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Let's look at truncating file

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size using the command truncate.

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Now the Linux truncate command is often used to shrink

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or extend the size of a file to specified size.

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Now remember one thing, truncate is not the same command as

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if you wanted to compress a file or gzip a file

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which will reduce or shrink the size of a file.

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truncate on the other hand, will actually

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chop the file into the specified size.

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So if your file size is, let's say 100 bytes and

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you use the command truncate and shrink it down to 50,

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then it will actually chop the file and you will lose

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the data or the content of a file.

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If you do cat to the file, you'll

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see half of your data is gone if

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you are chopping using the command truncate.

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So the command that you will need to use to run it

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is truncate -s, s for size, which is the option.

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Ten is the actual integer to the specified

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file, whichever file that you want truncate to.

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So this size option is everything that is there.

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So now let's go into our Linux machine and we

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will try our command, the truncate command over there.

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[No audio]

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Okay, so we are in our Linux machine to practice

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our truncate command or to go over it. I will

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create a file called, by the way I am in

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my home directory and I am logged in as myself,

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and my hostname is my Linux machine MyFirstLinuxVM of course.

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Okay, and now I want you to create

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a file, touch and call it seinfeldwords.

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The file is created, you could verify by doing ls -l,

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and the name of the file, and hit enter.

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You will see the file is there, it has zero bytes and

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it's owned by me and the permission and all that stuff.

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Now do echo and type the famous characters of the

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famous most words that you could think of Seinfeld.

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But if you don't know then just

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follow my lead and just keep typing.

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Like the first word is puffyshirt,

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[No audio]

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second word is giddyup,

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the third word is yadayada kavaorka serenitynow,

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and last one let's say festivus,

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and put that to our seinfeldwords file.

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So let's make it a little bigger.

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So you'll see all in one line.

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So I'm actually echoing out these words and I am putting

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it to the file name, the file that we just created, hit enter.

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Now go ahead and do cat on seinfeldwords and

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you will see all of these words inside of that file.

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Now do ls -l, and do seinfeldwords, and you

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will see the size of the file is now 57.

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Now if you want to shrink that file using the

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command truncate, then you would have to use,

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[No audio]

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command truncate

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-s as an option, space the size that you

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want to specify, and you want to shrink it to.

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So right now it's 57.

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Now let's make it 40, and the

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name of the files and hit Enter.

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Now do ls -l to seinfeld again and you

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will see the size has been reduced to 40 bytes.

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Now let's see the content of the file now, seinfeldwords.

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[No audio]

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Okay, you see the content right now, when

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I did cat, it says puffyshirt giddyup

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yadayada kavorka and sere, up to here. That's it.

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It did not complete the entire word serenitynow

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see right here, as I have right here, serenitynow.

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And then it actually removed festivus as well.

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So when I do cat again, seinfeld, you see

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right here, it actually removed the last few letters.

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Why? Because it has to chop it down.

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That's why we would use the truncate command

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if I wanted to chop the file.

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Now remember, truncate command is not

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used to actually compress or size

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make it smaller while keeping the same content.

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So be very careful.

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Anyway, so this is the lesson where

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I wanted to cover the truncate command.

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You could use this, or you could also use

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the truncate to extend or make the file bigger.

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So if I do truncate, hit up arrow key and

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I put it back to, let's say 60 and hit Enter.

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And now do ls -l seinfeldwords,

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you see, the size is 60.

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Now, it doesn't mean that we're going to get our

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whole word serenitynow and festivus back in that file.

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No, let's check, let's verify.

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Do cat, seinfeldwords and you see it's not there.

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It's still giving me, only the size that has all those

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words, because it does not have the information whatever that we

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lost while we did the truncate to shrink it.

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So it did extend it.

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But now where is that

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extension thing, that's been added? Where did it go?

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Well, it's just the empty letters, that actually,

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the truncate has added to this file.

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It is @ letter signs just to make it bigger.

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Right now we do not know how to use vi editor.

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So by the time we'll use the vi

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editor, you will know how to vi.

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But for now, just to show you, we

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could do vi seinfeldwords, and hit enter,

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and you will see right here all these @ signs.

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These all @ signs were added because when we

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extended the file, so operating system said, now you're

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extending, I have to put something in there, right?

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But I don't know what it had before, but

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I'm going to add something to make it bigger.

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So that's why you see it. Anyway,

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so if you're using vi right now, and you

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want to get out, hit Escape, shift, colon, q

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[No audio]

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q, bang, which is right above number one, and hit

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enter, and you will get out of vi.

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Anyway, don't get into vi right now if you're

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not familiar with it, we'll cover it later on.

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So anyway, I wanted to cover this truncate.

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I hope you understand how truncate works

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now. Try it out on different files, different contents in the file and

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see if you get familiar with it.

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[No audio]