Developer's Note:

Most developers can completely skip this section. This is for those that are unfamiliar with functions and tags and is less about how the CommandAPI works.

This section explains how functions are declared and set up for use in a Minecraft server. This is ideal for server owners who've never set up functions, or developers (like the Command API's creator) that has no idea how to set this sort of thing up.

Functions are text files (with the .mcfunction extension) which contains lists of functions which are executed one after another. Each line of the file is a valid Minecraft command. Say we have text.mcfunction:

killall
say Killed all living entities on the server

This will run the custom command killall (as declared in Chapter 5 - Functions), and then broadcast a message to all players stating that all entities were killed.

Tags are json files which contain a list of functions. Tags let you run multiple functions at a time. Say we have a tag called mytag.json:

{
    "values": [
        "mycustomnamespace:test",
        "mycustomnamespace:test2"
    ]
}

This will run the function test and the function test2, which are in the namespace mycustomnamespace.

The following hierarchy explains where functions and tags go. In this diagram, the two functions test and test2 are in a directory called functions. There is also a tag called mytag which is placed in the tags directory under functions. These are all under the namespace called mycustomnamespace

server/
├── world/
│   ├── advancements/
│   ├── data/
│   ├── datapacks/
│   │   └── bukkit/
│   │       ├── pack.mcmeta
│   │       └── data/
│   │           └── mycustomnamespace/
│   │               ├── functions/
│   │               │   ├── test.mcfunction
│   │               │   └── test2.mcfunction
│   │               └── tags/
│   │                   └── functions/
│   │                       └── mytag.json
│   └── ...
├── world_nether/
├── world_the_end/
├── ...
└── spigot.jar

To execute the test function, you would run the following command:

/function mycustomnamespace:test

To execute the mytag tag, you would run the following command:

/function #mycustomnamespace:mytag