Lua provides the debug.getinfo function to inspect the currently running code. This function takes one of two arguments, either a function or an integer. When the argument is an integer, getinfo will look the specified number of steps up the callstack. For example, let's assume you have the following code:

function one() 
  print ("one")
end

function two()
  one()
  print("two")
end

function three()
  two()
  print("three")

  debug.getinfo(1)
end

Providing an argument of 1 will inspect the function calling debug.getinfo, or function three. Providing 2 will go one more function up the callstack, inspecting function two. Or, providing 3 will look even further up the callstack and inspect function one.