Using the clear command with a [<maxCount>] of 0 will return the amount of items a player has, without actually clearing any of them.
That means we can use execute store to save that number somewhere and then execute depending on that:
# Setup
scoreboard objectives add diamonds dummy
# Commands
execute store result score @s diamonds run clear @s diamond 0
execute if score @s diamonds matches 5 run say I have exactly 5 diamonds in my inventory.
execute if score @s diamonds matches 1..4 run say I have somewhere between 1 and 4 diamonds in my inventory.
execute if score @s diamonds matches 10.. run say I have 10 or more diamonds in my inventory.
execute if score @s diamonds matches ..20 run say I have 20 or less diamonds in my inventory.
Since version 1.20.5 you can also use [execute if items](https://minecraft.wiki/w/Commands/execute#(if |
unless)_items) to count the number of items. |
The if items subcommand, when executed, returns the number of items that meet the specified conditions. For a quick example, running this command will show the count of all items in the player’s inventory (except for armor and left hand slots):
# In chat
execute if items entity @s container.* *
You can find out more details on how to detect specific items here: Detect a specific item
Below is an example for getting the amount of a custom item and executing some command depending on the result:
# Example item
give @s diamond[minecraft:custom_data={diamond:true},minecraft:item_name="'Custom Diamond'"]
# Command blocks
execute as @a store result score @s diamonds if items entity @s container.* *[custom_data~{diamond:true}]
execute as @a[scores={diamonds=5}] run say I have exactly 5 coins.
execute as @a[scores={diamonds=1..4}] run say I have somewhere between 1 and 4 coins.
execute as @a[scores={diamonds=10..}] run say I have 10 or more coins.
execute as @a[scores={diamonds=..20}] run say I have 20 or less coins.
Although you can use /clear on a player, if items can also count the number of items in a chest, shulker_box and other containers, can also count the number of items in a players ender_chest.
Here are some examples for this:
# Counting items in chest or any container
execute store result score #container diamonds if items block <pos> container.* *[custom_data~{diamond:true}]
# Counting items in ender_chest
execute as @a store result score @s diamonds if items entity @s enderchest.* *[custom_data~{diamond:true}]
In the 1.18.20 beta they added the hasitem target selector, which allows you to check for specific amounts (as ranges) of items in entities inventories. Below is an example (using 1.19.50 execute), check the link above for more information.
execute as @a[hasitem={item=apple,quantity=5..}] run say I have 5 or more apples in my inventory