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Hello the beautiful people and welcome to this very exciting section of the course all about bash scripts.

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And in the next few videos you're going to learn how you can create your own bash scripts, which are

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incredibly useful tools that will allow you to automate your workflows.

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Now, learning about Bash script is a massive field in and of itself, and it would require its own

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course to cover properly.

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But by the end of the next few videos, you're going to have the fundamental understanding required

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about how batch scripts work and how to create them so that you can begin automating your workflows

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using the commands that you've learned so far in the course.

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So this is going to be an incredible and incredible piece of learning for you to let you understand,

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like what bash scripts are, how to use them, and how they basically work.

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So it's going to be very, very exciting.

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I hope you're ready to gain some serious superpowers.

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So let's not let's not mess around anymore.

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Let's go jump right in and start making our very first batch script.

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All right.

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So let's go ahead and make a simple batch script.

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Now, to do that, all we need to do is just make a text file.

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So to do that, let's go ahead and open up Nano on our desktop and make a file called as script dot

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S-H.

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Okay, so all I'm doing here, when I give the file the dot S-H file file extension is just making it

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easier for us to see that this is a bash script with S-H being short for for the bash shell.

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Okay.

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So if I open that and press control and oh, to save it, you'll see that the script has popped up on

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the left.

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And if I just close that and clear the screen, we've now got this file.

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Now let's take a closer look at this file.

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Let's see if it's anything special to the shell using the file command.

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And if I do file our scripts page, we see that it's not it's nothing special as far as the shell is

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concerned.

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It's just an empty file.

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It doesn't matter whether this was dot stage or dot pablum or whatever, it's just an empty file.

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Okay.

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So with that piece of information, let's go ahead and open our script and let's do the most important

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thing that you need to do whenever you write a new bash script, you need to tell it that this is actually

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a special file and that this file isn't just a text file.

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It needs to be read.

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Using a certain interpreter.

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And an interpreter is something that will read a file and interpret each of the lines in that file as

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a certain type of code.

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So instead of just reading Cat, okay, if I told this that this is a bash script, it would read this

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as the cat command instead of just cat as in, you know, the animal.

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If I read, if I typed echo, it would interpret this file as the echo command.

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It wouldn't just interpret it as an echo that you hear in, you know, when you're in a cave, when

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you show it into into a hall or somewhere like made of stone.

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Okay.

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So this is the important part.

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We need to tell it that this isn't a normal text file.

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It needs to be interpreted as code and more specifically as a bash script.

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So to do that, you need to first type what's called the shebang.

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Now the shebang is a hash, so and then a bang, an exclamation mark and a hash symbol.

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Then an exclamation mark is called the shebang.

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And then you type the path to the interpreter.

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Now the bash interpreter is at slash bin slash bash.

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So this is our first line.

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We type the shebang, hash bang.

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Okay, then slash bin slash bash.

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Now that that slash bin slash bash is the path to our bash interpreter.

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And we can see that if I close out of Nano by using the which command and typing bash and we see that

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we get slash B and slash bash as the path to the the bash shell.

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Okay.

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So what we're saying here is, hey, this isn't a normal text file.

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You need to interpret this file using the bash, the bash shell interpreter, run this as a bash shell

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script.

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And the key is this line needs to be the first line.

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It cannot be the second line.

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It has to be the absolute first line.

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And there can't be any spaces on the line.

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So you finish the line right away.

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And when we save that now if we look at the script with the with the file command, we see that it is

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now a shell script, in fact, a born again shell script.

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Now the born again shell is.

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BASH So you've got born again shell.

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Born again shell is.

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BASH okay.

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So this is saying it's a bash shell script and it knows that because it's got this this shebang line.

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Now, if you know anything about Python programming, you'll know that the Python programming language

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is also an interpreted programming language and the command to run something as a Python script on,

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on, on Linux is Python three for Python three.

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So if we type A which Python three, it'll tell us the path to the, to the Python three interpreter

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Just like it did for the bash.

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Interpreter And if I copy that, open up our script again and I write the shebang line again.

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I write shebang, so shebang.

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And then I paste in there the path to the python interpreter.

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So slash user slash B and slash python three and save the.

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If I now look at our script, you can see that the shell sees that this is now a Python script.

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So that's how you would do this kind of stuff if you wanted to write a script in the Python programming

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language.

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But because we want to write a bash script, we're just going to give it the path to the to the bash

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interpreter, which is that slash pin, slash bash, save that.

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And then when we look, we see that it's again a born again shell script, a bash script.

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Okay.

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So with that important concept, understood.

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Let's go back to editing our bash script in Nano.

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So let's clear the screen and edit in Nano.

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Now, anything that we write in here with this special line added, anything that we write below, it

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will now be interpreted as they do in the normal shell.

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So for example, if I write Echo and then something like Hello World, this line will be interpreted

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as a command.

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It's as if I just typed echo hello world in my shell.

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So let's see this in action.

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Okay, let's save the file using control and.

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Oh, and now if we type bash our script, we see that it's run hello world.

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How cool is that?

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Right.

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So it ran the commands that are inside there.

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Now we can do whatever we want in our script, so let's just try and add more stuff.

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Okay, let's, let's add, let's open it up with Nano and now let's clear out this echo thing.

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Let's just get rid of this using the cut command, the control k I just got rid of the whole line.

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So that's a nice little shortcut for deleting a line.

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Now let's actually use in here.

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Let's, let's try and create a file a folder called Magic on our desktop.

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Now inside the magic folder, we're going to make 100 files and then we'll use the LS command to get

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information about each of those files and save it to save all that information to a log file on our

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desktop.

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So what command?

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Here's a test for you.

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Now what command would we need to create a folder called Magic on our desktop?

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Well the mkdir command write the mkdir command.

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So let's make a directory, let's type mkdir on our desktop, let's make a file called Magic.

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So that's going to be our magic directory.

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Now we need to make 100 files in it.

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So how how might we do that?

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Well, we might move into the directory, so we might move into that magic directory using CD.

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Then we might touch, I guess, 100 files of file 1 to 100.

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That might be what we do.

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So far, so good.

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So we've created a file called a folder called Magic.

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We've gone into the folder and then we've created 100 files.

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Now let's, let's like create, let's use the LS command to get data about each of those files.

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So if we use the LS command and we, let's say give it, let's say we want to use long form information

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and human readable information and save all that to a file on our desktop called Magic Log.

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And let's leave it there.

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Okay.

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So what we've done, we've used the Mac, we've made a directory on our desktop, we have changed into

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that directory.

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We've created 100 files and then we use the ls l command on our I should actually.

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Good, good thing I checked, I should check our magic folder and then redirect all that information

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into a file called Magic Dot log.

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So if I save that there.

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Close it.

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And now we we can see the contents of this file using the cat command just like any other file.

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We can just cap that out and we can see the contents.

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But now let's go ahead and actually run it.

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So if we try to bash our our script.

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Wow.

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Did you see that?

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We managed to create a folder on the desktop.

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Inside there there are now 100 files.

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And if we look in this magic log file.

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We see detailed information about every single one of the files inside that folder, just like we told

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the script to do.

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So isn't that absolutely awesome?

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So this is how bad scripts work.

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You basically type in there the commands that you want it to do, just as if you were typing them in

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in the in the normal shell.

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But the benefit is we now have this file that we can keep and do stuff with whenever we want.

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So you can actually save that for later.

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Now, this should be a moment of amazement for you.

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So think about this for a moment.

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In Linux, you can control anything using the command line, whatever you want.

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What if you want to change, whether it be your desktop background, whether it be your font color,

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whether it be, you know, messages that pop up when you log in, you can change anything using the

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command line and you can write scripts to hold command line commands.

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So therefore you can write scripts that can do anything on your computer and save them for later so

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that you can run them whenever you want.

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And batch scripts are therefore part of what gives you complete customizability over your Linux machine.

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And they are incredibly, incredibly powerful tools.

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So you've seen in this video how to make a bash script, but in the next video, what we're going to

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do is we're going to do it all over again and we're going to show you how you can write a batch script

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to make regular backups for you.

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So that's going to be very, very cool.

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And we're going to show you how to run it in a much more convenient way as well.

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So I'm going to break the video here.

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And in the next video we're going to pick it up again by showing you how to make a batch script to do

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backups.