Coding 101 24 (Transcript)
Shannon Morse: Today on Coding 101: The most important thing you will ever learn in programming. Also, dogs.
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Leo Laporte: Bandwidth for Coding 101 is provided by CacheFly. At C-a-c-h-e-f-l-y.com.
Father Robert Ballecer: Welcome to Coding 101, it’s the TWiT show where we give you the knowledge to live in the wonderful world of the code monkey. I'm Father Robert Ballecer.
Shannon: And I am Shannon Morse, and for the next thirty minutes we're going to get you all learned up on everything you need to know on how to be a code warrior.
Fr. Robert: Speaking of code warriors, Shannon, our codewarrior has been giving our folks at home a challenge the last couple of days with regular expressions, right? I mean, it’s been kind of a long slog.
Shannon: Regex is a little bit confusing.
Fr. Robert: Its one of these things, where I think everyone sees why it’s important, everyone understands why it’s something they need to learn, but at the same time there are so many modifiers and so many different ways to attach these different operators that people kind of get daunted by it a bit.
Shannon: Absolutely. You know, it was so funny, the other day I was working over at Hack5, and my coworker Darrin. He pulled up a terminal and he started putting in regular expressions, and I was like, "So, this is totally cross platform. This isn't just in perl. It’s so cool!"
Fr. Robert: Look, if you've got a mac, its built in. Yes, I know that. But, for example, I'm using a Windows pc, and I've perled an installment which means I can use perl regular expressions at any time to do searches through my entire computer or any drives that are connected. So, I mean, think of it as your own private Google.
Shannon: Oh. That's beautiful. That's perfect.
Fr. Robert: Yeah. But, if you're going to do that, you have to learn how to use it.
Shannon: You do. Which is why last week that's all we did. All we did was talk about regular expressions and today I wanted to show you a very quick and simple example that's similar to the one that padre showed us last week, to give you a really quick review. So, if we want to pull up my computer real quick, I'll go ahead and show you the one that I created. So I just called it Example Episode 47. So this asks, "Name your favorite youtubers."
Fr. Robert: We've got a standard input, and open. And we know that that's a regular expression. He's taking standard input, dropping it into a variable called 'quote' and then he's using a regular expression to look through quote.
Shannon: Yes. So we are searching for spaces, we are changing those spaces to enters.
Fr. Robert: New lines, right?
Shannon: New lines, yes. And then this is global, so it’s going to look through the entire standard input. And then when it outputs, it’s going to output each of their different youtubers on a different line. And then I do a second one where I print out, "Who is your favorite twitter folk?" So you put in standard input of all the different twitter people that you really like to follow. It does the same thing, then it says, "You said quote." Now, this quote, let me show you what it looks like. I'll pull that up. Okay, so favorite youtubers, we'll say, TWiT revision 3, and Padre and Hack5. So when I hit enter, and each one appears on a new line. And then it says what are your favorite twitter folks? So you know, I follow TWiT, so of course, Leo Laporte. And I also follow @snubs, that's me. And @mistersnubs.
Fr. Robert: Hi Darrin!
Shannon: So, when it does that, it says, "You said Leo Laporte, snubs, and mistersnubs. You should also check out twit coding 101."
Fr. Robert: We just hard coded some advertising into that program. Well done, very well done.
Shannon: Now another thing that I could also do with this is I could put, if they entered TWiT Coding 101, I could say, "Oh, well you should also follow this one." So I can see how this could be used on websites to make you purchase other things, like, say I want to go on Modcloth and buy this dress. And then they say, "Oh, well if you like this dress, you might also like this thing." So that could totally be used as a regular expression.
Fr. Robert: Well this is one of the things that we've tried to explain. The power of the regular expression, and this is why if you've done any search engine backend research, you understand this is what they use, because they don't want to just match the word. They're looking for particular strings. For example, Patrick loves, for some reason, rabbits.
Shannon: For some reason? They're adorable!
Fr. Robert: They are adorable. But there are many different strings and many different data sets that may include "Rabbit" in different capitalizations and different combinations. You want a command, you want a method, you want a class that will allow you to look through everything for that particular pattern, no matter what its attached to. And then you can make recommendations based on patterns that are found. That’s the power of regex.
Shannon: It’s so cool! It gets me super super excited about coding. Yay, I love this stuff!
Fr. Robert: Dr. Mobius is not excited about Regex but I think that's just because Dr. Mobius is dead inside.
Shannon: Hey, we've got a viewership example too, in our Google+ community. Do you want to check it out?
Fr. Robert: Yes please.
Shannon: Awesome. Okay, so this one comes from Scott. He posted an example that is basically a rock, paper, scissors game with the computer. It totally makes me feel like the computer is going to cheat. So, I click on rock, paper, scissors. I'll go ahead and show you what it looks like. It says, "Rock, paper, scissors - best of three. Please select for game number one. Rock, paper, or scissors." I'm going to say three, for scissors. It says, "Rock beats scissors, I win!" I swear its cheating. So this time I'll say rock. Hit one... It says, oh! It’s a draw. He picked rock too. Yes.
Fr. Robert: Wait a minute, I'm seeing a pattern here...
Shannon: Uh oh. Okay I'm going to choose three again and see if it does the same thing. Oh, it picked paper! "Scissors beats paper, I win!" No, I win!
Fr. Robert: Okay, so I like this.
Shannon: And then you hit a key to end. So now if I enter into this, I can go to edit. So he has... Basically he put in a whole bunch of 'if else's and he also put in this thing called random. So right here, the computer generates a random number for the computer right there. And then, depending on the number, it'll give you back a different choice.
Fr. Robert: Let me put a disclaimer here, because I know there are some advanced computer geeks out there who are saying, "Wait a minute. Your random number generator isn't really random." We know. We understand that. There is no real easy way to do a random number generation in any code base, no matter what language you're using, but this will give us enough to give us some variety between the choices that the computer makes.
Shannon: Yeah, it absolutely does. And then Scott did put in a lot of good comments into his code, so definitely check it out over on the Google+ community - that's over at G+.to/twitcoding101. And the last one I wanted to share with you guys today was from Daniel. So this isn't a code, exactly, but he decided to share some of his research and his areas that he found regular expressions online. So he has three different links on here, and I'll open those up for you. One of them, I believe, is a poster. But these are all different regular expressions that you can print out so you can get to know them. Very very very good sheets. Very helpful.
Fr. Robert: Oh, my goodness. This is actually exactly what we - believe it or not, we've been searching for a really good reference sheet for a long, long time. Even the really good books about perl don't have the collection of these things in one place. So this is incredibly valuable. Make sure to check this out. This will be in our show notes, thank you Daniel.
Shannon: Yes, thank you so, so much. This is very helpful.
Fr. Robert: This is why we love the group, because we have the hive brain. The hive brain seeks out the things that we need.
Shannon: We do, we're like bees.
Fr. Robert: I don't make honey. Okay.
Shannon: Moving on.
Fr. Robert: Now moving on, I know that we've had some people that are growing tired of us doing regular expressions. This is pretty much the third episode that we've been touching on it, the second which we've been going full on. I understand that it's kind of confusing, I understand that for people who already know regular expressions, it can be frustrating because you feel like we need to move on. But we've actually got a graphic here that was given to us by one of our users, SJHCanada. This is a classic XKCD reminding you why you need to know your regular expressions. Now this is fun, they're talking about a killer who's followed a roommate on vacation, and they're saying...
Shannon: Can I act this out? ... "Oh, no, the killer must have followed her on vacation!"
Fr. Robert: "But to find them, we'd have to search through two hundred megabytes of emails, looking for something formatted to look like an address!"
Shannon: "Oh, it’s hopeless!"
Fr. Robert: "Everybody stand back! I know regular expressions!"
Shannon: Now Padre is going to swing in, onto the set.
Fr. Robert: Perl! Hooray! Wow, that was actually really good. So folks if you ever start getting tired of learning regular expressions, just remember one day, you will save your roommate.
Shannon: Excuse my horrible laugh.
Fr. Robert: Let's move on, okay. Now this is going to be an abridged version of a regular expression episode, because we have spent a lot of time on regex already and I didn't want to beleaguer the point. This will be the last episode that we spend on regular expressions. But Patrick has promised us that in the codewarrior section, he's going to introduce us to the most important thing you will ever learn about any programming language ever. And yeah.
Shannon: Oh my gosh. Oh boy. Sounds kind of scary.
Fr. Robert: He says that if we don't agree we can have his bunnies.
Shannon: I'm a little intimidated... We can have his bunnies?
Fr. Robert: We can have his bunnies.
Shannon: Okay. I don't agree.
Fr. Robert: Automatic. Alright. I thought before we get there, I thought maybe we should do a quick look at the regular expressions so we can understand exactly what's going on, so that when we get to Patrick we can better understand. Now, when we've been dealing with regular expression, we understand that we put the name of the variable, right. We start with the name of the variable, and we put the equals signs and the tilde sign and that tells it, "Okay, I'm going to be running a regular expression." Everything after that is the confusing part. Everything before that, we've seen it before on the code base.
Shannon: Everything before that basically doesn't change, anything after that could be any regular expression.
Fr. Robert: It can be crazy, which is why we need to look through it and specifically look at the different pieces. Now, I like to separate it into four different pieces. You start off with the match operator, you move to the end number, you separate these by slashes. You move to the expression, you move to the second expression, and then you move to the match expression operator. Okay, so think of it as four different pieces. Now the question is, what goes into each one of those pieces? For the expression, we already know, right? The first expression is always going to be what you're trying to match, the pattern you're looking for.
Shannon: So in our case, it has been the standard input from the user.
Fr. Robert: Right, so you look at that and let’s say you're looking for "rabbit". So "rabbit" is what you're looking for, and you're looking through the variables, the string for "rabbit". The second expression, if you've chosen to replace, will be what it puts in its place. So that's really easy. The expression part is easy. What the difficult part is, is the match operator that goes at the beginning and the modifier that goes at the end. So remember that. Operator, modifier. These are the things that you need to know. Now according to what we've been doing most recently, there are three match operators that you will see most often. In fact, there's really only two, but we're going to give you three. The first one is M. M/ - do you remember what M does? M is just match.
Shannon: Oh, match. Okay.
Fr. Robert: Right. So, just find it. Don't do anything to it. Just find it. So, if I had, I don't know. Say, the script for Blade Runner and I looked for tears and I put the M to match it, it will find the place in the script where tears are used, and they can find the famous line of, "Like tears, lost in the rain." Which I can't do, though it was an awesome line, okay? Now S, S/ is slightly different, and folks, this is going to be in the show notes so don't worry. Don't write this down. Let it soak into your head. This is the one that we've been using most often. This is substitute. So where as M is just finding it, S means find this expression and then replace it with a second expression.
Shannon: So like, for us, we've been finding the word cat, and then substituting it with the word rabbit. With the /S.
Fr. Robert: By extending that, we only need that second expression if we're substituting. If there's no substitution, there's no second expression, right?
Shannon: So if you're just looking for a match, you only need one expression.
Fr. Robert: One expression. And you would do the match operator, the expression, and any modifiers.
Shannon: Ah, perfect.
Fr. Robert: Okay, so M and S, in reality unless you're doing some pretty high end stuff, those are the only two match operators you're going to use in Perl. You're going to find the match and substitute.
Shannon: There's three...
Fr. Robert: There's two, there's TR... Translator regular expressions. Patrick's smiling in here right now. He's like, "Yeah, we never use that." I have seen - that's the face of a programmer going, "There's some easier way to do this."
Shannon: They taught me that in college.
Fr. Robert: Exactly. Exactly. If you really want to use it, go ahead and take a look at the reference sheet that we got from Daniel, practice it, code with it, and then you're going to learn that you're never going to use TR.
Shannon: What does it do?
Fr. Robert: Patrick, I'm going to get to you when we get to Codewarrior. I want you to give an example of TR. Because I hate explaining it.
Patrick Delahanty: I've pretty much only used it to convert uppercase and lowercase back and forth. If I want to make something all upper case, I'll use TR to do it, or if I'm changing uppercase to lowercase.
Fr. Robert: We call it, "Changing Everything to Shouting Operator". Alright. Now, so we've got the match, the useful match operators. Those are the two. I'm going to call it two, not three. And then we've got the one or two expressions, depending if you're just matching or if you're also going to be replacing, or substituting. And then we've got what are called the Match Operators. These are the fun ones, because there are a whole ton of them.
Shannon: So these are the ones that go at the end?
Fr. Robert: They go at the end, right. I talked about we divide it into four pieces? These are in that fourth section. First one is G, we played with this. It means match global, look through the entire thing from beginning to end, looking for this pattern. I is insensitive. It means we don't care if its capitalized, we don't care if its lowercase. You could put capital C-A-T or lowercase C-A-T, or c, capital A, t. And it would still find it, because its ignoring capitalization, its ignoring case. And, it means to treat the streams as multiple lines verses "as" which would treat the strings as a single line.
Shannon: So, does that mean if they entered in several lines it would just treat it all as one?
Fr. Robert: It’s a different way of looking at the variable, so, they're talking about strings. They can actually be huge, right? They can be multiple lines, within a particular variable. A string is not like what we learned in C sharp, where it’s just a short phrase. A string in perl, could be the entire file. So, I don't know. Look at it with its proper spacing and its proper layout, or I'm going to look at it entirely as a single line. It makes a difference.
Fr. Robert: There is also M... I'm sorry. There is also O, which the value is the expression only once.
Shannon: Only once, okay...
Fr. Robert: So that's like, if for example, you just wanted to find the expression one time and then stop the search.
Shannon: Oh, okay.
Fr. Robert: And my personal favorite is X, which allows you to use extended regular expressions, which is another way of saying, "allows you to use white space in the expression".
Shannon: Oh, interesting.
Fr. Robert: Right, and again, you're going to need sometimes. All of these things are going to be contained within the reference file that we got from Daniel, so again, Daniel, thank you very much. We're going to include a link for that in center in our show notes. There are many more modifiers, so many more modifiers. But these are the ones that we want to play with. Please feel free to experiment with the other modifiers, with the other operators, see what they do. You can't destroy anything, but, if you want to cut down confusion stick with what we're giving you now.
Shannon: Got it.
Fr. Robert: Does that make sense?
Shannon: Yes, it does. I actually could have used that X modifier, the one that actually includes whitespace in your expressions. A couple of weeks back, I tried to write one where it searches for Amy Pond and replaces it with Rose. And I was like, "Why is it not working!?" And it was because I added a space in there. It would have been helpful...
Fr. Robert: Exactly, it’s a regular expression. Now this is the time where we introduce back into the show our Code Warrior. Now you know him, you love him, you've seen him for three episodes before this, plus all over the TWiT TV network. Ladies and gentlemen, its mister Patrick Delahanty. Patrick, thank you for coming back.
Patrick: My pleasure, great to be back.
Fr. Robert: When we were planning the show, you told me you would mark down a certain number before, and you said, "This will be the most important thing they ever learn." You wouldn't clarify what that meant, but I trusted you. Now tell me, what's the most important thing that they'll ever learn.
Patrick: I've been looking forward to this episode, because this is the most useful line of Perl that you'll ever learn. If you learn one thing in perl, learn this. It’s a command line search and replace. Some people call it Perl Pie, and you'll see why in a little bit.
Fr. Robert: Alright, so command line search and replace, so what you're saying, is what we've been doing is practicing with using the regex command inside of a program. So compiling it into some sort of usable form that we can run interesting programs like Replacing cat with bunny or looking at your favorite podcasters - you're saying I could actually use the regexp command at my command line, outside of my compere.
Patrick: Absolutely. And so you can have a search and replace that operates on one file, multiple files, just from one line of perl. So I use this very often, and it’s the most useful thing I've ever learned in perl and I'm happy to pass it on. So let’s actually take a look. I'm going to continue here, I've got some text files. I've got some bunnies too. But I've got some text files. Before you do anything, make a backup. I've already got a backup directory. If you save files...
Fr. Robert: Folks, you're doing a search and replace, so if you replace something you needed, its gone, just so you know.
Patrick: Yeah, so I want to have a backup of these files just in case, you know, fat fingers maybe I'll type it wrong or I'll erase the whole thing. So before you even try this, make a backup! So, I've got these files. This one, it’s got a list of TWiT hosts. I've got another one here that's just a list of mailing addresses. These are not correct addresses, so please don't try to mail these places.
Shannon: That's totally my correct address.
Patrick: That's the police station in Oakland, so...
Fr. Robert: Yeah, go there.
Patrick: I think the Star Wars script and Shannon's bio for the TWiT wookie... Yeah, and um, so I'm going to go into my command line here. And I don't have a perl program, I'm just going to type perl p - i dash e. This is where you get perl pie.
Shannon: So you're in the command line...
Patrick: Yes. And I'll explain that the p - i - e do after a second here. But they only do a single row with my regular expression. So I'm going to search for Shannon Morse and I'm going to replace that with Shannon's married name...
Shannon: The Dilatator.
Patrick: Shannon the Dilatator, that's your married name, right? So I'll put...
Shannon: So, global?
Patrick: Yeah, so global, then we do the single click to close that.
Fr. Robert: Make sure you go ahead and zoom in a little bit.
Patrick: Yeah, it’s up in the top line, people may have...
Fr. Robert: They may have issues.
Patrick: I could make that windowed. Oh, there we go. Okay. And so then I'll type *.txt.
Fr. Robert: Now we should show folks that even though we're using the command line, he's using the exact same format. So we've got the operator, we've got an expression, a second expression that you're going to use to replace it with, and we've got the modifier, which is G, which we know is global so it's going to look through the entire thing.
Patrick: And at the end, I put *.txt so it’s going to look through any file that ends in .txt.
Shannon: Is this any in your computer, or any in that specific folder.
Patrick: Any in this folder.
Patrick: And I could do, I mean this is just normal file operations. I could do this, and it would be everything, every subfolder.
Fr. Robert: Don't do that. Yeah, don't do that...
Patrick: Let's not go crazy here. I'll just do every text file, and it will replace Shannon Morse with Shannon the Dilatator. And now we'll go back to my files. If I reopen this -
Fr. Robert: You're going to have to zoom in on this one, now, Josh.
Patrick: Make this bigger, here... So if we look down, we'll see down here...
Fr. Robert: There you go!
Patrick: Shannon the Dilatator.
Shannon: That's funny.
Patrick: Now if we look in here, reload the normal file... Shannon the Dilatator. Replace that one, I don't think your name is in the Star Wars script, but in your bio I'll open that back up... Shannon the Dilatator.
Fr. Robert: Now there are some people in the chat room who don't understand why this is so powerful. Now let me give you an example - Here we have a series of files that control the profiles of the tricaster. Every once in a while we have to make a Global edit, like we change a line, we change the way we use the lower thirds, we change the timing on something. If we needed to do it manually, what we would have to do is have Alex go into the tricaster, load each profile individually, change it, make sure its right, exit and go into the next one. I mean, consider how many shows we have on the TWiT network.
Shannon: That would take days.
Fr. Robert: It would literally take days. Before we used regex, it would take days, but with this kind of command what you can do is, say look through the tricaster profile folder, look for everything that contains the line that we're looking for. So the lay, or the name of the advertiser, or the name of the segment that we're changing in every show, and change it to Y. It would go thru and within a couple of seconds it would do everything. It would change all of the settings in all of the profiles at the same time. Its amazingly powerful and I think that's why Patrick has a pretty good case for saying that this is the most important thing that a computer programmer is ever going to learn. Because it has applications beyond just programming.
Shannon: It can be used in the workplace, that would be so so easy.
Fr. Robert: It’s a Google for your computer.
Shannon: So useful.
Fr. Robert: Your personal Google!
Shannon: Now, Patrick, I know this isn't the necessary part of the tutorial for perl, but just in case anybody is wondering, can you show them how to change directory over to the correct directory of a text file?
Patrick: Change a directory to a correct directory...?
Shannon: Yeah, a terminal?
Patrick: Oh, just change directory. That's just... Let me go into my terminal here.
Shannon: So you do a, uh...
Patrick: Um, I had already typed the next command, but...
Shannon: I am so sorry!
Patrick: I was unprepared for these!
Fr. Robert: We've got some zings out in the chat room saying you could just use "said". Yeah, you could do that, but what's so nice about this is if you learn it for perl, which you're going to learn it for perl because it is so important if you're programming in perl, you cannot take that knowledge and use it without using any other utility, without starting up any other tool, or without having to put it on any other piece of software. Your perl experience to do the exact same thing that you would have it do when its inside one of your programs. That's actually very, very cool. When you think about it, that's a nice way to do it. Patrick, do you have an update for us?
Patrick: Yeah, I've got the... If you want to see the list of files, it’s just under Unix or Mac you can type windows, its DIR. If you're going to change the directory, I could have the backup directory, CD change directory, backup. And if I want to go up a directory back where I was, like that. So I can just move around.
Shannon: Yay! It’s pretty much the same in windows, except for that DIR.
Patrick: I have the command that I argue, that I mentioned earlier. I can explain what those do, if you'd like?
Fr. Robert: Yeah, actually, yeah. Could you show us and actually give us some more specific use, because there are some people saying, "Wait a minute, that's not all useful." Or maybe it's only useful if you're a system administrator, give us some better examples.
Patrick: That was just my first example, but first I'm going to explain what these arguments do. The first one is dash E, and that tells it that its running this as a command line and not executing a file. So dash E, is just this is a command line command. Dash I is used to modify the input file in place, so it means they're just updating the file I tell it to. And dash P runs the file as if it was in this perl code here, so it would be whatever I type would be in here, and then if it doesn't work it would give an error. But, perl pie. P I E. I can give another example here, let’s go to what I typed up for... Thanks Shannon.
Shannon: You're welcome. Just hit upper bench times.
Patrick: I didn't actually X from this so... Dash E... I'm going to look for /. but I'm not looking for the period with just any character, I'm actually looking for a period. I'm looking for .html and replacing it with .php.
Fr. Robert: If you had just put .h without the slash, it would have looked for everything with html after it. Whereas we're telling it, no, actually look for a dot, a file with the extension by html.
Patrick: Replacing it with php, and I want global in case it’s sensitive. If it's capital html, I want to replace it with php.
Fr. Robert: Right, so from what we know about regular expressions, what this should do is it should go through the directory and look for any file with a .html extension and change it to a .php extension.
Patrick: Yes. And I have a couple of html files in here that we can take a look at before I go and modify it. And see, this one here, you can see there's a bunch of links down here, with .html. There's one with html, so, it shouldn't change that one. There's also a couple of links here. There's another link up here, but there's no .html so it shouldn't change that. Then we'll look at this other file, because I want to change both. There's one... And... This doesn't have any .htmls so this shouldn't be modified at all. Alright let's go execute that code, and see what happens. It’s done! It’s going to go back. And reload this file... Oops I’ve got to close this and open it back up. I'll zoom in again, and yup. These three links are now .php. These are also .php, but I left on our content. So this is for if you were just updating some web page content, or whatever. If you're changing over to php, maybe in a future module for coding 101, then you could easily change all your links that way. And another example - you'll see in these html files, I've got some comments here. Maybe I want these comments for my own coding preferences, but I don't need them or want to publish them.
Fr. Robert: Actually, Davinci Wonder has a very interesting question and I actually don't know the answer to this one. Can you create a log of the changes? Because I don't think you can do that, right? This is making global changes, that's it. There is no record of what's happened.
Patrick: There's probably a way, but I can't think of one off hand. You could always actually do a full perl script that logs all the files and goes through, but for a command line... Off hand, I can't think of a way.
Fr. Robert: Again, I think the only way it would be is if you were actually recording your screen or logging your keystrokes. Sorry... Sorry DaVinci.
Patrick: But yeah, so these comments in html. Let's try to remove those. But you'll see they're all different, so I can't just search for this comment and remove it. So I've got to do some creative expressions here.
Shannon: They all start with bracket, exclamation marks...
Patrick: Yeah so they have that common bit, because they all start with this less than, exclamation mark, dash, dash. And they all end with dash, dash, greater than. So, what I'm going to do, is I'm going to clear this out, okay. Perl pie, and we will search for - and I'm doing the backslash before this unusual character just to be safe.
Shannon: That's to make sure that its actually searching for that character.
Patrick: Yeah, yeah.
Fr. Robert: The character, not for what the character represents.
Patrick: And the hyphens are fine, I don't have to put the backslash there. And now I'm getting a little fancy... So what this does, I have bracket and then close bracket. And the plus. And that means that it wants to find at least one of whatever's in the brackets. And what's in the bracket? I've got this greater than, with the backslash greater than, but I've also got this carrot. Which means "not". So what this is looking for is anything that is not closed bracket. Or, greater than. So, I'm looking for this open comment and then anything that isn't this and then we will go dash, dash, and at the end of the comment with the backslash greater than. And I'm replacing them with nothing. And global, close that up. And what it'll do, start html...
Shannon: I see what you did there, sort of.
Patrick: So I've pretty much said, the equivalent of what this star is over here, with all of this saying, "Anything that's not this and a comment."
Fr. Robert: Another way of saying this, is the pattern you're asking to look for is that open carrot, and the closed carrot with those special characters, and then anything in between those two you're going to replace with like, nothing.
Patrick: Yes. Absolutely. So if we look at the modified code here, all my comments are gone. It’s just a blank line. It’s beautiful.
Shannon: It also erases the greater than and less than signs. Everything.
Patrick: Yes. So it stripped the comments from this.
Fr. Robert: Now folks, there's going to be a lot of people saying, "Why would I want to remove the comments from my code?" What we're trying to show you here is how you can dynamically generate pages, how you can dynamically change code, say, within a webpage, in order to make it match something that you want it to do. This is one of the strengths of perl. We mentioned it in the very beginning. And it’s something that we're going to be covering in the next episode. But before we get to that, you have one more example, Patrick.
Patrick: Yes, I do. And we'll go back to the command line here, and let’s say that I want to get a little fancy with my search and replace, and I'm going to look for Shan. This? Can you guess what this does?
Shannon: S plus...
Patrick: S is space but it’s capitalized with a non-space. So this will match anything, it will match Shannon, Shenanigans...
Shannon:So it’s looking for the beginning of a word and anything that's included in that word.
Patrick: And everything for the rest of the word, until it gets to a space or a new line. Any space type character. And I've also got it in parenthesis, and what this does... I'll explain after I type out the rest of this. I'm going to get to the second part... How do I spell that... There we go. I copied it. Sailor... This dollar sign one is the first group in parenthesis. So, it’s taking whatever matched in here, and putting it wherever the dollar sign one is. If I put something else in parenthesis, that would be dollar sign two, and then dollar sign three, and so on. So I'm taking this, and I'm going to find Shannon, or Shenanigans, and I'm getting rid of Tilitator and replacing it with Sailor Shannon. And we'll do a G and we'll do that, and we'll do that star dot txt... And let’s take a look and see what happened. Did this work. Alright see, here's the file before, you've got... Let me make it larger. We've got Shannon The Dilatator, but if we open again... No I don't want to save it. Let's open it back up, and zoom in and if we look down, Sailor Shannon!
Fr. Robert: Fantastic.
Shannon: Da, da, da, daaaa. That's awesome.
Fr. Robert: Now, Patrick, I will say this. I think this is cool, I think this is something that you should definitely learn. But I'm seeing a lot of disagreement in the chat room, so I will say this: if you disagree, that this isn't the most important thing that you will ever learn in programming, if you think Patrick is full of it, if you think Patrick now owes you a bunny, please go to our G+ group and tell him why. Or tell him, even better, what you think actually is the most important thing to learn, while learning to program.
Patrick: If they disagree I'm going to search and replace their comment with something else...
Fr. Robert: Actually that would be interesting, search and replace Google+... Now folks, I know that this is a lot of information so don't worry we're going to make sure that this all ends up in the show notes. You're going to have our full notes, you're going to have all the code that Patrick used. And you're going to find that really cool reference sheet that Daniel gave us so you can start playing around with regular expressions without freaking out and thinking that you're going to erase everything on your computer, replacing it with Shannon the Dilatator. So Patrick, thank you so very much for being our Codewarrior yet again. Next week, I'm excited about this. Do you want to explain to these folks what we'll be doing?
Patrick: We're actually moving onto the web and we'll be doing, if I'm remembering the schedule right, we're going to be doing printing to the web with perl, so dynamic web pages.
Fr. Robert: Which is what you do all day, so this should be interesting. Patrick, thank you again. Do you want to tell the folks where they can find you?
Patrick: Sure, you can find me at Twitter at PDelahanty and also check out my websites down there on the lower third... Animecons.com, entirely coded with perl.
Fr. Robert: Its perl. It’s for the real world.
Shannon: The Real World. MTV, TWiT style!
Fr. Robert: That's enough of that... Shannon, we did promise them that they're going to be able to find out all of this stuff that we gave them, right? We told them to go to our show page... Where are they going to find that?
Shannon: Yeah, that's over at TWiT.TV/twitcoding101.
Fr. Robert: And if you want to get more than just that, you're also going to find a link there to the github site, that we're still using. I know, I know, it’s horrible. We're starting to realize.
Shannon: I like github!
Fr. Robert: Get hub is nice, but we need to... There's a couple of tools that we're going to use to make it more useful. Because right now, you know this, it’s difficult for them to find part of it on the show notes page, and part of it on the github page. We can't put it on the show notes page, because the formatting goes all wonky and it’s useless to you. So we are going to find a better way for you to get our show notes. Thanks to everyone who's been sending in suggestions. We've been evaluating them. The reason we haven't moved is we don't want to change it, and change it again when we realize it doesn't fit something else. So it’s going to take some time, please bear with us.
Shannon: We'll take some looking around but we'll choose the best one possible for this show. Also we are on iTunes too. You can find us over on iTunes, just search for Coding 101 and you'll find us in the search queries. I believe its available audio and video, so whatever you need. It’s great for commutes, thats for sure.
Fr. Robert: Yeah, and it's not just audio and video, its audio, its low quality video, standard video, and high definition video, so you can find a version that you want, yes. Now also, did you know that we do this show live. We're live right now. This is actually happening.
Fr. Robert: I know, weird, right? Every Thursday, 1:30PM pacific time, you can find us at live.twit.tv and as long as you're going to watch us live, why not jump into the chat room, yeah?
Shannon: IRC.twit.tv, we check it out during the show. We'll answer your questions.
Fr. Robert: Its right down there. We see that little... He's mad, he's upset. Guy's threatening to beat me up, that's strange... We love the chat room anyways. But of course, the big place to get ahold of us is going to be our Google+ community. That's where she pulls examples from the audience, and puts it into the program. So if you want to end up on the show, go to g+.to/twitcoding 101 and go ahead and join. I think we're at almost eleven hundred...
Shannon: It's over eleven hundred...
Fr. Robert: Over eleven hundred? I want to get it over nine thousand.
Shannon: Over nine thousand!
Fr. Robert: We're going to join and see what the old and the young geeks over there can do for you. Finally, if you're not into the G+ groups, yeah the twitters, right?
Shannon: We are on the twitters. I am @snubbs.
Fr. Robert: And I'm @padresj.
Shannon: Oh, and you know what? We should say, Cranky Hippo is @crankyhippo, who is just happening to get married today. But he's not here...
Fr. Robert: But actually, if you could, go to Alex's twitter page. That's An Elf. He's got a picture of him and Bryan when they were kids. It’s so cute.
Shannon: Awww, congratulations Bryan.
Fr. Robert: If you could retweet that picture, and tell them congratulations on Alex and Bryan getting married, that would be fantastic.
Shannon: Oh, boy. And also, thanks to Josh for filling in today. Thank you so much!
Fr. Robert: Yeah, Josh. You did good! Until next time, I'm father Robert Ballecer.
Shannon: I'm Shannon Morse.
Together: End of line!
- - -
Fr. Robert: What is he doing with his arms?
Shannon: I don't know.
Fr. Robert: That's so weird.
Shannon: He's an awkward child.
Fr. Robert: The thing... Go back to that picture, you know the thing about Alex, is that he hasn't changed. He still looks like that. Except for the hair. The hair is not so afro... But you know Bryan looks like...
Shannon: Bye everybody! Awww...
Fr. Robert: Look at that! We've got Padre, we've got Alex...
Shannon: What is that?
Patrick: That's today.
Shannon: That's today? Holy crap, that's a lot of people...