Question

I see this all the time in Ruby:

require File.dirname(__FILE__) + '/../../config/environment'   

What does __FILE__ mean?

Answer 1

It is a reference to the current file name. In the file foo.rb, __FILE__ would be interpreted as 'foo.rb'.

Edit: Ruby 1.9.2 and 1.9.3 appear to behave a little differently from what Luke Bayes said in his comment. With these files:

# test.rb puts __FILE__ require './dir2/test.rb' 

# dir2/test.rb puts __FILE__ 

Running ruby test.rb will output

test.rb /full/path/to/dir2/test.rb