What does #{$$} inside a double quoted string in Ruby on Rails ?

Question

I have a doubt concerning #{$$} inside a double quoted string, in concrete I have this string:

"#{command}#{$$}#{(Time.now.to_f * 1000).to_i}"

If I execute "#{$$}" in console I get an integer number but I would like to read an explanation to this.

Thank you !!

Answer 1

That would be the global process ID.

If you're asking what the #{...} syntax means, that prints the variable inside the braces. So if it would work like this..

command = "print"
puts "cmd: #{command}" #=> cmd: print

Answer 2

$$ is the interpreter's process ID.

Ruby has quite a few global variables you can use, see here.