Mark file backward

To mark file backward (mark file and move the cursot back to the previous line, opposite with when you press m), add this to your .emacs. If you just want the cursor to stay at the current file, remove (call-interactively ‘dired-previous-line) in the code. Change s-b to the key binding that you like.

(defun dired-mark-backward ()
  (interactive)
  (call-interactively 'dired-mark)
  (call-interactively 'dired-previous-line)
  (call-interactively 'dired-previous-line))
(define-key dired-mode-map (kbd "s-b") 'dired-mark-backward)

Open files by default programs

Both functions on MacOS and Ubuntu are bounded to s-o. You can mark multiple files and then s-o to open it using the default program on Mac OS.

Mac OS:

(defun tmtxt/dired-do-shell-mac-open ()
	(interactive)
	(save-window-excursion
	  (let ((files (dired-get-marked-files nil current-prefix-arg))
			command)
		;; the open command
		(setq command "open ")
		(dolist (file files)
		  (setq command (concat command (shell-quote-argument file) " ")))
		(message command)
		;; execute the command
		(async-shell-command command))))
(define-key dired-mode-map (kbd "s-o") 'tmtxt/dired-do-shell-mac-open)

Ubuntu: Source: https://github.com/ubolonton/.emacs.d/blob/master/config/ublt-dired.el
You need to replace gnome-open with your open command in your OS.

(defun ublt/dired-open-native ()
  "Open marked files (or the file the cursor is on) from dired."
  (interactive)
  (let* ((files (dired-get-marked-files t current-prefix-arg))
         (n (length files)))
    (when (or (<= n 3)
              (y-or-n-p (format "Open %d files?" n)))
      (dolist (file files)
        (call-process "gnome-open"
                      nil 0 nil file)))))
(define-key dired-mode-map (kbd "s-o") 'ublt/dired-open-native)

MacOS/Windows/Linux: Source: http://ergoemacs.org/emacs/emacs_dired_open_file_in_ext_apps.html
This method uses xdg-open for Linux, which is a more general one than gnome-open.

(defun ergoemacs-open-in-external-app ()
  "Open the current file or dired marked files in external app."
  (interactive)
  (let ( doIt
         (myFileList
          (cond
           ((string-equal major-mode "dired-mode") (dired-get-marked-files))
           (t (list (buffer-file-name))) ) ) )

    (setq doIt (if (<= (length myFileList) 5)
                   t
                 (y-or-n-p "Open more than 5 files?") ) )

    (when doIt
      (cond
       ((string-equal system-type "windows-nt")
        (mapc (lambda (fPath) (w32-shell-execute "open" (replace-regexp-in-string "/" "\\" fPath t t)) ) myFileList)
        )
       ((string-equal system-type "darwin")
        (mapc (lambda (fPath) (shell-command (format "open \"%s\"" fPath)) )  myFileList) )
       ((string-equal system-type "gnu/linux")
        (mapc (lambda (fPath) (let ((process-connection-type nil)) (start-process "" nil "xdg-open" fPath)) ) myFileList) ) ) ) ) )

Open current directory in default file manager

MacOS

  (defun tmtxt/dired-open-current-directory-in-finder ()
	"Open the current directory in Finder"
	(interactive)
	(save-window-excursion
	  (dired-do-async-shell-command
	   "open .")))
(define-key dired-mode-map (kbd "s-O") 'tmtxt/dired-open-current-directory-in-finder)

It’s bounded to s-O. Pressing s-O in a dired buffer will cause your default file manager to open the current directory. In other type of buffer, such as file buffer, you can call this function interactively by M-x and tmtxt/dired-open-current-directory-in-finder (MacOS) or tmtxt/dired-open-current-directory (Ubuntu). In that case, the default file manager application on your computer will open the directory that contains the current file.

MacOS/Windows/Linux: Source: http://ergoemacs.org/emacs/emacs_dired_open_file_in_ext_apps.html

(defun ergoemacs-open-in-desktop ()
  "Show current file in desktop (OS's file manager)."
  (interactive)
  (cond
   ((string-equal system-type "windows-nt")
    (w32-shell-execute "explore" (replace-regexp-in-string "/" "\\" default-directory t t)))
   ((string-equal system-type "darwin") (shell-command "open ."))
   ((string-equal system-type "gnu/linux")
    (let ((process-connection-type nil)) (start-process "" nil "xdg-open" "."))
    ;; (shell-command "xdg-open .") ;; 2013-02-10 this sometimes froze emacs till the folder is closed. ⁖ with nautilus
    ) ))

Unmount disk in Dired

Source: http://blog.nguyenvq.com/2009/12/01/file-management-emacs-dired-to-replace-finder-in-mac-os-x-and-other-os/
Both functions on MacOS and Ubuntu are bounded to s-u.

MacOS

(defun dired-do-shell-unmount-device ()
	(interactive)
	(save-window-excursion
	  (dired-do-async-shell-command
	   "diskutil unmount" current-prefix-arg
	   (dired-get-marked-files t current-prefix-arg))))
(define-key dired-mode-map (kbd "s-u") 'dired-do-shell-unmount-device)

Ubuntu

(defun dired-do-shell-unmount-device ()
	(interactive)
	(save-window-excursion
	  (dired-do-async-shell-command
	   "umount" current-prefix-arg
	   (dired-get-marked-files t current-prefix-arg))))
(define-key dired-mode-map (kbd "s-u") 'dired-do-shell-unmount-device)

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