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Module: command_meta.chain

Overview​

Module

This module provides the /chain command, which allows executing two commands sequentially:

  1. The first command, is any command. (Required)

  2. The second command, is /chain command. (Optionally)

Color Boxes​

Note

◉ What is the purpose of /chain command?

Its typical use-case is to condense two commands into one command.

So that you can put more than 1 command in some places.

For example: /execute run chain say 1 chain say 2

◉ The return value of a vanilla Minecraft command.

In vanilla Minecraft, the return value of a command, is a integer.

If integer less than zero, it's failed.

If integer equals zero, it's passed.

If integer grater than zero, it's success.

So, we can know whether a command was executed successfully or not, based on the return value of that command.

◉ How the /chain command works?

The /chain command takes exactly one argument, whose type is greedy string.

A greedy string argument type is always be the last argument of a command.

Once the command parser sees a greedy string argument type, it knows this is the last argument.

So the parser will feed the greedy string argument all the remaining characters.

In other words, a greedy string argument will eat all the remaining characters that are still not be consumed by preceding arguments.

For example, the /say Hello Alice also has exactly one argument, whose type is greedy string.

You didn't need to use " character to escape the space character, this is because the argument type of /say is greedy string.

Take /chain say 1 chain say 2 as an example:

The first /chain command will receive the say 1 chain say 2 as the value of its first and only argument.

Then the /chain command will split the value into two parts.

The first part is say 1, and the /chain command will submit it to the command executor.

The second part is chain say 2, and the /chain command will decide whether to submit it based on the return value of the previous submitted command.

It's a recursive process.

Example

◉ A nested chain

Issue: /chain say 1 chain say 2 chain say 3

◉ A breakable chain

Issue: /chain bad command here chain say 2

◉ Use chain command with predicate command

Issue: /run as player Alice chain test-level-perm %player:name% 4 chain say value is true

◉ Leverage the /execute if command.

Issue: /chain execute if block ~ ~-1 ~ minecraft:diamond_block if entity @s[nbt={Inventory:[{id:"minecraft:diamond"}]}] chain say You are standing on diamond block and have diamond.

NOTE: This use-case is similar to command_meta.if module.

Commands​

Command

  • Command Syntax: /chain <GreedyString rest>

  • Document: Chain commands and executes them in sequence, the chain will break if the previous one command fails.

  • Can be executed by console: true

  • Required Level Permission: 4

  • Required String Permission: null