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getenv.c revision 1.18.26.1 
      1 /*	$NetBSD: getenv.c,v 1.18.26.1 2010/11/22 00:20:27 riz 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 1.18.26.1 2010/11/22 00:20:27 riz 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 	if (strchr(name, '=') != NULL)
     71 		return NULL;
     72 
     73 	rwlock_rdlock(&__environ_lock);
     74 	result = __findenv(name, &offset);
     75 	rwlock_unlock(&__environ_lock);
     76 	return result;
     77 }
     78 
     79 int
     80 getenv_r(const char *name, char *buf, size_t len)
     81 {
     82 	int offset;
     83 	char *result;
     84 	int rv = -1;
     85 
     86 	_DIAGASSERT(name != NULL);
     87 
     88 	if (strchr(name, '=') != NULL) {
     89 		errno = ENOENT;
     90 		return -1;
     91 	}
     92 
     93 	rwlock_rdlock(&__environ_lock);
     94 	result = __findenv(name, &offset);
     95 	if (result == NULL) {
     96 		errno = ENOENT;
     97 		goto out;
     98 	}
     99 	if (strlcpy(buf, result, len) >= len) {
    100 		errno = ERANGE;
    101 		goto out;
    102 	}
    103 	rv = 0;
    104 out:
    105 	rwlock_unlock(&__environ_lock);
    106 	return rv;
    107 }
    108 
    109 /*
    110  * __findenv --
    111  *	Returns pointer to value associated with name, if any, else NULL.
    112  *	Sets offset to be the offset of the name/value combination in the
    113  *	environmental array, for use by setenv(3) and unsetenv(3).
    114  *	Explicitly removes '=' in argument name.
    115  *
    116  *	This routine *should* be a static; don't use it.
    117  */
    118 char *
    119 __findenv(const char *name, int *offset)
    120 {
    121 	size_t len;
    122 	const char *np;
    123 	char **p, *c;
    124 
    125 	if (name == NULL || environ == NULL)
    126 		return NULL;
    127 	for (np = name; *np && *np != '='; ++np)
    128 		continue;
    129 	len = np - name;
    130 	for (p = environ; (c = *p) != NULL; ++p)
    131 		if (strncmp(c, name, len) == 0 && c[len] == '=') {
    132 			*offset = p - environ;
    133 			return c + len + 1;
    134 		}
    135 	return NULL;
    136 }
    137