Keeping GUI apps alive after exiting emacs.
In Linux, emacs sends a SIGHUP (http://en.wikipedia.org/wiki/SIGHUP) to all processes before exiting. When starting a GUI app from emacs on a Linux system, the app will terminated once the emacs process is exited or once the associated buffer is killed.
For instance, assuming no instance of xmms has been started, then the following snippet will create an instance of xmms which will be killed 2 seconds later:
(progn (shell-command "xmms &" "*xmms*") (sleep-for 2) (kill-buffer "*xmms*"))
Killing all subprocesses can be a nuisance. For instance,
‘browse-url’ can easily create an instance of a browser. With a tabbed browser like firefox, make useful webpages can be loaded but, if the emacs parent process exits, then the child firefox browser will terminate. All the webpages will then be lost.
The following function will start a persistent process:
(defun startup-persistent-process (process) (save-window-excursion (let ((startup-buffer (generate-new-buffer-name "*persistent process buffer*"))) (shell startup-buffer) (ansi-color-for-comint-mode-off) (insfmt "%s &" process) (comint-send-input) (insert "exit") (comint-send-input) (while (eq 'run (process-status (get-buffer startup-buffer)))) (ansi-color-for-comint-mode-on) (kill-buffer startup-buffer))))
For example, the following can be executed and the xmms process will persist even if emacs is exited:
‘startup-persistent-process’ has a 1-2 second pause until the “run”
‘browse-url’ to create a persistent browser such as firefox, the following code can be used:
(setq browse-url-browser-function 'my-browser) (defun my-browser (url &optional new-window) (if (string= (sshfmt "firefox -remote \"ping()\"") "Error: No running window found\n") (startup-persistent-process (format "firefox \"%s\"" url)) (browse-url-mozilla url new-window)))
So, executing this command:
and, then, this command:
will load one webpage and, then, overwrite with another webpage (unless, as described in BrowseUrl, new-tab or new-window is used).
Is there a cleaner approach for persistent processes, especially for web browsers?
"nohup firefox &"
as the command, instead of
just as you would in the shell.
Q: What if it is too late. Can I somehow disown my already created process?
Try the EmacsLisp function
Type C-h w32-shell-execute RET
‘C source code’.
Note if operation is “open”, and document is an executable, then you may also send in parameters.