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      1 /*	$NetBSD: unsetenv.c,v 1.11 2015/01/20 18:31:25 christos Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1987, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. Neither the name of the University nor the names of its contributors
     16  *    may be used to endorse or promote products derived from this software
     17  *    without specific prior written permission.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     29  * SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 #if defined(LIBC_SCCS) && !defined(lint)
     34 #if 0
     35 static char sccsid[] = "from: @(#)setenv.c	8.1 (Berkeley) 6/4/93";
     36 #else
     37 __RCSID("$NetBSD: unsetenv.c,v 1.11 2015/01/20 18:31:25 christos Exp $");
     38 #endif
     39 #endif /* LIBC_SCCS and not lint */
     40 
     41 #include "namespace.h"
     42 
     43 #include <assert.h>
     44 #include <errno.h>
     45 #include <stdlib.h>
     46 #include <string.h>
     47 #include <bitstring.h>
     48 
     49 #include "env.h"
     50 #include "local.h"
     51 
     52 /*
     53  * unsetenv(name) --
     54  *	Delete environmental variable "name".
     55  */
     56 int
     57 unsetenv(const char *name)
     58 {
     59 	size_t l_name;
     60 	ssize_t r_offset, w_offset;
     61 
     62 	_DIAGASSERT(name != NULL);
     63 
     64 	l_name = __envvarnamelen(name, false);
     65 	if (l_name == 0) {
     66 		errno = EINVAL;
     67 		return -1;
     68 	}
     69 
     70 	if (!__writelockenv())
     71 		return -1;
     72 
     73 	/* Search for the given name in the environment. */
     74 	r_offset = __getenvslot(name, l_name, false);
     75 	if (r_offset == -1) {
     76 		/* Not found. */
     77 		(void)__unlockenv();
     78 		return 0;
     79 	}
     80 	__freeenvvar(environ[r_offset]);
     81 
     82 	/*
     83 	 * Remove all matches from the environment and free the associated
     84 	 * memory if possible.
     85 	 */
     86 	w_offset = r_offset;
     87 	while (environ[++r_offset] != NULL) {
     88 		if (strncmp(environ[r_offset], name, l_name) != 0 ||
     89 		    environ[r_offset][l_name] != '=') {
     90 			/* Not a match, keep this entry. */
     91 			environ[w_offset++] = environ[r_offset];
     92 		} else {
     93 			/* We found another match. */
     94 			__freeenvvar(environ[r_offset]);
     95 		}
     96 	}
     97 
     98 	/* Clear out remaining stale entries in the environment vector. */
     99 	do {
    100 		environ[w_offset++] = NULL;
    101 	} while (w_offset < r_offset);
    102 
    103 	(void)__unlockenv();
    104 	return 0;
    105 }
    106