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Hello there, you beautiful people.

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And welcome to this video where we're going to be learning how to turn source code into run programs

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with our own little modifications.

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So in this video, you're going to learn how to download source code, edit it and use the new C compiler

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to turn that code into reasonable binary programs.

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You're also going to learn how to install software from source code using the make command.

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And we're also going to modify the code slightly so that we can see that it is indeed our modified code

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that is being installed.

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And by the end of the video you should have a much better understanding of the awesomeness of open source

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free software, and you should also know how to compile software from source code for yourself.

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So let's go ahead and get right into it.

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All right.

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So here we are again on the new org website and we can see on the software tab here that we can get

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each of the packages scrolling down to the bottom.

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That comes with the new operating system.

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Now, all the source code for the commands that we've run so far, such as the fine command, the RLS

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command and so on, can all be found in this core utils package over here.

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So let's go ahead and download this package and take a look at it.

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So to do that, we click on the link and it will open up another page.

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And if we scroll down to the download section here, it'll give us a couple of links and it tells us

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that the stable source releases can be found at this link and the test source releases can be found

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at this link.

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Now the difference between the stable and test is that stable source releases are known to work.

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They've been tested, whereas test source releases maybe where they're trying out new things and you

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know, it's not fully stable.

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It might it's not final.

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Right.

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So we're going to try out the stable source.

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I'm going to click on that link.

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And we can see here that we get a bunch of packages, a bunch of bundles that are that are in a list

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format.

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And the most recent versions are towards the bottom of the list.

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So if we scroll down as far as we can to the bottom of the list, we'll see we get core utils version

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8.28.

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And what we're going to click on is the one that ends in dot z.

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So not the one that ends in dot z cig just the one that ends in dot x z.

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So if I go ahead and click on that right now, we'll see that.

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We see a pop up come here and I'm going to click Save File, I'm going to click.

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Okay.

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And that has been saved in our downloads folder.

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So if I just if I head over to our downloads folder right now in the terminal and you can see at the

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minute I'm in our home directory, I go to the downloads folder and list it out and you can see that

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we have got this core utils version 8.2 8xz.

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Now that's a compressed tar archive that's been compressed using the x z compression algorithm.

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So if I look at that, we'll see with the find command, we'll see that it's x, z, compressed data.

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Now X Z is just a compression algorithm, just like the B zip or the GZIP compression algorithms that

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we touched on in the file compression and archiving video very briefly, because it's not one of the

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more common algorithms, but we can unpack it using the TAA Command.

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So let's just do that.

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What we can do is we can type TAR and as you know, how to how to extract a file, you give it the X

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and F options and then you tell it which archive.

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But to extract through the zip compression algorithm, you need to give it the capital j option.

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So the lower case j option is for B zip two, but the capital j option is for x zip.

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And if you want more information on this, check out the file compression and archiving cheat sheet

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that I gave you in the appropriate video.

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Okay.

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So if we go ahead and press enter, we'll see that we didn't get any information because we didn't give

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the talk about the V option.

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But if now I use LZ, we'll see that we've now got a new folder called Core Utils 8.28.

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So if we see the internet, so we see the intercall utils and take a look, we can see that we've got

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a whole bunch of stuff in there.

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Okay?

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But we can specifically pay attention to this CRC directory now that CRC is short for source and that's

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where the source code is kept.

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So if we seed into CRC and take a look by clicking the screen, take a look, we can see that we've

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got a whole bunch of files in here.

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Let's pipe that ls data into the less command.

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First of all.

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Now, now this makes a bit easier to scroll up and down and you see now we can see that we get loads

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of files that end in dot C.

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Now that dot C indicates to us that these files are all written in the C programming language, which

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is a very common programming language that the new software is written in, given the date of when it

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was written being in, you know, the 1980s, 1990s.

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So let's take a look at the code behind the LS command.

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For example, we could lhs let's just grep out ls we can see that we've got this ls dot c file going

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on here.

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So let's take a look at it.

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Nano ls dot C and there we are.

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This is actually the source code in here.

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This is all the source code and we maximize it a bit.

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The source code for the LS command.

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So isn't that awesome right now?

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If you had the time, the ability and the intention, you could go through this code and study exactly

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what it was doing, which is one of the freedoms that the free software movement aims to.

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I give you.

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But we can actually also modify this code and recompile it into a running software, which is what we're

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going to do now.

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Now, this isn't a course on C programming, but in every C program there is a function in there called

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the main function, and it's a very important function that always runs.

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Okay.

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Now I'm going to modify that function so that whenever LHS runs, the computer will print out.

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Hello there, you beautiful people onto the screen.

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Okay, so I'm going to type a bit of code into the main function that makes that happen.

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Now, after preparing a bit for this lecture, I found that the main function in this file starts at

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about line 1443.

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So if we use Nano's, go to line function using the control and underscore option.

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If I put in line one, four, four, three and press enter, you can see that we've ended up at the

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main function magic.

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So I'm going to line the code right at the top here that does that printing stuff.

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So print F and I'm going to put in there.

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Hello there, you beautiful people.

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And make sure that it ends on a new line with the backslash n character right there.

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And I'm just going to tab this over.

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It doesn't make a difference, but you know that that's a bit nicer and let's try and get rid of this

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extra space at the end line.

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It doesn't matter.

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But okay, there we are.

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So we've put in the function there.

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Hello there.

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Beautiful people with a new line character.

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So the line, it goes to a new line.

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Now, if we save the file with control and O and we exit with control of X, we've now modified the

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LS commands code, so that's pretty cool.

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But now how do we turn this code into a reasonable program and install it on our computer?

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Well, because they're written in C, the code needs to be compiled into machine language before it

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can be run.

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And for that we need a compiler and more specifically a compiler for the C programming language.

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Now the new C compiler or CC is the compiler that's used on GNU Linux Systems and we can get it by entering

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the following command and that following command is sudo apt get install DCC now for now, I don't want

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you to worry too much about this because we'll be explaining in great detail later on what this command

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actually means and we'll be doing it in this section of the course.

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But in short, what we're doing is we're telling the computer to look on the software repositories available

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for Ubuntu and download and install the new C compiler or GCC package.

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Again, this will become much clearer in the next few videos, but just type it as I have done so here

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and when you're happy press enter and because we've used sudo it will ask us for our password just like

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when we've used sudo before.

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So I'm just going to enter that in there hopefully correctly.

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Fingers crossed.

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Nope.

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Let's try it again.

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There we go.

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And now it's saying, hey, we've got to install a whole bunch of packages in order to get this GCC

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package.

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And it's going to be about 72 megabytes of additional disk space.

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Do you want to continue now?

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I can just type.

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Yes, I'm just going to type.

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Why press enter and it's going to go ahead and do that.

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And this might take a bit of while depending on your Internet connection, but it appears to have downloaded

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it in my case and now it's just doing the installation.

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It's going to start unpacking each of those different packages that it's download and we are actually

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seeing an installation process happen right now.

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We will look into this a lot more in more detail later on in the course, but you can see that we didn't

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have to download any wizard and click next, next, next, next, next, agree to any terms of conditions

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or anything like that.

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Because all of this software is under the new public license and it all gives you the same, same,

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uh, different, uh, the same freedoms as each other.

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So now that's gone ahead and installed, we didn't have to do anything.

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We've now installed the new C compiler and a whole bunch of other stuff.

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So now we're ready to compile our code.

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Okay, so let's turn our attention to our beautiful source code.

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Now, because different computers have different architectures, we need to configure the installation

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of this code to our specific machine.

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And there's a script that comes with that called Configure.

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Now we're in the source, we're in the source folder here.

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So let's just go back up the folder with CD, dot, dot to go back up a folder, clear the screen and

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take another look.

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And you can see here there's a script called Configure and we know it's a script because it's green.

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Okay, so let's run that by typing, bash configure and we press enter.

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And what this is doing is it's configuring the new C compiler, the GTC, to get make sure that when

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it compiles all this, the software that we tell it to, it's going to do it in a way that's appropriate

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for our computer's architecture.

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And it's making the appropriate adjustments.

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And the important thing that this configure script does besides configuring the new C compiler is that

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it creates a new file called the Makefile.

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Now the Makefile is responsible for the installation of this new software package, but to make the

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Makefile work, which is a massive tongue twister, by the way, we need a new command called Make.

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So when this thing has finished configuring, we're going to install the make command in a very similar

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way to the we just installed the new.

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C compiler.

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So if we just sit tight here for a second while we see all this beautiful text flying up the screen,

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it looks pretty awesome, though, right?

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It's like something you might see on like a unlike a film with hackers, you know, and stuff like that.

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And it's we're literally doing that right now.

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So so be very proud of yourself.

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Okay.

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So now that's finished.

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If we just take a look in this directory, we should be able to see this new file here called the Makefile.

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Now, the Makefile is an important file, but we need to to be able to run that.

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We need to have the main command.

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So to get that we're going to type sudo apt get install make and when we press enter, it's going to

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go through a very similar process of installation and now that's all installed very quick, very easy

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to install that one.

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Okay.

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So now when we're in the same folder as the Makefile, if we just run the make command, you can see

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that it's going to go through and it's going to compile all of the all of the C files that it finds

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have not been compiled recently in.

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There are still some changes outstanding, which is effectively all of the C code in this folder, including

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our LS file.

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So what this is doing is it's compiling it all into, into machine code, into binary code that can

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be run on the computer.

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Okay.

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So this is what's necessary when you run a compiled language like the C programming language.

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So when that's done, we'll be able to install the newly compiled programs.

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But I'm going to cut the video here to save time and, you know, stop you waiting around too much.

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Okay.

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Now that's completed.

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So what's happened is we found the code for the LZ command.

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Okay?

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We edited that code, and then we installed something called the new C compiler, which is what's required

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to turn that code into machine code that the computer needs in order to run.

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Okay.

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So what we did is we installed the C compiler and we had to configure that compiler before it would

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could work correctly for our computers specific requirements.

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So we configure the compiler and then when it was configured, we've just run it using the make command

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to make sure that every single bit of code is now turned into machine code.

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Okay.

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So the only step that remains now that we've got this machine code is to install that machine code in

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the required places on our path for it to actually work.

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And the way that we can do that is using the pseudo sudo make install command.

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So if I click the screen type sudo make install, what it's doing is it's installing all of the stuff

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like that.

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And that was very, very quick.

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We've now installed each of the different pieces of software that came with this version 8.28 of the

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core UTILS package.

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Okay.

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So let's take a look at how that works.

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Okay.

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So if we just close our terminal and re-open it again, then now if we run the LZ command, we can see

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that it says hello there, you beautiful people, every time that it runs because we modified our code

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and installed it.

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How awesome is that?

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Right.

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So hooray for open source and free software.

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So this is actually a much faster process in reality than what I've showed you here.

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So to change back, we would just re-edit the source code, recompile with make, then reinstall with

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make install.

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So if I head back to our ad downloads, it's actually a much faster process when you get a bit better

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with it.

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So here we are.

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We're in our core utils file.

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We're going to go over to our source code folder that we're in there.

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Okay.

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So let's go to Nano.

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LZ C, let's head over to line 1443 and we're going to delete this, this line that I put in there,

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save the file.

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Okay?

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Now if I just clear the screen now all we have to do is do make and sudo make install.

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Oh because I'm in the wrong folder.

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There we go.

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Make and sudo make install.

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Okay.

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So now notice how the make command is just really compiling the RLS command because it notices that's

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what's different.

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Let me run with our end to my password there so it can install it.

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And now when I close the terminal and reopen it and use the LZ command, now it's back to normal.

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So you see how much faster that was, right?

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Once we've configured the C compiler once or at least for F for the package, it's really fast to just

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go and edit, edit it thereafter.

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That's because the main command knew as well that it only needed to recompile the code that was affected

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by our change, not the whole package which was new to the system the first time we did it.

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Okay, so make is a very clever program and as I say, now that we've installed the new version of the

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LZ program, now the hello the You Beautiful People message has disappeared and it's back the way that

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it was.

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So there you are you beautiful people in this video you've seen her to access source code from the dot

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org website.

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How to modify that source code and how to use, configure, make and make install to install the new

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software.

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Now the great thing is you can access and modify the source code for everything on a GNU Linux operating

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system.

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And if you care to exercise it, you have absolute power over how your computer works.

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So hopefully you can see how having open source free software running on your computer is a great asset.

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And you also that you can appreciate the effort that the pioneers of such a system took to build it.

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But the process that we went through in this video is relatively lengthy, and sometimes you just want

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to install software and get on with what you were doing.

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So for this, there are massive bodies of maintained and pre compiled code in what are known as the

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software repositories.

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And we use the repositories in this section actually to install the new C compiler.

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And the make command and software repositories are what you'll use to install software 99% of the time

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and they come with so many really cool features.

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So now that you understand that, yes, you can look up source code and modify how your computer works

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however you like manually.

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Let's take a look at how the software repositories which give you access to a massive library of software

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that is priority pre compiled and ready to go.

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So have a look at how they work as well.

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So for all that goodness, I'll see you in the next video.