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All right.
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So in this lesson, I want to introduce you to directory creation, file creation, and directory manipulation.
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And we're going to be doing all of this inside the command line just with our keyboards.
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S,o again, right now I'm starting in my root directory over him and I am going to create a new folder
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right here. So, obviously, I can go through the right click.
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New Folder all of that.
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But we are pro developers now,
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so we're going to get used to using the command line.
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So the command is mkdir or make directory,
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and then we're going to give our directory a name.
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So let's just call it Angela,
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right?
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And you can see, there you go, pops up a new folder called Angela.
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Now, let's cd into this new directory. And you can see that if I click on here or if I use "ls," there's
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absolutely nothing in there, it's a empty folder.
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So what if I wanted to create a file?
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So in our graphical user interface, I could say open up an application like TextEdit, and I could make
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a file and write something in it, and then save it inside my new directories.
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So I would have to do a little bit of navigating in order to get there, and then I have to give my file
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a name.
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Let's call it Text and hit Save.
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So, now we have to exit the application.
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And after all of that work, I've got a text file. And if we do "ls," now, you can see that Text.rtf exists.
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But if you want to do the same thing using the command line, then it's as simple as simply typing "touch"
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to create a new file,
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then we're going to specify the name of the file, let's call it Text2, and then we give an extension .txt.
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And you can open in either by double clicking on it, which is what we're used to,
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or you can simply write open Text2, and it will open it using the default application which is TextEdit
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in a Mac. Now, you can specify which application you want to open this file in.
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And all you have to do is, say, the "open," and you're going to use the -a flag,
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then you're going to specify the application that you want to use.
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So let's say that we want to open it inside Atom, so I can write Atom, and then I can specify the
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file that I want to open, so Text2.txt, and hit enter.
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And it will open up the Atom application that I've got, and then open up my files for me to be able
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to edit.
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So what if you wanted to delete files inside the command line? So currently, I'm inside the Angela folder
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and there are two files, and I want to delete 
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my Text.rtf.
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So then all you need to do is just use "rm"command which removes files.
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If you type the command as is, so just "rm,"
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and then we're going to specify Text.rtf to remove.
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And once I hit enter,
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you'll see it disappear also in the Finder as well.
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Now, what if I want to remove all the files inside a folder?
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So let's create some more text files.
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So let's call it Text.txt, and then let's create Text 3.txt.
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So now I've got Text, Text2, Text3. A little bit of a tongue twister there.
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And I want to remove all of them.
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So to do that, all you have to do is just hit--
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So to do that, you have to be inside the directory that you want to remove all the files from.
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And now I want to remove all of them in one go without having to type remove Text.txt, et cetera.
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So, again, we're using the remove command and then we're simply going to use the asterisk as a wildcard which
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matches everything that has every single name.
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And now if I hit enter, you can see that all my three files inside my current directory are removed.
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So do you remember in the beginning of this module, we mentioned that using the command line gives you
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more power, more control.
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And as we all know, with great power comes great responsibility, and that means that you have to be careful
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when using certain commands because the graphical user interface isn't there to protect you.
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So, for example, if you were not inside the directory that you wanted to delete, say, if you were inside
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your root directory and, you know, trying to remove all the files inside your root directory,
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then it's probably not such a great idea.
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So always check which location you're in before you're doing some of these destructive commands.
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Now, if you're here, now if you're inside your root directory and you tried to do remove--and you tried
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to do remove star, nothing bad is actually going to happen, because there aren't any files that are inside
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this directory,
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there's only folders. And to remove folders or remove directories,
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there's a different command.
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So, now I want to remove this Angela folder that I've created and I'm inside the right place to do it,
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I'm inside my root directory which is at this level. And, again, always check where you are
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by using the "ls" command. You can see that I am at this level.
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So, now I want to remove this Angela directory and if I just simply write remove Angela, and I hit enter,
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you can see it says that Angela is a directory.
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So this remove command by itself is not going to work.
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So to do it, we actually have to add a flag which is the -r flag.
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So this allows you to remove a directory.
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So, now let's try that again. 
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Remove -r,
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and then we're going to use the Angela directory.
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And if we watch over here and I hit enter, you can see that that directory is now gone including all
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the files that it held, all the folders that are inside the Angela folder, and it removes all of its child
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components.
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So, again, these are destructive commands.
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Be really careful when you're using them.
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And in fact, there's a pretty hilarious bit of internet history which is where somebody submitted a question
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to StackExchange serverfault which is similar to StackOverflow,
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but it's more for assistant admin and network admins.
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So what he said was "Monday morning mistake,"
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he used the sudo command which stands for super user do, which uses your admin privileges to basically
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allow you to do things that are, probably, a little bit dangerous, and use the remove command, and then the
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"-rf" flag.
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So we've already seen the "-r" which allows you to remove entire directories and all the folders and
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all the child folders it contained.
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He also used the "f" flag which stands for force. So this doesn't ask you for a confirmation.
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And then the very last thing which is something that you should probably never ever write and there's
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very few cases where this is actually useful which is the "no-preserve-root."
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And what that means is that along with everything else inside this command, it basically wipes your hard
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disk to the point where you cannot recover it.
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This guy said, "Monday morning mistake."
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"I basically just wiped my entire server," which obviously contains data from other people who are using
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his server.
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"And what do I do?"
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So as it turns out, this is actually a hoax where this guy is trying to advertise his server company.
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And I mean it's clever or is it not clever?
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I'm not sure that it's positive PR, but it got a lot of attention on the internets.
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So if you're interested, you can have a read of this and a link to it in this lesson.
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But basically, if you have a look at the answers, you can see that this is something really bad to never
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do. So with great power comes great responsibility.
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And in this module, I've introduced you to some of the most common commands that you're going to be finding
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yourself using,
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and also some of the most common shortcuts. In the last lesson, I posted a link to a cheat sheet of some
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other shortcuts that you can have a look at.
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And if you want to learn more about the command line, then this is a website that I highly recommend.
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I have nothing to do with them.
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It's just something that I found to be written quite well.
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So it's completely free and it's called the Command Line Tutorial, Learn Enough Command Line to Be Dangerous.
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Again, the title is repeating what we just said before, but it goes into more depth like a grepping kerl,
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all those things that you might have come across, and you will certainly come across more of it in your
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journey as a developer.
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So have a look at that if you're interested.
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And just before we head off, I want to show you something quite cool. Let's call it a bonus.
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And if you go into a Terminal and you type emacs -batch -l, and it's dunnet with two "Ns,"
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and hit enter,
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you will get taken into a text-based to your own adventure game that dates back a long time, and it's
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included in emacs which is a text editor that comes bundled with all macOS.
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So you might have heard of Vim and Emacs, a highly divisive issue, and it's a really cool game that you can
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play within Terminal.
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And I myself have probably spent more than, you know, a good few hours on this before.
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So, again, play at your own peril.
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So it tells you a bit of a story and you can write text commands to play the game.
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So, for example, at this point, you're at a dead end of a dirt road and you find a shovel.
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So let's say something like, "Use a shovel."
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"I don't understand that."
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Okay, let's try something else.
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What about "pick up the shovel"?
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"I don't understand that."
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What about "take shovel"?
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Okay, great.
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So it recognizes that. "Taken."
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And what can we do with the shovel? Let's try "dig." "Digging here reveals nothing."
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And this is my personal favorite.
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What if let's just "eat shovel"?
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So as you can see, there's some pretty interesting end points. And have a play with it if you're interested,
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but otherwise, I will see you on the next module.