lib/libc/stdlib/getenv.c

   1 /*      $NetBSD: getenv.c,v 1.18 2005/09/25 20:08:01 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[] = "@(#)getenv.c    8.1 (Berkeley) 6/4/93";
  36 #else
  37 __RCSID("$NetBSD: getenv.c,v 1.18 2005/09/25 20:08:01 christos Exp $");
  38 #endif
  39 #endif /* LIBC_SCCS and not lint */
  40
  41 #include "namespace.h"
  42 #include <assert.h>
  43 #include <errno.h>
  44 #include <stdlib.h>
  45 #include <string.h>
  46 #include "local.h"
  47 #include "reentrant.h"
  48
  49 #ifdef _REENTRANT
  50 rwlock_t __environ_lock = RWLOCK_INITIALIZER;
  51 #endif
  52 extern char **environ;
  53
  54 __weak_alias(getenv_r, _getenv_r)
  55
  56 /*
  57  * getenv --
  58  *      Returns ptr to value associated with name, if any, else NULL.
  59  *      XXX: we cannot use getenv_r to implement this, because getenv()
  60  *      cannot use a shared buffer, because if it did, subsequent calls
  61  *      to getenv would trash previous results.
  62  */
  63 char *
  64 getenv(const char *name)
  65 {
  66         int offset;
  67         char *result;
  68
  69         _DIAGASSERT(name != NULL);
  70
  71         rwlock_rdlock(&__environ_lock);
  72         result = __findenv(name, &offset);
  73         rwlock_unlock(&__environ_lock);
  74         return result;
  75 }
  76
  77 int
  78 getenv_r(const char *name, char *buf, size_t len)
  79 {
  80         int offset;
  81         char *result;
  82         int rv = -1;
  83
  84         _DIAGASSERT(name != NULL);
  85
  86         rwlock_rdlock(&__environ_lock);
  87         result = __findenv(name, &offset);
  88         if (result == NULL) {
  89                 errno = ENOENT;
  90                 goto out;
  91         }
  92         if (strlcpy(buf, result, len) >= len) {
  93                 errno = ERANGE;
  94                 goto out;
  95         }
  96         rv = 0;
  97 out:
  98         rwlock_unlock(&__environ_lock);
  99         return rv;
 100 }
 101
 102 /*
 103  * __findenv --
 104  *      Returns pointer to value associated with name, if any, else NULL.
 105  *      Sets offset to be the offset of the name/value combination in the
 106  *      environmental array, for use by setenv(3) and unsetenv(3).
 107  *      Explicitly removes '=' in argument name.
 108  *
 109  *      This routine *should* be a static; don't use it.
 110  */
 111 char *
 112 __findenv(const char *name, int *offset)
 113 {
 114         size_t len;
 115         const char *np;
 116         char **p, *c;
 117
 118         if (name == NULL || environ == NULL)
 119                 return NULL;
 120         for (np = name; *np && *np != '='; ++np)
 121                 continue;
 122         len = np - name;
 123         for (p = environ; (c = *p) != NULL; ++p)
 124                 if (strncmp(c, name, len) == 0 && c[len] == '=') {
 125                         *offset = p - environ;
 126                         return c + len + 1;
 127                 }
 128         *offset = p - environ;
 129         return NULL;
 130 }