getline (LineCache)

    # File lib/linecache.rb, line 186
      def getline(filename, line_number, reload_on_change=true)
        filename = unmap_file(filename)
        filename, line_number = unmap_file_line(filename, line_number)
        lines = getlines(filename, reload_on_change)
        if lines and (1..lines.size) === line_number
            return lines[line_number-1]
        else
            return nil
        end
      end