lisp/env.el

   1 ;;; env.el --- functions to manipulate environment variables.
   2
   3 ;;; Copyright Free Software Foundation 1991
   4
   5 ;; Maintainer: FSF
   6 ;; Keywords: processes, unix
   7
   8 ;;; This file is part of GNU Emacs.
   9
  10 ;;; GNU Emacs is free software; you can redistribute it and/or modify
  11 ;;; it under the terms of the GNU General Public License as published by
  12 ;;; the Free Software Foundation; either version 2, or (at your option)
  13 ;;; any later version.
  14
  15 ;;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;;; GNU General Public License for more details.
  19
  20 ;;; You should have received a copy of the GNU General Public License
  21 ;;; along with GNU Emacs; see the file COPYING.  If not, write to
  22 ;;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  23
  24 ;;; Commentary:
  25
  26 ;; UNIX processes inherit a list of name-to-string associations from
  27 ;; their parents called their `environment'; these are commonly used
  28 ;; to control program options.  This package permits you to set
  29 ;; environment variables to be passed to any sub-process run under Emacs.
  30
  31 ;;; Code:
  32
  33 ;;;###autoload
  34 (defun setenv (variable &optional value unset)
  35   "Set the value of the environment variable named VARIABLE to VALUE.
  36 VARIABLE should be a string.  VALUE is optional; if not provided or is
  37 `nil', the environment variable VARIABLE will be removed.
  38
  39 Interactively, a prefix argument means to unset the variable.
  40 This function works by modifying `process-environment'."
  41   (interactive
  42    (if current-prefix-arg
  43        (list (read-string "Clear environment variable: ") nil t)
  44      (let ((var (read-string "Set environment variable: ")))
  45        (list var (read-string (format "Set %s to value: " var))))))
  46   (if unset (setq value nil))
  47   (if (string-match "=" variable)
  48       (error "Environment variable name `%s' contains `='" variable)
  49     (let ((pattern (concat "\\`" (regexp-quote (concat variable "="))))
  50           (case-fold-search nil)
  51           (scan process-environment)
  52           found)
  53       (while scan
  54         (cond ((string-match pattern (car scan))
  55                (setq found t)
  56                (if (eq nil value)
  57                    (setq process-environment (delq (car scan) process-environment))
  58                  (setcar scan (concat variable "=" value)))
  59                (setq scan nil)))
  60         (setq scan (cdr scan)))
  61       (or found
  62           (if value
  63               (setq process-environment
  64                     (cons (concat variable "=" value)
  65                           process-environment)))))))
  66
  67 (provide 'env)
  68
  69 ;;; env.el ends here