/* Copyright (C) 1992,1995-1999,2000-2002,2005-2006 Free Software Foundation, Inc.
  This file is part of the GNU C Library.

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2, or (at your option)
  any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License along
  with this program; if not, write to the Free Software Foundation,
  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */

#include <config.h>

#include <errno.h>
#if !_LIBC
# define __set_errno(ev) ((errno) = (ev))
#endif

#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#if !_LIBC
# define __environ      environ
# ifndef HAVE_ENVIRON_DECL
extern char **environ;
# endif
#endif

#if _LIBC
/* This lock protects against simultaneous modifications of `environ'.  */
# include <bits/libc-lock.h>
__libc_lock_define_initialized (static, envlock)
# define LOCK   __libc_lock_lock (envlock)
# define UNLOCK __libc_lock_unlock (envlock)
#else
# define LOCK
# define UNLOCK
#endif

/* In the GNU C library we must keep the namespace clean.  */
#ifdef _LIBC
# define unsetenv __unsetenv
#endif


int
unsetenv (const char *name)
{
 size_t len;
 char **ep;

 if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
   {
     __set_errno (EINVAL);
     return -1;
   }

 len = strlen (name);

 LOCK;

 ep = __environ;
 while (*ep != NULL)
   if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
     {
       /* Found it.  Remove this pointer by moving later ones back.  */
       char **dp = ep;

       do
         dp[0] = dp[1];
       while (*dp++);
       /* Continue the loop in case NAME appears again.  */
     }
   else
     ++ep;

 UNLOCK;

 return 0;
}

#ifdef _LIBC
# undef unsetenv
weak_alias (__unsetenv, unsetenv)
#endif