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[No audio]

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Standard output to a file using the command tee.

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Now we have learned how to actually

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populate a file using the redirect commands,

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like the greater than sign.

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You echo something you output to a

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file using the greater than sign.

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Now there's another way that you could do

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the same thing with using the command tee.

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What tee command does, tee command is used to store and

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view (both at the same time) the output of any command.

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So in other words, the command is named

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after the T-splitter used in plumbing.

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So you've seen the T-splitter, right?

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So you put in the water from one

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side, it comes out from the both sides.

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This tee command works pretty much the same way.

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So it basically breaks the output of a

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program so that it can be both displayed

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on the screen and saved into a file.

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It does both the task simultaneously. Copies

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the result into a specified files or

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variable and also displays the result.

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So if you look at the picture, you'll

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see right here we have a command.

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So whatever the command you run, you run echo, you run

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ls, pwd, chmod or whatever the command that you run,

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right, you put a tee in front of it, and then

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it will not only send the output on the screen, but

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it would also put it into a specified file, the file

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that you wanted the output to go to.

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So that's how the tee command works.

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The reason we want the tee command

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over the greater than sign command,

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which both do the same thing,

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is because if you wanted to run a command,

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and you want to output to a file, you

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also wanted to view while you're running the command.

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You wanted to view how or what the output

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looks like and whatever that goes into the file

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actually go in the right output that you're looking for.

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Okay, so let me go into my Linux

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machine and I have it right here open.

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Let's clear the screen and type whoami.

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And you will see the name of the user account

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that I've been logged in with. Which directory I'm in?

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I am in my /home/iafzal directory.

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Of course, one more thing you should also check

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is the hostname that you logged in.

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The hostname is the correct hostname,

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which is MyFirstLinuxVM.

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These are the few things, of course, you need

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to check all the time to make sure that

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you are logged in to the correct system.

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Now let's get back to our command tee.

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Now let's say if you want to echo

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something on the screen, let's say we echo.

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[No audio]

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David Puddy is Eliane's boy friend.

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David Puddy is just a character in a show Seinfeld,

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and he was the boy friend of Eliane Bennis.

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So it's just a statement that I'm putting in.

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And then you hit enter and you will

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see that same echo on the screen.

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Now we could use the greater than

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sign to output to a file.

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So let's say if I wanted to output to a file

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eliane-david, this is the name of the file, right?

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I could do that. When I hit enter, you'll see it has added

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this text to a file name, eliane-david.

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Now, what if I verified by running the command cat eliane-david, and

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you will see the file has the correct text

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that I wanted to have it in the file. Perfect.

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Now, if I replace it, the same thing,

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let's clear the screen one more time,

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and run the command one more time.

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and you will see when you run this command with

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uppercase sorry, not uppercase with redirect sign, it actually runs

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it, but it doesn't throw anything on the screen.

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But if you replace this with pipe, and tee, then you

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will not only see the output going into eliane-david file,

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the output will also show up on the screen.

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So hit enter and you'll see

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David Puddy is a Eliane's boy friend.

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So it is going both ways.

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As I said that tee is like

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a plumber's T that goes both ways.

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So when you do cat eliane-david

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David Puddy is Eliane's boy friend.

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So now don't be confused that, hey, we ran

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that command earlier and it has that same text

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message that we ran it with greater than sign.

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If that's what it's in your mind, that's fine.

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Let's go ahead and remove eliane-david file,

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so it doesn't exist. Yes.

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So clear the screen.

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Now run the same command by hitting up arrow key.

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All right. echo, David Puddy is Eliane's boy friend.

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So, and tee eliane-david.

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This is the file. Hit enter.

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Okay, now do cat david,

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sorry, eliane-david,

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and you'll see the file there. Perfect.

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Now, what if you wanted to add

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or append to the same file?

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Because if you type, let's say,

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[No audio]

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echo

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David and Eliane

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into the same file and hit enter, and you'll do

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cat eliane-david, you'll see it removed the older file

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and created a new file with a newer output.

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So you want to append it to a file

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that the older text message does not get deleted.

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For that, you would have to use a

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command, same command but with -a.

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So hit up arrow key and go back

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to the same command that we ran earlier,

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and this time, type tee -a. Same thing echo

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David Puddy is Eliane's boy friend.

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This is just a text,

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pipe it and tee it,

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end with the option -a,

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and the file name same file,

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and now go ahead and hit enter.

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Now go ahead and do a cat on eliane-david

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file and you will see it has two lines.

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First line is that we created without -a option,

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and second line we created with -a option.

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So that's how you append or add or create a new file.

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Now let's try to see how many characters

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do we have in eliane-david file.

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So the command is wc -c, and you

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will see it has 52 eliane-david characters.

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We could also output whatever that came

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on the screen to another file.

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So I use this command, which can be

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discussed or which I will cover later on

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of course, this command actually count every

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word in the file called eliane-david

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and it will output on the screen.

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You could actually redirect that output using a

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tee command to another file as well.

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Now, let's say if you want to do ls -l,

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and you see that listing, entire listing of your directory.

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So let's say if you wanted to have all that, with

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the tee, meaning I wanted to view it, and at the

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same time I want to put it to a file.

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So I'll put it as, name it listdir,

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and hit enter, and you will see the entire listing,

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from here till bottom,

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and you'll also see your file listdir.

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If you do cat listdir, and

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hit enter, and you will see the same listing.

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So let's clear the screen, and now hit up

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arrow key to cat listdir file again,

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and you will see that ls -l output.

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So basically it's outputting on the screen

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and it is outputting to a file.

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If you wanted to do the same thing, let's

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say echo ls -l, and you could also output

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to multiple files, meaning ls -l tee, to

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let's say file1, file2, file3, and hit

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enter, you see it actually ran and it has all

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the listing of all three files as well.

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And when I do cat file1, it has the

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same content, cat file2, it has the same content,

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and so on, to cat file3, same ls -l output.

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So this is how the tee command works.

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If you wanted to get more help or more options

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on the tee command, you simply type tee --help, and

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you'll see it will tell you exactly the options that

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is being offered by the help command.

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See -a is to append, and -I

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is to ignore, and version, and help.

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So if you type tee --version to see the version of

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this command, you will also see that this command version is

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8.22, and it tells you this is a free software.

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You are free to change and redistribute it.

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There is NO WARRANTY, to extend the permitted by law.

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And so on, and so on.

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Written by Mike Parker, Richard M.

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Stallman, and David MacKenzie.

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So these are the people

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who actually built this command.

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Again, since Linux is an open source, you could

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even create your own command, write your own code,

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and introduce it to the Linux world.

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So that's how the tee command works.

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I hope you understand.

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If you have any questions, you could just shoot me an

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email and try it out, try it with different options, a

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couple of options, and I'm sure it will work just fine.

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[No audio]