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getenv.c revision 1.13 
      1 /*	$NetBSD: getenv.c,v 1.13 1999/09/16 11:45:33 lukem 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. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *	This product includes software developed by the University of
     18  *	California, Berkeley and its contributors.
     19  * 4. Neither the name of the University nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  */
     35 
     36 #include <sys/cdefs.h>
     37 #if defined(LIBC_SCCS) && !defined(lint)
     38 #if 0
     39 static char sccsid[] = "@(#)getenv.c	8.1 (Berkeley) 6/4/93";
     40 #else
     41 __RCSID("$NetBSD: getenv.c,v 1.13 1999/09/16 11:45:33 lukem Exp $");
     42 #endif
     43 #endif /* LIBC_SCCS and not lint */
     44 
     45 #include <assert.h>
     46 #include <errno.h>
     47 #include <stdlib.h>
     48 #include <string.h>
     49 #include "local.h"
     50 #include "reentrant.h"
     51 
     52 #ifdef _REENT
     53 rwlock_t __environ_lock = RWLOCK_INITIALIZER;
     54 #endif
     55 
     56 /*
     57  * getenv --
     58  *	Returns ptr to value associated with name, if any, else NULL.
     59  */
     60 char *
     61 getenv(name)
     62 	const char *name;
     63 {
     64 	int offset;
     65 	char *result;
     66 
     67 	_DIAGASSERT(name != NULL);
     68 #ifdef _DIAGNOSTIC
     69 	if (name == NULL) {
     70 		errno = EFAULT;
     71 		return (NULL);
     72 	}
     73 #endif
     74 
     75 	rwlock_rdlock(&__environ_lock);
     76 	result = __findenv(name, &offset);
     77 	rwlock_unlock(&__environ_lock);
     78 	return (result);
     79 }
     80 
     81 /*
     82  * __findenv --
     83  *	Returns pointer to value associated with name, if any, else NULL.
     84  *	Sets offset to be the offset of the name/value combination in the
     85  *	environmental array, for use by setenv(3) and unsetenv(3).
     86  *	Explicitly removes '=' in argument name.
     87  *
     88  *	This routine *should* be a static; don't use it.
     89  */
     90 char *
     91 __findenv(name, offset)
     92 	const char *name;
     93 	int *offset;
     94 {
     95 	extern char **environ;
     96 	size_t len;
     97 	const char *np;
     98 	char **p, *c;
     99 
    100 	if (name == NULL || environ == NULL)
    101 		return (NULL);
    102 	for (np = name; *np && *np != '='; ++np)
    103 		continue;
    104 	len = np - name;
    105 	for (p = environ; (c = *p) != NULL; ++p)
    106 		if (strncmp(c, name, len) == 0 && c[len] == '=') {
    107 			*offset = p - environ;
    108 			return (c + len + 1);
    109 		}
    110 	return (NULL);
    111 }
    112