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getenv.c revision 1.18 
      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 	return NULL;
    129 }
    130