/*      $NetBSD: unsetenv.c,v 1.11 2015/01/20 18:31:25 christos Exp $   */

/*
* Copyright (c) 1987, 1993
*      The Regents of the University of California.  All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "from: @(#)setenv.c      8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: unsetenv.c,v 1.11 2015/01/20 18:31:25 christos Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#include "namespace.h"

#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <bitstring.h>

#include "env.h"
#include "local.h"

/*
* unsetenv(name) --
*      Delete environmental variable "name".
*/
int
unsetenv(const char *name)
{
       size_t l_name;
       ssize_t r_offset, w_offset;

       _DIAGASSERT(name != NULL);

       l_name = __envvarnamelen(name, false);
       if (l_name == 0) {
               errno = EINVAL;
               return -1;
       }

       if (!__writelockenv())
               return -1;

       /* Search for the given name in the environment. */
       r_offset = __getenvslot(name, l_name, false);
       if (r_offset == -1) {
               /* Not found. */
               (void)__unlockenv();
               return 0;
       }
       __freeenvvar(environ[r_offset]);

       /*
        * Remove all matches from the environment and free the associated
        * memory if possible.
        */
       w_offset = r_offset;
       while (environ[++r_offset] != NULL) {
               if (strncmp(environ[r_offset], name, l_name) != 0 ||
                   environ[r_offset][l_name] != '=') {
                       /* Not a match, keep this entry. */
                       environ[w_offset++] = environ[r_offset];
               } else {
                       /* We found another match. */
                       __freeenvvar(environ[r_offset]);
               }
       }

       /* Clear out remaining stale entries in the environment vector. */
       do {
               environ[w_offset++] = NULL;
       } while (w_offset < r_offset);

       (void)__unlockenv();
       return 0;
}