What is the meaning of $$ in Ruby?

Question

irb(main):002:0> $$
=> 5052

What is the meaning of $$ in Ruby and How/Where to use it?

Answer 1

$$ is the process ID. It's named that way to follow Perl, which in turn followed the Bourne shell; both of them also use $$ in the same way.

Answer 2

This seems like a good reference for stuff like this...has a lot of symboly goodness.

Answer 3

It's the process ID of the Ruby interpreter. $ is a prefix for global variables, see here for a list.