Re: server-start preempted by other emacs window

[Jari Aalto+mail.linux]

* Thu 2004-01-29 Thorsten Bonow <thorsten.bonow <AT> post.rwth-aachen.de>
* 
<http://groups.google.com/groups?oi=djq&as_umsgid=%3C87ad46ob01.fsf@herrrossi.mmweg.rwth-aachen.de>
| >>>>> "Stefan" == Stefan Monnier <monnier <AT> iro.umontreal.ca> writes:
| Hi, this was discussed before. I could not find the thread, but since
| then I have this solution in my .emacs to prevent starting a second
| server if one is already running:
| 
| --- cut here ---
| ;; ** emacsclient
| (defun my-server-start-filter-function (process output)
|   "Filter function for `my-server-start', which checks for an
| accessible Emacs process acting as a server by calling
| `emacsclient --eval t' as an external asynchronous
| process. Process output is filtered by this function which only
| calls `server-start' when no server is running, id est the call
| to emacsclient has failed."
|   (if (equal output "t\n")
|       (message "Not starting server, one instance already running...")
|     (message "Starting server...")
|       (server-start)))
| ;;
| (defun my-server-start ()
|   "Call `server-start' only if no other accessible Emacs process
| is already acting as a server for client processes."
|   (let ((process-connection-type nil))
|     (set-process-filter (start-process "my-process" nil "emacsclient" 
"--eval" "t")
|                       'my-server-start-filter-function)))
| ;;
| (my-server-start)

Unfortunately the emacsclient that Cygwin or Debian provides, does not
know --eval option. The above code fails, because the filter function
expects "t\n", when the real output is:

    /bin/emacsclient: unrecognized option `--eval'                           
    Usage: /bin/emacsclient [-a ALTERNATE-EDITOR] [-n] [--no-wait] 
[+LINE[:COLUMN]]\
     FILENAME                                                                   
    
    Or /bin/emacsclient --version                                               
    
    Report bugs to bug-gnu-emacs <AT> gnu.org. 

It seems to be impossible to make and automatic test to see if one
Emacs is already running as server. Stefan's remark to upcoming network
connection functions offers a  solution.

Jari

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