How to detect that the case for a file path is correct on a case-insensitive file system

file_definitely_exists.rb

class File
  # Does a case-sensitive check for file existence. 
  # Unlike the normal File.exists? method on OS X with its case-insensitive-by-default FS
  def self.definitely_exists? path
    folder = File.dirname path
    filename = File.basename path
    # Unlike Ruby IO, ls, and find -f, this technique will fail to locate the file if the case is wrong:
    not %x( find "#{folder}" -name "#{filename}" ).empty?
  end
end