lib/putenv.c

   1 /* Copyright (C) 1991, 1994, 1997-1998, 2000, 2003-2012 Free Software
   2    Foundation, Inc.
   3
   4    NOTE: The canonical source of this file is maintained with the GNU C
   5    Library.  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 Lesser General Public License as published by the
   9    Free Software Foundation; either version 3 of the License, or 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 Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include <config.h>
  21
  22 /* Specification.  */
  23 #include <stdlib.h>
  24
  25 #include <stddef.h>
  26
  27 /* Include errno.h *after* sys/types.h to work around header problems
  28    on AIX 3.2.5.  */
  29 #include <errno.h>
  30 #ifndef __set_errno
  31 # define __set_errno(ev) ((errno) = (ev))
  32 #endif
  33
  34 #include <string.h>
  35 #include <unistd.h>
  36
  37 #if _LIBC
  38 # if HAVE_GNU_LD
  39 #  define environ __environ
  40 # else
  41 extern char **environ;
  42 # endif
  43 #endif
  44
  45 #if _LIBC
  46 /* This lock protects against simultaneous modifications of 'environ'.  */
  47 # include <bits/libc-lock.h>
  48 __libc_lock_define_initialized (static, envlock)
  49 # define LOCK   __libc_lock_lock (envlock)
  50 # define UNLOCK __libc_lock_unlock (envlock)
  51 #else
  52 # define LOCK
  53 # define UNLOCK
  54 #endif
  55
  56 static int
  57 _unsetenv (const char *name)
  58 {
  59   size_t len;
  60   char **ep;
  61
  62   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
  63     {
  64       __set_errno (EINVAL);
  65       return -1;
  66     }
  67
  68   len = strlen (name);
  69
  70   LOCK;
  71
  72   ep = environ;
  73   while (*ep != NULL)
  74     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
  75       {
  76         /* Found it.  Remove this pointer by moving later ones back.  */
  77         char **dp = ep;
  78
  79         do
  80           dp[0] = dp[1];
  81         while (*dp++);
  82         /* Continue the loop in case NAME appears again.  */
  83       }
  84     else
  85       ++ep;
  86
  87   UNLOCK;
  88
  89   return 0;
  90 }
  91
  92
  93 /* Put STRING, which is of the form "NAME=VALUE", in the environment.
  94    If STRING contains no '=', then remove STRING from the environment.  */
  95 int
  96 putenv (char *string)
  97 {
  98   const char *const name_end = strchr (string, '=');
  99   register size_t size;
 100   register char **ep;
 101
 102   if (name_end == NULL)
 103     {
 104       /* Remove the variable from the environment.  */
 105       return _unsetenv (string);
 106     }
 107
 108   size = 0;
 109   for (ep = environ; *ep != NULL; ++ep)
 110     if (!strncmp (*ep, string, name_end - string) &&
 111         (*ep)[name_end - string] == '=')
 112       break;
 113     else
 114       ++size;
 115
 116   if (*ep == NULL)
 117     {
 118       static char **last_environ = NULL;
 119       char **new_environ = (char **) malloc ((size + 2) * sizeof (char *));
 120       if (new_environ == NULL)
 121         return -1;
 122       (void) memcpy ((void *) new_environ, (void *) environ,
 123                      size * sizeof (char *));
 124       new_environ[size] = (char *) string;
 125       new_environ[size + 1] = NULL;
 126       free (last_environ);
 127       last_environ = new_environ;
 128       environ = new_environ;
 129     }
 130   else
 131     *ep = string;
 132
 133   return 0;
 134 }