elf/dl-environ.c

   1 /* Environment handling for dynamic loader.
   2    Copyright (C) 1995-2021 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    <https://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 _dl_next_ld_env_entry (char ***position)
  28 {
  29   char **current = *position;
  30   char *result = NULL;
  31
  32   while (*current != NULL)
  33     {
  34       if (__builtin_expect ((*current)[0] == 'L', 0)
  35           && (*current)[1] == 'D' && (*current)[2] == '_')
  36         {
  37           result = &(*current)[3];
  38
  39           /* Save current position for next visit.  */
  40           *position = ++current;
  41
  42           break;
  43         }
  44
  45       ++current;
  46     }
  47
  48   return result;
  49 }
  50
  51
  52 /* In ld.so __environ is not exported.  */
  53 extern char **__environ attribute_hidden;
  54
  55 int
  56 unsetenv (const char *name)
  57 {
  58   char **ep;
  59
  60   ep = __environ;
  61   while (*ep != NULL)
  62     {
  63       size_t cnt = 0;
  64
  65       while ((*ep)[cnt] == name[cnt] && name[cnt] != '\0')
  66         ++cnt;
  67
  68       if (name[cnt] == '\0' && (*ep)[cnt] == '=')
  69         {
  70           /* Found it.  Remove this pointer by moving later ones to
  71              the front.  */
  72           char **dp = ep;
  73
  74           do
  75             dp[0] = dp[1];
  76           while (*dp++);
  77           /* Continue the loop in case NAME appears again.  */
  78         }
  79       else
  80         ++ep;
  81     }
  82
  83   return 0;
  84 }