Function to find a file or open a URL depending on argument?

Question

Q: in there a function that can find a file or open a URL as needed?

I have a string that can be either a) a local filename, or b) a URL. Is there an existing function that I can call on the string that will do what I mean and open the file if it's a file, or open the URL in a browser if it's a URL?

It wouldn't be hard to write such a function, but I'd rather not reinvent the wheel.

Answer 1

browse-url.el can easily be configured that way.

The following section of the doc of browse-url-browser-function is relevant:

If the value is not a function it should be a list of pairs (REGEXP . FUNCTION). In this case the function called will be the one associated with the first REGEXP which matches the current URL. The function is passed the URL and any other args of `browse-url'. The last regexp should probably be "." to specify a default browser.

Example configuration:

(custom-set-default 'browse-url-browser-function
            '(("^/" . browse-url-emacs)
              ("\\`[^:]+\\'" . browse-url-emacs)
              ("\\`file://" . browse-url-emacs)
              ("." . browse-url-default-browser)))

(browse-url "/temp/test.txt") ;; opens in a new Emacs window

(let ((default-directory "/temp"))
  (browse-url "test.txt")) ;; opens the same file in Emacs window

(browse-url "file:///temp/test.txt") ;; opens the same file in Emacs window in read-only-mode

(browse-url "https://emacs.stackexchange.com") ;; opens in default browser