The Well-Grounded Rubyist, Second Edition

15.3. Introspection of variables and constants

Ruby can tell you several things about which variables and constants you have access to at a given point in runtime. You can get a listing of local or global variables, an object’s instance variables, the class variables of a class or module, and the constants of a class or module.

15.3.1. Listing local and global variables

The local and global variable inspections are straightforward: you use the top-level methods local_variables and global_variables. In each case, you get back an array of symbols corresponding to the local or global variables currently defined:

x = 1 p local_variables [:x] p global_variables.sort [:$!, :$", :$$, :$&, :$', :$*, :$+, :$,, :$-0, :$-F, :$-I, :$-K, :$-W, :$-a, :$-d, ...