XK0-004: CompTIA Linux+ certification video training course by prepaway along with practice test questions and answers, study guide and exam dumps provides the ultimate training package to help you pass.

Unit 03 - File and Directory Management

16. vi Commands

If you used the VI, you could edit or add commands, as I previously stated. Well, if the command or the letter A stood for the command "append," how did you know you didn't really want to type the letter A or you wanted to do "append"? Text commands always began with a cold. So you hit the colon. That meant append, or I for insert. If you needed to delete something, you were in the right place. Or you had several options with the colon D for deletion and control. Commands also work for you, as do methods to be able to deal with things.

You could yank or cut the file, paste it, undo it, and exit it. That means getting out of VI altogether. The Hjkl moved left, down, up, and right. And if you think about where they are on the keyboard, then it makes sense why they are the letters that they are. So these are just the commands we would use to navigate because, again, we didn't have a mouse. We couldn't just move the mouse, click on the word, and press C. We had to find a way to move up to navigate Hjkl, get to the location, and yank things. I mean, that's what we had to deal with. Often, if we wanted to delete a word or a letter, we would have to keep hitting the D key several times. Or you could do things like type "D5", and it would delete five things.

And now I'm really pulling these from memory because I don't have to use VI today. I guess I had a bad experience back in the old college days. I suppose one of those things I thought to myself was, "Oh, it's going to go away while it's still there." It's still very practical and very well used, especially in the routers and the PDAs and these little things that have embedded Unix-like programs, so, you know, I'm stuck with VI still. But anyway, you had those commands, and it didn't take long. It wasn't that hard. You just had to remember when you were typing in a letter for a text or when you were issuing a command. And don't forget, if you were performing a command and accidentally pressed D and typed the letter D, you only have yourself to blame, right?

17. Demo - Editing a File with vi

All right, we are going to use an editing programme called VI, which stands for Visual. And I'm going to open up a VI file, or, in a way, a new file called my VI file. And we're going to see why I like to nickname it "very irritating." So here we are. We're in a nice visual programme from 30, 40 years ago.

It looks like a command line. I realise the little tildes that you see along the left edge are not printable characters. That's just kind of a visual indicator to you that there's plenty of room for you to start typing whatever you wanted to type, going up and down. This editor at the bottom indicates that these are not printable characters. This last line is called your status bar. I know it doesn't look like a bar, but again, 30 or 40 years ago, that's what it was. MyVI file is a new file, according to what this says. And if I started trying to type something in here, as many of you are used to doing, I wouldn't get very far because you open up this thing in what's called command mode.

Now, I'm going to type or press the letter A. And when I did that, I got into append mode, and then I could actually start typing stuff in. So I'll just type in the quick Fox. Now, if I press the escape key, I'm going to leave my insert mode and go back to my command mode. I'm going to move my cursor back to the F in Fox. I'll then type the letter I for insert rather than append, because append means go to the end and here.

Then I'm going to type a red space. So I've got the red fox, I hit the escape key, and I'm back in command mode. Okay, so now that I've got that done, I'm going to move to the R in red. I'm going to say, "You know what?" That wasn't what I meant. So I want to delete the word "I'm in command mode." The delete command is the letter D, followed by the word command, which is the letter W. And just like that, you deleted the word. Yes. Believe it or not, that's how we did it 30 or 40 years ago. Now I'll type "I" once more to insert type in brown space. And there's my brown fox; press the escape key to exit edit mode. Okay, now I'm going to go to the very end of this command line.

And now that I'm at the very end, I'm going to type the letter A. Notice how it moved the cursor. because A is appended. I'm going to hit enter, and I'm going to type over or type the new one. I'm going to type "jump over the lazy dog." All right, so now that I've gotten that part of it done, I've got two lines now. I'm going to hit escape. So it takes me back into command mode, and I'm going to move my cursor back over to this little B here for the brown fox. And what I'm going to do, I don't know; maybe I want to start that line. I'll leave it there. I'm going to copy that word. I want to copy the word brown. In the world of VI, that is not called copy. It's called Yank. So I'm going to hit the letter Y for yank, followed by the letter W. And now I've just copied it. And I know you're probably saying, "Well, I didn't see that." Well, that's okay.

Let's see what happens if I try to put it back in a new spot. So I'm going to put it in front of the letter D. I'm going to type in the P for paste. And there you see, I just put it in the wrong spot. I didn't necessarily want to do that. So I'm going to hit you to undo my change. And now we're okay. So you can imagine that there are many more commands, and there really are many commands left. Let me hit escape to make sure I'm in command mode. There are commands to delete three whole lines if you want to. I mean, it just goes on and on with a lot of really cool stuff. So if you're not sure what commands to use and you want to work with VI, then you can get some online help. Use the manual pages. But I'm going to tell you my opinion only: you have text editors. This is a text editor. When I'm done with this, it will be a text file.

It was just what we had many, many years ago to be able to do this kind of editing that we didn't have before. Now I'm going to execute a command. I'm going to use the colon to execute a command. Now, the colon puts me down; if you didn't see it, down on the bottom left here in my command line, I'm going to type W to write or save my file and then Q to quit. I could have also just typed "WQ" to write it and quit. But just like that, I'm now out of myVi, so I do an LSL. You see that? I've got a file there called my VI file. If I say "cat myvi file," it shows itself to you right there on the screen. So that was VI. The visual editor that we have now was popular in the days of C++, which was a programming language. That was pretty much how we did everything in Unix environments. That's why, with all the new things, you can see why I like to have a nickname. It is very irritating because you have to memorise all those little tools. Anyway, it's a kind of archive, a history, and it's critical that you know it exists and how it works.

18. Links

Now one of the other things we look at with files is this idea of what we call links. Now, links are basically things that allow us to associate a name with an actual file. We'll start off by talking about this thing called inodes. Now, inodes are just metadata. Metadata would include what we call the message. Mace was an acronym that stood for modified, last accessed, created, or entered into the file system. The iNotes also contained the location of where a file was actually stored on a hard drive. It included ownership information as well about a particular file, so that actually had links to that information.

I knew it would. Hard links were another way of having an alternate name for the exact same file. That just meant that this hard link was named the same as this other file name. They both pointed to the exact same spot on the hard drive where this file was a symbolic or soft link, sometimes even called a SIM link. But a soft link was very much like a shortcut. It referenced a hard link or an actual file name and worked so long as you didn't move the actual file name. Then that link continued to work. So think of those like Windows shortcuts or your Macintosh aliases. Anyway, again, another method of working with files is by having these shortcuts or these links to the actual profiles themselves.

19. Demo - Creating and Using File Links

We're going to talk about creating links and doing so with a command line in our GUI. I'm going to start off again in the home directory of my user. My username is live user, and we're going to do the LS with the LF. So you can see what's currently here. I have two files. One is called "my non-empty file," but oddly enough, it's empty. And then this other one is called My File. So as a quick flashback, I'm going to rm the files that start with "My" and say, "Yes, let's get rid of those." And so now I feel pretty comfortable knowing that I have nothing but directories, and we verified that again with the LF, and I have just directories left.

Okay, so I'm going to clear this out. I'm going to use the T command. I'm going to create a file called Contact Info, and look, I'm going to put an extension on it. It doesn't really matter because this is Linux, and I'm going to say Ken Mayor and home, followed by Ken Mayor's work. Okay? So for all of you Hollywood types, you know that these five, five, five numbers don't exist, right? And I've included a couple of contact information, including the Kent Mayor's address, and let's make it a palace.

That's good. I've always wanted to live there, and I'll take care of Control C. We'll cat that file real quick so you can see what's on there, and I've got some contact information in that particular file.

Okay, now we'll try to make a hard link for this specific file, which we'll call MyHeartLink Text. And in doing that, to create the link, we're going to use the command Ln. Let us, in fact, do what is Ln. And if you notice, I remember again, in a little flashback, some of these things that help you learn how things work. It says Ln is a command that makes links between files. In fact, we can help, and we can see that we have a few options here. We can force the links and allow the superuser to create the hard link, the interactive mode. It can be a symbolic link instead of a hard link.

So this is important to know because with this option, it tells us in a way that we are making a hard link unless we turn on the S option. Okay? So let's clear our screen and we'll type in "Ln" and we're going to use the contact info and call it My Hard Link TXT. Now again, I use the "Complete" tab whenever at all possible. Now that I've made that link, LSL with a capital F, we can see my hardline text as well as the contact nfo text. All right, so I've got both of those, and I'm going to do a cat command on my hard link and notice how it basically links right over to the file contact information just like we said it would to the file contact info. Okay, now we're going to do another LN, this time with the dashes, as we know it's symbolic contact information. And we'll create a soft link called mylink, and I'll hit the enter key.

There is another LSL, with a capital F. Notice that this one no longer looks like the actual file but has an L for my soft link. And it tells you directly that it is softly linked to this contact information. Now if I actually moved contact information to another folder, this link would fail; it wouldn't work anymore. So here I'm going to count my links, and it gives me the same information. So that was a quick rundown of doing that through the command line. Now we're going to open up the "My Home" folder through our visual tools. I'll minimise this other one and maximise this; you can kind of see my link files in there, and what we're going to do is try to do something very similar to what we've had before.

Now if I double-click my contact information text, you can see that I can open it up in an editor, make a new edit, and I'm going to right-click this thing and click "make link." Now, I'm not going to take you through how I go about creating the files in the visual part. We've done that already; I don't like the name of it. So up on this thing here, I can hit F2 and make a change to the name if I don't like the way it reads. and I'm going to call it my visual link. I suppose that's as good as any because when I put the capital letters in there, I have to make sure I always type it in by that command so that it works because Linux is case sensitive, and just like that, I've got my case made. I was able to do that.

I did the right click and the make link, and you'll notice that when I created it, it had the same GUI as this soft link. So this is actually a soft link to the file, and now I'm going to take that and I'm going to actually drag that to my desktop. So now it's in a new location as far as where that symbolic link is going. And I'll close this down, and here is my link on my desktop, and I'm going to double-click it, and it opens up the text information that I would have expected it to open from the original location. Notice I moved the soft link, but I did not move the original file, so it's still linked to that original file. I just put it on my desktop, which is where most of you are probably used to seeing shortcuts in a Windows environment.

20. File Information Commands

Now there are many commands you can use to pull up information about a file. So let me go back to a statement I made earlier, which is that everything in Linux gets treated like a file. We don't have an executable. We have programmes that you can type into and they will launch and run. But when you look at them in the directory, there's no way you can say, "Oh, that's an executable, that's a document, that's a spreadsheet, that's a presentation." You cannot tell. Maybe the person who created the file gave it a very descriptive name.

Maybe they got used to the Windows way and added an extension for nothing more than just to change the name so it looks like something in particular. Great. However, there is no way to tell what type of file it is just by looking at the name. But there are commands that you can use to get the file information. The first is the LS command. Now the LS has a list function that will list the files and list details about the files, and you can see from there what type of file it is. You can use the file command. The file command, by entering the file's name, would describe the type of file, whether it was a file, a link, or some data; if it was a programme or executable, the stat command would be used. The stat would get information about the file, including its type, where it's stored, and all the other mace information you can use.

Test, which is not really a go, retrieve the file, and tell me what kind it is, but just a comparison test where you could say, "Test this file and tell me if it is a programme or if it is a file, and get the answer yes or no." So there are things you can do. Now, in lieu of remembering all those commands, Maybe it might be an idea—just an idea—to give it a naming convention so that you can look at the name of a file and actually be able to tell what kind of file it is from that naming convention. Now, I know not everybody wants to do that or is willing to go through that kind of painful exercise. So if you don't, you can still figure out the type by using one of these commands: ls, file, or stat.

Prepaway's XK0-004: CompTIA Linux+ video training course for passing certification exams is the only solution which you need.