DATAis in fact an IO object, that you can read from (or anything else you’d do with an IO object). It contains all the content after__END__in that ruby script file*. (It only exists when the file contains__END__, and for the first file ruby invokes though. Seefootnotefor more details.)

How can we use this, and why indeed do I love this fickle constant? I mostly use it for quick scripts where I need to process text data, rather than piping to STDIN.

DATA.each_line.map(&:chomp).each do |url| `open "#{url}"` end __END__ http://google.com/ http://yahoo.com/

Link: Why I love DATA – Caius Theory via caiustheory.com