Opening files with default Windows application from within emacs

Question

I'm trying to tweak the dired-find-file function in emacs on Windows XP so that when I open (say) a pdf file from dired it fires up a copy of Acrobat Reader and opens that file with it, instead of opening it within emacs. But I can't work out what variant on shell-command/call-process to use. Here's what I have so far:

(defadvice dired-find-file (around dired-find-file-external (filename &optional wildcards))
  "Open non-text files with an appropriate external program."
  (if (string= ".pdf" (substring filename (- (length filename) 4))) ; obviously I'll replace this with something more general/robust
    (shell-command filename) ;; what should go here?
    (ad-do-it)))

(ad-activate 'dired-find-file)

I know I could hard-code it to start Acrobat Reader by giving it the location of the .exe file. But I'd rather have something which requires less searching from me and which won't break when default applications move/change. What should I use?

Answer 1

I found this terrific web page via google, which let me to a technique using RunDll that works. I'm putting it up here in case anyone else is curious.

Here is the key piece of code, which opens filename using the appropriate application:

(shell-command (concat "rundll32 shell32,ShellExec_RunDLL " (shell-quote-argument filename)))

And here is my full solution. (Note that dired-find-file is just a wrapper round find-file which doesn't know the filename, so that you have to advise find-file rather than dired-find-file as in the question. If you don't want the behaviour for find-file you will probably need to rewrite dired-find-file or write more complicated advice.)

(defun open-externally (filename)
  (shell-command (concat "rundll32 shell32,ShellExec_RunDLL " (shell-quote-argument filename))))

(defun is-file-type? (filename type)
  (string= type (substring filename (- (length filename) (length type)))))

(defun should-open-externally? (filename)
  (let ((file-types '(".pdf" ".doc" ".xls")))
    (member t (mapcar #'(lambda (type) (is-file-type? filename type)) file-types))))

(defadvice find-file (around find-file-external-file-advice (filename &optional wildcards))
  "Open non-emacs files with an appropriate external program"
  (if (should-open-externally? filename)
      (open-externally filename)
    ad-do-it))

(ad-activate 'find-file)

Answer 2

Tom Smith's answer is nice, but you can also just run the program "start" with the filename as an argument.

(shell-command (concat "start " (shell-quote-argument filename)))

Answer 3

1. Evaluate the following elisp
2. run dired (M-x dired)
3. browse to directory and file
4. w/ point on file, pressing F3 will open the file based on the windows extension.

(defun w32-browser (doc) (w32-shell-execute 1 doc))

(eval-after-load "dired" '(define-key dired-mode-map [f3] (lambda () (interactive) (w32-browser (dired-replace-in-string "/" "\" (dired-get-filename))))))