How can I detect if a player is wearing a specific piece of armour?

Question

How can I detect if a player is wearing a piece of armour?

Let's say it was leather and named bob with a single lapis dye added to it. what would I do? I can't use comparators and such, only command blocks - it will have a constant clock attached

Answer 1

Since 1.13 you can do the check and do something based on it in one command. This for example does something as the closest player who wears elytra:

/execute as @p[nbt={Inventory:[{id:"minecraft:elytra",Slot:102b}]}] run <command>

Slot 102 is the chestplate slot, 103 is the head, 101 the legs and 100 the feet.

This for example does something only if a player with a Protection 4 diamond helmet exists somewhere in the world, but still in the same position that the command is executed at and as the same executor:

/execute if @p[nbt={Inventory:[{id:"minecraft:diamond_helmet",Slot:103b,tag:{Enchantments:[{id:"minecraft:protection",lvl:4s}]}}]}] run <command>

Answer 2

Use scoreboard partial nbt test

Setup:

/scoreboard objectives add armor dummy

Clock:

/scoreboard players set @a armor 0
/scoreboard players set @a armor 1 {Inventory:[{Slot:103,id:"leather_helmet", tag:{color:255}}]}
<Run command with selector score_armor_min=1>

The slot is 100 for boot, 101 for leg, 102 for chest, 103 for helm. The color is calculated as Red << 16 + Green << 8 + Blue.