lib/libc/stdlib/unsetenv.c

   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 }