lisp/env.el

   1 ;;; env.el --- functions to manipulate environment variables
   2
   3 ;; Copyright (C) 1991, 1994 Free Software Foundation, Inc.
   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 the
  22 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23 ;; Boston, MA 02111-1307, USA.
  24
  25 ;;; Commentary:
  26
  27 ;; UNIX processes inherit a list of name-to-string associations from their
  28 ;; parents called their `environment'; these are commonly used to control
  29 ;; program options.  This package permits you to set environment variables
  30 ;; to be passed to any sub-process run under Emacs.
  31
  32 ;;; Code:
  33
  34 ;; History list for environment variable names.
  35 (defvar read-envvar-name-history nil)
  36
  37 (defun read-envvar-name (prompt &optional mustmatch)
  38   "Read environment variable name, prompting with PROMPT.
  39 Optional second arg MUSTMATCH, if non-nil, means require existing envvar name.
  40 If it is also not t, RET does not exit if it does non-null completion."
  41   (completing-read prompt
  42                    (mapcar (function
  43                             (lambda (enventry)
  44                               (list (substring enventry 0
  45                                                (string-match "=" enventry)))))
  46                            process-environment)
  47                    nil mustmatch nil 'read-envvar-name-history))
  48
  49 ;; History list for VALUE argument to setenv.
  50 (defvar setenv-history nil)
  51
  52 (defun setenv (variable &optional value unset)
  53   "Set the value of the environment variable named VARIABLE to VALUE.
  54 VARIABLE should be a string.  VALUE is optional; if not provided or is
  55 `nil', the environment variable VARIABLE will be removed.
  56
  57 Interactively, a prefix argument means to unset the variable.
  58 Interactively, the current value (if any) of the variable
  59 appears at the front of the history list when you type in the new value.
  60
  61 This function works by modifying `process-environment'."
  62   (interactive
  63    (if current-prefix-arg
  64        (list (read-envvar-name "Clear environment variable: " 'exact) nil t)
  65      (let ((var (read-envvar-name "Set environment variable: " nil)))
  66        ;; Here finally we specify the args to give call setenv with.
  67        (list var (read-from-minibuffer (format "Set %s to value: " var)
  68                                        nil nil nil 'setenv-history
  69                                        (getenv var))))))
  70   (if unset (setq value nil))
  71   (if (string-match "=" variable)
  72       (error "Environment variable name `%s' contains `='" variable)
  73     (let ((pattern (concat "\\`" (regexp-quote (concat variable "="))))
  74           (case-fold-search nil)
  75           (scan process-environment)
  76           found)
  77       (if (string-equal "TZ" variable)
  78           (set-time-zone-rule value))
  79       (while scan
  80         (cond ((string-match pattern (car scan))
  81                (setq found t)
  82                (if (eq nil value)
  83                    (setq process-environment (delq (car scan) process-environment))
  84                  (setcar scan (concat variable "=" value)))
  85                (setq scan nil)))
  86         (setq scan (cdr scan)))
  87       (or found
  88           (if value
  89               (setq process-environment
  90                     (cons (concat variable "=" value)
  91                           process-environment)))))))
  92
  93 (defun getenv (variable)
  94   "Get the value of environment variable VARIABLE.
  95 VARIABLE should be a string.  Value is nil if VARIABLE is undefined in
  96 the environment.  Otherwise, value is a string.
  97
  98 This function consults the variable `process-environment'
  99 for its value."
 100   (interactive (list (read-envvar-name "Get environment variable: " t)))
 101   (let ((value (getenv-internal variable)))
 102     (when (interactive-p)
 103       (message "%s" (if value value "Not set")))
 104     value))
 105
 106 (provide 'env)
 107
 108 ;;; env.el ends here