LSL 101/A Gentle Introduction

A Gentle Introduction to Scripting in Second Life

LSL 101: The Wikibook

• A Gentle Introduction
• The Structure of a Script
  • Simple Script Skeleton
  • Comments, White-space and Formatting
• Events & Event Handlers
  • The touch start Event
• Variables
  • Strings and Simple Output
    • String Concatenation
  • Integers
  • Using Variables
    • Global vs Local Variables
    • Variable Initialization
• Functions
  • Functions That Return a Value

The End Game

• Creating a Script
• Compile Time Errors
• Logic
• Conclusion

This section of LSL 101: The Wikibook is written for the SL user who has no experience with computer programming; or, for users with programming experience who would like a gentle introduction to LSL.

This section assumes you have basic building skills, since scripting is just one aspect of building. You should be able to create and edit a prim, then take it in and out of inventory. You should be able to do the same with a notecard and know how to add it to a prim's inventory.

If all of this sounds like you, welcome!

Scripts are used to make SL objects do something. They can detect things that happen (i.e., noticing a mouse click or the approach of an avatar); and, that script can then act in response (i.e., moving, changing appearance, greeting an avatar with a message, displaying a current stock quote). Scripts are at work any time an object has any kind of behavior.

In SL, scripts are written using LSL (Linden Scripting Language), a simple but powerful programming language that was created for the SL environment. (Here, "simple" is used to suggest that LSL is more limited than other programming languages; not that it is easier to learn. Like any other language, learning LSL requires practice.)

When you learned to speak you discovered that you needed to know not only some words (vocabulary) but also the order in which to use them (grammar). It is the same with computer languages: you have to learn the words and you have to learn the order in which to use them. When you learned to read and write you discovered that there is also punctuation - commas, full stops (periods, if you are American), brackets, etc. - which help to clarify how different words and phrases relate to each other. The difference between computer languages and human languages is that with human languages people can generally understand your meaning even if your pronunciation or spelling is not completely correct or your grammar is slightly wrong. Computer languages are not like that. If your spelling, punctuation or structure is even slightly wrong the computer will report an error or, at best, not do what you expected it to do. This can be very frustrating for beginners.

I'm sure, if you have ever attended a writing class, you were told that a story has a beginning, middle, and end. This we can call the structure of a story. In LSL the structure is very important and we will discuss that (and introduce you to some of the vocabulary, grammar and punctuation) in the next section.

You can continue with Simple Script Skeleton or The Structure of a Script.