(setenv): Rewrite. Provide a way to unset interactively.

1 files changed, 23 insertions, 15 deletions

diff --git a/lisp/env.el b/lisp/env.el
index cbf6dcf2156..dc591ab26f2 100644
--- a/lisp/env.el
+++ b/lisp/env.el
@@ -31,30 +31,38 @@
 ;;; Code:
 
 ;;;###autoload
-(defun setenv (variable &optional value)
+(defun setenv (variable &optional value unset)
   "Set the value of the environment variable named VARIABLE 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 "sSet environment variable: \nsSet %s to value: ")
+  (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 `%s' contains `='" variable)
     (let ((pattern (concat "\\`" (regexp-quote (concat variable "="))))
           (case-fold-search nil)
-          (scan process-environment))
-      (if scan
-          (while scan
-            (cond
-             ((string-match pattern (car scan))
-              (if (eq nil value)
-                  (setq process-environment (delq (car scan) process-environment))
-                (setcar scan (concat variable "=" value)))
-              (setq scan nil))
-             ((null (setq scan (cdr scan)))
+          (scan process-environment)
+          found)
+      (while scan
+        (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)))))
-        (setq process-environment
-              (cons (concat variable "=" value) process-environment))))))
+                    (cons (concat variable "=" value)
+                          process-environment)))))))
 
 (provide 'env)