lib/libc/stdlib/unsetenv.c

   1 /*      $NetBSD: unsetenv.c,v 1.10 2010/11/14 18:11:43 tron 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 1.10 2010/11/14 18:11:43 tron 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 "reentrant.h"
  51 #include "local.h"
  52
  53 /*
  54  * unsetenv(name) --
  55  *      Delete environmental variable "name".
  56  */
  57 int
  58 unsetenv(const char *name)
  59 {
  60         size_t l_name;
  61         ssize_t r_offset, w_offset;
  62
  63         _DIAGASSERT(name != NULL);
  64
  65         l_name = __envvarnamelen(name, false);
  66         if (l_name == 0) {
  67                 errno = EINVAL;
  68                 return -1;
  69         }
  70
  71         if (!__writelockenv())
  72                 return -1;
  73
  74         /* Search for the given name in the environment. */
  75         r_offset = __getenvslot(name, l_name, false);
  76         if (r_offset == -1) {
  77                 /* Not found. */
  78                 (void)__unlockenv();
  79                 return 0;
  80         }
  81         __freeenvvar(environ[r_offset]);
  82
  83         /*
  84          * Remove all matches from the environment and free the associated
  85          * memory if possible.
  86          */
  87         w_offset = r_offset;
  88         while (environ[++r_offset] != NULL) {
  89                 if (strncmp(environ[r_offset], name, l_name) != 0 ||
  90                     environ[r_offset][l_name] != '=') {
  91                         /* Not a match, keep this entry. */
  92                         environ[w_offset++] = environ[r_offset];
  93                 } else {
  94                         /* We found another match. */
  95                         __freeenvvar(environ[r_offset]);
  96                 }
  97         }
  98
  99         /* Clear out remaining stale entries in the environment vector. */
 100         do {
 101                 environ[w_offset++] = NULL;
 102         } while (w_offset < r_offset);
 103
 104         (void)__unlockenv();
 105         return 0;
 106 }