Opening a file from dired as OS would in Linux

[David Vanderschel <DJV5@Austin.RR.com>]

I have this handy function in my .emacs for Emacs on Windows:

;; dired stuff to open files a la Windows from Howard Melman
(defun dired-execute-file (&optional arg)
  (interactive "P")
  (mapcar #'(lambda (file)
      (w32-shell-execute "open" (convert-standard-filename file)))
          (dired-get-marked-files nil arg)))

I am now switching over to Ubuntu, and I do not know how to say the equivalent
of "(w32-shell-execute "open" ...".  But I would certainly like to be able to
launch files from dired.  E.g., open this .PDF file in the viewer.  Maybe it is
already there, but I have difficulty framing the question in an effective way
for search.  Thanks for any pointers.