lisp/env.el

   1 ;;; env.el --- functions to manipulate environment variables
   2
   3 ;; Copyright (C) 1991, 1994, 2000, 2001, 2003 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 ;; Note that the environment string `process-environment' is not
  33 ;; decoded, but the args of `setenv' and `getenv' are normally
  34 ;; multibyte text and get coding conversion.
  35
  36 ;;; Code:
  37
  38 ;; History list for environment variable names.
  39 (defvar read-envvar-name-history nil)
  40
  41 (defun read-envvar-name (prompt &optional mustmatch)
  42   "Read environment variable name, prompting with PROMPT.
  43 Optional second arg MUSTMATCH, if non-nil, means require existing envvar name.
  44 If it is also not t, RET does not exit if it does non-null completion."
  45   (completing-read prompt
  46                    (mapcar (lambda (enventry)
  47                              (list (if enable-multibyte-characters
  48                                        (decode-coding-string
  49                                         (substring enventry 0
  50                                                    (string-match "=" enventry))
  51                                         locale-coding-system t)
  52                                      (substring enventry 0
  53                                                 (string-match "=" enventry)))))
  54                            process-environment)
  55                    nil mustmatch nil 'read-envvar-name-history))
  56
  57 ;; History list for VALUE argument to setenv.
  58 (defvar setenv-history nil)
  59
  60
  61 (defun substitute-env-vars (string)
  62   "Substitute environment variables referred to in STRING.
  63 `$FOO' where FOO is an environment variable name means to substitute
  64 the value of that variable.  The variable name should be terminated
  65 with a character not a letter, digit or underscore; otherwise, enclose
  66 the entire variable name in braces.  Use `$$' to insert a single
  67 dollar sign."
  68   (let ((start 0))
  69     (while (string-match
  70             (eval-when-compile
  71               (rx (or (and "$" (submatch (1+ (regexp "[:alnum:]_"))))
  72                       (and "${" (submatch (minimal-match (0+ anything))) "}")
  73                       "$$")))
  74             string start)
  75       (cond ((match-beginning 1)
  76              (let ((value (getenv (match-string 1 string))))
  77                (setq string (replace-match (or value "") t t string)
  78                      start (+ (match-beginning 0) (length value)))))
  79             ((match-beginning 2)
  80              (let ((value (getenv (match-string 2 string))))
  81                (setq string (replace-match (or value "") t t string)
  82                      start (+ (match-beginning 0) (length value)))))
  83             (t
  84              (setq string (replace-match "$" t t string)
  85                    start (+ (match-beginning 0) 1)))))
  86     string))
  87
  88 ;; Fixme: Should `process-environment' be recoded if LC_CTYPE &c is set?
  89
  90 (defun setenv (variable &optional value unset substitute-env-vars)
  91   "Set the value of the environment variable named VARIABLE to VALUE.
  92 VARIABLE should be a string.  VALUE is optional; if not provided or is
  93 `nil', the environment variable VARIABLE will be removed.  UNSET
  94 if non-nil means to remove VARIABLE from the environment.
  95 SUBSTITUTE-ENV-VARS, if non-nil, means to substitute environment
  96 variables in VALUE with `substitute-env-vars', where see.
  97 Value is the new value if VARIABLE, or nil if removed from the
  98 environment.
  99
 100 Interactively, a prefix argument means to unset the variable.
 101 Interactively, the current value (if any) of the variable
 102 appears at the front of the history list when you type in the new value.
 103 Interactively, always replace environment variables in the new value.
 104
 105 This function works by modifying `process-environment'.
 106
 107 As a special case, setting variable `TZ' calls `set-time-zone-rule' as
 108 a side-effect."
 109   (interactive
 110    (if current-prefix-arg
 111        (list (read-envvar-name "Clear environment variable: " 'exact) nil t)
 112      (let* ((var (read-envvar-name "Set environment variable: " nil))
 113             (value (getenv var)))
 114        (when value
 115          (push value setenv-history))
 116        ;; Here finally we specify the args to give call setenv with.
 117        (list var
 118              (read-from-minibuffer (format "Set %s to value: " var)
 119                                    nil nil nil 'setenv-history
 120                                    value)
 121              nil
 122              t))))
 123   (if (and (multibyte-string-p variable) locale-coding-system)
 124       (let ((codings (find-coding-systems-string (concat variable value))))
 125         (unless (or (eq 'undecided (car codings))
 126                     (memq (coding-system-base locale-coding-system) codings))
 127           (error "Can't encode `%s=%s' with `locale-coding-system'"
 128                  variable (or value "")))))
 129   (if unset
 130       (setq value nil)
 131     (if substitute-env-vars
 132         (setq value (substitute-env-vars value))))
 133   (if (multibyte-string-p variable)
 134       (setq variable (encode-coding-string variable locale-coding-system)))
 135   (if (and value (multibyte-string-p value))
 136       (setq value (encode-coding-string value locale-coding-system)))
 137   (if (string-match "=" variable)
 138       (error "Environment variable name `%s' contains `='" variable)
 139     (let ((pattern (concat "\\`" (regexp-quote (concat variable "="))))
 140           (case-fold-search nil)
 141           (scan process-environment)
 142           found)
 143       (if (string-equal "TZ" variable)
 144           (set-time-zone-rule value))
 145       (while scan
 146         (cond ((string-match pattern (car scan))
 147                (setq found t)
 148                (if (eq nil value)
 149                    (setq process-environment (delq (car scan)
 150                                                    process-environment))
 151                  (setcar scan (concat variable "=" value)))
 152                (setq scan nil)))
 153         (setq scan (cdr scan)))
 154       (or found
 155           (if value
 156               (setq process-environment
 157                     (cons (concat variable "=" value)
 158                           process-environment))))))
 159   value)
 160
 161 (defun getenv (variable)
 162   "Get the value of environment variable VARIABLE.
 163 VARIABLE should be a string.  Value is nil if VARIABLE is undefined in
 164 the environment.  Otherwise, value is a string.
 165
 166 This function consults the variable `process-environment'
 167 for its value."
 168   (interactive (list (read-envvar-name "Get environment variable: " t)))
 169   (let ((value (getenv-internal (if (multibyte-string-p variable)
 170                                     (encode-coding-string
 171                                      variable locale-coding-system)
 172                                   variable))))
 173     (if (and enable-multibyte-characters value)
 174         (setq value (decode-coding-string value locale-coding-system)))
 175     (when (interactive-p)
 176       (message "%s" (if value value "Not set")))
 177     value))
 178
 179 (provide 'env)
 180
 181 ;;; env.el ends here