gl/unsetenv.c

   1 /* Copyright (C) 1992,1995-1999,2000-2002,2005-2006 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program 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
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License along
  15    with this program; if not, write to the Free Software Foundation,
  16    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
  17
  18 #include <config.h>
  19
  20 #include <errno.h>
  21 #if !_LIBC
  22 # define __set_errno(ev) ((errno) = (ev))
  23 #endif
  24
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28
  29 #if !_LIBC
  30 # define __environ      environ
  31 # ifndef HAVE_ENVIRON_DECL
  32 extern char **environ;
  33 # endif
  34 #endif
  35
  36 #if _LIBC
  37 /* This lock protects against simultaneous modifications of `environ'.  */
  38 # include <bits/libc-lock.h>
  39 __libc_lock_define_initialized (static, envlock)
  40 # define LOCK   __libc_lock_lock (envlock)
  41 # define UNLOCK __libc_lock_unlock (envlock)
  42 #else
  43 # define LOCK
  44 # define UNLOCK
  45 #endif
  46
  47 /* In the GNU C library we must keep the namespace clean.  */
  48 #ifdef _LIBC
  49 # define unsetenv __unsetenv
  50 #endif
  51
  52
  53 int
  54 unsetenv (const char *name)
  55 {
  56   size_t len;
  57   char **ep;
  58
  59   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
  60     {
  61       __set_errno (EINVAL);
  62       return -1;
  63     }
  64
  65   len = strlen (name);
  66
  67   LOCK;
  68
  69   ep = __environ;
  70   while (*ep != NULL)
  71     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
  72       {
  73         /* Found it.  Remove this pointer by moving later ones back.  */
  74         char **dp = ep;
  75
  76         do
  77           dp[0] = dp[1];
  78         while (*dp++);
  79         /* Continue the loop in case NAME appears again.  */
  80       }
  81     else
  82       ++ep;
  83
  84   UNLOCK;
  85
  86   return 0;
  87 }
  88
  89 #ifdef _LIBC
  90 # undef unsetenv
  91 weak_alias (__unsetenv, unsetenv)
  92 #endif