Introduction to Arma Scripting
Scripting is one of the most powerful and most versatile tools available in the Arma sandbox. Unfortunately, it is also one of the most complex and unforgiving aspects of addon (i.e. mod) and mission creation.
Arma 3, Arma 2, Armed Assault and Arma: Cold War Assault all use a scripting language called SQF. Its predecessor SQS has been considered deprecated since Armed Assault (2006) and is no longer used. As of Arma Reforger (2022), SQF has been succeeded by Enforce Script. This introduction only considers SQF.
There is a plethora of topics to learn about in the context of Arma scripting (see the table below). Fortunately, there is no need to acquire detailed knowledge about all of these things in order to get started with scripting. To aid with prioritization, this page provides three selections of topics, each relevant to beginner, intermediate and advanced scripters respectively.
Variables are a fundamental building block of scripting (and programming in general). Like in mathematics, they serve as placeholders for values. A few examples:
- A = 1; The variable A now has the value 1.
- B = 2; The variable B now has the value 2.
- C = "Hello World!"; The variable C now has the value "Hello World!".
A variable always has a Data Type. In the example above, the variables A and B both have the data type Number, while C has the data type String. The data type of a variable is not fixed and changes automatically based on the current value of the variable.
Commands and Operators
Two other basic tools of scripting are commands and Operators. In fact, they are so basic that the examples in the Variables section above already had to make use of an operator: The equals sign (=) serves as the assignment operator, assigning values to variables. Similarly, symbols such as +, -, * and / are also operators. Using operators is quite simple:
Commands are often more versatile and complex than operators and can sometimes be used to interact with the game in some way. For instance, the setPosATL command can be used to change the position of an object in the game world, the damage command returns the amount of damage an object has suffered and the systemChat command can be used to display a message in the system chat.
While operators are usually fairly intuitive to use, commands are often more complicated. As such, every single command (and every single operator) has a dedicated Community Wiki page documenting it. This makes the Community Wiki an essential resource for scripting as it can be consulted whenever an unfamiliar command is encountered or needs to be used. The documentation commonly includes information about the behaviour and effect of the command, its return value and the purpose and data types of its parameters.
Control Structures, Conditions and Booleans
Control Structures allow scripts to accomplish complex tasks. See the following:
This code behaves differently depending on the damage status of the player. The systemChat output and whether or not the player is healed changes dynamically based on how much health the player has when the code is executed.
- First, damage player is evaluated and returns a number.
- Then, the > operator compares that number to 0.5:
There are three basic operations that can be performed on Boolean values:
|Operation||Description||SQF Operator||SQF Command|
|NOT (Negation)||Inverts the input value.||!||not|
|AND (Conjunction)||Combines two Booleans into one. Only returns true if both input values are true.||&&||and|
|OR (Disjunction)||Combines two Booleans into one. Returns true if at least one of the input values is true.||||||or|
Both the input and the output of these operations are Boolean values. Their behaviour is defined as follows:
Boolean operations can be used to create complex conditions by combining multiple conditions into one.
An array is a useful way to keep data together and is used for example to store positions.
Positions are represented as 2D or 3D Arrays of Numbers (usually in the format [X, Y] or [X, Y, Z]) where X represents West-East, Y represents South-North and Z represents altitude. However, there are some important caveats and distinctions one should be aware of - for instance, the positions [0, 0, 0] ASL (Above Sea Level) and [0, 0, 0] AGL (Above Ground Level) are not necessarily equivalent. It is therefore highly recommended to read the Positions page before working with positions.
Scripts are usually placed in Script Files. It is of course possible and sometimes even necessary to use short pieces of code in the Editor (e.g. in the On Activation expression of a Trigger), but scripts can become long and complex, and then working with them is far easier when they are properly placed in script files. Additionally, some features are only accessible through the use of script files (Event Scripts for example).
Script files are basically just text files with a certain filename extension. For script files, that file extension is .sqf (or .sqs), but in the broader context of Arma scripting, modification, configuration and mission design, more file extensions can be encountered: .ext, .hpp, .cpp and .cfg to mention the most common ones.
Unfortunately, Windows does not make the creation of blank files with a desired file extension easily accessible.
For instance, a common pitfall when trying to use Description.ext (a file that is used to configure certain mission features such as the respawn settings) for the first time is (unknowingly) creating Description.ext.txt instead of Description.ext because the Windows File Explorer hides file extensions by default. Obviously, Description.ext.txt will not work and will not have any of the desired effects on the mission because the game does not recognize it as Description.ext, but identifying a wrong file extension as the root cause of an issue when troubleshooting is notoriously difficult as one is usually looking for errors in the code and not in the filename.
While there are many different ways to create a blank text file with a specific file extension, the easiest method using native Windows tools is probably this:
- Preparation (only needs to be done once):
- Open the File Explorer
- Open the View tab at the top
- Tick the File name extensions checkbox
- File Creation:
- Navigate to the location where you want to create a new script file
- Go to New
- Click on Text Document
- Rename New Text Document.txt to what you need
In the context of mission creation, script files generally need to be placed in the corresponding scenario folder (often also called the mission root folder). Every mission has its own scenario folder, it is created by the Editor when saving the scenario for the first time. By default it only contains a single file called mission.sqm; this file mostly stores data regarding Editor-placed entities and does not need to be touched when scripting.
Description.ext and Event Scripts have to be placed directly in the root of the scenario folder (i.e. next to mission.sqm), but all other files can be placed in subfolders of the scenario folder. A well-structured scenario folder could look like this:
Apex%20Protocol.Tanoa/ ├── functions/ │ ├── fn_myFirstFunction.sqf │ └── fn_mySecondFunction.sqf ├── scripts/ │ ├── myFirstScript.sqf │ └── mySecondScript.sqf ├── description.ext ├── initPlayerLocal.sqf ├── initServer.sqf └── mission.sqm
Each scenario folder is stored in either the missions or the mpmissions subfolder of the folder containing the Arma Profile that was used to create the scenario. For instance, the path to the scenario folder from the example above could be:
C:\Users\Scott Miller\Documents\Arma 3 - Other Profiles\Keystone\missions\Apex%20Protocol.Tanoa
The Editor uses percent-encoding for scenario folder names, that is why whitespaces in the scenario name are replaced with %20.
- 2D Editor: External
- Eden Editor: Scenario Folder
- Profile (the possible profile folder paths are listed there)
Editing Script Files
Because script files are essentially plain text files, they can be edited with just about any text editor. For instance, the native Windows Notepad can be used, but working with it is not very comfortable. As such, regular scripters typically use more versatile applications such as Notepad++ or Visual Studio Code, usually in combination with plugins that add additional support for SQF. One feature commonly provided by these plugins is syntax highlighting, and for good reason: Syntax highlighting makes code significantly more readable and helps recognizing and avoiding basic syntax errors. Consequently, it is highly recommended to use syntax highlighting.
See Community Tools - Code Edition for a selection of community-made applications and plugins for Arma Scripting.
The execVM command is used to execute script files.
For instance, myFirstScript.sqf from the File Locations example above can simply be executed like so:
- Is your idea necessary?
- Will players even notice or use what you want to script? Just because you can does not mean you should. Sometimes less is more!
- Is it possible to do this in the editor?
- The Eden Editor is a powerful tool and with it alone one can achieve a lot of things without writing a single line of code.
- Poorly written scripts are a frequent cause of poor performance, both in singleplayer and multiplayer scenarios.
- Can it be scripted using SQF?
- This question might be hard to answer. Try to get as much information about what you want to do and what commands and functions there are before spending time on writing a script, just to find out that what you hoped to achieve is not possible after all.
The following is a collection of terms frequently encountered when talking or reading about scripting.
- Game Engine
- The core program of the game which executes your scripting commands at run time.
- Script / Script File
- Scripts are usually placed in script files. Script files contain code.
- A Variable is a named storage container for data.
- The name of a variable is called its Identifier.
- Data Types
- The Data Type of a variable specifies which kind of data that variable can contain.
- See Operators
- Control Structures
- See Control Structures
- See Function
These pages cover further aspects of scripting:
- Example Code
- Control Structures
- Multiplayer Scripting
- Exception handling
- Script File
- SQS to SQF conversion
Consider the following resources for more general learning: