Returns the current environment used by the nominated function f.
f can be a function or a number representing the stack level, where 1 is the currently running function, 2 is its parent and so on.
The environment is where "global" variables are stored.
print (getfenv (1)) --> table: 02072780
print (_G) --> table: 02072780
The default for f is 1 (the current function).