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diff --git a/lisp/eshell/esh-module.el b/lisp/eshell/esh-module.el
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+;;; esh-module --- Eshell modules
+
+;; Copyright (C) 1999, 2000 Free Sofware Foundation
+
+;; 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
+;; the Free Software Foundation; either version 2, or (at your option)
+;; 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, Inc., 59 Temple Place - Suite 330,
+;; Boston, MA 02111-1307, USA.
+
+(provide 'esh-module)
+
+(eval-when-compile (require 'esh-maint))
+
+(defgroup eshell-module nil
+  "The `eshell-module' group is for Eshell extension modules, which
+provide optional behavior which the user can enable or disable by
+customizing the variable `eshell-modules-list'."
+  :tag "Extension modules"
+  :group 'eshell)
+
+;;; Commentary:
+
+(require 'esh-util)
+
+(defun eshell-load-defgroups (&optional directory)
+  "Load `defgroup' statements from Eshell's module files."
+  (with-current-buffer
+      (find-file-noselect (expand-file-name "esh-groups.el" directory))
+    (erase-buffer)
+    (insert ";;; do not modify this file; it is auto-generated\n\n")
+    (let ((files (directory-files (or directory
+				      (car command-line-args-left))
+				  nil "\\`em-.*\\.el\\'")))
+      (while files
+	(message "Loading defgroup from `%s'" (car files))
+	(let (defgroup)
+	  (catch 'handled
+	    (with-current-buffer (find-file-noselect (car files))
+	      (goto-char (point-min))
+	      (while t
+		(forward-sexp)
+		(if (eobp) (throw 'handled t))
+		(backward-sexp)
+		(let ((begin (point))
+		      (defg (looking-at "(defgroup")))
+		  (forward-sexp)
+		  (if defg
+		      (setq defgroup (buffer-substring begin (point))))))))
+	  (if defgroup
+	      (insert defgroup "\n\n")))
+	(setq files (cdr files))))
+    (save-buffer)))
+
+;; load the defgroup's for the standard extension modules, so that
+;; documentation can be provided when the user customize's
+;; `eshell-modules-list'.
+(eval-when-compile
+  (when (equal (file-name-nondirectory byte-compile-current-file)
+	       "esh-module.el")
+    (let* ((directory (file-name-directory byte-compile-current-file))
+           (elc-file (expand-file-name "esh-groups.elc" directory)))
+      (eshell-load-defgroups directory)
+      (if (file-exists-p elc-file) (delete-file elc-file)))))
+
+(load "esh-groups" t t)
+
+;;; User Variables:
+
+(defcustom eshell-module-unload-hook
+  '(eshell-unload-extension-modules)
+  "*A hook run when `eshell-module' is unloaded."
+  :type 'hook
+  :group 'eshell-module)
+
+(defcustom eshell-modules-list
+  '(eshell-alias
+    eshell-banner
+    eshell-basic
+    eshell-cmpl
+    eshell-dirs
+    eshell-glob
+    eshell-hist
+    eshell-ls
+    eshell-pred
+    eshell-prompt
+    eshell-script
+    eshell-term
+    eshell-unix)
+  "*A list of optional add-on modules to be loaded by Eshell.
+Changes will only take effect in future Eshell buffers."
+  :type (append
+	 (list 'set ':tag "Supported modules")
+	 (mapcar
+	  (function
+	   (lambda (modname)
+	     (let ((modsym (intern modname)))
+	       (list 'const
+		     ':tag (format "%s -- %s" modname
+				   (get modsym 'custom-tag))
+		     ':link (caar (get modsym 'custom-links))
+		     ':doc (concat "\n" (get modsym 'group-documentation)
+				   "\n ")
+		     modsym))))
+	  (sort (mapcar 'symbol-name
+			(eshell-subgroups 'eshell-module))
+		'string-lessp))
+	 '((repeat :inline t :tag "Other modules" symbol)))
+  :group 'eshell-module)
+
+;;; Code:
+
+(defsubst eshell-using-module (module)
+  "Return non-nil if a certain Eshell MODULE is in use.
+The MODULE should be a symbol corresponding to that module's
+customization group.  Example: `eshell-cmpl' for that module."
+  (memq module eshell-modules-list))
+
+(defun eshell-unload-extension-modules ()
+  "Unload any memory resident extension modules."
+  (eshell-for module (eshell-subgroups 'eshell-module)
+    (if (featurep module)
+	(ignore-errors
+	  (message "Unloading %s..." (symbol-name module))
+	  (unload-feature module)
+	  (message "Unloading %s...done" (symbol-name module))))))
+
+;;; esh-module.el ends here