lib/putenv.c

   1 /* Copyright (C) 1991, 1994, 1997-1998, 2000, 2003-2011 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 HAVE_GNU_LD
  38 # define environ __environ
  39 #else
  40 extern char **environ;
  41 #endif
  42
  43 #if _LIBC
  44 /* This lock protects against simultaneous modifications of `environ'.  */
  45 # include <bits/libc-lock.h>
  46 __libc_lock_define_initialized (static, envlock)
  47 # define LOCK   __libc_lock_lock (envlock)
  48 # define UNLOCK __libc_lock_unlock (envlock)
  49 #else
  50 # define LOCK
  51 # define UNLOCK
  52 #endif
  53
  54 static int
  55 _unsetenv (const char *name)
  56 {
  57   size_t len;
  58   char **ep;
  59
  60   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
  61     {
  62       __set_errno (EINVAL);
  63       return -1;
  64     }
  65
  66   len = strlen (name);
  67
  68   LOCK;
  69
  70   ep = environ;
  71   while (*ep != NULL)
  72     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
  73       {
  74         /* Found it.  Remove this pointer by moving later ones back.  */
  75         char **dp = ep;
  76
  77         do
  78           dp[0] = dp[1];
  79         while (*dp++);
  80         /* Continue the loop in case NAME appears again.  */
  81       }
  82     else
  83       ++ep;
  84
  85   UNLOCK;
  86
  87   return 0;
  88 }
  89
  90
  91 /* Put STRING, which is of the form "NAME=VALUE", in the environment.
  92    If STRING contains no `=', then remove STRING from the environment.  */
  93 int
  94 putenv (char *string)
  95 {
  96   const char *const name_end = strchr (string, '=');
  97   register size_t size;
  98   register char **ep;
  99
 100   if (name_end == NULL)
 101     {
 102       /* Remove the variable from the environment.  */
 103       return _unsetenv (string);
 104     }
 105
 106   size = 0;
 107   for (ep = environ; *ep != NULL; ++ep)
 108     if (!strncmp (*ep, string, name_end - string) &&
 109         (*ep)[name_end - string] == '=')
 110       break;
 111     else
 112       ++size;
 113
 114   if (*ep == NULL)
 115     {
 116       static char **last_environ = NULL;
 117       char **new_environ = (char **) malloc ((size + 2) * sizeof (char *));
 118       if (new_environ == NULL)
 119         return -1;
 120       (void) memcpy ((void *) new_environ, (void *) environ,
 121                      size * sizeof (char *));
 122       new_environ[size] = (char *) string;
 123       new_environ[size + 1] = NULL;
 124       free (last_environ);
 125       last_environ = new_environ;
 126       environ = new_environ;
 127     }
 128   else
 129     *ep = string;
 130
 131   return 0;
 132 }