elf/dl-environ.c

   1 /* Environment handling for dynamic loader.
   2    Copyright (C) 1995-2016 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <string.h>
  20 #include <stdlib.h>
  21 #include <unistd.h>
  22 #include <ldsodefs.h>
  23
  24 /* Walk through the environment of the process and return all entries
  25    starting with `LD_'.  */
  26 char *
  27 internal_function
  28 _dl_next_ld_env_entry (char ***position)
  29 {
  30   char **current = *position;
  31   char *result = NULL;
  32
  33   while (*current != NULL)
  34     {
  35       if (__builtin_expect ((*current)[0] == 'L', 0)
  36           && (*current)[1] == 'D' && (*current)[2] == '_')
  37         {
  38           result = &(*current)[3];
  39
  40           /* Save current position for next visit.  */
  41           *position = ++current;
  42
  43           break;
  44         }
  45
  46       ++current;
  47     }
  48
  49   return result;
  50 }
  51
  52
  53 /* In ld.so __environ is not exported.  */
  54 extern char **__environ attribute_hidden;
  55
  56 int
  57 unsetenv (const char *name)
  58 {
  59   char **ep;
  60
  61   ep = __environ;
  62   while (*ep != NULL)
  63     {
  64       size_t cnt = 0;
  65
  66       while ((*ep)[cnt] == name[cnt] && name[cnt] != '\0')
  67         ++cnt;
  68
  69       if (name[cnt] == '\0' && (*ep)[cnt] == '=')
  70         {
  71           /* Found it.  Remove this pointer by moving later ones to
  72              the front.  */
  73           char **dp = ep;
  74
  75           do
  76             dp[0] = dp[1];
  77           while (*dp++);
  78           /* Continue the loop in case NAME appears again.  */
  79         }
  80       else
  81         ++ep;
  82     }
  83
  84   return 0;
  85 }