Garry's Mod Wiki

Coding - Getting Started

Introduction

A Lua file is called a script. Lua scripts are plain text files. To create and edit Lua scripts, you need a plain text editor such as notepad.

You can use any plain text editor, but to make your life easier, we recommend that you use Notepad++. A plugin you may want to use with Notepad++ would definitely be the Gmod Lua highlighter: https://github.com/kylefleming/npp-gmod-lua

For the sake of simplicity we'll refer to both notepad and Notepad++ as "notepad".

Do not use Wordpad.

It is a formatted text editor, not a plain text editor. It will put useless tags in around your code that will cause it to fail when loading. As a rule of thumb, if you can have text that uses two different fonts in one file, then it is not a plain text editor.

Creating the script

For our first script, we're not going to do anything too complex. We'll learn how to print a message into the console.

The print function does exactly that. Type the following code into your chosen editor :

print( "Hello world" )

You're done! Wasn't that easy? It should have been.

Explanation

print is a function. A function is a command that does something when you call it. Many functions can take arguments, which is data you give the function to change exactly what it does. In this case, print() takes only one argument, which is a string (a series of letters, numbers, spaces, and so on), and when print() is called, it puts that string into the console in Garry's Mod.

Saving the script

You're now ready to save the actual Lua file. To find your Lua folder, follow the following path - depending on where you have installed Garry's Mod on your computer, this path may be different, but will look something like this:

C:\Program Files\Steam\steamapps\common\GarrysMod\garrysmod\lua\ ^^^^^^^^^^^^^^^^^^^^^^ This may be different!

In the filename box, type helloworld.lua (Note that you must specify .lua), and in the Save As type box, select All Files. Now, just press enter (or press the save button) to save your script.

Check the "File name extensions" box in File Explorer

Make sure you have the "File name extensions" checkbox checked in File Explorer. Unless this is checked, your text editor might accidentally save your .lua file as a .lua.txt. To make sure this box is checked, open a File Explorer window, click the View tab at the top, and check the box (it's inside the "Show/hide" category at the top).

Running the script

To run any of your scripts, you need to be playing a map. Once in game, open the developer console and type the following:

lua_openscript helloworld.lua

Press enter. If you did everything correctly up to this point, you should see a message in the console:

Hello World!

Congratulations, you have written and run your first Lua script.

Auto running the script

To make your script run automatically when the server starts, you simply put it into one of these folders. Again, if you have Garry's Mod installed somewhere else, navigate there instead.

  • For shared scripts ( Loaded on either client or server )
C:\Program Files\Steam\steamapps\common\GarrysMod\garrysmod\lua\autorun
  • For client-only scripts ( Loaded only on client )
C:\Program Files\Steam\steamapps\common\GarrysMod\garrysmod\lua\autorun\client
  • For server-only scripts ( Loaded only on server )
C:\Program Files\Steam\steamapps\common\GarrysMod\garrysmod\lua\autorun\server

For this specific tutorial, any of those paths will work just fine.

All client and shared files must be put for download using AddCSLuaFile for them to work in multiplayer.

Loading portions of a script on the client or server

If you want to use a single file for clientside and serverside code, but want separate parts of the code between client and server, we can do something like this:

  • To run code only on the client
if CLIENT then --Your clientside code here end
  • To run code only on the server
if SERVER then --Your serverside code here end
  • To load onto shared (either Client or Server), don't specifically check for CLIENT or SERVER, just put your code down without the if block.

Example:

print( "Hello Shared!" ) if SERVER then print( "Hello Server!" ) end if CLIENT then print( "Hello Client!" ) end

The CLIENT and SERVER variables you see up there are explained on the States page.

What's next?

Next we will learn about variables.

Clientside, Serverside, and Shared are explained here: States

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