minetest.find_nodes_in_area
From Minetest Developer Wiki
Syntax
minetest.find_nodes_in_area(minp, maxp, nodenames)
Description
Finds node in the area from minp to maxp. nodenames is either a string or a table of strings, direct nodenames and "group:groupname" are supported.
Returns a list of positions.
Example
minetest.find_nodes_in_area({x=-4, y=-4, z=-4}, {x=4, y=4, z=4}, {"group:water"})