Perl Lesson 1

M 101 here. Today, this is going to be a Pearl lesson. Um, what Pearl is, is a programming language. See, a few of you, who happen to be older than most of our viewers, want something more complex and advanced than just these simple terminal commands. So, I'm going to be showing you how to make a program with terminal and how to make it do stuff.

So, this is Pearl lesson one. There are going to be a few of these, but for now, I'm going to be demonstrating this to you on my desktop like normal. Um, so as you can see, I'm gonna have to go into VI or Nano to make a document. I'm just going to do VI, but you can use Nano, so I'm going to do VI, and I'm going to call my program wi.

Now, um, the first line of your Pearl script you're going to want to make is hashbang slash user slash bin slash Pearl. Put that up on the screen, and yes, user has no e in it. Now a hash is shift three, and the bang, also known as an exclamation point, is shift one.

Now, uh, we go on to the next line, and we want to type our Pearl script. So now we can type there are a few commands for the script. I'll just start you off with something simple that you're going to be bored with, but it's useful and worth it. Print, and this displays text on the screen.

So with print, you do print space quote, and now we want to type something to print out, like "Hello, my name is Dave," and then we're going to do a close quote. At the end of every line, except for the first line, which is hashbang user bin Pearl, we want to put a semicolon.

Um, so now hit enter, and now I printed out "Hello, my name is Dave." And so I'm just gonna save this right now. So here's my text document on my desktop called wi. Now we want to type a command to basically activate it: chmod space +X space and then the name of your document, by in case it's WI.

So now my document looks like this on Tiger. It should look like a terminal. On Tiger, you're not just going to be able to double-click it, but that's okay. So now you want to, um, I'm just going to edit wi again, and now say I have a print that says "Hello, my name is Dave." It's going to print out "Hello, my name is Dave," because that's what I wrote.

So on Tiger, you can just drag wi into your terminal and then click the terminal and hit enter, and then it says "Hello, my name is Dave" right there. Unfortunately, it didn't print a new line, so it goes straight to my prompt. So I need to edit that.

So here's how you do a new line; in the quotations, you do backslash n. Backslash n is a new line, so "Hello, my name is Dave!" backslash n. So I'm printing a new line after "Hello, my name is Dave." Now I'll just drag wi in, click enter, now I printed out "Hello, my name is Dave" and then went to the next line.

Now wi happens to be an executable, and it's in my current path. wi is right there, so I can just type ./wi and say "Hello, my name is Dave." And on Leopard, I can just open it up and it'll say "Hello, my name is Dave."

So yeah, so now I'm going to edit wi again, and on the next line, I'm going to say print "What is your name?" backslash n quote semicolon. So now it's going to ask me what my name is. Now, unfortunately, I can’t type anything back. As you can see, look at this: "What is your name?" Now I'm typing on my prompt again. I'm not going to type my name as a command because it’ll say command not found.

So how am I going to take my name as input? I want to type dollar sign. Then let's just call it shizzel for now space equals space less than STDIN greater than semicolon. So now, here’s what dollar sign shizzel is. Whenever you have a dollar sign and then a word, it declares a variable called whatever the word after the dollar sign is.

In my case, it's shizzel. I say shizzel, which is now a variable equals, you know, less than STDIN greater than. What does STDIN stand for? Standard input. So that would be the way of input, which in this case is the terminal. So shizzel is standard input.

So now I’m just going to run wi again, and it says "What is your name?" Now it's giving me a chance to type, and I type my name. So now, of course, my name has been assigned to whatever they type in the standard input. Now let me just explain a variable.