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+;;; esh-ext --- commands external to Eshell
+
+;; 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-ext)
+
+(eval-when-compile (require 'esh-maint))
+
+(defgroup eshell-ext nil
+  "External commands are invoked when operating system executables are
+loaded into memory, thus beginning a new process."
+  :tag "External commands"
+  :group 'eshell)
+
+;;; Commentary:
+
+;; To force a command to invoked external, either provide an explicit
+;; pathname for the command argument, or prefix the command name with
+;; an asterix character.  Example:
+;;
+;;   grep        ; make invoke `grep' Lisp function, or `eshell/grep'
+;;   /bin/grep   ; will definitely invoke /bin/grep
+;;   *grep        ; will also invoke /bin/grep
+
+;;; User Variables:
+
+(defcustom eshell-ext-load-hook '(eshell-ext-initialize)
+  "*A hook that gets run when `eshell-ext' is loaded."
+  :type 'hook
+  :group 'eshell-ext)
+
+(defcustom eshell-binary-suffixes
+  (if (eshell-under-windows-p)
+      '(".exe" ".com" ".bat" ".cmd" "")
+    '(""))
+  "*A list of suffixes used when searching for executable files."
+  :type '(repeat string)
+  :group 'eshell-ext)
+
+(defcustom eshell-force-execution nil
+  "*If non-nil, try to execute binary files regardless of permissions.
+This can be useful on systems like Windows, where the operating system
+doesn't happen to honor the permission bits in certain cases; or in
+cases where you want to associate an interpreter with a particular
+kind of script file, but the language won't let you but a '#!'
+interpreter line in the file, and you don't want to make it executable
+since nothing else but Eshell will be able to understand
+`eshell-interpreter-alist'."
+  :type 'boolean
+  :group 'eshell-ext)
+
+(defun eshell-search-path (name)
+  "Search the environment path for NAME."
+  (if (file-name-absolute-p name)
+      name
+    (let ((list (parse-colon-path (getenv "PATH")))
+	  suffixes n1 n2 file)
+      (while list
+	(setq n1 (concat (car list) name))
+	(setq suffixes eshell-binary-suffixes)
+	(while suffixes
+	  (setq n2 (concat n1 (car suffixes)))
+	  (if (and (or (file-executable-p n2)
+		       (and eshell-force-execution
+			    (file-readable-p n2)))
+		   (not (file-directory-p n2)))
+	      (setq file n2 suffixes nil list nil))
+	  (setq suffixes (cdr suffixes)))
+	(setq list (cdr list)))
+      file)))
+
+(defcustom eshell-windows-shell-file
+  (if (eshell-under-windows-p)
+      (if (string-match "\\(\\`cmdproxy\\|sh\\)\\.\\(com\\|exe\\)"
+			shell-file-name)
+	  (or (eshell-search-path "cmd.exe")
+	      (eshell-search-path "command.exe"))
+	shell-file-name))
+  "*The name of the shell command to use for DOS/Windows batch files.
+This defaults to nil on non-Windows systems, where this variable is
+wholly ignored."
+  :type 'file
+  :group 'eshell-ext)
+
+(defsubst eshell-invoke-batch-file (&rest args)
+  "Invoke a .BAT or .CMD file on DOS/Windows systems."
+  ;; since CMD.EXE can't handle forward slashes in the initial
+  ;; argument...
+  (setcar args (subst-char-in-string directory-sep-char
+				     ?\\ (car args)))
+  (throw 'eshell-replace-command
+	 (eshell-parse-command eshell-windows-shell-file
+			       (cons "/c" args))))
+
+(defcustom eshell-interpreter-alist
+  (if (eshell-under-windows-p)
+      '(("\\.\\(bat\\|cmd\\)\\'" . eshell-invoke-batch-file)))
+  "*An alist defining interpreter substitutions.
+Each member is a cons cell of the form:
+
+  (MATCH . INTERPRETER)
+
+MATCH should be a regexp, which is matched against the command name,
+or a function.  If either returns a non-nil value, then INTERPRETER
+will be used for that command.
+
+If INTERPRETER is a string, it will be called as the command name,
+with the original command name passed as the first argument, with all
+subsequent arguments following.  If INTERPRETER is a function, it will
+be called with all of those arguments.  Note that interpreter
+functions should throw `eshell-replace-command' with the alternate
+command form, or they should return a value compatible with the
+possible return values of `eshell-external-command', which see."
+  :type '(repeat (cons (choice regexp (function :tag "Predicate"))
+		       (choice string (function :tag "Interpreter"))))
+  :group 'eshell-ext)
+
+(defcustom eshell-alternate-command-hook nil
+  "*A hook run whenever external command lookup fails.
+If a functions wishes to provide an alternate command, they must throw
+it using the tag `eshell-replace-command'.  This is done because the
+substituted command need not be external at all, and therefore must be
+passed up to a higher level for re-evaluation.
+
+Or, if the function returns a filename, that filename will be invoked
+with the current command arguments rather than the command specified
+by the user on the command line."
+  :type 'hook
+  :group 'eshell-ext)
+
+(defcustom eshell-command-interpreter-max-length 256
+  "*The maximum length of any command interpreter string, plus args."
+  :type 'integer
+  :group 'eshell-ext)
+
+;;; Functions:
+
+(defun eshell-ext-initialize ()
+  "Initialize the external command handling code."
+  (make-local-hook 'eshell-named-command-hook)
+  (add-hook 'eshell-named-command-hook 'eshell-explicit-command nil t))
+
+(defun eshell-explicit-command (command args)
+  "If a command name begins with `*', call it externally always.
+This bypasses all Lisp functions and aliases."
+  (when (and (> (length command) 1)
+	     (eq (aref command 0) ?*))
+    (let ((cmd (eshell-search-path (substring command 1))))
+      (if cmd
+	  (or (eshell-external-command cmd args)
+	      (error "%s: external command failed" cmd))
+	(error "%s: external command not found"
+	       (substring command 1))))))
+
+(defun eshell-remote-command (handler command args)
+  "Insert output from a remote COMMAND, using ARGS.
+A remote command is something that executes on a different machine.
+An external command simply means external to Emacs.
+
+Note that this function is very crude at the moment.  It gathers up
+all the output from the remote command, and sends it all at once,
+causing the user to wonder if anything's really going on..."
+  (let ((outbuf (generate-new-buffer " *eshell remote output*"))
+	(errbuf (generate-new-buffer " *eshell remote error*"))
+	(exitcode 1))
+    (unwind-protect
+	(progn
+	  (setq exitcode
+		(funcall handler 'shell-command
+			 (mapconcat 'shell-quote-argument
+				    (append (list command) args) " ")
+			 outbuf errbuf))
+	  (eshell-print (save-excursion (set-buffer outbuf)
+					(buffer-string)))
+	  (eshell-error (save-excursion (set-buffer errbuf)
+					(buffer-string))))
+      (eshell-close-handles exitcode 'nil)
+      (kill-buffer outbuf)
+      (kill-buffer errbuf))))
+
+(defun eshell-external-command (command args)
+  "Insert output from an external COMMAND, using ARGS."
+  (setq args (eshell-stringify-list (eshell-flatten-list args)))
+  (let ((handler
+	 (unless (or (equal default-directory "/")
+		     (and (eshell-under-windows-p)
+			  (string-match "\\`[A-Za-z]:[/\\\\]\\'"
+					default-directory)))
+	   (find-file-name-handler default-directory
+				   'shell-command))))
+    (if handler
+	(eshell-remote-command handler command args))
+    (let ((interp (eshell-find-interpreter command)))
+      (assert interp)
+      (if (functionp (car interp))
+	  (apply (car interp) (append (cdr interp) args))
+	(eshell-gather-process-output
+	 (car interp) (append (cdr interp) args))))))
+
+(defun eshell/addpath (&rest args)
+  "Add a set of paths to PATH."
+  (eshell-eval-using-options
+   "addpath" args
+   '((?b "begin" nil prepend "add path element at beginning")
+     (?h "help" nil nil  "display this usage message")
+     :usage "[-b] PATH
+Adds the given PATH to $PATH.")
+   (if args
+       (progn
+	 (if prepend
+	     (setq args (nreverse args)))
+	 (while args
+	   (setenv "PATH"
+		   (if prepend
+		       (concat (car args) path-separator
+			       (getenv "PATH"))
+		     (concat (getenv "PATH") path-separator
+			     (car args))))
+	   (setq args (cdr args))))
+     (let ((paths (parse-colon-path (getenv "PATH"))))
+       (while paths
+	 (eshell-printn (car paths))
+	 (setq paths (cdr paths)))))))
+
+(defun eshell-script-interpreter (file)
+  "Extract the script to run from FILE, if it has #!<interp> in it.
+Return nil, or a list of the form:
+
+  (INTERPRETER [ARGS] FILE)"
+  (let ((maxlen eshell-command-interpreter-max-length))
+    (if (and (file-readable-p file)
+	     (file-regular-p file))
+	(with-temp-buffer
+	  (insert-file-contents-literally file nil 0 maxlen)
+	  (if (looking-at "#!\\([^ \t\n]+\\)\\([ \t]+\\(.+\\)\\)?")
+	      (if (match-string 3)
+		  (list (match-string 1)
+			(match-string 3)
+			file)
+		(list (match-string 1)
+		      file)))))))
+
+(defun eshell-find-interpreter (file &optional no-examine-p)
+  "Find the command interpreter with which to execute FILE.
+If NO-EXAMINE-P is non-nil, FILE will not be inspected for a script
+line of the form #!<interp>."
+  (let ((finterp
+	 (catch 'found
+	   (ignore
+	    (eshell-for possible eshell-interpreter-alist
+	      (cond
+	       ((functionp (car possible))
+		(and (funcall (car possible) file)
+		     (throw 'found (cdr possible))))
+	       ((stringp (car possible))
+		(and (string-match (car possible) file)
+		     (throw 'found (cdr possible))))
+	       (t
+		(error "Invalid interpreter-alist test"))))))))
+    (if finterp                         ; first check
+	(list finterp file)
+      (let ((fullname (if (file-name-directory file) file
+			(eshell-search-path file)))
+	    (suffixes eshell-binary-suffixes))
+	(if (and fullname (not (or eshell-force-execution
+				   (file-executable-p fullname))))
+	    (while suffixes
+	      (let ((try (concat fullname (car suffixes))))
+		(if (or (file-executable-p try)
+			(and eshell-force-execution
+			     (file-readable-p try)))
+		    (setq fullname try suffixes nil)
+		  (setq suffixes (cdr suffixes))))))
+	(cond ((not (and fullname (file-exists-p fullname)))
+	       (let ((name (or fullname file)))
+		 (unless (setq fullname
+			       (run-hook-with-args-until-success
+				'eshell-alternate-command-hook file))
+		   (error "%s: command not found" name))))
+	      ((not (or eshell-force-execution
+			(file-executable-p fullname)))
+	       (error "%s: Permission denied" fullname)))
+	(let (interp)
+	  (unless no-examine-p
+	    (setq interp (eshell-script-interpreter fullname))
+	    (if interp
+		(setq interp
+		      (cons (car (eshell-find-interpreter (car interp) t))
+			    (cdr interp)))))
+	  (or interp (list fullname)))))))
+
+;;; Code:
+
+;;; esh-ext.el ends here