stdlib/getenv.c

   1 /* Copyright (C) 1991-2023 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <stdlib.h>
  19 #include <string.h>
  20 #include <unistd.h>
  21
  22 char *
  23 getenv (const char *name)
  24 {
  25   if (__environ == NULL || name[0] == '\0')
  26     return NULL;
  27
  28   size_t len = strlen (name);
  29   for (char **ep = __environ; *ep != NULL; ++ep)
  30     {
  31       if (name[0] == (*ep)[0]
  32           && strncmp (name, *ep, len) == 0 && (*ep)[len] == '=')
  33         return *ep + len + 1;
  34     }
  35
  36   return NULL;
  37 }
  38 libc_hidden_def (getenv)