lib/putenv.c

   1 /* Copyright (C) 1991, 1994 Free Software Foundation, Inc.
   2
   3
   4 NOTE: The canonical source of this file is maintained with the GNU C Library.
   5 Bugs can be reported to bug-glibc@prep.ai.mit.edu.
   6
   7 This program is free software; you can redistribute it and/or modify it
   8 under the terms of the GNU General Public License as published by the
   9 Free Software Foundation; either version 2, or (at your option) any
  10 later version.
  11
  12 This program is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with this program; if not, write to the Free Software
  19 Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  20
  21 #include <errno.h>
  22
  23 #ifdef HAVE_CONFIG_H
  24 #include <config.h>
  25 #endif
  26
  27 /* Define-away any (possibly conflicting) prototype of putenv.
  28    Many systems omit the `const' attribute on the argument.  */
  29 #define putenv _sys_putenv
  30
  31 #if defined (__GNU_LIBRARY__) || defined (HAVE_STDLIB_H)
  32 #include <stdlib.h>
  33 #endif
  34 #if defined (__GNU_LIBRARY__) || defined (HAVE_STRING_H)
  35 #include <string.h>
  36 #endif
  37 #if defined (__GNU_LIBRARY__) || defined (HAVE_UNISTD_H)
  38 #include <unistd.h>
  39 #endif
  40
  41 #undef putenv
  42
  43 #if !defined (__GNU_LIBRARY__) && !defined (HAVE_STRCHR)
  44 #define strchr index
  45 #endif
  46 #if !defined (__GNU_LIBRARY__) && !defined (HAVE_MEMCPY)
  47 #define memcpy(d,s,n) bcopy ((s), (d), (n))
  48 #endif
  49
  50 #if HAVE_GNU_LD
  51 #define environ __environ
  52 #else
  53 extern char **environ;
  54 #endif
  55
  56
  57 /* Put STRING, which is of the form "NAME=VALUE", in the environment.  */
  58 int
  59 putenv (string)
  60      const char *string;
  61 {
  62   const char *const name_end = strchr (string, '=');
  63   register size_t size;
  64   register char **ep;
  65
  66   if (name_end == NULL)
  67     {
  68       /* Remove the variable from the environment.  */
  69       size = strlen (string);
  70       for (ep = environ; *ep != NULL; ++ep)
  71         if (!strncmp (*ep, string, size) && (*ep)[size] == '=')
  72           {
  73             while (ep[1] != NULL)
  74               {
  75                 ep[0] = ep[1];
  76                 ++ep;
  77               }
  78             *ep = NULL;
  79             return 0;
  80           }
  81     }
  82
  83   size = 0;
  84   for (ep = environ; *ep != NULL; ++ep)
  85     if (!strncmp (*ep, string, name_end - string) &&
  86         (*ep)[name_end - string] == '=')
  87       break;
  88     else
  89       ++size;
  90
  91   if (*ep == NULL)
  92     {
  93       static char **last_environ = NULL;
  94       char **new_environ = (char **) malloc ((size + 2) * sizeof (char *));
  95       if (new_environ == NULL)
  96         return -1;
  97       (void) memcpy ((void *) new_environ, (void *) environ,
  98                      size * sizeof (char *));
  99       new_environ[size] = (char *) string;
 100       new_environ[size + 1] = NULL;
 101       if (last_environ != NULL)
 102         free ((void *) last_environ);
 103       last_environ = new_environ;
 104       environ = new_environ;
 105     }
 106   else
 107     *ep = (char *) string;
 108
 109   return 0;
 110 }