cmd_dist

command: /dist

quick ref:

/dist [@entityname]

description:

return the block distance from current player to given player.
This command is usually run from NPC or command block to obtain distance to a nearby player. 
@param entityname: name of the entity.
@return the block distance. if entity is not found, it will return a very large number
e.g.
/if $(dist @a) <= 2 /tip hello  : when the distance to closest nearby player is less than 2 meters, say hello

实行把物体或方块从这个人物分配给另外一个人物。