So we are currently in the LMS and when I give enter I'm back to the desktop folder right the desktop directory. Now again if I uh give the same command again then from desktop I need to go back to this edurea directory. Correct? So there we go. Till day symbol here it represents that we are in the home directory. Okay. So the home directory is basically I can also access the home directory by just giving cd and enter. Okay that I can do it from any other directory. So let's say I am just doing an ls and I'm changing directory to downloads. Okay. D O w n l o a ds. Okay. So just you got to remember to give the exact name of the folder or the directory that you want to travel to. So only then it'll work. Otherwise, if you just give d, it won't really work. Okay. So, after this uh if you give enter, then you go to the downloads uh folder. And uh do we have anything inside downloads? No, we don't have any other folder or directory under download. So, now let's try going to the uh home directory from here straight away. Okay. So, I initially told you that by having two period marks after uh you know CD, you go to the previous directory in that path, right? So instead of that if I uh just give a cd okay and if I give enter then I'll straight away go to the home directory and this is with respect to uh any directory no matter in uh which directory I am in so if I just give cd then it'll go to the home directory okay so that's what the benefit with the cd command is you can give cd to move to any directory okay so I have a question here from uh shashiant and shashikant is asking me uh should we have to do cd and ls every time it seems a little complicated so shashikant You don't need to really do that because uh I was just about to get to that point. Okay, if you want to go to a different directory or a different folder, you don't need to give cd and ls every time. Okay, so ls is basically only for you to figure out or understand what are the different directories inside a particular directory. Okay, if I know the path then I can just feed it right away in one command and enter that directory. Now let's say I am currently in the CD directory. So this is uh CD. So this is my home directory. Okay. Okay. Now if I click on desktop and if I click on LMS and then you have another folder here. Okay. You have hedge base. Okay. Now supposing I want to go to any of these uh directories from my terminal then I don't have to you know put CD three different times and uh followed by ls and then go to those directories. I can just uh specify this thing in just one command. So what I'm going to do is I'm going to say cd space or since right now we are in the uh home directory I need to give uh desktop. Okay. Now one more thing which I want to show you people is there is this option of tab on your keyboard right when you give tab then the command here will be autofilled right the option will be autofilled so uh let me explain that again so I'm just going to go back so in the home directory right so you have different options you have desktop and documents so what I'm going to show you is by clicking on uh cd and space and then if I just type three or four characters of desk okay I want to go to this directory But I've just typed dsk. Okay. Now if I click on tab then the remaining uh characters of that particular option is already filled. Okay. It gets autofilled. So that is what the tab would do. By clicking on tab it will get autofilled. So similarly under desktop you have the option of LMS. Right? So I'll just put L and if I press tab the remaining will get autofilled. Correct? And inside LMS you have different directories. We saw that we have hedgebas we have hive and all these things. So let me go there and show you what are the different directories that are there. So we have hbase, hive, map reduce and uzi. Okay. Now uh let's go to the terminal again. Supposing I want to go to uzi directory. Okay. Now when I just click on capital and if I click on tab then uh it kind of autofills the directory. Okay. But in case let's take the example of h or hb over here. Okay. Now since both start with h I'm going to type h and if I click on tab that doesn't work. Okay. It gives me further options of HB and hive. So that is because there are more than one options for uh you know starting with H right? There are more than one folders or directories that start with H. So that's why you're getting further options. That's why it's not autofill length. But if you see the second character here is B and the second character here is I. So if you either give B and now if you press tab then HB is what is going to be picked up. Okay. Because uh after H and B there's only the only option is uh of HB. There's no other folder that has HB as the first letters of the name. So similarly, if I just type IV and if I do tab, then hive gets autofilled. So things like that. So uh since our mission was to go to the HB uh directory, I'm just going to say HB. Okay. Now inside HBase, I wanted to go to one of the directories in here. So let's say we go to advanced Hedgebase practicals. Okay. Now for that, if you want to go there, then you just got to give this. Okay. So this is your complete path to access that particular folder and when I give enter then I am in uh the advanced hedgebased practicals module 9. Okay. So I'm in this particular folder or this particular directory. So that is what you can do with the help of feeding a path after CD. So now if I want to go back to my home directory I'm just going to click on cd and put enter. Okay. So uh that is this. Now let me go back to my slides. I'm just going to close all these uh folders. Okay. Now, going back to my slides, I showed you the print working directory command and I showed you the root directory and uh I showed you the clear. Okay. So, the echo and the pseudo commands are something that I did not show you. But I also spoke about the ls and the cd commands. Right? So, what I'm going to do is uh before I go into details of cd and ls, right? I'm going to just show you the echo command and the uh pseudo user. Okay? Now going back to my terminal, the echo command, right? So what is uh the echo command? So uh what is the echo command? Echo command is something that writes its arguments to standard output. So when we say arguments, it means whatever we type after uh echo, we'll type echo space and followed by that whatever we write so that will be specified to standard output. And when we say standard output, uh it is the output that will be displayed by the u CLI. So in your terminal whatever output you get so you'll get specified to that particular standard output. Okay. Now let me show you a practical example only then you'll be able to understand that. So let just clear the screen. So another shortcut to clear the screen is ctr L. Okay. If not you can just give the clear command like this. Okay. This will clear your screen. Otherwise you can just give control + L which will again uh you know just clear the screen. It's a keyboard shortcut. Okay. So I told you that I was talking about the echo command. So when I say echo and if I give enter then there is nothing that is displayed. But if I uh say echo and say hi see what the output came. So when we executed this command this was the output that came back. It says hi and uh if I say echo hi my name is uh vdan. When I say this then whatever uh was specified as arguments right? So this was basically specified as arguments to this command. So the argument is specified as uh the output. This is the takeaway from the definition. So the definition was basically that whatever the argument is that is specified to standard output. So that's what it happens. So that's what comes here. So this is one thing and in fact there's another uh functionality also. Now uh you were all aware of the concept of variables, right? So we can assign some kind of value to a variable and we can also print that with the help of the echo command. Now u let's say that we have a variable x okay and let's give it a value 100 okay so now if I uh just say echo dollar x then the value that is stored in this variable right that be printed uh because echo is something that's just going to print the uh argument to standard output okay it'll display the value that is present over here so if it's just a string then that will be printed and if it's a variable that I'm specifying then even that will be printed So the difference between uh the variable and string is this dollar. Okay. Now if I just give echo dollar x then I've set the 100 value to x. Right? So that 100 will be printed here. So like I told you 100 is printed. But uh the same thing if I give echo x without the dollar then see what's printed. It is x which is printed. So that is the difference between the string and a variable. Okay. So you can you know have again a variable uh called name or you can have a variable called van and you can store the value of 10. Okay. But if you want the value to be displayed then you got to append dollar before the variable name. Okay. So that is about the echo command and uh in fact there are lot of advantages with this command and I will talk about the other features and the other places where this is used later during the session but uh till then this kind of an introduction is enough for now. Okay. So going back to the uh slides what else do I have? Uh okay so we have the su command correct so as it says su is used to switch to the root user okay uh so that use super user permissions can be used to execute commands all right and then you have su username used to switch to a different user and then you have pseudo command which executes only that particular command with the root or super user privileges now what these three what they essentially mean is that you get more permissions so if I go back to my terminal so if If you guys remember then I logged into CentOS with the Edka user right so that is uh displayed here also. So uh it says EDA at localhost right. So uh this is the username of this account and uh similarly you have something called as the root user okay this is my user and then you have the root user and what the root user is is the root user gives you a lot of permissions. So that's like the ultimate uh super user of this particular system. So basically if there is any folder that cannot be accessed uh by my user okay my user name is uh and if I do not have the permissions to access that particular uh directory or that particular folder then we can use the root user because root has the ultimate privileges so any command that is executed with the root user then that will be executed okay so because root has all the privileges it has all the permissions so that's what uh the root user is and uh you know there are certain uh functionalities which need the SU user or the root user's uh permission. And I will show you all those things later. But for now, what you need to understand is by just giving SU then you can switch to the root user. Okay. And it asks for the password. Of course, you got to know what is the password for your root user. And when you give the password, you will be logged in as a root user. So you're not eda anymore. Okay. And as you can see here, you are root at rate local. So this is the host name and this is my uh username. Okay. Root. So earlier you might have noticed that there was a dollar symbol. Okay. But now it is a hash. So this basically this hashtag represents that we are inside the root user and we are accessing the you know executing commands as a root user. So that's what it means. And if you want to get out or exit the root user then you can just type exit and give enter. So now you're back as yourself. Now you're going to be executing commands as eda user. Okay. And uh another thing that you can do is if you have multiple users okay and if you want to switch to one of the other users then you can also give the su command and go to switch to the user. uh supposing the username is uh let's say ABC is the username then I can just give su space ABC okay now since I don't have any user uh uh you know a user account called ABC it will probably throw me an error or tell me that it does not exist okay but the point that you need to note is that if you have any user then you can just switch to that user from the terminal by using the su command okay su space the name of the user account so again uh later during the session there's a topic about uh creating and deleting user. So at that time I will show you how you can switch to another user uh from the terminal. Okay. So let's park it for for later because it's a little complicated if I tell you that right now. So u I think I've covered pretty much uh everything about su and there's one other command called pseudo. Okay. So sudo basically lets you execute a particular command as a root user. So when I give uh sudo and ls then what happens is uh this particular command ls command which will list down all the other directories or folders in the current working directory right so this will be executed as a root user okay so uh similarly so earlier I executed the su command and I gave a password for that the difference between the two is that with the help of p sudo then only that particular command will be executed as a root user but whereas with su then the entire set of commands after that will be executed as the root user as you will be logged in as a root user itself. So let me just show it to you again. So this was the ls command which I executed as a pseudo user. Okay, as a pseudo user or as a root user. But if I just give su and if I give the password then I enter and I can uh enter the same details. Okay, I can put the same command ls as a root user. So basically the kind of results I get will be the same. Okay, but it's just the difference is that the uh user that will be executing that particular command. So I hope uh this clears your doubt. Okay, so I'm just going to say exit and clear the screen. And if I go back to my slides, I'll just read out the definition. So sudo basically executes only that particular command with the root or the super user privileges. Okay. And uh when you give pseudo username, you can switch to a different user and when you give SEO, you can switch to the root user. So that's what uh I showed you the differences between the three. You first give SEO and then it'll ask you for the password. You specify the password and then you'll be logged in as a root user and then you can execute your uh commands. You can execute any number of commands you want to and then you can exit that particular root access and then come come out of it. And if you want to execute another command with the uh root permission okay and if it's just one command which you want to execute then you can just give pseudo and then you can put your command there. Right? So I will uh you know talk about these things later but uh for now what you need to understand is the basics and these are the basics okay the pwd the echo the su commands because all these things come in handy when you go to the advanced uh concepts. So going on to the next slide we have the ls commands here. Okay I showed you one command that is what happens when you just put the ls command. So now there are different options that you can use along with the ls right. So basically ls stands for listing all the contents in the current working directory. Okay. And uh if I go back to my slides right now we are in the uh home directory. And if I give ls here it'll list down all the directories that are uh present in my home directory. Okay. So let me just clear the screen and execute that again. ls. So uh right now we have desktop downloads and music. So these three are some folders. We have documents which is another folder. All these things are folders and these are documents. Okay, documents and files. So these are the uh directories or folders. These are the documents or files. So this is what you get when you execute the ls command. Now if you go to the slides then you will notice that you have certain options that you can type along with the ls. So when you say ls path then you can uh you know probably list down the list of contents that is there in that particular path. Okay. Uh let me go back to the uh terminal. If I say ls and if I say the path where I want to list down the contents. Okay, right now I might be in the home directory. Okay, but what if I want to list down the contents that are present in the uh desktop directory? Then at that time I can use ls path. So what I'll do is uh I can just put desktop. Okay. And inside desktop there are many other folders. If you remember there was one folder called LMS. So if I put LMS okay this is the path right? So I have given ls followed by the path desktop/ lms. Now if I give enter then the uh folders or the directories that will be present in this uh particular directory or this folder will be displayed to me that is hbase hive map reduce uzi and ping. So that is what ls and path does. Now if you go to the slides there are other options right. So these options they can be also referred to as flags. So uh there is a hyphen followed by one letter character. Okay, there's one character here that is L. There is a character called A. There's another set of characters here author. So all these are called options or they're also called as flag. We refer to them as L flag or A flag or author flag all these things. Okay. Now if you give the L flag, what happens is it lists down all the contents similar to just giving LS but along with its owner settings, its uh permissions and the time stamp. So when we say owner settings, permissions and time stamp it is with respect to uh the particular folder inside that directory. So let me show you an example of that. So by uh giving ls you have all the different folders that are present in this root directory. Okay. Now if I give ls-l so the same directories or same documents are listed down here but we have additional uh options here, right? So we have additional information. So these are the set of permissions that a particular user has. we have uh different we have username and we have the host name we have the memory size we have the date the time stamp and all these things followed by the name of the file so if you see desktop desktop is something uh it was created on this day and this is the size of it and all these things okay so this is called the long format I will explain each of these permissions and what each of these stands for what one stands for what isa here and what isa here I'll explain the all these things in some more time Because before I explain those things, there are other commands which I want to show with respect to ls. Right? So in ls other than ls minus l, you have ls minus a you have ls author. Okay. So let's see what happens when we give the a flag. It should ideally show you the list of all the hidden contents in the specified directory. Okay. And then if it's uh if you're using the author flag, then it list down all the contents in that directory along with its owner. Correct? So let's try executing lsy a first. So when we give a all the hidden directories also should be displayed. So as you can see these were the other uh folders which were not visible when I gave just ls because ls just shows the list of contents that are available in the GUI right. So in the GUI if you go to u if go to desktop from the GUI aspect you only get to see these. Okay. So these are the regular files which are not hidden. But of course there are going to be many hidden and those can be accessed by uh the terminal by giving the ls minus a command. Okay. So that is what this uh helped in doing. Now if I give ls and if I use the author flag now see what happens. You have the author also. So instead of having the username and the host name here you have the author of that particular uh document. So if this is the particular uh folder or file or a document then who is the author for that? It is eda because I'm the user right. So the author name will be present over here followed by the size and the time stamp it was created and all these things and we get the list of contents for all the directories or folders which are present in uh that particular uh directory. So that's what ls does. Okay. So guys uh that was about uh the author flag and uh in case we want to use a combination of uh these flags then even that is possible. So I showed you earlier that there is this ls minus l flag and then there is ls minus a flag right. So minus a displays all the hidden contents in that directory. So let me use a combination of them. So let me say ls - l and a since there are two flags which I want to use then I'm just going to use one hyphen symbol for two different flags. So when I do this then all the hidden contents will also be displayed along with their extended long format. Okay. So uh those are the different folders or directories which are present in this uh home directory of mine. Okay. So that is the combination of ls minus l and ls - a. So we saw a combination and again so similarly if I instead of those flags if I use the hyphen s flag then it will sort that entire list by the size. Okay. And let me show you an example of that. So we used ls minus l. Right? Now if I use s over here, it will sort this entire list of directories with the size. The high the the folder with the largest size will be on top and the one with the smallest size will be at the bottom. So as you can see here, it was all jumbled. It was uh this is basically the size block, right? So this is basically for the size block here. If you see the previous time when I just ran ls- l then it was in a different order. But uh since I ran ls - la and capital s this has sorted the result in as per the uh size of the blocks of the folders the folder with the highest size is displayed first and the one with the lowest is displayed last. So that is about the ls hyphen s. So there is one more command that I want to uh show you which can be executed with the help of the ls command. Okay, we executed the ls- l a and s flags right. So we executed this one previously. Now what if you want to uh store these details? So whatever the output here was, if you want to store it into another file, how will you do that? We have uh an option for that. Okay, and that is this symbol greater than symbol. Okay, it's called the direction flag. Input output direction flag. And by using this flag, whatever the result or the output of the command that comes right prior to this symbol, those will be stored in the file that precedes this symbol. So let's say that you know I want to create a new file. I'm going to create that. Okay, I'm currently in the home directory, right? So, let's not execute it here. What I'm going to say is uh let me first change directory to documents. Okay. Now, in here, of course, uh I don't think there are any uh hidden documents either. So, there are no folders here. So, what I'm going to do is u ls minus l a s. Okay. And I'm going to run the uh this command at the home/ edurea directory. Okay, I'm going to uh basically run the same l. So basically the same results I will run them by specifying this uh directory and I will be storing this file inside my new file. Okay. Now let me name that file file 1.xt. Okay. Now uh the reason I moved to uh this directory is because I can store the file in this directory. Okay. Uh had I not moved to this directory and had I just executed this uh ls minus l followed by uh this direction then what would have happened is it would have just created this new file in my the home directory itself. Okay. So if I give an enter here there's a new file that would have been created under my uh documents directory. Okay. Now when I ran ls inside documents there was no folder but now let's uh run ls. So now you can see that there's a new file that's created and that is called file 1.xt. Now that is because I uh used this uh direction symbol nothing but the greater than uh symbol and when I do this whatever result that gets generated from uh this command right from these options on these flags those will be stored in a new file and uh the file name needs to be specified over here. Okay, so that was the wrong command that I used. It's not ls. So, uh what I need to do is let me just view that file. Okay, so to view this particular file or any file, we have to use the vi editor or we have to use a gedit editor or we can use the cat command. Okay, now the most common one is the vi editor. So, let's uh just execute the vi and open this file from here. Okay. And the reason that this ls do file did not execute was because it lists down the files, right? And this is a wrong usage. I did a mistake by specifying ls and uh by not giving a directory. So I should have used vi instead. So that's why that did not come. But anyways, if I give vi and file name, then that file opens, right? So the file which I created and this file has the output that was displayed earlier. Okay. So basically whatever was generated by the ls and a flags of ls. So that result instead of coming in the terminal, it got stored in a different file. Okay. Now uh let's just exit this via file and explain the same thing. So what you saw inside this file file 1.txt the content is the same as uh this one. Okay. So we ran the same command ls - las but it is that instead of getting the output in the terminal we gave a direction command over here to uh save it in a different file and we stored this file in the home/ora directory. Okay. Okay. Now supposing if I want to store this file in the same directory then even that can be done. Okay. It's not a big deal. So this is the command right. So if I remove the path over here then what happens is whatever the output gets that gets generated from uh this option and this command that will be stored in the file one.txt inside my uh home directory. Okay. If I'm inside the documents directory right? So let me just go back one path. So right now I am inside the uh home directory. Right. So here if I execute that uh command okay then a new file will be created with uh the name file 1.xe and it will have the same details. So I'm have done that and uh let's see what are the contents of that file. Okay. So it's nice right? So you can uh in this way whatever output that you have that you can directly store it into another file. So it's a very handy uh command and a very handy option and I'll talk about more such advantages like this later. Okay, so for now I just wanted to show you how the direction uh works. So uh getting back to my slides, I think I've shown you how to work with uh the ls uh command and in the previous slide I showed you the basic commands with respect to uh present working directory and clear directory and the pseudo and the echo commands. So I've done with ls also and now I'm going to show you how to work with the cd directory. So some of the CD directories I showed you earlier also I showed you how to switch to a new directory. So uh when you type cd it'll just change the directory to the home directory. Okay. So the /home/ora. Okay. Now that is my home directory. My home directory is set to that path. So if I go cd it will uh go to that particular home directory. And uh similarly if I uh you know give even cd and space till day symbol as you can see here then even this command will uh change the directory to the home directory. Okay. But however if you give uh cd space uh just slash this will change it to the root directory. So it changes the current directory to the root directory. That is because uh the forward slash here it represents the root. I uh told you this a number of times earlier. Okay. And if there's any other path or any other folder which you want to move to then you start from the root. So you specify the absolute address right you start from the root you say slash and then you put the folder name you again uh say slash and then you put the next folder name. So uh it is similar to that the first forward slash represents the uh root directory and the subsequent slashes are to differentiate between the different parent and the subdirectories. So that's what they are. So this will change you to the root directory and then you have the uh cd-en double period mark okay two period symbols and when you give uh cd space dot right if you give two dots cd space dot dot then it'll change to parent directory. So supposing I'm inside the desktop directory. So desktop's parent is home directory right so it will change me to the home directory. But supposing if I was uh inside let's say the uh if I'm inside a directory called uh directory C and if C's parent was B then by running CD space dot dot from the C directory then it will switch me to the parent directory which is B. So that's what this does and then we have one more command here that is uh CD within single quotation marks we have some kind of path. Now this is useful at times when your folder name or your directory name has two words. Okay. So if you have two words then if you have a space in between then the space will be considered as an argument. Okay. So terminal will consider that as an argument. So if you want to switch to a document in that kind of a situation you know or if you want to switch to a directory which has a space or a document which has a space in the middle. So in that kind of situation you can use a single quotation mark or double quotation mark. Okay. So it's uh you know you also have the comfort to switch to double quotation mark. So I'll execute all these things and show you. Okay. So first I'll show you the uh the CD till day then with the forward slash then with the dot mark this of course I showed you earlier also and then I'll show you how to switch to another folder with you know which is having two different names with a space in the middle. So going back to my uh root. So um right now we are inside the uh home directory itself. So if I give uh cd - desktop okay now in here we have my other directories and if I do cd and lms I'm inside the lms directory okay now from here if I give cd and if I give use the till day option right then it will switch me to the uh root directory uh so see this was the till day symbol earlier okay so this till day symbol represents root and since I uh said change directory to t symbol this which implies root it basically uh decodes it as change directory to the root directory. So when I did that I have automatically switched to root directory while earlier it was lms. So uh similarly if you're in the uh lms directory and if you also just press cd right if you just give this command even this will switch you to the root directory. So basically uh cd and cd space till day they are uh both the same. But uh however if you give cd with forward slash then it will uh switch you to the root directory. So when I give enter as you can see I'm in the root directory. So if I give ls over here I have a list of other directories which I showed you earlier. So in in your file system right? So yeah so inside your file system if you open this folder then you have the root directory. So inside this directory you have home and network and this is where desktop and documents are all present as a subdirectory of this parent directory. Okay. So this is the root directory where everything is stored. So any document or any folder in your Linux operating system they can be referred or they can be accessed from this root directory. Okay. Now going back to the terminal let me show you an example of that. I've already moved to the uh root directory. Now let me say cd bin and uh okay we have this. So now when I uh gave cd space bin then it moved me to the bin folder inside my root directory. So uh I ran the root directory added an ls which listed down the list of uh folders inside my root directory. These were the options uh bin boot dev. These are all the different folders. And when I said change directory to bin, it uh shifted me or it moved me to this particular folder. Okay, inside the uh root directory. So right now I am in the bin directory. And inside the bin directory, I ran the ls command which basically uh means listing down all the uh contents whether it's documents or whether it's uh folders or directories all those will be listed down. Okay, so these are the list of all those uh contents in the uh bin directory. Okay, now that we are in bin, let me go back to my root directory by giving double dot. Okay, so from bin it again I go back to my uh uh root directory. Okay, so this uh for/ represents root directory like I told you earlier and if I do ls then I'm back to this directory where we have bin boot dev and etc home and all these things. So now what I'm going to do is uh so now that I'm in the root directory now let me say change directory to home and inside home there is EDA I want to go to EDA inside Eureka let's go to desktop and then there is LMS okay and uh in here if I do ls then these are the list of uh folders here okay now I'm going to change directory to hbase and if I do an ls over here then you can see that there is one particular folder called advanced hbase practicals module 9. Okay, if I now just say cd and if I put adv space hb then I will not be able to autofill the option. Okay, that's because uh the terminal or the CLI is not able to recognize this particular uh command because there's a space over here. Okay, so it treats ADV as a separate folder. But since it's not able to find any folder here as ADV, that is the uh problem. Okay, let me show you via the GUI what it looks like. So we are in the desktop and inside LMS we have hedgebase. Inside HedgeBase we have advanced hedgebased practical. So this was what I was talking about this particular folder. Correct. So let me minimize this for you. Okay. Now this is a classic situation of when you need to use double quotation mark or single quotation mark. Okay. Now if I just uh put the same name uh like say ADV and uh HB then it kind of autofills automatically right. So even the quotation mark ends over here. So that indicates that this is another folder that's present. So if I uh you know just put enter then it will change my directory to this particular folder. So that is what the uh quotation mark does. So when I do enter then I'm inside this folder. When I do ls I have the list of folders and directories inside this advanced hbase practicals folder. All right, guys. So, I'm just going to do a CD to my home directory. And I'm here. And that was about the different uh CD commands that are available which I wanted to show you. Okay. So, let me just go back to my slides now and go to the next slide. I showed you all the uh different commands here. Okay. So, the next set of commands that I'm going to talk about are those of cat, GP, sort, and pipe commands. Okay. So uh let's first go to the next slide and start off with cat command. Okay. So when would we use the cat command guys? So it's pretty obvious right from what it's written here. It says when you're working with files that time you can use the cat command. So uh the cat command it is basically used to display the content of the text files and concatenate several files into one. So uh what this means is if I have a particular uh you know I have a text file. So earlier we created one text file having all the file permissions right. So if I have that kind of text file and if I want to uh display the content of that text file then I can use the cat command. I can say cat and if I give the file name then that content will be displayed. So when I use only the cat command with one file name it's very similar to how the vi command works or how the nano command works. Right? So it will display the content in the terminal itself. Correct. But the difference with cat command is that with cat I can list down the contents of multiple files. So it's not just one. Okay. I can have I can even display I can specify three different file names. And if I put enter then the content of all the three files will be displayed in my terminal. The same thing won't happen with vi. So if I say vi then only that particular files content will be displayed. So same thing with nano right. So uh let me just go to the terminal and show you an example of the cat command. So right now we are in the cd directory. Let me just maximize this. Okay want to clear the screen. Present working directory is uh the home/rea directory. This is the uh home directory. And from here let me go to uh documents. Okay. If I do an ls there is this file one.xe which I created earlier. Correct. So this was where the different file permissions were present. Right. So if I do cat-y file name and if I give enter then I get the list of the contents of that particular file. So in that file there are only these three rows because this was the latest updated permissions that I specified in the file 1.xt. Okay. So guys I earlier told you that you can enter uh details to a file by using the direction command. Right? So that was the greater than symbol. So I'm going to use that kind of a symbol over here and I'll create a new file by adding details by using that command. Okay. So, initially it was I used the ls minus l. But this time I'll use the cat command itself and uh say I'm going to give the direction symbol here and when I'm done with that let me give the name of the new file. Let's say file 2.txt. Now when I hit enter the command is not executed completely. Okay. So I'm inside this place where I can enter the text. So it's basically going to create a new file. Okay. Now whatever text I enter here that will be stored inside this file. So uh let's say hi my name is uh Vardan and if I give enter I can go to the next line and uh here let's say welcome to Linux tutorial by Edurea. Okay now if I want to uh you know just add these two lines to this particular uh file called filecore.txt txt then I can press Ctrl D now. Okay, by pressing Ctrl D I come back to my uh command line. So what this command basically does is this CAT command would have uh created a new file file.xt and the uh text that we entered below it right uh this will be entered inside this text. So if I do cat file 2 txt then whatever I typed earlier that got saved in this file. Now similarly if you see the uh file 1.txt the contents are these. Okay. So this is the contents of this one and this is the content of uh this file. Now I told you that with the help of cat command you can uh display the content of two different files. So let me show you that option. Okay. I'm going to say file 1.xt and then I'm going to say file 2.xt. So in this way I'm going to basically display two files cat. I want to display file one and file two. When I go enter, first the file two contents will be displayed and then the file two contents or the lines in file 2.txt will be displayed. Right? So first these were the permissions that were there in the first file and then uh this was what was there in the second file. All right guys, now uh this brings us to another important concept of how to append files. So cat basically stands for concatenate, right? So that's the most important option. So if you want to concatenate a particular file with you know some kind of lines then I showed you how that is done by creating a new file what I did was I I created a new file file 2.xt and I concatenated these lines into this particular file. So if I just give cat and uh if I give file one dot txt and if I give uh double marks okay so double direction marks which is uh nothing but the greater than symbol okay we also call it direction marks. So if you uh give file 1.txt and followed by this if you give file 2.txt then what's going to happen is whatever contents are there in file one those will get appended or concatenated to this file 2.txt. Okay. So in my file 2.txt we have these two lines. Okay. Hi my name is Van and welcome to Linux by Eda. And file one has uh these three lines. So basically when I uh enter now there will be uh a file two in which there will be extra lines. Okay. So let me uh do a cat file 2.txt. So as you can see initially when I ran my uh cat file2 txt over here I had only these two lines right but now after using the birectional uh symbol okay the direction symbol what has happened is I have three extra lines. So it says hi my name is van welcome to Linux tutorial bya. After that I have the permissions which was present in the previous uh file. Okay. So uh that's what happens here. Okay. In fact it's actually four other lines. Thanks for pointing that out. So Hmon you know who's another person in our session. He said that there are four lines in the fire. Actually he's correct. So total eight. So this is the first line and these are the other three lines. So you can also see that from uh here. Okay. So the first time when I ran cat file one.txe, txt right I first got total 8 this was the first line and after that I got the permissions okay so this is the first line and then you have the list of the other contents so when we ran the ls minus l the total number of entries were right so that was what uh the total eight stands for so these are the four lines that got appended to my file 2 txt okay but however there wouldn't be any changes to my file 1 txt because I didn't make any changes there so let me anyway show you that also uh if you see here again the contents here are the same it's only that the file 2 has got these four lines extra. So that is what the direction symbol does. So these are the uh advantages with the uh cat command. All right. So u what I'm going to do now is uh let me go back to my slides and show you some more options. Okay. So we have flags like we have the B flag, the N flag, S flag and E flag. Let's see what each of those stand for. Okay. So when we use the B flag, it's going to add line numbers to the non-blank lines. Okay. So whichever line there is some text. So those lines are going to be numbered. Okay? And when you say minus n then it is used to add line numbers to all lines. It doesn't matter if it's blank lines or non-blank lines. It's just going to add numbers everywhere line numbers. Okay. And when you give the s flag, it is basically to squeeze all the blank lines. Supposing you have three blank lines one after the other then it will squeeze all those blank lines and it will reduce it. Okay. So that's what the S does. And then the e flag is going to uh show you a dollar at the end of each line. So let me go back to my terminal and show you this uh option. So first of all let's see the cat file 2.xt and uh let me use the uh flag minus n. So this will list the number of lines right. So there are basically four lines from file one and these were the two lines that were ear present. So these are the six lines in total we have in this file 2.txt. Okay. Let me just clear the screen because uh it's a little uh tough to see everything, right? So yeah, so when I ran the minus n command, the file 2.txt, the lines in there were numbered. Okay, 1 to six. Uh and then we have another uh flag called minus b flag, right? Minus b flag will add numbers to also the uh non-blank lines. So but for that we need to first have blank lines over here. So what we'll do is uh I'm going to do a cat and u do this and file 2.txt. So when I do this, I'll be adding uh lines to this file 2.xt. Okay, I'll be appending lines over here. So let me just give one blank line. Enter some random text and then enter, you know, blank line and then random text. Okay, so this is what I'm going to just enter or append to my file totxt. Okay, you press Ctrl D to exit this. And now these would have been saved to my file 22. TXT. So let me just run the same command again. Oh, sorry. I should have ran this cat file 2.txt. Okay, when I do this, as you can see, uh it starts from here and these were the other lines that were appended. Okay, and now if I use the cat hyphen B flag, okay, see what happens. Only the non-blank lines are uh numbered, right? So these lines are not numbered. But if I use the minus N which I used earlier, what it would do is it will number each and every line. So that's the difference between minusb and the minus n flag. Okay. So n numbers all the lines irrespective of it being empty or not. But whereas minusb numbers only lines which are non-blank. Okay. So that is uh this one. And there is another flag which is the uh hyphen s flag. Okay. So it's not capital s it is small s. Right. So when I say minus s then you get the list of the documents. So as you can see here all the u spaces are squeezed into one. Uh seems like there were no multiple spaces right no multiple blank lines. So what we'll do is let's edit the file 2.txt again. Okay or in fact let me open it via the uh editor vi editor. Okay. So when I do this these are the uh existing ones. So when you uh press insert or when you press I button or insert button, you can start entering text details inside this file. Okay. Now u right now I'm here. Let me add multiple blank lines here. Okay. So as you can see there are around three blank lines here. 1 2 3 4. There are four blank lines. And here there are three blank lines. Okay. Now uh let me press escape. Okay. Now if I give escape. Okay. So now we are in insert mode. So what I do is uh I'm going to press escape and then followed by that if you give colon and wq this would uh save this file. Okay. So I've made changes right? I've added lines here. So it would save that changes and it would quit the vi editor mode. So if I give enter so I'm outside that file. So now if you see the uh cat file 2.xt then it has additional lines right? So uh now I'm going to run the command that I ran earlier. Cat hyphen flag s and then file name. So when I do this all the u multiple blank lines are squeezed into one. So as you can see here there there have been multiple lines here when I ran the file 2.xt. But here when I ran the cat hyphen with the yes flag then there are all these multiple black things are squeezed into one. Okay. So that is uh the option with the cat command. Okay. So I think with that I think I've covered all the different option. Okay, there is one left. There is uh the minus E option right. So okay now let me show you what that does. So when we use the capital E flag okay there is a dollar sign that is appended after every line. So uh the first line is total eight or let's say the first line is this one. So there's a dollar sign here and after this line there's a dollar sign. After this there's a dollar sign. And since these are blank lines you'll only find the dollar sign here. And again after this one you have a dollar sign and uh you know blank lines have dollar signs and yeah so that's how the uh e flag works. Okay. So every the end of the line is uh appended with the dollar symbol. Okay. So with this I'm done with all the uh cat commands. So going back to my slides now. Let's go to the uh next command that is grip. Okay. So uh grip command working with grip command. So what does the grip command do? you guys have any idea? Okay. Well, I don't expect you people to but uh yeah. So, if people if any of you know if you have an introduction to Linux, then you can answer it. But it's fine if you don't because I'm going to explain that. It's my duty. And the grip command is basically used to search for a particular string or a word in a text file. Right? We have a file document like the one which we created. Now, like we we have two documents like file 1.xt and file 2.xt. And what if you want to search for a particular string, right? Or a particular uh word. So in this case it's pretty simple because you can easily find them. But what if you want to do it to uh you know a very big pile document which has like millions of lines right? So supposing you have any document then you'll have multiple lines right and if you want to find one particular word or if you want to go to one particular string then how will you do it? So in Windows you have the control F option right but via a CLI you can't use it right so via CLI you use the uh grip command okay and the format for executing the command is this so you specify gp and then you specify the string that you want to search for so options is the string that I have searched in this command and then the file name okay and it will return the result of the matching string options so similarly if you use the i flag then it will uh return the results for even case insensitive strings So basically if you do not use the I flag then it is uh it's case sensitive right so it'll only search for options with these letters but if there is a word called options with a capital O where the first letter is capitalized then uh in that case only when you use I will even that particular result be uh shown okay so that is the advantage with the I flag and then you have the N flag which is the GP hyphen N which will again returns the matching strings along with their line number in which line was that or that word found. So that's what n does and when you give minus v flag then what happens is uh you will not be shown the list of lines where the results were present but instead you will be shown the list of lines where the results were not found where there was no matching string right so those lines will be printed with the help of v flag and then with the c flag it returns the number of lines in which the uh results matched the search string so supposing you have like four words okay you have a big document and uh your word your string matched four times then uh if you use the minus C flag then it will display the number four instead of displaying the search string. Okay, so let me go to the uh VM let me go to my CentOS and uh show you how to execute these commands. Okay, so right now we are in the documents folder. If I want to execute uh that then we need to edit this in a different way. Okay, we need to have a different text and this directory has uh these documents right? So let me just quickly go to the uh documents folder and here if I do an ls we have the two files which we created. We have file 2.txt and file 1.xt. So what I'm going to do is uh I'm going to see what's there in file 1.xt. Okay. So let me edit this file. Okay. Or let's say let's just create a new file. What do you say? We can create a new file by uh doing this right by uh giving the direction symbol followed by the uh name of the file. Let's say automobiles. Automobiles. This is the name of my uh file automobiles.txt. And I can start listing down the automobiles that I want. So let's say car or let's say motorbikes. Okay, we can say train. Well, train is technically not a automobile but uh still or let's uh go into details of the companies. Okay, let's say Maruti, let's say Ferrari, Lamborghini. These are some of the most famous uh companies, right? So, when it comes to bikes, you have Bamaha, then you have uh Honda, right? You have Suzuki, you have Acillia and uh to name a few more. We can add some more companies like BMW, we can add Audi, we can add Foxwen to this list. Okay. Now, if I do control D, then uh this will be the list of content in my automobiles.xt. Okay. Let me I'm going to clear the screen now. And if I do cat command here, then it displays a list of contents here. Right? Okay. Now, let's use the grip command to search the content that is uh present in this uh text. So u I'm going to do a grip and uh the string that I want to search for is uh let's say y because in Lamborghini we have the search string y am and even in yamaha we have uh the am right we are supposed to get two results for this. So in this case so if I uh just say gp yam and if I specify the file name automobiles.txt txt and if I give enter then I get the two different words right the two uh names where this was present where am was present okay now if I use the same thing with the uh i flag then it will display the list of files in a case insensitive fashion but in my file there's no uppercase file I'm going to say see automobile txt I'm going to append I'm going to append this word called amber. Okay. So, Amber is another uh automobile company. And when I do this and if I run the cat command now, okay, you will see that along with uh these names which were there initially, there is amber has been appended. Okay. And this time when I search for y, right? So, it should not show me this because even though there is am here, uh the a is capital here, but I'm searching for small am. So, it should not show me this result. Okay? I should get the same result that I got previously. So if I uh do a grip am like earlier I got the Lamborghini and Yamaha as the only options. Okay. But now if I uh append this with minus I or the I flag. So what happens is I'll get the option of even amber along with this because it would search for the string in a case insensitive fashion. Okay. So this time as you can see amber is uh added to this list because uh it did not consider case insensitive words letters. Okay. So that is about the i flag and uh there is another n flag right. So let's see what the n flag does. So every time you use the uh minus n flag then it'll list down the line in which the word was present. So that's what I mentioned earlier. So over here in line number six and line number seven we have lamborghini and yamaha. Right? So the line number is mentioned. Okay. Now u so that's what the n flag does. Okay. So we have the v flag and the c flag left. So let's execute them and uh see what happens. So when I remove n and when I execute v as you can see all the uh results except for yamaha and for lamborghini would be present here. Okay. But if I give minus IV okay which indicates IV flag then even amber would not be present in the output I will get now okay when I give enter as you can see amber is not present because uh amber is part of the case insensitive option right when we included I this should be chosen as the search result and since it's considered as a search result we will display only the result uh the set of results which were not found so the other lines which text was not found were these and that's why we got these options okay Now we have one more flag which we need to see and that is the C flag. And when you enter the uh C flag then it displays the list of uh the number of times that string was found. So AM was found two times in once in Lamogi and once in Yamaha. So that's why we got the answer as two. Now if I use C with the combination of I all right I'm going to get three. That's because even amber will be considered in this case. Okay guys. So uh this is uh what is uh there with respect to the grip command. I spoke about the uh grip command. Okay. And now in the next slide let me talk about the sort command. Okay. And so we use a sort command to sort the results of a search either alphabetically or numerically. All right. And uh we can sort either files or file contents or directories. So what this means is whatever results you get right or uh I mean not just results or even if uh it's the list of items that is present in a particular directory even when you run an ls command right you'll have a list of files and the list of folders that are there in that particular directory so we can sort even those things okay now that result can be sorted and uh also we can sort anything else we can sort the contents of a file right we can sort the contents of the file or uh you know all these things so that's what this means So without wasting much time, let me just uh show you how that is done. So you can give sort and the file that you want to uh search. Alternatively, you can also search two files at the same time by giving uh file 1.txt and file 2.txt. Okay. So and the and the syntax for that is uh sort and the file name. Okay. When you say sort on the file name, then the contents of this file will be returned in the alphabetical order. Okay. If you want to sort two files at the same time, then you can uh in arguments you can just give both the file names and it will sort the contents for both file one.txt and file 2.txt. Okay. And again if you want to uh display them in the reverse order, then you can specify the R flag. And uh for case insensitive sorting, you can do the hyphen F flag. And then if you want to sort the results based on the number in a numerical order, then you can use the N flag. Okay guys, so uh let me first of all go to my terminal and start executing them. Okay, so what I'm going to do is I'm going to clear my screen and currently let me just list on the contents of this directory. So we have automobiles uh file, we have file one and we have file two when I just give a sort and press enter. Then I enter the interactive mode. Okay, so here I can uh type all this. I can type random words. Okay, I can say U A B C D or I can say B C D A or I can say E F E D FG all these things. Okay. And then when I press Ctrl D, it gets me out of the interactive mode. And when I exit the interactive mode, the text that I typed in, right, the input that has been sorted. So this up till this line was what I entered as input if you remember and uh up till EDFG, right? So basically this text has been ordered as per alphabetical order and since a comes first in alphabetical chronology this is first the BCDA is second and then you have the other lines okay uh these have been sorted in an alphabetical order now if I give sort with the file name okay that is uh automobiles.exe exe and if I give enter then this particular uh file will be ordered in the alphabetical order. Okay, the contents will be uh listed down in an alphabetical order. Uh let me clear the screen and show that again. So let me first just do a cat and show you how the order is. Okay, now let me run the sort with the file name. Okay, so now if you see it was in this order initially, right? So car was the first option, motorbike was the second, train was the next, Maruti and then came Ferrari and Lamborghini. But if you look at the sorted uh result then it's in a sorted manner right so first comes Amber then comes Aprilia then comes Audi and then the others so that's what sorting does okay and the same thing can be done for two different files at the same time. So this was the automobiles .txt. Supposing I want to list down even my file 2 contents. Then I can just type file 2.txt here and the results of both the files will be in my uh terminal. Okay. But before that let me just uh clear the screen so that it'll be easier for you to view the results. Okay. So now that I've cleared the screen, let me uh sort these two files. Okay. So let's the command is sort and this is what I had previously and let me add file two to it. Okay, file 2.txt. Now what this would do is the results of both these files right automobiles and file two the results of those would be sorted in the alphabetical manner. Okay, now if I give an enter as you can see here first initially you have blank space. Okay, now that is because blanks are ahead of the capital A, right? This is the alphabetical order. Correct. So first comes blank space then comes u white space and then comes the characters. So once we are done with those things then we have amber Aprilia Audi this was the order in which the files were listed in the automobiles and right after C D comes okay now this line is part of the file one while these were part of automobiles. This was part of file 2.txt. So yeah these results were a part of the automobiles txt file. The blank lines here these were part of the file 2.txt and u again these two lines right these were part of file 2.txt txt. Okay, so this is what happens when you give two files as arguments. Now, uh there are other options that I want to show you though. So there were flags like R flag, right? So R flag lists the uh results in the reverse order. Okay, I'm just going to clear the screen and yeah, for clearing the screen, the shortcut is Ctrl L. All right, guys. So um let's say sort automobiles.txt. Okay, it's cat, right? Right? I don't want to do cat. I want to do sort automobiles. txt and I want to use the flag minus r. So when you use minus r, it will display the result in the reverse order. So we have the reverse order in which yamaha comes first and amber comes last. So that is the reverse order. And we have another flag here. The other flag is the f flag which will return the results in uh the case insensitive uh fashion. Okay. So that is the uh minus f and then if you go back to the slides there is uh n option right so n will return the results in the numerical order. Now let me go to my uh terminal and let me use the n flag now. But of course I don't think it will sort anything because there are no numericals here. So what I'm going to do is I'm going to u use the file 2.txt here. Okay. File2.txt. Okay. So there are no numericals here either. What I can do is I can edit these details. So let me go vi and uh say file 2.xt and I'm going to enter the insert mode. I'm going to remove all these unwanted lines. Okay. So I've removed all the blank lines. Now I'm going to put one here. I'm going to put two here. I'm going to add three to this line. I'm going to add four to this line. Okay. All right guys. Or let's say let's give the order seven here. Okay. You have two here. Okay. So there are some kind of uh numericals ahead of uh you know before every line starts. Right. So when we run the minus n command now the sort command with the n flag now then it would sort these lines with respect to the lines with the numerical order. Okay. So first this line would be uh shown the blank line. Okay. Then you would be shown the uh uh you know the total line. Then you would be shown the third line and like that. So let me just uh escape colon and save and quit. Okay. Now let me uh run that same sort command. Sort-en file 2.txt. So as you can see the uh alphabets are first sorted. Okay. So the lines where there are text characters or alphabetical letters so those are displayed and after that the lines that are formatted after that are in numerological fashion. Okay. So if I don't give the n it would be a different fashion altogether. So earlier the file was just displayed in the regular numerological order. Okay. So where 1 2 3 4 5 the numbers came first and then came the text. But since we ran the hyphen n the alphabetical letters or the characters came first. Okay, after that it was sorted by uh numerical letters. So that's what the n flag does and and that brings us to the end of the sort commands. Okay, so uh after the sort command, the next one that we have in line is that of pipe command. Okay, so this is referred to as the pipe. So you'll find this in your uh in your keyboards right above the enter button. Okay, uh where you have the backward slash. So in that button if you press uh shift and if you press that button you'll get this pipe command and what the pipe command helps you does is it uh lets you perform two operations in the same command like it'll uh let me search let's take the example that's specified here okay we using the gp to search for a particular string from a file and uh we are using that and then we are sorting that result okay now since there are two operations involved okay one is the sort and one is the uh search since there are two operations involved in the same command we separate the two operations with the help of the pipe command. So that's what uh this is and uh as the definition says the pipe command is used to output the result of one command as input to another command. Okay, the same thing can be said over here also. So we'll first search the file for a particular string and whatever result you get that will be given as input to the sort command over here. Right? So this uh saves us time in not having to mention the uh file name after sort again. So we'll just be performing one GP search and then we'll just whatever result comes that result will go to the operation that's performed over here. Right? So um let me just go to the terminal and show you an example of this. I'm going to clear the screen and uh let's run the grip command to search for am from the automobiles.txt. Okay, I'm going to use the pipe command and uh sort this. So these were the two results, right? So when you do a cat command or when you do when you just run the gp command with am right so what would happen is you'll get these two results because these two lines or these two words have the am characters inside right now when you give the sort it would sort it alphabetically right and if I if I want to sort it in the other way then I can just run the same command with the r flag so when I do r then this result will be sorted in the reverse fashion so yamaha comes first and lamoggony comes first so that's how the pipe command can be used to get the output from one operation and feed that output as the input to the next operation. Right? So um this is relatively smaller topic. Okay. And we quite often we'd be using uh the pipe command when you want to use multiple uh operations in the same command. So that's about the pipe command. Okay. So let me just clear the screen and get back to my presentation and see what's my next slide all about. Okay. So now that I've shown you how to sort the contents of the file, let's go to the next uh slide. Right. So the next section of uh this Linux tutorial is going to be about the copy, move, make directory, remove, remove directory, and the user permissions. All right. So let's get started with this section. Okay. Uh CP stands for copy and that will be the first slide uh that we're going to talk about. Okay. So as you know copy is basically used to copy files or directories. Okay. The point to notice files and directories. So in Windows you have the option of right clicking on any file or any folder and you know saying copy or copy paste or cut paste right that's in Windows and you can do that even through the GUI in Linux. But how will you do it through the CLI right through the terminal? You specify this command. you specify CP and if you have any flag you enter the flag and then you specify the source and the destination. Okay, so the source is basically this will be the path of the folder that you want to copy and this is the place where you want to copy it to. All right, so uh let's uh get back to executing and showing you a demonstration of this. So I'm going to go back to my terminal. So uh first of all uh we are in the documents directory and let's see what is there in this directory. Okay, there are the three files that we created, right? There is automobiles.txt. There is file 1.xt and file 2.txt. Now what I'm going to do is I'm going to copy the automobiles.txt and uh paste it in my uh desktop. Okay. So let me just minimize this. So this is my desktop, right? So right now I don't have the automobiles. But through the terminal I'm going to run a command which will copy the uh automobiles.txt to this folder. Okay. So I'm just going to minimize the terminal now to show you that it happens. Okay, real time. So what I'm going to do is u ls and I'm going to say copy automobiles.txt. This is the source and the destination is uh root home edurea and uh in edureka it's the desktop folder right when I hit enter there will be a new automobiles.txt file that'll be created over here. So as you can see the new file got created over here and uh yeah so it's it's a very simple command that you can uh execute. So you can do the same thing to even uh directories and uh files. All right. Uh so what I'm going to do is uh I'll go to the home directory and from the home directory I'm going to go to the desktop directory and copy the LMS folder. Right? So the LMS folder is again uh you know it's it's a folder this time. It's not a file. So last time we copied a file. This time I'm going to show you how to copy the folder itself. Okay, I'm going to copy this folder and paste it somewhere else. So let me go to the terminal cd and I'm going to go to the desktop here. All right. So we have uh LMS here. So I'm going to say copy LMS. All right. So I'm going to remove the slash from here because I'm going to copy this uh folder now. And uh this would make it the source that would make LMS the source. And the destination is we have to put the absolute path here. Right? So we got to start from the root directory and go to home edurea. And let's say I want to put it in the uh documents directory. Okay. So something that is present uh in the desktop directory that is uh being copied and pasted inside the documents directory. Okay. So when we give enter. So guys uh we're getting an error here, right? So it says copy cp omitting directory lms. Can you all guess why that is the case? Can you all like understand the meaning of this error? Omitting directory. Don't break your sweat too much because u the meaning is simple here. It just it has just omitted a directory. Okay. Now the reason is so that is because uh the cp command it by default it copies only files. Okay. If you want to copy directories also then you got to add another flag called r flag. So let me just quickly go to the slides and show you uh the functionality there. Okay, as you can see here uh we have the R flag right. So CP minus R it is for recursive copy and that is for copying directories also. Okay, and it copies also hidden files. If there are any hidden files or if you have directories which you want to copy inside that directory then it will uh it will copy that that itself. So that is the thing because you cannot copy uh directories without the R flag. You can only copy files. So that is the uh meaning here and uh we have another flag here called the V flag and that is verbose. Well, what verbose means is it prints informative messages. Supposing you're executing a command okay and supposing the command is going to take time like it's going to take a good 5 10 seconds then during that time it would print the status of the system like supposing it has completed like step one to step three okay and it's stuck at step four then it would print that message and as an event when step four is completed you will get a message uh saying that's completed and yeah similarly it's like progress wise it tells you what is the progress and what are the action that the system is taking and what step it's performing so it just prints such informative messages just minus V. Okay. Okay. Let's first start off with the I flag. Okay. So we have something called as a CP flag I. Okay. So when you give the I flag, it enters the interactive mode. So when you say interactive mode, it is because u at times you might have files which will all be already be present in in a particular directory. Okay. Uh you saw me copy automobiles.txt once from documents to desktop. Okay. Now if I do the same operation again if I run the same command again at that time it'll automatically overwrite the file right because uh the file name is the same the automobiles or txt is was the one that is there in my documents folder and again even over here on my desktop it is documents uh sorry it's automobiles when I copy them what would happen is that file would be replaced okay now uh in that kind of a situation when you're copying multiple files you might want to be notified before something happens right so if you specify something like the i flag then you will get an interactive mode so the system will not take a decision on its own but instead it will not use any defaults okay that's what we mean by uh on its own okay so it would uh you know ask you it prompt you for an answer. It will tell you that okay this file already exists in this directory and do you want to replace it and then it'll give you an option Y or N. Y stands for S, N stands for no. So that's what the CP and I flag does and when you give the N flag it will not override the file. Okay, because by default it overrides the file and if you specify the N flag it will not override the file. But the whole concept here is it is based on the file name. What if the file name is the same and the file contents are different? Okay, at that situation you might want something like the flag u. Okay, now what the flag U does is it will update the destination file only when the source file is different from the destination file. So by using the N flag, you will make sure that the file is not overwritten. Okay, but then if you use the U flag, you will have another benefit. Okay, what will happen when you use the U flag is so first it would check the file name. If the file names are different, then it would create a new file. If in case there is another file by the same name then it would check the contents of that file. If the contents of that file and the file that's being copied if they are the same then it would not get copied and it would only get copied when the content is different. So at that time you'll have two different files with the same name. So that's the advantage with the uh CP and U flag. Okay. So let's try executing uh these options. All right. So I'm just going to go back to my terminal here. So first and foremost let's execute the uh R flag. Okay, it's capital R. So do note that. And uh when you say enter, so the item is copied. So if you go back to your documents folder, you can see that there's a new folder called elements that's been created. So this was initially not present and it's uh present now. Okay. Now what we'll do is I'll delete this. Okay. I'm going to minimize this. Execute the same command along with the verbose flag. All right. So, as you can see, the uh status of the system was also displayed in the meanwhile even though I entered my uh text somewhere here. Yep, it's right here. Correct. So, this was the earlier uh command that I executed without the verbos. Okay, here it just straightway copied the file. Okay, the LMS sorry, the LMS folder to my uh documents folder. But when I gave V, the informative message also came, right? So it uh the step-by-step process of what all is being copied came. So first uh this was the first folder being copied. This was the first subfolder being copied and after that all the other files that are being copied each and every document step by step it is all listed down and u you'll get all those details here if you give minus v in your command. So that's what the minus v does. Okay. So I'm left to show you the i, n and u flags, right? So what I'm going to do is um let's say I just want to clear the screen now. Okay. I'm going to remove this command here and go back to the documents folder and show you that the LMS has been copied okay with the verbos when I created this folder. Okay. Now what I wanted to show you is I want to show you copy with the interactive mode. So earlier if you see the uh desktop and there's already an automobiles txt right so what I'm going to do is I'm going to copy automobiles.txt txt I'm going to copy this one again to the desktop but this time it should uh you know I'm going to use an I flag and it will not overwrite the existing flag. So I'm going to say cp automobiles txt to destination is uh home/ora slash All right. Uh I think I'm in the wrong directory right now. Okay. So I need to go one uh path back. Switch to documents. All right. Now here I need to copy the automobiles from here right and put it in the desktop. So home/ora/ desktop. Okay. So I'm going to copy the automobiles.txt over here. So when I give enter the automobiles.xt has been copied here again. So let me just go back to my desktop and see that even though I've run run this command two times one now and uh one earlier and one uh now just a couple of seconds back there has been no duplicate that's been created. That's because this file has been overwritten. Okay, the one with the name automobiles has been overwritten with the latest command. So what I'm going to show you now is I'm going to use an I flag here. Like I told you flag is what gets you into interactive mode. So you will start interacting with the uh Linux uh kernel or the Linux shell over here. So as it says the uh home eda desktop automobile.txt it says overwrite. Do you want to overwrite this particular uh file because it's already present. If you want to override if you say y and if you enter then the file would be overwritten. Okay. But if you uh give n and enter then that file would not be overwritten. So if I say no and if I enter then uh that copy would have failed. Okay. But if I do the same thing again and if I press Y, it would have overwritten the file would have been overwritten. So that is uh what the I flag is. And then you have another option okay of the N flag. So the N flag what it does is it does not overwrite the file by default. So for that option I told you that uh by default it overrides right. So I also showed you earlier that uh no duplicate was created and the existing file was overwritten. Supposing you don't want to do that then you can just use the n flag which would automatically indicate and tell the uh Linux runtime engine that uh not to overwrite this particular file. Okay. So you can have any number of files there. So even if the contents are different here okay so even in caseh the new file that's being copied has a different content okay but it has the same name then even in that case by specifying the end file it will not be overwritten because there's a good chance that you might have made changes to the latest file and by copying another file with the same name to that same directory then there's a good chance that you'll be losing out on the changes that you made right so at that time you can uh use the n flag so in fact let me show you that with an example uh what I'm going to do is uh Right now we are in the documents directory. So I'm going to do a cat and automobiles. Okay. So these are the contents here. And let me update this. Okay. What I'm going to add is I'm going to add another uh company of another bike. Okay. Uh let's say we are adding KTM to that list. Okay. So when I do Ctrl D and exit the interactive mode and if I do cat automobiles txt then KTM would be added over here. Okay. Now this uh automobiles file in the documents right now this is the updated one. Okay. But in the desktop the updated file is not present. Okay. In the desktop the file with only uh this much of content is there. Now I'm going to execute the command with the n flag. Okay. So with the n flag it's basically indicating that you're not supposed to override the file. Okay. So when it says that when it finds out that automobiles.xe txt is present over there also in the desktop also it would not copy the file at all okay so when I go enter and of course so there's nothing here now if I go to the uh desktop okay if I click on automobiles txt here you can see that uh ktm is not present all right but however when I close it and if I uh remove the n flag right if I remove this flag and execute it and if I go back to the automobiles txt you'll find that km is updated awesome right so that's the power of this N flag. Okay, so that is uh the end of uh all the different flags that I was about to show you from my PPT. Okay, so additionally there is one other thing that I want to show you. Okay, now I showed you how to copy from source to destination. Okay, and now you know what if you know the path of something and you want to copy it to your present directory to where you are currently. So this is basically I'm just teaching you this option to you know save some time. Uh you know at times you might want some shortcuts or some hacks, right? you don't want to provide the complete path everywhere. So at that situations at that scenarios you can uh use this uh hack and let me explain that before I uh execute it in my uh terminal. So what I'm saying is uh right now I'm in my desktop and I have only my automobiles and my readme text files. Okay. Now but in my documents folder I have three other text. I have file 1.xt and file 2.xt. Okay. Let's say I just want to copy the file 2.xt. What will I do if I want to copy my file 2.txt txt into my desktop. I'll have to go to my uh documents folder then put the cp command and then enter the file name and then copy it to this folder. Right. I have to specify the path of this desktop. So instead of that there is another hack over there. Okay. Now instead of doing that what I can do is I can just go to my terminal. I need to first go to the desktop folder button. Okay. So I'm going to go one step back. I'm going to say change to desktop. And here yes there is only automobiles.txt and there is uh readme.txt. Now what I'm going to do is I'm going to run the cp command such that I copy file from this particular directory to the current directory. Okay. So the file 2.txt if you remember that is present in my documents directory. Right? So I'm going to specify the path to the documents directory and the path to documents directory is / home edora and documents. Okay. and the file name is uh file 2.txt. Okay, I'm going to copy this file which is under this path to my current directory. Okay, instead of uh having to specify my complete current directory, I can just give one dot. So this one dot represents the current working directory. Okay, I'm currently in my desktop and what this command would do is it would copy this file into this uh current directory. Okay. Now when I give enter and if I go back to my uh desktop, you'll see that the file 2.txt has been created. Okay. That's because it it went to this path, picked up this file and pasted it in my uh current direct. Okay. So that's what this is about. All right. So this is what I wanted to show you guys. This was something additional which was not there on the slides. So I'm uh done with that. So moving on to the next slide. Okay. So uh next up we have uh is the move command. Okay. So the MV like CP stands for copy. The MV here stands for move. Okay. And this is uh used at times when you want to cut paste something. Okay. Uh this would when we used copy then the original copy of that file was also present in the existing directory and it was created in another directory. Right. But if you use the MV command then it's going to basically work like cut paste where it'll remove the content from the uh source directory and the only copy would be present in the destination directory. All right. So uh let me straight away get started. It's not too much of an explanation needed over here because uh it's self-explanatory. If you use the I flag, it basically enters into interactive mode again like before. So the U flag is again the same as what it was in the copy command. It updates the destination file only when the source file is different from the destination file. And uh the MV minus V again it would uh you know uh move it would print the system state. Okay, prints the source and the destination files. Uh gets into the interactive mode where the okay, not interactive mode. It basically means uh the system status will be displayed over here. Okay, that's what the verbose is all about. Uh so let me go back to my terminal and uh show you how this copy is done. All right, so let me clear the screen and currently I'm in my uh desktop folder. Okay, and here I have these files. I have automobiles.txt and readme and file 2. Okay. Now, what I'm going to do is uh I'm going to use the move command to move file 2.txt to another uh destination. I'm going to move it to the LMS. Right? So, when I give uh LMS, okay, this means that this move command will work such that this file will be moved to LMS folder. Okay, let me give enter and go back to my desktop and find that it's not it's missing. That's because I ran a command over there. If I go to LMS, however, I'll find the file 2.txt over here. All right. Awesome. Right. So, that's what the MV file does. And supposing I want to uh you know, similar to copy, you can move multiple uh files at the same time. All right. So, I can uh move, you know, supposing uh I go back to my desktop. Okay. And I'll find that there is automobiles and readme. Suppose I want to move both of these to the uh LMS directory, then I can do that also. I can just uh simply give move. I can give automobiles.txt and readme.txt and specify the destination. I can move to any other folder or I can move to LMS folder. If I'm moving to LMS folder, then I just need to give LMS. Okay. But however, if I'm moving uh to another uh folder, then I got to start from the root say home eda and from here let's say I want to go to downloads. Okay. So downloads if I want to go I'll give this path. I'll give enter. And if you notice both are missing from my uh desktop. And if I go to my eda and if I go to downloads I can find the two files over here. So that's how simple it is guys. So that's the uh move command. And if you want to see the system status then you can use the V flag like we use for CP. So a similar log will be generated and shown. If you want to enter interactive mode then you can use the I flag. All right. If you're moving like two files right at that time you might need the interactive uh interactive file. So similar to copy where if you're moving to the destinations folder where there's already another file with the same name then at that time you might want to use the i flag. It would ask you whether you want to override it or not. If you don't want to override it at all then you can just give the n flag. But there again if you don't want to use the n flag either then you can uh use the minus u flag which would update the destination file only when the source and the destination files are different. Okay. So these are the uh different flags that can be used with MB. So the basically the flags that can be used here are the same as the flags that can be used with the copy command. So guys uh that's it with the uh move command and we can go to the next slide. Okay. We can go to the next topic. But before that there is one more functionality that I want to show you with respect to both copy and move. I uh actually forgot to show you this aspect. Okay. Now uh for this let me first show you the GUI aspect. Okay. All right. I go to my ederka and if you go to my documents you'll find all these uh three text files and also my LMS folder right now whether be it copy or whether be it move commands I've showed you how to copy like one file or two files or three files okay but what if you have like 25 files right so what you have like I mean just think about this what if you're a proper uh Linux user and you and you want to just transfer all your files of some particular format right you want to just transfer it to another folder you want to take a backup or something like that what would you do instead you know you can do a control A over here and choose all the files okay or you can choose one after the other like this but through the CLI how do you do it correct so you have such problems right so for that you know we have options also for CLI and uh those work with both CP and the move commands so what I'm going to do is I'm going to show you how that is done uh so for that purpose I'm going to first go to my documents directory I'm going to make that my uh pwd so I'll just go on back and here I um go to documents. Okay, now I'm here. So, what I'm going to do is uh I'm just going to clear the screen. So, of course, for clearing the screen, the shortcut is uh Ctrl L. Okay, if you guys have forgotten that and uh I also mentioned that earlier. So, Ctrl L is the shortcut for that. Uh so, yeah, we have automobile.txt, file 1 and file 2 and LMS. So, we have these four files and one folder there. Okay. Now if I want to move this one of the directory then there's another option. So what I can do is I can use something called as regular expressions. Okay. Uh regular expressions is one topic which I'm going to cover in detail later during the session. But just because we're in the CP or in the move commands uh stage of this uh demonstration. I want to continue and I want to show you this also. Okay. I want to just get finished with this part. So you will get an idea of what I'm saying when you see me do this. Uh so here we have these four files. So first let's use the copy command. So if I want to copy all the files which are in the form of a file. Okay. So they are all in the txt format. Right. So what I can do is I can uh just do a cb I can uh click on dot or rather asterric dot txt. Okay. Now what this essentially does is instead of uh searching for the text file by its name and you specify an asterric it searches for all the files with the uh txt. Okay which is ending with a txt. So that's what this would do. And when we say cp followed by asterric txt, it means copy all the files that are ending with txt. So in our case we have automobiles.txt, file 1.txt and file 2.txt. Right? So what this command would do is it would copy these things and put it in the path where I suggest here. So let's say I want to put it in another folder. Okay. Let me start off from the root home eda. Then here I think we have you know we have these options right? Okay this is the documents. So in the edrica we have okay we have the music folder we have downloads pictures. Okay downloads of course I've already copied something in there. So what I'll do is I'll move that to the music folder. Okay. So the music directory. So I'm going to say this and give enter. So your copying has been successful. So if you go back to the uh music directory you'll see that there are three new files. One is automobiles, the other one is file one and the other one is file two. Okay. Now, uh the same thing can be done for even move, right? Uh the same way we executed a copy, we can also execute the move command. Move is going to completely move it. It's more like cut pasting. Okay? Similar to how you remember from Windows. Let's move it to pictures. Okay. So, currently in pictures, there's nothing. And in uh music, we have these three. So, when I execute the move command, this folder should become empty. And they should all go to the pictures uh folder. All right. So, move. Okay. But we have a problem for that. What we need to do is we got to move to our uh music folder, right? So it would this would probably show an error. So I'm going to first uh go back or rather go to music folder. Okay, we are in documents, right? So what we're going to do is uh cd music. All right. And I have my commands here. Right. So here I'll execute that move command. So it was this one. And I'm just going to replace CP with MV. Okay. So from my uh music directory, it's going to move all the folders or files which will have the .txt format. Okay. All the files, not folders. It will move all the files with the .txt format. And it will move it to home/ora/ let's move it to pictures. What do you say? Okay. So when I give enter, that would have moved. So let's go back to our folders. Music. There's nothing here. This has been cut pasted to the pictures directory. All right. So this is what I want to show you. Okay. This is what I missed showing you earlier while executing the cp command. But yeah, here we are. I've done this. And similarly, if you want to go also uh you know, if you're from the music directory and if you want to move something to the uh present working directory, even that is possible. Okay. So another possibility which I would like to show you is that uh of going back going to pictures and then we have all this here right I'm going to clear the screen ls again we have automobiles file one txt and file 2 txt right so uh we can do a move command and u so right now we are in the u so let me clear the screen So I'm going to do a CD. I'm going to clear the screen. And uh currently I'm going to do an ls. So some of our items are present in pictures. So what I'm going to do is I'm going to uh move back to music. If I do an ls, there's nothing over here. So what I'll do is I'll say move slashhome/reka slash pictures dot okay asterric first dot txt and I want to move it to the current directory. So when I do this again from the pictures everything would have moved back to music. All right. So that is the other uh thing that I want to show you. Okay. So similarly it works for even the copy command. I'm pretty sure you'll understand how it works. So I'm not going to waste too much time on that. Okay, I've cleared my screen and now let's uh start with the next topic. Okay, I'm going to go back to my slides and yeah, the next topic is uh make directory commands. Okay, so the next topic is uh make directory. Okay, that's what mkdir stands for make directory. All right. So it's simple again if it's all about creating a new directory or creating a new folder. Okay. So uh to create a new directory you just specify mkdir and uh the path. Okay the directory path. Okay. That would create a new subdirectory in that path. Okay guys so currently we are in the uh documents right. So I'm going to do an ls. I have these many uh things. So I'm going to do a mkdir and create a new folder over here. So that folder name is going to be uh let's say folder one. Okay. When I do this a new folder is created. So when I do the ls command again so you can see that the folder one is extra. Okay. It was not there the previous time that we executed the ls command. Okay. So that's how you create a new folder. So it's pretty simple. Now comes the other question. Okay. I can go into uh the folder one. Okay, of course there'll be nothing inside. Now what if I want to create multiple folders okay and uh parent directories. Let's say something like I want to create folder one inside which I want to create a folder two and create a folder three. Is that possible? Okay. So I'm going to try doing that and show you if it's possible or not. Okay. So I'm going to say make directory folder one/ folder two. Okay. This would be folder two because I'm already inside folder one. This would be folder three and folder four. Okay. So this basically will run the make directory command inside folder one and it will make a directory 2 3 and four. Now when I give enter these folders should be created. Ideally they should be created. Okay. Ideally speaking. So let me just verify everything once and show it to you. So it was documents. This was a new folder I created. Folder one. There is nothing inside. Okay. Now uh from the terminal if I click enter it says make directory cannot create directory folder 2 3 and four okay because there's no such file or directory okay do you know why that is I as you specifically can we do it that is because when we try to enter one directory it's possible okay when like in this case we specified just one one directory right just folder one so it created the directory once but in this case there are too many directories that we need to create okay it's like two three and four. How can make directory create so many folders? Because this is going to be in the form of a parent, child or a subdirectory, right? We are creating folder two inside which there's a folder three inside which there's a folder four. So in this case, MKD is not enough. So this is when we need to use another flag called the hyphen P flag that stands for parent. Okay, let me go to my slides and just cover that aspect once. So as you can see here, there's a flag called hyphen P. Okay, and what it does is it creates both a new parent directory and a subdirectory. And it's essentially used only when you're creating like two three directories and I mean you're creating one directory and a couple of subdirectories under that directory. Okay. So that's when you use this. Uh alternatively you can also use this hyphen parents. All right. And uh if you want to create one parent directory and multiple subdirectories inside that directory then you can use these flower brackets. Okay. Inside the flower brackets you can have the different folder names. Okay. So let me just quickly go to the terminal and show you that aspect. So make directory these were there and now I'm going to give minus p and when I execute this everything would have been created. So let me do a cd folder 2. Now do an ls there's a folder three. Now let me do this and enter and let me do an ls again. There's a folder four. Of course here there would be nothing. Right? So let me uh enter this folder four and here there would be nothing. Folder four. So that's what I was talking about. Okay. Uh let me also verify that once from the terminal folder one we created a folder two inside which there's a folder three and there's a folder four. Okay guys so this is what we just created. So what I'm going to do is uh I'm going to just go back to my folder one here. Okay. In fact yeah okay folder one should be good. Now I want to show you executing the same command with the flower bracket. Right. Right? I told you that creating a flower bracket will let you create multiple directories inside that directory. So if I'm going to say make directory folder uh because it's inside folder one, I can create one here. Folder two, I can say comma folder 3, folder 4. Okay. And if I close this flower bracket, then these three sub directories or folders would be created inside my folder one. All right. So I've given enter here. If I go back to my GUI. So I go inside folder one. So initially there was one folder two. Okay. That was the folder two which I created earlier. Okay. And now I created folder two. All in small small F, small F and small F here. So folder two, folder three, folder four was created. Now folder this one was created earlier. Okay guys. So that's how uh you know you make directories. In fact, you can even append this with a parent. Say you're supposeding you're now in folder uh one, right? You can say make directory. You can say f_sub_2 put a slash and then inside this f2 folder, these subdirectories will be created. Okay. Now, if I give enter, I know what the problem here is. Uh it says because f2 is not created right now. Correct. This is the time when you got to use the uh hyphen p command, parents command, right? So which I showed you earlier. So now that I've used the minus P. So the parent is created and the uh children are also created. So if I go back to folder one, this was F2 is what I created recently. All right. So inside F2, there should be folder 2, folder 3, folder 4. All right. So this is uh what we can do with respect to make directory commands. All right. So let me close this and go back to my slides. Okay. And uh go to the next topic. Okay. So uh next up is the uh rmdir and the rm commands. Okay. So this is the remove and this stands for remove directory. Now there's a subtle difference between the two. Okay. Now uh when you say okay the basic difference between the two is that when you say remove directory it'll only remove that particular directory. But when you say remove it can also remove the subdirectories or the child directories inside that one. So let me just go to my terminal and show you how these are executed. Okay. I'm going to go to my terminal. So currently I am in my folder one right. So let's go to folder two and then do an ls cd folder 3 ls cd folder folder 4. Okay. Of course there's nothing here. So what I can do is I'm in folder three now. Okay. LS again. Yes I'm in folder three. And I if I want to remove this folder then I can do uh remove directory folder 4. All right. So when I do this this particular folder would have been deleted. Now from folder two I can uh again remove folder three. Okay. Similar to how I removed folder four. But how about I go one more path back. Okay. So right now I'm in ls. Okay. So if I do a pwd you'll find that I'm in folder one. Okay. And when I do an ls I have f2 folder 2. I have a capital folder two. This is where my folder three and folder four is present. Okay. So I have that and then I have folder three and I have four and four. Now however if I try doing a remove directory and if I try to remove folder two right it will not work. It failed because the folder two which we are trying to delete right from inside folder one we are trying to delete the folder two. This is that folder two. And inside this folder two, there's another folder that is folder three. Let me just uh show it to you once so that I can remove your confusion. So inside this uh folder two, I have folder three. Okay. And because I'm trying to delete this uh folder two, it's not able to delete because there is already a folder three inside this folder. That is a problem with remove directory. So guys, I'll just clear the screen and let me just do an ls again. So now I'm going to show you how to remove these folders. I showed you removing folder four. Okay. So inside this folder three, I went and I removed folder four. Okay. Now I'm going to show you how to remove multiple folders. Okay. At the same time. Now let's say I'm running the same remove directory again. So I'm going to say remove folder 2. And u when I give enter, it says failed to remove folder 2 because the directory is not empty. Okay. Uh do you know what the problem is? it's uh telling right because the directory is not empty it's not able to delete. So because folder 3 is contained inside folder two it's not able to delete this folder. So if I want to delete folder two also then what I got to do is you know I got to first delete the folder three and then delete the folder four. So I have to provide the absolute path of the child directory. Okay. So I'm going to say remove directory. Okay. Same like before I'm going to say folder 2/ folder 3. when I run this command then my folder three will get deleted. Okay, the child will get deleted but the parent will still be uh active. Folder two will be active. Okay, because uh when I use the rmdir with folder two and folder three only folder three will get deleted. Let me show you why that's the case. When I give enter when I do an ls folder two should be available. See folder two is available but when I do a folder uh two there's nothing in here. Okay, there's nothing in here. So if you want to do that, if you want to delete both the parent and the child at the same time, you got to use a minus p flag. So let me show you to use a minus p flag. Okay. So I'm just going to make the folder three now. And I'm going to show you how to use a p flag. So similar to how we use while creating a folder, we got to use the same remove directory. Okay. Rmdir with the uh hyphen p and folder 2 and folder three. Folder 2/ folder 3. So in this case both the folder two and the parent and the child will get deleted. Okay. Enter. When I do an ls I don't have a folder two here. Okay. This one is also deleted. So that's what a minus p flag does. Now let me just create make a new directory. And uh what I want to show you is the verbos. Okay. So I'm going to make directory. So again the the ones which I deleted have come back again would have been created again. So I want to show you the usage of the verbos directory. when I add a V here as for the slides it said right verbose. So when I add a v here and when I hit enter, okay, I've done the make directory again. So I have to actually remove the directory now. Okay. Now when I say remove directory and when I uh try to print the uh verbosph so it says first it's deleted the folder 3. Okay, which is inside folder two after deleting that it has come and deleted folder two. Okay, so that's what this is all about. This is what uh you know you need to know about the remove directory commands. Now uh let me just clear the screen. So guys uh now let's uh see how the rm command works. Okay. Now uh the rm command here as it says from the slides it can be used to remove even non- empty directories. Okay. If we use the rm with the r flag and if we use the r and p flags together then it removes the non-mpt directories including the parent and the uh sub directories. Okay. So the one limitation that we had with rmdir command was that we could not remove uh non-mp directories. we had to first empty them and then only delete them. Okay, otherwise we had to specify the entire path and then uh you know use the p flag to remove all the parents and all the child subdirectories in that path. Right? That was the limitation that we had with remove directory. But in RM we don't have that problem because uh let's see okay in ls we have so many folders okay so if I try going to f2 okay and I do an ls here then I have three different folders folder two folder three folder four okay now if it's an rmdir command it cannot technically delete this folder called f_sub_2 f_sub_2 is basically a non-mpy directory inside f_sub_2 there are other directories like folder 2 3 and four so let me just uh show to you once so inside f_sub_2 we have three folders folder 2 folder 3 and folder four. So with the uh rd diir command we cannot definitely remove but with f2 we have a chance of removing it. Okay that's because uh we can make use of the r flag here. Okay but however this will also it will delete f2 and its subfolders. Okay so let me do an ls and uh if you can see here initially under folder one we had f_sub_2 and these three. Okay but now we don't have that under f2 because that whole f2 folder is missing. If I go back to my folder one here, you'll see that the F2 is uh missing over here too. That's because on the remove, right, it uh removed the whole F2 folder in spite of it containing some folders. Okay, and that's what the R flag does. That's the advantage of using the R flag. Okay, so if the same thing if we use the R flag with the V flag, then it'll print the uh status also. It's like the verbose, right? It'll print it'll tell you what all has been deleted and how it has been deleted. So that's the advantage with using RM over uh RMDR. Okay. At times this is more beneficial. So I'm just going to clear the screen and uh getting back to my presentation. I'm done with all the concepts in this slide. So let me go on to the next topic. Okay. So the next topic is going to be that of uh working with user permissions. Okay. It's very important for a Linux administrator to know what these uh user permissions are. Okay. because uh the different files will be there, different directories will be there and he has to determine what kind of access will be available for which user right so that's what is control here so uh the different permissions are basically read write and execute okay R stands for read W stands for write and uh execute is X okay so uh initially you'll get this kind of an output okay you know what let me go to my terminal and show you what happens when you run an ls ns ls minus L command because user permissions is something which will appear and which you can control via the ls-l command right because when you do that all the different file contents whether it's a directory or whether it's another file all those things along with their uh permissions will be visible in long format right so let me go to my terminal first and uh go to cd all right now when I do an ls I have a list of all these uh documents okay but however when I do an ls-l I get it in long form for okay so I get it something like this so for each folder I have the permission set so for desktop I have the permission sets and then I have the other components okay I'm going to explain what this entire component what the entire row means so to not let you get too complicated first I'm going to explain only this part okay the first 10 characters if you see here the first 10 characters are these and I will explain this part first and then I'll explain this set these three blocks and then I'll explain the remaining blocks blocks. Okay, so getting back to this uh first block in my slides, you can see that the first block it determines what is the file type. Okay, it's either the file or directory type. In fact, if that is a directory, then it would be represented by D. Okay, if you have a D as the first character over here, then that's a directory. Okay, as it says, but it can also be any other thing. If it's a hyphen like this, then it means that it's a normal file. Okay, buth in the first letter, if it's a C, then it means that it's a character special file. And uh if there is B over here in this part of the first letter then it's a binary special file. So basically there can be four different letters over here. It can be either a hyphen or D, B or C representing four different aspects. Okay. So uh that is the first information that you have about that particular file. And then you have three different blocks. Okay. So the next nine letters are going to determine the user permissions. Okay. And those nine are divided into three three. Okay. So the first three represent the user permissions. Okay. The second block having three uh RWX representatives are those of group permissions and the final block represents other permissions. Okay, this means other users. Now this user is the actual user who is logged into the system. Okay, that particular user. So this is the user permissions. This is the group permissions which the user belong to and what the other group can view. And this is with respect to the other users. Okay, that's what is meant by this others. So if we have uh and the order always goes by RWX and RWX and here also it'll be RW and X. Okay. So that is the order read, write and execute. So if the first three blocks are all R, W and X then it means that the user has all the three permissions or the owner of the file or the user has uh the read, write and the execute permissions. Okay. And in this place if there are three characters right, W and X in this order it means that the owner or the user has the permissions to read, write and execute that particular file. Okay. And if there is R, W and X in the next block, then it means that the group has the read, write and execute permissions on that particular file. So every file that's created, right, it will have a user and it will also have a default group that it will be assigned to. So all the users a part of uh that group will have the read, write and execute permissions. Okay. But whereas the last three here it stands for other users permission. So there can be multiple users, right? The same system can have multiple users. One of course will be the root user. The other will be the owner or you and besides you there can be any number of users. It can be your friends, your colleagues or uh you know other people. So this others represents that. And uh if you have a blank in any place okay so in this case there's a blank over here in place of w there's a blank it means that this others they don't have the right access they only have the read access and the execute access all right and similarly if you go back to the terminal okay and if you see here take the example of this particular file desktop okay desktop folder is where we were executing a lot of commands right it is under the folder so yeah this was the folder that we are talking code the desktop right now it's a directory basically okay that you all agree with then these three characters represent that the person who's using it okay right now the person who's using it uh because I'm logged in right now and I've logged in with this username right sorry for that guys yeah and I've logged in with this username right Eda so uh me being the owner and me being the user I have the read write and execute permissions okay but the group that I belong through. Okay, that group does not have the read, write and execute permissions and the group that uh this file belongs to. Now, because uh this file is either owned or used by me, okay, now because I'm the user, I have this access and then this file will also belong to a group, right? So, whenever you create this file, it'll be assigned to that particular user creating it and it'll be assigned to a default group. So, we're talking about that group here. Okay? And that particular group does not have all three rights. It has only the read permission and the execute permission. It doesn't have the right permission. Okay. And the same thing can be said for uh even the other users. So the other users in that system who'll be using that system, they'll only have the read and execute access on the uh desktop. Okay. But whereas if you take the example of this file one.txt, right, which I created sometime back uh during this session, this one if you see the permissions are such that the first one is a hyphen. Okay, what hyphen technically means is it's a normal file. Okay, I explained that hyphen is normal. B stands for binary special file and C stands for character special file. So of course we don't have uh those options here. We don't have the B and C options. But what you got to understand is uh is that this is a normal file and this is a directory. Okay, wherever there is D. So since this is a file and the access for the user is such that I have the read and write access. Okay, but I can't execute it. The user can't execute it. And when it comes to the group, even the group has the read and write access, but it cannot execute it. The other users, however, they have only the read access and they cannot execute this particular file, right? So they cannot execute or they cannot write this particular file. So that's what these group permissions mean. And if you go forward from group permissions, there are more other blocks, right? So let's go back to the slides and see what they stand for. So in this slide, let's talk about the next three blocks. Okay, so the next block is that of a number. Okay, you have a number over here and that represents the symbolic links. All right, the block after that is the one that represents the owner name and the one followed by that represents the group name. Okay, so that is with respect to these three blocks. All right, and then after that comes the file size of the particular file and then you have the time stamp, the time when the file was created, the file or the folder was created. This is the actual file size of the block. Okay, now that's what the user permissions here represent. So if I quickly go back to the uh terminal and show you this is basically the symbolic link. This is the uh owner name. This is the group name of the file. This is the uh block size. Okay. And this is all in kilobytes. Okay. And uh this is the time stamp and this is of course the name of the file. Right? So we have the name of the file and that file will have first be the file type then user permissions then symbolic links then the owner name then group name then the file size then comes the time stamp at the end. So that's what the different file permissions are. The read, write, and execute. And if you want to modify any of these file permissions, then it's also possible. Okay. Now, let me go to my slides and show you how that's possible. Let me show you some theory first. Okay. So, first of all, if you want to change the permissions, then you can use the chod command. Okay. You can use the chod command as shown over here. And uh you can use it to change the access permission of both the files and the directories. If you want to change the owner of the particular file, okay, change the owner of that particular file or directory, then you can use the ch own command. And then if you want to change the group ownership of that file, then you can use a chb. Okay, so when you use the chod command, you got to specify whom are you referring to? Are you referring to the uh the user, are you referring to the group or are you referring to the other people? Okay, the other users, you got to say that and then you got to use either a plus symbol or a minus symbol. Okay, when you use plus, it means that you're adding these two rights. Uh so in this case when you're saying G plus WX so G stands for group right so as you can see from uh this particular slide G stands for group U stands for users and others stands for O okay and all stands for A okay so as for this if you're using G over here then it means that you're talking about the group and you're adding the W that is a write and the execute permissions that means you're giving them the W and the right and the execute permissions okay and after you got to specify file name. So this means it will modify the permissions to this for this particular file and similarly you can use the equal to symbol and also the minus symbol. So when you use the equal to symbol then whatever rights you have initially that will be overwritten. So when you say chod u is equal to rwx and then uh it doesn't matter what the previous set of permissions were then the the previous set of permissions will be replaced by whatever you specify here. So you'll be setting that particular user to have the read write and execute access for that file. Okay. And then um you can in fact specify uh you know uh you can set access control for multiple people. You can set it for uh groups users all at the same time. So in this place this command we've set it for the users. Here we are setting it read, write and execute for users. And then after that we are setting it for the other people. Okay, for the other users we are removing the write and the execute access. Okay, the execute permissions. So let me just quickly go to my uh terminal and show you that. So currently uh let's take the example of this pictures okay let's take an example of this particular folder the user that is me I have the read write and execute permissions the group has read and execute only okay and uh they of course the other users they also have only the read and execute now what I'm going to do is I'm going to say chmod uh I don't want to change my permissions okay so I would rather uh change the permissions that my group has so I would say G is equal to read and W. Okay. So if you see here right now the group has read and execute. Okay. I don't want to give them execute. So if I want to remove execute I have to do G minus R and then I have to give comma G + W. Okay. But uh those are two different arguments right? So instead of using two different arguments I can just give an equal to which would replace this entire list with the uh current arguments. So instead of having R and X I will replace that with R and W. read and write. Okay, I'll give a command and then we have others here. The other users they have read and execute again. So what I'll do is I'll uh say O minus execute because I want to give others only the read access. Okay, so in this case when I do this the X over here that will become hyphen and the hyphen here will become W. Okay, I'll be enabling the W for them and removing the execute and for these people I'll be removing the execute. And now that I've specified what are the permissions and who are the recipients, I'm going to give the file name. So let's say pictures. Okay. So I'm going to give the ls minusl command again. And now you can see that if you go to pictures, it's been reset. So the others have only the read access. The others are blank. Okay. And the uh group have the read and write access and this execute has been taken away from them. So that is with respect to the read, write and execute permissions that users can have. All right. So I'm just going to clear the screen and go back to my slides. So similarly you can change even the ownership of certain files and uh certain groups. Okay. So u if you use a ch own, okay, ch ownership with that's what it stands for. And when I follow that with the username and the file name, then this particular file will have a new user or will have a new owner. And uh this will be the username. Okay. And similarly even the group command works in the same fashion. So uh this is something that you can always uh work on and you can figure it out. All right guys. So working with Linux repositories. Okay. And it says that stable versions of most softwares will already be available in Linux repositories. And the command to install them is this. So you would have heard me say earlier that it's very easy to update software and the operating system itself by just running one simple command, right? you can update the software. So, uh this is what I'm talking about. So, you can just run one command. So, this is the only command that you need to run. Okay? If you just give sudo yum install and if you give the package name, then that particular package will get updated. Okay? The pseudo is something that you would recognize from what I told you earlier. The pseudo is to uh we give it to to execute this uh command as a root user. Okay? And uh if you see that there are two other lines and the only difference between these three lines is the letter that the word we are using here. Okay. So in the first case in case of any Red Hat enterprise Linux system or uh even CentOS right which falls under Red Hat we use Yum. Okay. But if it's a Debian based system like Ubuntu or Eduntu X Ubuntu or any any other Debian Linux system then you would have to use apt get. Okay. And then if you're using a federal based system then you got to use the dnf. Okay. So these are the three different commands and these are the that's because the repository name for real it's called as yum repository and the repository name for debian is called as the apt repository. Okay. And for fedora it's called dnf repository. So that's why we say we are first we will have to first give the sudo uh sudo command which would make sure that we execute this command as a root user. And from the command perspective, the first part would be calling or referring to the repository. Okay. So from the CentOS, it would refer to the yum repository or from the Ubuntu if it is. If I give appget, it would refer to the apt repository. And then we have something called as install. And when we say install and then follow that by package name, then that particular package will get installed. So for example over here it is Java, right? I'm trying to show how to install Java on your system. So in this case if you first give yum update then it will uh first of all update your links to your repositories okay it would update the yum command and the links that you have between the repository and yourself so it's not something related to installation of java okay this is just another command that you specify if any of your installation fails okay so this is not a compulsory command that you need to run but besides that what you have is uh yum install java 1.8.0- 0 - open JDK. Now the package name that you see here right that is Java. So if I want to install Java then I would just give this particular package name and I would say install. Okay because the package name of Java that's present in the Linux repository that is called as Java 1.8.0 open JDK. And similarly, if you want to install any other uh software, right? If you want to install any other technology like Hadoop, then you can just give one such uh package name. You just got to find out what is the name of the package that they have in the repository. You can just simply Google it and uh it will give you the package name and you can just say yum install or pseudo yum install followed by package name followed by Hadoop - 2.0 or 2.3.0 or very soon Hadoop 3.0 is coming. So you can say Hadoop 3.0 something like that. And yeah, if it's uh if you want to install Docker, then again you can say sudo yum install docker and uh probably the version name. I don't think docker needs a version though. And uh for installing docker you can uh do it also through Ubuntu. Okay. So when I installed docker in my other Ubuntu VM right which I showed you earlier. So that VM has docker installed and uh the uh command that I ran that time was sudo app get install docker and uh that downloaded and installed the latest version of docker that was available in the uh repository. Okay. Yeah. So that is it and once you're done with the installation it would take quite some time to install and once when everything is done then you'll have to just you know update your environment variables. Okay. Here you have to set the environment variables over here in your dot bash rc file and once you set the environment path over there then you can just do source and then your software is ready it's installed okay now this was another step which I skipped out because this is not really necessary for you to uh execute this okay I'll tell you why because uh this command which is update alternatives - config java it is only to select a particular version of java now let's say that you're new to Linux okay and uh you're downloading Java for the first time then you just need to run this command. So after running this command you can straight away just uh you know probably when you're done with this Java is installed basically okay but it's just that you need to go to your pseudo you should do pseudo gedit go to your bash rc file and update the path where java is installed okay you got to specify to your uh environment variables to your runtime engine that java has been installed in this path so you have to just copy the path of your java and paste it in the environment variables over here and then you have to source that particular bash rc. So when you're done with these two things, your Java is installed. Okay. But if you already have a Java package installed, okay, so in my case when I'll be showing you this now, I already have a Java 1.7 package. Okay. So now if I do a pseudo yum install Java 1.8.0 open JDK, then I'll have multiple versions of Java. Okay. And my environment variables would be currently set to Java 1.7 because that's what I already have. But uh since you have you know multiple versions of Java and since there are different packages you can have multiple packages of Java installed but you can only run one of them. Okay. So you set which one you want to run right? That one you set over here whether I want to choose to execute seven or whether I want to choose to execute eight that I can choose by updating over here. So I'll show you this command also. Okay. So that is what I want to show you with respect to Linux repositories. So similarly you can even uh you know you can do a pseudo yum install PHP if you want to install a PHP server you can just say PHP MySQL server if you want to install any other software like wget you can do that also. So this is what we are saying you know it's very simple to install software. So if you're doing it with the GUI then you'll have a lot of steps that you need to do. You need to go to the website download the appropriate package then extract them then install them all those things. So instead this is just simpler and it's uh much faster. Okay, now let me go back to my terminal and show you how that is done. Okay, so I'm going to go to my uh CD and the command is sudo yum install and uh now would come the Java package. So the package I'm going to install is Java 1.8.0. Okay. Uh that's because Java 8 is uh plays with this name. Okay. Okay. So the package name of Java 8 in uh the Linux repositories is uh Java - 1.8.0 - Open JDK. Now when I hit enter, it asks for the password because uh this particular uh sorry for that guys when I use pseudo to execute this particular command then it asks for a password because I'm executing this as a root user. So that's why if I try executing this as a local user, as my own user, then it wouldn't be possible to execute this command. Okay, I have to execute this as a root user and uh root user is the one that has the ultimate privileges, the ultimate access. He has access to everything. So you just enter the password and put enter. Then automatically your packages will get downloaded and uh it'll get installed. So uh now it says you know total download size is 33 MB and uh it asks is it okay to download it. Y stands for yes and N stands for no. Now if it's uh you when you're trying to download Java when you give this command you got to say why and hit enter because that would download the 33 MB package and install in your Linux machine. Okay. But however I have already downloaded Java and since I've done it already so I don't need to. Okay. I don't want to waste my time here because uh this is a session right? I don't want to waste your precious time. So what I'm going to do is I'm just going to click on end and give enter. Is it fine? Uh Sedat Hmon all you guys who are in the session is it fine because I want to save some time here by hitting N. Okay. Because otherwise it would take some time to set up the installation process. So okay fine. Yeah I'm getting a yes from uh you both. All right. So I'm just going to click on no. Okay. So it says uh exiting on the user command. Great. Uh yeah. So the the only thing you got to note is that instead of n if you put y and if you hit enter it would download for you and it would complete the installation. All right and uh there's one more thing that I would actually like to add to this. Supposing while uh installing the same package right while uh doing the pseudo yum install java this package when you're trying to run this command if you want this y option to be chosen automatically okay because right now it entered into the interactive mode. Okay, interractor mode is when the colonel was asking you should you download this and do you want to download this and execute it later and I had to press N and get out of it. Okay, but however you might not want to. Okay, so so there may be times when you might want to by default just click on yes. So what you can do at that time is you can just uh go back here sodom you have a flag here you can just put hyphen y and if you uh then install it then it will not ask you it will not get into this interactor mode. So it will take this y flag y option automatically and it will uh you know install the java package. So that is what I wanted to show you. That's what I want to tell you. So that's how you install uh java. Okay. So now I've just cleared the screen guys. Okay. So the when you execute this command in your Linux machine and when you finished downloading and installation of your uh Java, what you got to do is you got to set your environment variables. Okay. So as it was written in the slide, you got to give the pseudo gedit bash rc to enter into the bash rc file and set the enment variables here the path to where your java is installed. Okay. So uh what I'm going to do is uh I'm going to do the same to and your bash rc is something that will be present only in your home directory. Okay. So you got to remember to uh go to cd and from cd you got to access that. You got to say sudo gedit space dot bash rc. When you do this, it'll ask you for the password. But of course, I've entered the password previously, so it didn't ask me. But yeah, when you do that, you will open this uh bash rc file. Okay, so right now my java path is set to this. Okay, so this means when during runtime when any application is using or requesting for java, then it will look for Java in uh this path. So you just need to find out where your Java has been installed in your system. So it would most probably be in your user/lib/jvm folder. Okay. So let me uh go to the same. So it'll be there under your root directory. So uh if you uh go to your my computer from your file system under the lib folder we have various uh packages that will all be installed over here. Okay. So in my system it's all installed over here. So this is the JVM folder and inside here I have all the different Java packages which I have downloaded over a period of time. So guys uh in this case supposing see I have Java 1.7.0 open JDK installed. Okay. Now in your case you will have a Java 1 8.0 open JDK installed. So what you got to do is you got to just right click on that folder. Okay. Similar to what I'm doing now. Okay. I'm going to right click and just click on copy and go here and paste the path over here. Okay. If anything is existing already then remove that and paste the new path. So the path is nothing but where your JVM is located from your root. So it's in root usr library folder and then inside library it's in JVM and here it's this is the folder it's present in. Okay. And then you got to also additionally give the path to your bin directory. Okay. So you have this is your bin directory. So what you do is you right click on bin again copy go to your dot bash rc. Okay. You got to uh paste it over here. All right. So this is how uh this is what you do. This is how simple it is. So when you do it, you just got to save it. And you got to, you know, close this uh dot bash rc file. And when you're done with uh saving and closing it, just go back to your terminal and you got to run this command source dot bash rc. Okay. So when you do this, then your terminal will get synced with the updated environment variables. Otherwise, even if you don't run it, it's fine. You can just start executing your commands from a new terminal. Then it would all be fine. But yeah, the source.bass back is only to sync your environment variables with this particular terminal that is uh opened. Okay, so that's how you install Java in your uh system. Okay guys, so u I'm just going to clear the screen now. Okay, and I'm going to go back to my slides. Okay, so I'm done with showing you how to work with Linux repositories and uh the next topic that I'm going to talk about is that of uh tar files. So what are tar files? Okay, so all of you Windows users might be aware of uh this software called Vinszip or VRA. Okay, what are they? What do they do? They are basically to extract your files, right? So they'll be in compressed form and you'll have to extract them. So uh in Linux we have an equivalent format. So in Linux it is either the tar file or the gzip and the gunzip files. Okay, so tar is the preferred option. So I'm going to show you how to compress and decompress a file with tar format. But however even gzip and gunzip is something that can be used if you want to compress a files with the gz format okay then you got to use this command but however if you are going to decompress it then you got to give guns okay and the syntax is here okay but however with tar you for both compressing and decompressing you'll use the same tar command itself so you'll just have tar and in the arguments there'll be a minor change so when you're compressing the file you'll have to specify hyphen c okay and when you're decompressing the file, you'll have to give the uh flag minus x otherwise it's all fine. Uh the vi here stands for verbos and the f here indicates that you want to compress the file that is mentioned followed by uh the command here. Okay, so this f just basically indicates that you got to compress this particular file otherwise the uh colonel will be wondering which file to compress and it will throw an error to you later. Okay, so that is what the xvf stand for. These are the different flags that are available with the star command. Okay. Okay. Before I go and show you how to do the start, let me show you a place where tar files will be present. So in Linux, right? So no matter what kind of software you're downloading, whether it's a Java package or if it's a Hadoop package, if you're downloading them manually from the internet, okay, then you would get them in the tar format. Okay? Or you might find them in uh TGZ format. Okay? So tar is something the most I mean I would prefer a few people download tar because that's the easiest uh it's easiest to extract and you know also compress them. So I can just download the tar file. It's very common and you can just by just running this one command you can compress the file. So the Hadoop packages that are available on Apache's website right that would almost be around 2 to 3 GB but you the compress format will only be around 100 or 200 MB. Okay. So same thing can be said for uh something like Tomcat if you're you know downloading the Tomcat package or Nagios. So anything like that. So those packages would have a lot of MB and uh to download them you'll need to compress them right. So because the lesser you download the more uh you save on bandwidth. So it's also easier to transfer them in a compressed format. So for transferring especially you use the tar files. Okay, you compress them into tar format and then later when you're done downloading, you can extract them and bring them to regular file format. So, I'll show you how that is done. So, uh first of all, let me go to my terminal and uh let's go to the documents folder. Okay. Um here I'm doing an ls. We have this. So, what I'm going to do now is I'm going to say ls-l. Okay. When I run this, you can see the different files and the size. Okay. You can see that the uh LMS folder right the LMS folder here it has it's the highest okay it's it's showing it's 4 40 496 MB. So what we can do is I'm going to show you how to compress this and convert it into a tar file. So to convert it into a tar file you got to say tar - cvf. Okay x is when you're trying to decompress it but uh cvf is when you're trying to compress it. So you're going to say tar - cvf and then here comes the uh tar file name. So what you want to be the name of the tar file. Okay. So I just want to have it as lms do tar. Okay. So this is the name of the file I want to keep. So I will put that here. And then you got to specify the file which you want to compress whether it's LMS or whether it's any other folder. So I want to do it for LMS. So I can just say LMS. Okay. And when I run this command then this particular document would have been compressed and it's present. Okay. So if I do an ls now you can see that there's an LMS folder and an LMS star file. Okay. So this is the compressed version of this folder. Now when I do an l ls minus l command, you'll see that there's a new tar file that's created. Okay, lms.tar. And then you have this folder whose tar file this one is. So that's how uh simple it is guys. And uh what you can uh do now is if you uh you can just transfer this file over FTP or via SSH or you know just upload this to your internet and let people download this because this is a smaller file compared to this proper folder. Right now uh in case you want to uh extract a file. So in case you have downloaded this kind of a tar file, okay, from the internet, how will you untar it? What is the package to uh know decompress it? So uh to answer that question, I can we can give the command tar- xvf and the package name. So in my case, it's lms.tar. So when I just do this and when I hit enter, then that package would get extracted. So now if I do an ls command you can see that this particular tar file has been extracted but you can't see two different folders because uh the existing LMS folder has been uh rewritten okay so it has been uh well let's just say it has been overwritten and that's why you can't see two different files but yeah as you can see this was the process which was taken to untar the LMS package okay so that's it with respect to the compressing and decompressing of files So uh let me quickly go to the next topic in my slide. Okay. So the next topic is that of environment variables. So what are environment variables? I told you that we had to set the environment variables in the bashrc file, right? While installing Java. So what are they? As the definition says here, environment variables control the behavior of the software packages installed in Linux. Okay. The path where the packages have been installed will be specified in the environment variables. So if you're installing Java okay and if there is some other application which needs Java let's take the example of Hadoop okay so Hadoop is basically a Java framework okay so the map produce concepts it's all Java related and you need Java to run Hadoop otherwise it will not run Hadoop so by just downloading uh the Hadoop tar file from the internet and extracting that tar file is not enough okay what you got to do is you got to download Java also and uh set the environment variables for both Java and for Hadoop so In our case when Hadoop is running because it's based on the Java framework it would need Java to work right. So at times it will ask the runtime engine where is Java installed so that I need some commands to be run on Java. So at that time when the runtime engine is asked that kind of a question it will go to the environment variables and it will look for the path over there. Okay. So that was the environment variables I was talking about earlier. Okay. You go and set your environment variables in your dot bash rc file. And your dot bash rc file can be uh accessed by going to your home directory. From your home directory just run gedit dot bash rc. Okay. And here you can set your path. So if you've installed Hadoop recently then you can just set the path of Hadoop over here. And if you've installed Java then you can set the path of Java over here. So basically whenever any other application wants access to uh some program right? So it can uh get access by looking at its path from here. So that's what the uh bash rc file is all about. Okay, that's what the enamement variables are all about. So uh that was about the enamement variables and we have some of the most common environment variables are these. Okay, print env. So this will basically list or prints the list of all the enamement variables. Okay, all or almost all the enamment variables. That's what this will do. And then when you say echo, you know, dollar home, this will print the path of the home directory of the user. So this uh hom that you see here this is a variable okay and uh the path of your home directory has been specified over here. So whenever you press cd on your terminal right so it goes to the home directory correct so that is the home directory I'm talking about over here and the path of that is what is set over here. So when you say echo dollar home like I told you earlier I showed you that echo will basically print whatever arguments you give it will print it to standard output right. So when you say echo dollar home it will print the path of your home whatever stored in this variable and similarly when you give echo dollar path then it will print the list of all the directories in which the shell looks for commands. Okay. And all those directories will be separated by colon. Okay. So you'll have multiple directories which you'll get as a result and they will all be separated by a colon. Okay. And similarly for host name whatever is the name of your host of your system. Right? That will be printed when you give this because this again is a variable and this uh is all set as environment variables. Okay. And then you have username your username will be printed. So and when we say language it's basically the uh the language right in which the whole uh system works. It can be either Chinese or it can be English. So in our case, it will all be English, right? So because we are all uh working on English. So it'll all print either US English or UK English, something like that. And when you say echo bash version, this will print the version of uh this instance of bash. So let's just go ahead and execute some of these uh environment variables. Okay, I'm just going to clear the screen and go to cd. Clear the screen. And first of all, let's uh put dollar or let's say echo. when you give echo you have nothing. Okay, I showed you earlier that when you just put in echo and uh when you say hi you will get high as return the output will be high. So similarly when you say echo dollar x right I set the path of x to to 100 earlier. So when when I say this right x I will get the value of 100 now and similarly the path of home will already be set. So if I just give uh echo and u dollar path then all the directories where the shell will look for to execute commands those paths will be present here. So scope is located over here in this uh bin path and separated by a colon we have the next thing. So I have installed pig in my system. So pig is installed here. Ui is installed here. H is installed here. Okay. And similarly uh if you see java java is installed here. Okay. and Hadoop 2.2.0 Z that's installed over here right and uh similarly there are all the directories where your shell will look for right they will all be specified in uh this path so similarly you have another command that is for uh home this will print the home directory and my home directory is home/reka you can also alternatively print your host name right so my host name is localhost dot localadmin okay so this is my host name right so my uh basically My host name is local host. So that's what's being printed here. And when I say echo and follow that with language, okay, with a dollar, then it would print the language. So this is uh using English, US English, okay, UTF - 8. So that's what this means. And in case if you want to print the list of all the uh enamement variables, then you can just run this command print env. So all the enamement variables uh that are there in your system, they will all be displayed here. Okay, so u that's it with respect to environment variables. Let me get back to my slides now and continue with my session. So going on to the next slide now I'm going to talk about regular expressions. Okay, so regular expressions or reg x they are used to search through data. It can be piped along with the grip command to find patterns of text in the file. Okay, now what this means is that you'll have multiple different files or you know multiple a lot of data in probably even one file. Okay. Uh with the help of regular expression, what you can do is you can search for patterns of that data. So you can use the GP to search through data and you can uh use the regular expressions to search through patterns of data. That kind of a pattern. Supposing you have a spelling mistake in the middle. Okay. Supposing the spelling of apple is a ple e. Okay. And uh you know you might have made a mistake in one of the files you have saved it as a okay. and you're not able to find when and when you're using Apple AB you're not able to find that actual string okay then it's uh you'll be wondering why you're not able to find it okay then you'll realize that okay it may be because the spelling that I would have entered in the file it's uh that might be wrong by mistake I would have entered a so in that kind of a situation you can use regular expressions to find patterns of text in the file so you're all aware of uh the pipe I spoke about earlier right you can use the pipe to use one operations output as the input to another operation, right? So you can use that and you can use the regular expressions with the combination of GP. Okay, with the combination of GP command. So you have uh a lot of regular expressions and uh the most common of them are these. Okay, so the dot here it basically means it can replace any character. Okay, it can mean any character the dot. So and then you have the carrot symbol here. So the carrot symbol here, it basically uh matches the start of the string. Okay. Now what that means is let me give you an example. Supposing you're doing a cat file.xt. You're looking for some kind of data inside this filone.xt and you're using the gp command to search this data. Cat will basically list down all the uh file contents. GP will search that data. And how will it search? When you give a, it will just display you know all the lines or all the words where a is present. But when you give carrot a, it means that the starting of the string starts with a. Supposing I have uh three different lines or three different strings in my uh document in my file 1.txt. Okay. Supposing I have uh abc uh a fg and uh a df. Okay. And if I uh give character a then the result that will be out would be uh given given back to me is those three lines because those three lines are starting with the character a. So that's what this character means. It matches the start of the string. Okay. So that's about carrot. And similarly, if you want to match something with the end of the string, you can use the dollar symbol. And supposing you know that this particular word or string that you're searching for, it ends with XT. Okay, in that case, you can uh put XT and then you can uh suffix that with a dollar. Then all the strings in that particular file uh you know which are uh all the all the strings in that file which are ending with XT, they will be displayed. Okay, so that's how you can search for data. And uh similarly if you give asterk uh asteric basically means that the character that is uh you know preceding the preceding character is it matches zero or more times. So let's take an example of this. Okay. Now in this case we have u in front of the asterk. Okay. So the asterk basically means preceding character matches zero or more times. Supposing I have two different strings in my file. Okay. One string is abc and the second string is uh d e f. So then comes the asterk. Okay. So when you give asterk, it basically means that the uh preceding character it occurs zero or more times. But uh however if you give a question mark it means that the character that that comes preceding before the question mark that appears exactly one or it can appear more times. Okay. And then you have uh you know these brackets here which can be used to group these regular expressions. Supposing you have you know more than one or two regular expressions, you can use them to group them. And uh again the uh backslash here it represents special characters. Okay. So let me uh just run a couple of examples of uh this for you. Okay let me go to my terminal and go to my home directory. I'm going to clear the screen. I'll go to documents. Okay. So in here I have my three different text documents. Automobiles file one and file two. So if I uh do cat and automobiles txt then I have a list of uh all these uh strings right I have a list of all the cars and bikes and the different uh automobile companies. So what I'm going to do is uh I'm going to say cat automobiles txt and I'm going to use a pipe. I'm going to use a grip command to search for strings starting with the letter a. Okay. So if I give a then all the strings where there is a present that will appear. Okay. Now first let me show you without the regular expression. So when I give a then these are the strings where a is present. Okay. Uh however if I uh give rep then it will list down those strings where a is not present. Okay. So you might see a present in these two things. But the truth is it's looking for small a. Okay. If you want case insensitive searching then you can just use uh I also all right so uh you can see as you can see from here in these four strings a is not present right so that kind of uh searching is what we need to do so I can use a regular expression to search for those strings starting with a particular character okay by using the carrot command so in uh if you take this example so these are the list of strings in which a is present right so in here where is a starting okay so a is probably starting only in uh this one particular uh string. Okay, but maybe also over here but because I haven't included the in case insensitive. So what I'm going to do is I'm going to remove this v once I'm going to print it. Okay, I'll just do a control l and execute it again. So now if you see uh all the strings where a is present whether it's a capital a or small a those will be listed here. Okay. And now I can use a regular expression to uh basically filter out those letters or those strings which are starting with a. Okay. By uh specifying this command. Okay. So I have to ideally get the answer I should get is Aprilia Audi and Amber. Okay. So when I hit enter, okay, so uh there's a space here. So that's the problem. And as you can see uh it says that there is no string that's matching with this a. Okay. Now that's because I removed the hyphen. Okay. I removed the hyphen I which stands for uh case insensitive searching. So it basically returns that uh it's not returning any result here. So that basically means the there was no search. But however if I add hyphen I okay hyphen I and enter then I will get these three as my results because I've added the case insensitive searching here. So did you all guys get this concept here of using regular expression of uh you know this is carrot. Okay this matches the starting of the string. Now I can do something similar. I can search for the end of the string. Okay. Now let's see again if I use a itself and if I give dollar then it will look for all the strings which are ending with a. Okay. So uh that's happening because of uh this problem. The whole dollar a should come inside brackets. Okay. I should be in uh quotation marks. So that's the thing. So when I do this I'm not getting any result. So u similarly I can uh execute another uh command. Okay. So another one involving regular expressions of asterric. So what I'll do is I'll say gp - n let's say I want to search for the character a itself. Okay. So um when I say a in asterisk so it when when I use this asterisk it basically means zero or more occurrence of a. Correct. So I'm going to search for that from uh here and then I have to specify the file name over here. So I'm not using any cat command and I'm not using a pipe to get data in over here. Okay. So I'm just going to display the number of times that happens by specifying the file name here. I'm going to say automobiles.txt. When I hit an enter, I get all the occurrences where zero or more times a is occurring. Okay. So that is uh one aspect. And uh the other command that I can show you is that of respect to echo itself. So I can run an echo inside flower brackets. I can say a to z. Now when I print this, okay, sorry there should be just uh two dot symbols. So when we say two dot symbols it basically fills the characters the sequence of a b c a ab a ab a b c e f g h uh you know the entire alphabetical sequence that will happen as you can see so that's because there were just two dots specified but had there been three this wouldn't happen okay it would just display this whole uh thing again so the thing you got to note is that the regular expression that we are using here is this one two dots okay so similarly you can replace it with even numbers so we can have 89 9 and you can say 33. So from 33 to 89 all the numbers will be uh you know the sequence of the numbers will be present here. You can also have a combinations like you know I can have uh say p over here and I can have an a over here. Yeah when I do this the combination of a with all of these uh numbers would be visible. So as you can see so a 33 p a 34p so things like that right so patterns are also being generated. So that is the advantage with some of these uh regular expressions. Okay. So I'm just going to clear the screen now and uh go on to the next topic. Okay. So we are done with regular expressions now. And uh this takes us to the final part of uh this uh Linux demonstration. Okay. This Linux webinar. And here we're going to talk about processes adding users and SSH. All right. So let's get started. Okay. So um guys processes is something that's really important from the administration uh perspective of Linux. Okay. Well it's I mean it's basically something that's necessary not more than you know uh an important thing. It's was basically necessary. I mean uh you should know what this is and when I say processes I'm pretty sure that you know that we are talking about the programs or instances of programs right? So uh anything that you start on your uh system so whether you're starting a web browser or whether you're you're using a media player so everything every software there it will have a process involved okay there can be multiple instances of that particular project uh supposing I'm viewing a presentation on my uh computer okay supposing I'm seeing five different presentations at the same time I mean I can see only one at a time but I can have the remaining open and I can put them in the background right so uh that's what we mean so the different instances of that particular system can also be considered as a process. So at any point of time only one application or only one process will be in the foreground. Okay. But many such uh instances of many softwares or also of that particular software or program can be present in the background. Okay. So the example of that is uh me opening uh two chrome browsers. So I can have two different chrome windows and uh you know one can be in the background, one can be in the foreground. Okay. So similarly PPTs or whether it's uh a media player anything like that. So that's what a process is. Okay. Now going back to definition an instance of a program is called a process. All right. Any command given to the Linux kernel starts a new process. And there can be multiple processes of the same program. There can be multiple processes. When we say processes it basically means instances. So we can have any number of instances of any of your application right of chrome or of VC media player of all those things. You can have multiple such uh instances at the same time and all these instances are referred to as processes. Okay, official term is processes and each of those processes have some process ID. Okay, so uh yeah, like I told you they'll be divided into two different processes. One is the foreground processes and the other one is the background processes. Okay, so um how will you determine what are the different processes that are running in your uh system in Windows? You can just do control altdelete and then you'll uh get the list of programs, right? And you can even terminate them. You can end the programs from there, right? So you have different tabs. So let me show you an example of that. Okay. So this is my Windows system. Okay. And when I do control altdelete, it starts my task manager and it asks me for applications or processes and all these things. So this is the process that I'm talking about. Okay. You can have any number of processes in running in your system. Okay. You might not be aware of all of those things. So yeah anyways uh some may be started by you and some may not be started by uh you right some may be started uh at system boot and some of those uh processes might be started by you when you're running some command so that's what this is so every time you specify uh you know a command in the uh terminal or the kernel that will boot a program or a software and that will also alternatively start a process okay and every time you start it you will have a new process defined and if you want to see the list of all the processes running in your system then you can use this top command. Okay. And what you get followed by that will be the list of processes and their P ID their user username their uh priority all these things. So I will talk about all these aspects in sometime. So let me first show you the different things and how they look in the uh Linux in my VM. Okay. So I'm going to run here. I'm going to run the top command. And when you do that you can see that you have something called as P ID. you have user, you have uh PR, you have a whole taskbar and you have with respect to which software is running, which program is running, what is the application name and all these things. Okay, so right here uh you can't probably see anything that I have created on my own. Okay, except for this uh virtual box client and maybe the terminal. Okay, but if you want me to create one, then I can also create one. So what I'll do is I can just uh end this here by pressing Ctrl C. I can get out of this uh top and what I'll do is I'll create a Firefox instance. Okay. So Mozilla Firefox is installed in my system and through my uh terminal I will start Firefox. Okay. When I hit enter my Firefox has been initiated. Okay. See now I did not make any change. Okay. I did not touch the Firefox icon but instead of that on its own Mozilla Firefox opened. That is because I hit Firefox and I put enter in the terminal. So when I did that the uh Firefox opened. Okay. Now I can just minimize this and if you go back to the terminal you'll see that I'm still inside uh you know the terminal is assuming that I'm still working on Firefox. Okay, I've still not ended Firefox over there. So when I uh when I close Firefox that's when I'll come out of the terminal over here. But instead of doing all that I can simply do Ctrl Z or control W. Okay. When I do Ctrl Z it means that I'm stopping my Firefox instance. Okay. So whatever Firefox browser that was open that is stopped. The process however would not be stopped. the process would be running in the background. Okay, now supposing I want to push it, if I want to bring it to the foreground, I can just say FG and I can give uh Firefox. Okay, this will again uh initiate Firefox for me. But otherwise, I can just uh you know close it and I can push it also to the background. I can say bg and I can say Firefox and if I give enter then my Firefox has been pushed to the background. So now uh what I'll do is let me run that top command again. And if you see over here the Firefox was not visible. Okay. But since I started and pushed my Firefox to the background and all since I've done all these things, my Firefox will be visible in this list of processes. Okay. Now seems like I've sent it to the background, right? So that's why it's not coming. So let me uh hit Firefox again. And it's opened the uh terminal now. And what I'm going to do is uh of course it's in the background. So I'm going to run the top command again and show you that Firefox is here. Uh so we have the Firefox here, right? As you can see there's a Firefox process that of course keeps moving up and down and uh it's all sorted by the priority that each process has. Okay. So u yeah so every single uh instance or every single program or application that you start right so they will be started in this way and they will have a process ID associated with them. they will have the time for how long they've been instantiated. They'll have the CPU memory they're using, the virtual memory they're using, uh, and all these things. Okay, so let me explain each of these things by going to my slide first. So if I go back to my slides, okay, as you can see here, these are the different blocks that you saw earlier. Okay, on the uh terminal. So the first P ID stands for the process ID. So each process that is initiated, which will have a unique process ID, okay, and the user here is uh the name of the user who started that process. And PR is uh refers to the priority of that process because uh every process that is running in your uh Linux it'll have a priority associated with that. Okay. And the greatest priority process is what will be executed first and that'll be executed at the top. And then so along with the priority of that process you have the niceness value. So niceness value is again you know the value ranges from minus 20 to + 20 and even the priority value it varies from minus 20 to + 20. Okay. So basically the nicest value is uh somewhere it's opposite to priority. Okay. So the lesser the nice value the greater will be the priority of your uh process. You can also manually set the niceness value of your uh process to increase the priority if you want to give a particular uh program or a particular process more priority. Then you can probably decrease the niceness value and uh that will lead to the increase in priority on its own. So that's what this is. And then after that you have uh this VRT block. Okay. So VRT stands for virtual memory. RS stands for the physical memory. SSR stands for the shared memory. S is the status of the uh process. So that's what S is. So S speaks about the status of that particular process. Okay. And then percentage CPU is it is about the percentage of the CPU time. Okay. And percentage of the memory of the physical memory that's being used. Okay. And then you have the time block which uh refers to the total CPU time that this process has been running for. And then finally you have the command. Okay. And then f and then after the command you'll have the process that is uh actually running. Okay. So um let me just quickly go back to my thing here. So the command is basically the uh application that's running. Okay. So yeah that's about the different processes. I'm just going to end this uh top by giving uh control zed. When I give control z uh this stops and I can just clear my screen. So that's about my processes. Okay. Now uh I showed you how the top command works. Okay. Now along with that if you want to see the list of all the uh processes that are running okay then you can see that by running this command ps uh hyphen uh space ux or uh you can do this or you can even run ps- p. So when you do that you will only get the list of processes that are uh you know being started by you. Okay. So you're the user I'm the user and my name is Eda right? So all the uh processes which I have started right. So all my processes will be visible. Of course uh uh the other user's process will not be visible to me. It will be only visible for him. Okay. So I can also give uh P ID otherwise PS I okay the PS UX it basically displays the process that you have started. Okay. So you any any program or anything that you have started that you can uh see it here. You can see you know what is the percentage of the memory that's being used because of that process. What is the process ID for that particular process and all these things. Okay. So uh similarly if you have uh you know anything else. So that's what uh this command does. Okay. The next thing that I want to tell you is that of finding the p of a particular uh process. So you know that we've started uh a particular process. Okay. We started the Firefox process that time. And what I can do is I can find out the uh P of that particular process by giving this command P off and uh what is the name of the process? Uh so in my case it's Firefox. So I'm just going to give P off and Firefox. That will give me the P ID of that particular uh process 5836. Okay, I'm going to clear screen. Okay, I'm going to run the process again. Okay, I'm going to start Firefox again. And when I do this, there is a new instance of Firefox that starts. Okay, so a new process would have started by now. And uh when I just give control Z, I'm kind of stopping my process. And uh now if I give ps- ux then you can see here that there's a new firefox process that starts that's running. Okay the ID is 660. Okay you can verify that by also giving uh by seeing what is the answer that I get f P I of Firefox. When I do this I get 660. So that is uh what this is all about. Okay. And if you see the status it's also showing as TL. Okay. This means that I've uh terminated that process. Okay. So process of Firefox has been instantiated. It has a P of 660. Okay. And uh you know if I want to kill this process then I can give the command kill 60060. All right. Great. So that's about the different process that I want to talk to you about. Okay. So um what's next is uh let me go back to the