query(e, 'uuid')

Syntax

query(entity, 'uuid')

Returns the UUID (unique id) of the entity. Can be used to access entities with the other vanilla commands and remains unique regardless of the dimension, and is preserved between game restarts. Apparently players cannot be accessed via UUID, but should be accessed with their name instead.

map(entities_area('*',x,y,z,30,30,30),run('kill '+query(_,'id'))) // doesn't kill the player