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;;; server.el --- Lisp code for GNU Emacs running as server process.

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;; Copyright (C) 1986, 1987, 1992, 1994, 1995 Free Software Foundation, Inc.
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;; Author: William Sommerfeld <wesommer@athena.mit.edu>
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;; Keywords: processes
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;; Changes by peck@sun.com and by rms.

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation; either version 2, or (at your option)
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;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to
;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.

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;;; Commentary:
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;;; This Lisp code is run in Emacs when it is to operate as
;;; a server for other processes.

;;; Load this library and do M-x server-edit to enable Emacs as a server.
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;;; Emacs runs the program ../arch-lib/emacsserver as a subprocess
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;;; for communication with clients.  If there are no client buffers to edit, 
;;; server-edit acts like (switch-to-buffer (other-buffer))

;;; When some other program runs "the editor" to edit a file,
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;;; "the editor" can be the Emacs client program ../lib-src/emacsclient.
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;;; This program transmits the file names to Emacs through
;;; the server subprocess, and Emacs visits them and lets you edit them.

;;; Note that any number of clients may dispatch files to emacs to be edited.

;;; When you finish editing a Server buffer, again call server-edit
;;; to mark that buffer as done for the client and switch to the next 
;;; Server buffer.  When all the buffers for a client have been edited 
;;; and exited with server-edit, the client "editor" will return
;;; to the program that invoked it.  

;;; Your editing commands and Emacs's display output go to and from
;;; the terminal in the usual way.  Thus, server operation is possible
;;; only when Emacs can talk to the terminal at the time you invoke
;;; the client.  This is possible in four cases:

;;; 1. On a window system, where Emacs runs in one window and the
;;; program that wants to use "the editor" runs in another.

;;; 2. On a multi-terminal system, where Emacs runs on one terminal and the
;;; program that wants to use "the editor" runs on another.

;;; 3. When the program that wants to use "the editor" is running
;;; as a subprocess of Emacs.

;;; 4. On a system with job control, when Emacs is suspended, the program
;;; that wants to use "the editor" will stop and display
;;; "Waiting for Emacs...".  It can then be suspended, and Emacs can be
;;; brought into the foreground for editing.  When done editing, Emacs is
;;; suspended again, and the client program is brought into the foreground.

;;; The buffer local variable "server-buffer-clients" lists 
;;; the clients who are waiting for this buffer to be edited.  
;;; The global variable "server-clients" lists all the waiting clients,
;;; and which files are yet to be edited for each.
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;;; Code:
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(defvar server-program (expand-file-name "emacsserver" exec-directory)
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  "*The program to use as the edit server.")
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(defvar server-visit-hook nil
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  "*List of hooks to call when visiting a file for the Emacs server.")

(defvar server-switch-hook nil
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  "*List of hooks to call when switching to a buffer for the Emacs server.")

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(defvar server-done-hook nil
  "*List of hooks to call when done editing a buffer for the Emacs server.")

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(defvar server-process nil 
  "the current server process")

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(defvar server-previous-string "")

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(defvar server-clients nil
  "List of current server clients.
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Each element is (CLIENTID BUFFERS...) where CLIENTID is a string
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that can be given to the server process to identify a client.
When a buffer is marked as \"done\", it is removed from this list.")

(defvar server-buffer-clients nil
  "List of clientids for clients requesting editing of current buffer.")
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(make-variable-buffer-local 'server-buffer-clients)
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;; Changing major modes should not erase this local.
(put 'server-buffer-clients 'permanent-local t)

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(defvar server-window nil
  "*The window to use for selecting Emacs server buffers.
If nil, use the selected window.
If it is a frame, use the frame's selected window.")

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(defvar server-temp-file-regexp "^/tmp/Re\\|/draft$"
  "*Regexp which should match filenames of temporary files
which are deleted and reused after each edit
by the programs that invoke the emacs server.")

(or (assq 'server-buffer-clients minor-mode-alist)
    (setq minor-mode-alist (cons '(server-buffer-clients " Server") minor-mode-alist)))

;; If a *server* buffer exists,
;; write STRING to it for logging purposes.
(defun server-log (string)
  (if (get-buffer "*server*")
      (save-excursion
	(set-buffer "*server*")
	(goto-char (point-max))
	(insert string)
	(or (bobp) (newline)))))

(defun server-sentinel (proc msg)
  (cond ((eq (process-status proc) 'exit)
	 (server-log (message "Server subprocess exited")))
	((eq (process-status proc) 'signal)
	 (server-log (message "Server subprocess killed")))))

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;;;###autoload
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(defun server-start (&optional leave-dead)
  "Allow this Emacs process to be a server for client processes.
This starts a server communications subprocess through which
client \"editors\" can send your editing commands to this Emacs job.
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To use the server, set up the program `emacsclient' in the
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Emacs distribution as your standard \"editor\".

Prefix arg means just kill any existing server communications subprocess."
  (interactive "P")
  ;; kill it dead!
  (if server-process
      (progn
	(set-process-sentinel server-process nil)
	(condition-case () (delete-process server-process) (error nil))))
  (condition-case () (delete-file "~/.emacs_server") (error nil))
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  (condition-case ()
      (delete-file (format "/tmp/esrv%d-%s" (user-uid) (system-name)))
    (error nil))
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  ;; If we already had a server, clear out associated status.
  (while server-clients
    (let ((buffer (nth 1 (car server-clients))))
      (server-buffer-done buffer)))
  (if leave-dead
      nil
    (if server-process
	(server-log (message "Restarting server")))
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    ;; Using a pty is wasteful, and the separate session causes
    ;; annoyance sometimes (some systems kill idle sessions).
    (let ((process-connection-type nil))
      (setq server-process (start-process "server" nil server-program)))
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    (set-process-sentinel server-process 'server-sentinel)
    (set-process-filter server-process 'server-process-filter)
    (process-kill-without-query server-process)))

;Process a request from the server to edit some files.
;Format of STRING is "Client: CLIENTID PATH PATH PATH... \n"
(defun server-process-filter (proc string)
  (server-log string)
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  (setq string (concat server-previous-string string))
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  ;; If the input is multiple lines,
  ;; process each line individually.
  (while (string-match "\n" string)
    (let ((request (substring string 0 (match-beginning 0)))
	  client
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	  (files nil)
	  (lineno 1))
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      ;; Remove this line from STRING.
      (setq string (substring string (match-end 0)))	  
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      (if (string-match "^Error: " request)
	  (message (concat "Server error: " (substring request (match-end 0))))
	(if (string-match "^Client: " request)
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	    (progn
	      (setq request (substring request (match-end 0)))
	      (setq client (list (substring request 0 (string-match " " request))))
	      (setq request (substring request (match-end 0)))
	      (while (string-match "[^ ]+ " request)
		(let ((arg
		       (substring request (match-beginning 0) (1- (match-end 0)))))
		  (setq request (substring request (match-end 0)))
		  (if (string-match "\\`\\+[0-9]+\\'" arg)
		      (setq lineno (read (substring arg 1)))
		    (setq files
			  (cons (list arg lineno)
				files))
		    (setq lineno 1))))
	      (server-visit-files files client)
	      ;; CLIENT is now a list (CLIENTNUM BUFFERS...)
	      (setq server-clients (cons client server-clients))
	      (server-switch-buffer (nth 1 client))
	      (run-hooks 'server-switch-hook)
	      (message (substitute-command-keys
			"When done with a buffer, type \\[server-edit]")))))))
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  ;; Save for later any partial line that remains.
  (setq server-previous-string string))
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(defun server-visit-files (files client)
  "Finds FILES and returns the list CLIENT with the buffers nconc'd.
FILES is an alist whose elements are (FILENAME LINENUMBER)."
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  ;; Bind last-nonmenu-event to force use of keyboard, not mouse, for queries.
  (let (client-record (last-nonmenu-event t) (obuf (current-buffer)))
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    ;; Restore the current buffer afterward, but not using save-excursion,
    ;; because we don't want to save point in this buffer
    ;; if it happens to be one of those specified by the server.
    (unwind-protect
	(while files
	  ;; If there is an existing buffer modified or the file is modified,
	  ;; revert it.
	  ;; If there is an existing buffer with deleted file, offer to write it.
	  (let* ((filen (car (car files)))
		 (obuf (get-file-buffer filen)))
	    (if (and obuf (set-buffer obuf))
		(if (file-exists-p filen)
		    (if (or (not (verify-visited-file-modtime obuf))
			    (buffer-modified-p obuf))
			(revert-buffer t nil))
		  (if (y-or-n-p
		       (concat "File no longer exists: "
			       filen
			       ", write buffer to file? "))
		      (write-file filen)))
	      (set-buffer (find-file-noselect filen))
	      (run-hooks 'server-visit-hook)))
	  (goto-line (nth 1 (car files)))
	  (setq server-buffer-clients (cons (car client) server-buffer-clients))
	  (setq client-record (cons (current-buffer) client-record))
	  (setq files (cdr files)))
      (set-buffer obuf))
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    (nconc client client-record)))

(defun server-buffer-done (buffer)
  "Mark BUFFER as \"done\" for its client(s).
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This buries the buffer, then returns a list of the form (NEXT-BUFFER KILLED).
NEXT-BUFFER is another server buffer, as a suggestion for what to select next,
or nil.  KILLED is t if we killed BUFFER (because it was a temp file)."
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  (let ((running (eq (process-status server-process) 'run))
	(next-buffer nil)
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	(killed nil)
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	(first t)
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	(old-clients server-clients))
    (while old-clients
      (let ((client (car old-clients)))
	(or next-buffer 
	    (setq next-buffer (nth 1 (memq buffer client))))
	(delq buffer client)
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	;; Delete all dead buffers from CLIENT.
	(let ((tail client))
	  (while tail
	    (and (bufferp (car tail))
		 (null (buffer-name (car tail)))
		 (delq (car tail) client))
	    (setq tail (cdr tail))))
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	;; If client now has no pending buffers,
	;; tell it that it is done, and forget it entirely.
	(if (cdr client) nil
	  (if running
	      (progn
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		;; Don't send emacsserver two commands in close succession.
		;; It cannot handle that.
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		(or first (sit-for 1))
		(setq first nil)
		(send-string server-process 
			     (format "Close: %s Done\n" (car client)))
		(server-log (format "Close: %s Done\n" (car client)))))
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	  (setq server-clients (delq client server-clients))))
      (setq old-clients (cdr old-clients)))
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    (if (and (bufferp buffer) (buffer-name buffer))
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	(progn
	  (save-excursion
	    (set-buffer buffer)
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	    (setq server-buffer-clients nil)
	    (run-hooks 'server-done-hook))
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	  (if (server-temp-file-p buffer)
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	      (progn (kill-buffer buffer)
		     (setq killed t))
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	    (bury-buffer buffer))))
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    (list next-buffer killed)))
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(defun server-temp-file-p (buffer)
  "Return non-nil if BUFFER contains a file considered temporary.
These are files whose names suggest they are repeatedly
reused to pass information to another program.

The variable `server-temp-file-regexp' controls which filenames
are considered temporary."
  (and (buffer-file-name buffer)
       (string-match server-temp-file-regexp (buffer-file-name buffer))))

(defun server-done ()
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  "Offer to save current buffer, mark it as \"done\" for clients.
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This buries the buffer, then returns a list of the form (NEXT-BUFFER KILLED).
NEXT-BUFFER is another server buffer, as a suggestion for what to select next,
or nil.  KILLED is t if we killed the BUFFER (because it was a temp file)."
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  (let ((buffer (current-buffer)))
    (if server-buffer-clients
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	(progn
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 	  (if (server-temp-file-p buffer)
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	      ;; For a temp file, save, and do make a non-numeric backup
	      ;; (unless make-backup-files is nil).
	      (let ((version-control nil)
		    (buffer-backed-up nil))
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		(save-buffer))
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	    (if (and (buffer-modified-p)
		     (y-or-n-p (concat "Save file " buffer-file-name "? ")))
		(save-buffer buffer)))
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	  (server-buffer-done buffer)))))
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;; Ask before killing a server buffer.
;; It was suggested to release its client instead,
;; but I think that is dangerous--the client would proceed
;; using whatever is on disk in that file. -- rms.
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(defun server-kill-buffer-query-function ()
  (or (not server-buffer-clients)
      (yes-or-no-p (format "Buffer `%s' still has clients; kill it? "
			   (buffer-name (current-buffer))))))

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(add-hook 'kill-buffer-query-functions
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 	  'server-kill-buffer-query-function)

(defun server-kill-emacs-query-function ()
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  (let (live-client
	(tail server-clients))
    ;; See if any clients have any buffers that are still alive.
    (while tail
      (if (memq t (mapcar 'stringp (mapcar 'buffer-name (cdr (car tail)))))
	  (setq live-client t))
      (setq tail (cdr tail)))
    (or (not live-client)
	(yes-or-no-p "Server buffers still have clients; exit anyway? "))))
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(add-hook 'kill-emacs-query-functions 'server-kill-emacs-query-function)
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(defun server-edit (&optional arg)
  "Switch to next server editing buffer; say \"Done\" for current buffer.
If a server buffer is current, it is marked \"done\" and optionally saved.
When all of a client's buffers are marked as \"done\", the client is notified.

Temporary files such as MH <draft> files are always saved and backed up,
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no questions asked.  (The variable `make-backup-files', if nil, still
inhibits a backup; you can set it locally in a particular buffer to
prevent a backup for it.)  The variable `server-temp-file-regexp' controls
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which filenames are considered temporary.

If invoked with a prefix argument, or if there is no server process running, 
starts server process and that is all.  Invoked by \\[server-edit]."
  (interactive "P")
  (if (or arg
	  (not server-process)
	  (memq (process-status server-process) '(signal exit)))
      (server-start nil)
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    (apply 'server-switch-buffer (server-done))))
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(defun server-switch-buffer (&optional next-buffer killed-one)
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  "Switch to another buffer, preferably one that has a client.
Arg NEXT-BUFFER is a suggestion; if it is a live buffer, use it."
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  ;; KILLED-ONE is t in a recursive call
  ;; if we have already killed one temp-file server buffer.
  ;; This means we should avoid the final "switch to some other buffer"
  ;; since we've already effectively done that.
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  (cond ((and (windowp server-window)
	      (window-live-p server-window))
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	 (select-window server-window))
	((framep server-window)
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	 (if (not (frame-live-p server-window))
	     (setq server-window (make-frame)))
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	 (select-window (frame-selected-window server-window))))
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  (if (window-minibuffer-p (selected-window))
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      (select-window (next-window nil 'nomini 0)))
  ;; Move to a non-dedicated window, if we have one.
  (let ((last-window (previous-window nil 'nomini 0)))
    (while (and (window-dedicated-p (selected-window))
		(not (eq last-window (selected-window))))
      (select-window (next-window nil 'nomini 0))))
  (set-window-dedicated-p (selected-window) nil)
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  (if next-buffer
      (if (and (bufferp next-buffer)
	       (buffer-name next-buffer))
	  (switch-to-buffer next-buffer)
	;; If NEXT-BUFFER is a dead buffer,
	;; remove the server records for it
	;; and try the next surviving server buffer.
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	(apply 'server-switch-buffer
	       (server-buffer-done next-buffer)))
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    (if server-clients
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	(server-switch-buffer (nth 1 (car server-clients)) killed-one)
      (if (not killed-one)
	  (switch-to-buffer (other-buffer))))))
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(global-set-key "\C-x#" 'server-edit)
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(provide 'server)
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;;; server.el ends here