How to search a folder and all of its subfolders for files of a certain type

Question

I am trying to search for all files of a given type in a given folder and copy them to a new folder.

I need to specify a root folder and search through that folder a

Answer 1

Another fast way of doing this is delegating the task to the shell command "find" and splitting the output:

pdf_file_paths = `find #{dir} -name "*.pdf"`.split("\n")

Does not work on Windows.