* rlogin.el (rlogin): recognise the `-l user' option to rlogin and

[bpt/emacs.git] / lisp / env.el

diff --git a/lisp/env.el b/lisp/env.el
index a3933f2..e0eebae 100644 (file)
--- a/lisp/env.el
+++ b/lisp/env.el
@@ -1,9 +1,9 @@
-;;; setenv.el --- functions to manipulate environment variables.
+;;; env.el --- functions to manipulate environment variables.
 
-;;; Copyright Free Software Foundation 1991
+;;; Copyright 1991, 1994 Free Software Foundation, Inc.
 
 ;; Maintainer: FSF
-;; Keywords: extensions
+;; Keywords: processes, unix
 
 ;;; This file is part of GNU Emacs.
 
@@ -21,26 +21,49 @@
 ;;; along with GNU Emacs; see the file COPYING.  If not, write to
 ;;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 
+;;; Commentary:
+
+;; UNIX processes inherit a list of name-to-string associations from
+;; their parents called their `environment'; these are commonly used
+;; to control program options.  This package permits you to set
+;; environment variables to be passed to any sub-process run under Emacs.
+
 ;;; Code:
 
-(defun setenv (variable value)
+;;;###autoload
+(defun setenv (variable &optional value unset)
   "Set the value of the environment variable named VARIABLE to VALUE.
-VARIABLE and VALUE should both be strings.
-This function works by modifying process-environment."
-  (interactive "sSet environment variable: \nsSet %s to value: ")
+VARIABLE should be a string.  VALUE is optional; if not provided or is
+`nil', the environment variable VARIABLE will be removed.  
+
+Interactively, a prefix argument means to unset the variable.
+This function works by modifying `process-environment'."
+  (interactive
+   (if current-prefix-arg
+       (list (read-string "Clear environment variable: ") nil t)
+     (let ((var (read-string "Set environment variable: ")))
+       (list var (read-string (format "Set %s to value: " var))))))
+  (if unset (setq value nil))
   (if (string-match "=" variable)
-      (error "Environment variable name contains `='")
+      (error "Environment variable name `%s' contains `='" variable)
     (let ((pattern (concat "\\`" (regexp-quote (concat variable "="))))
-         (scan process-environment))
+         (case-fold-search nil)
+         (scan process-environment)
+         found)
       (while scan
-       (cond
-        ((string-match pattern (car scan))
-         (setcar scan (concat variable "=" value))
-         (setq scan nil))
-        ((null (setq scan (cdr scan)))
-         (setq process-environment
-               (cons (concat variable "=" value) process-environment))))))))
+       (cond ((string-match pattern (car scan))
+              (setq found t)
+              (if (eq nil value)
+                  (setq process-environment (delq (car scan) process-environment))
+                (setcar scan (concat variable "=" value)))
+              (setq scan nil)))
+       (setq scan (cdr scan)))
+      (or found
+         (if value
+             (setq process-environment
+                   (cons (concat variable "=" value)
+                         process-environment)))))))
 
-(provide 'setenv)
+(provide 'env)
 
-;;; setenv.el ends here
+;;; env.el ends here