lib/putenv.c

   1 /* Copyright (C) 1991, 1994, 1997, 1998, 2000, 2003 Free Software Foundation, Inc.
   2
   3    NOTE: The canonical source of this file is maintained with the GNU C
   4    Library.  Bugs can be reported to bug-glibc@prep.ai.mit.edu.
   5
   6    This program is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published by the
   8    Free Software Foundation; either version 2, or (at your option) any
   9    later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software Foundation,
  18    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  19
  20 #if HAVE_CONFIG_H
  21 # include <config.h>
  22 #endif
  23
  24 #include <stddef.h>
  25
  26 /* Include errno.h *after* sys/types.h to work around header problems
  27    on AIX 3.2.5.  */
  28 #include <errno.h>
  29 #if !_LIBC
  30 # if !defined errno
  31 extern int errno;
  32 # endif
  33 # define __set_errno(ev) ((errno) = (ev))
  34 #endif
  35
  36 /* Don't include stdlib.h because some (e.g., Solaris 7) declare putenv
  37    with a non-const argument.  That would conflict with the declaration of
  38    rpl_putenv below (due to the #define putenv rpl_putenv from config.h).  */
  39
  40 void *malloc ();
  41 void free ();
  42
  43 #include <string.h>
  44
  45 #if defined (__GNU_LIBRARY__) || defined (HAVE_UNISTD_H)
  46 # include <unistd.h>
  47 #endif
  48
  49 #if HAVE_GNU_LD
  50 # define environ __environ
  51 #else
  52 extern char **environ;
  53 #endif
  54
  55 #if _LIBC
  56 /* This lock protects against simultaneous modifications of `environ'.  */
  57 # include <bits/libc-lock.h>
  58 __libc_lock_define_initialized (static, envlock)
  59 # define LOCK   __libc_lock_lock (envlock)
  60 # define UNLOCK __libc_lock_unlock (envlock)
  61 #else
  62 # define LOCK
  63 # define UNLOCK
  64 #endif
  65
  66 static int
  67 unsetenv (const char *name)
  68 {
  69   size_t len;
  70   char **ep;
  71
  72   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
  73     {
  74       __set_errno (EINVAL);
  75       return -1;
  76     }
  77
  78   len = strlen (name);
  79
  80   LOCK;
  81
  82   ep = environ;
  83   while (*ep != NULL)
  84     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
  85       {
  86         /* Found it.  Remove this pointer by moving later ones back.  */
  87         char **dp = ep;
  88
  89         do
  90           dp[0] = dp[1];
  91         while (*dp++);
  92         /* Continue the loop in case NAME appears again.  */
  93       }
  94     else
  95       ++ep;
  96
  97   UNLOCK;
  98
  99   return 0;
 100 }
 101
 102
 103 /* Put STRING, which is of the form "NAME=VALUE", in the environment.
 104    If STRING contains no `=', then remove STRING from the environment.  */
 105 int
 106 rpl_putenv (const char *string)
 107 {
 108   const char *const name_end = strchr (string, '=');
 109   register size_t size;
 110   register char **ep;
 111
 112   if (name_end == NULL)
 113     {
 114       /* Remove the variable from the environment.  */
 115       return unsetenv (string);
 116     }
 117
 118   size = 0;
 119   for (ep = environ; *ep != NULL; ++ep)
 120     if (!strncmp (*ep, string, name_end - string) &&
 121         (*ep)[name_end - string] == '=')
 122       break;
 123     else
 124       ++size;
 125
 126   if (*ep == NULL)
 127     {
 128       static char **last_environ = NULL;
 129       char **new_environ = (char **) malloc ((size + 2) * sizeof (char *));
 130       if (new_environ == NULL)
 131         return -1;
 132       (void) memcpy ((void *) new_environ, (void *) environ,
 133                      size * sizeof (char *));
 134       new_environ[size] = (char *) string;
 135       new_environ[size + 1] = NULL;
 136       if (last_environ != NULL)
 137         free (last_environ);
 138       last_environ = new_environ;
 139       environ = new_environ;
 140     }
 141   else
 142     *ep = (char *) string;
 143
 144   return 0;
 145 }