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[No audio]

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Text to files or redirects.

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Here we will learn how can we add text or digits

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or letters, or how can you populate an empty file.

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We created some of the empty files using touch command and

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touch is just a way to create an empty file.

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But now how can we add text to those files

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or anything that you like to add to it?

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There are three simple ways to add text to a file

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and the basic main way is to add text to files.

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The first one is through the vi editor.

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vi is the editor.

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It's a command that is used in Linux to

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create a file and add text messages to it.

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Then the next one is redirect command output using the

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right direct and the two right directs to a file.

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And in this lesson, we'll cover these redirects

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through a command output into a file.

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And the second way we will learn through echo,

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when you want to echo whatever that you

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type, you could output to a file.

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That's how the file gets created or that's

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how the file gets populated with information.

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So let's look on our

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Linux machine and run these commands.

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[No audio]

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So here we have our Linux machine.

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Let's make sure we are in our home directory.

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Yes, we are in our home directory.

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Let's clear the screen and let's check what are

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the different files we have in our home directory.

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Okay, we have all those different files

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and directories that we created earlier.

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Now we wanted to add something

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to a file, any empty file.

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Because if you see here, these are the few

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files that we added and all of them have

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zero bytes in it because these are empty files.

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So when you want to do echo and you type

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hi my name is Imran, and you hit enter, it

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brings you back the exact same thing that you type.

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So the command echo actually echoes

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back what you shouted out.

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So how about if we output this to a file?

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So I will say let's say, echo "Jerry seinfled

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is the main character in the show Seinfled".

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So this is the text that I wanted to type,

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I wanted to add into the file called jerry.

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And how we're going to do it? We're going do it by redirecting, the redirect,

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which is a key right above the dot,

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you type that with the shift and then you

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specify the name of the file which is jerry.

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Hit enter, you'll get your prompt back.

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Now when you do ls-l and you hit enter, you're

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going to see jerry has 58 bytes inside of that file.

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Now all other files are 0 because

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we didn't put anything in there.

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Now that's good.

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We added something to our first file.

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This is amazing.

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Okay, now how do we know what's inside of this file?

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How do we check it? How do we verify it?

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We do know that the cd gets into our directory,

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lists all the files, and pwd tells us where we are.

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But how are we going to see

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what's inside of directory in Windows? How do you do it?

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How do you open up a file?

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Well, you do a double click and it opens up. In Linux,

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there is no double click. Then how do you do it?

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There is a command called cat. cat is a

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command to read the content of a file.

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We'll cover the cat command a little

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more in detail in the next lessons.

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But for now that we want to know what's inside

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of the file, we will use the command cat, followed

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by the name of the file which is jerry.

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When you hit Enter and there you see, you have

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Jerry seinfeld is the main character in the show Seinfeld.

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Now this is what we typed right here in our

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echo and we outputted that to a file called jerry.

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Now what happened if we do, echo and

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[No audio]

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echo,

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and do,

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and we wanted to type another line in that same file.

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So let's say Jerry show was created

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[No audio]

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in 1989,

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and you output,

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[No audio]

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to a file jerry.

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Remember why we are using two output arrows here,

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it is because if you use one arrow like this,

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it will overwrite your last file and remove this

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line that we added into this file.

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You'll remove this line and create a new file

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with the content of this Jerry show was created in 1989.

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Now, we don't want to remove it.

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We want to keep this line, the first line,

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and we want to add a second line.

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If you want to add a second line,

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then you need to use the double redirect

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signs. When you do that, hit Enter.

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How do you verify what's inside or whether

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it went inside the file or not?

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Again, I want you to use up arrow key twice.

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Because the first up arrow key

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brings you the last command.

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The second time you hit up arrow key brings

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you the command to cat the jerry file.

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Hit Enter and there you go.

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Now you have two lines in your file.

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When you do ls -l, last time we had 58 bytes.

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Now we have 89 bytes because the file keeps growing.

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Now this is the simple way to add contents to

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a file, if we running the same command again.

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[No audio]

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There you go. Jerry seinfeld is the main character in the show.

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If you take out that and we just

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do Jerry seinfeld is the main character, right?

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And now we want to use one

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redirect and we want to redirect jerry.

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Now remember this, it will wipe out

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all the contents of the file jerry.

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Basically it will wipe out the entire file

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jerry, recreate the file with the new text

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message text that I am typing here. Try it.

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Let's say hit Enter.

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Do cat jerry, enter, and there you go.

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Jerry seinfeld is the main character.

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It does not have all the typing that we did

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earlier, it took the latest one, the latest typing, the

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latest echo we did in the file, and it added

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into the jerry file. The same way

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I want you to add a few things

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about anything that you know about these characters.

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By the way, these characters are actually taken from

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those hit shows, american hit shows of Seinfeld, Simpsons,

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and of course, the main movie Superman.

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If you know a little bit about any

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of these characters, please do write inside of

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these files with using the echo command.

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And this would be a very good exercise

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for you, how you could populate each file

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with different things that you know about.

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Again, remember, if you do one single

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output, that will overwrite the file.

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If you do double, that will append to the file.

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Okay, now, this is about echo.

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What if you wanted to do, let's create a new file

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called touch,

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and this time we'll call it,

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[No audio].

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listingoffile.

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No, listingofdir.

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Let's say we call this, right.

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You hit enter, verify, the file is created. Yes.

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listingofdir.

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It's just the name I picked.

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You could pick any name.

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Now, how do I populate that file

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with whatever I want to type in?

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Of course, you know, that way you could

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do it is through echo and whatever you

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want to type and output to a file.

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But now I want to show you a second way that you

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could populate through the output of a command, which is, if I

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do ls -l, hit enter or ls -ltr, let's say,

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which brings me the latest one at the bottom,

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I wanted to have this entire

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output. Starting from here to here,

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I wanted to output this entire result

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of my ls -ltr into the file

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I created listingofdir.

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So we will do ls -ltr, output to listing.

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Hit tab, it auto completes your file,

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and now you hit enter.

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[No audio]

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You see what just happened?

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It did not give you the output

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of ls -ltr on your screen.

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What it did, instead of giving you the

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the screen, it is outputting to a file,

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you call listingofdir.

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Now ls -ltr, shows you that the total

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number of bytes this file has is 1140.

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Okay, awesome.

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Now, what's inside of this

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file? You could check by typing the command

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cat listing, tab, and hit enter.

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You see guys, it's the same output that you

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have as you would have it on this one.

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The only difference that you see this

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output gives you a different color because

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it is actually running the command.

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Whereas this output cat of this listing is just

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the simple text messages, text inside of a file.

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You could change it, you can update

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it, whatever you want to do.

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If you want to do date, and you want to append

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that date, by the way, the output of date is today's date.

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And if you want to append that

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to the file jerry, hit enter.

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Now verify jerry, you see, it has the first line that we

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type through echo command, and then it has the second

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line that we got it from the date.

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So these two, funny characters, the two outputs, appends to

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your existing file, and does not delete your file.

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So, again, these are the two ways that we learn.

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One through the echo and redirecting, and one through the

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output of a command and redirecting to a file.

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And, of course, there's another way that

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we'll cover later in the lessons.

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But now, right now, you have to practice these

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two ways of adding or appending to a file.

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[No audio]