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getenv.c revision 1.17 
      1 /*	$NetBSD: getenv.c,v 1.17 2003/08/07 16:43:39 agc 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 1.17 2003/08/07 16:43:39 agc Exp $");
     38 #endif
     39 #endif /* LIBC_SCCS and not lint */
     40 
     41 #include <assert.h>
     42 #include <errno.h>
     43 #include <stdlib.h>
     44 #include <string.h>
     45 #include "local.h"
     46 #include "reentrant.h"
     47 
     48 #ifdef _REENTRANT
     49 rwlock_t __environ_lock = RWLOCK_INITIALIZER;
     50 #endif
     51 extern char **environ;
     52 
     53 /*
     54  * getenv --
     55  *	Returns ptr to value associated with name, if any, else NULL.
     56  */
     57 char *
     58 getenv(name)
     59 	const char *name;
     60 {
     61 	int offset;
     62 	char *result;
     63 
     64 	_DIAGASSERT(name != NULL);
     65 
     66 	rwlock_rdlock(&__environ_lock);
     67 	result = __findenv(name, &offset);
     68 	rwlock_unlock(&__environ_lock);
     69 	return (result);
     70 }
     71 
     72 /*
     73  * __findenv --
     74  *	Returns pointer to value associated with name, if any, else NULL.
     75  *	Sets offset to be the offset of the name/value combination in the
     76  *	environmental array, for use by setenv(3) and unsetenv(3).
     77  *	Explicitly removes '=' in argument name.
     78  *
     79  *	This routine *should* be a static; don't use it.
     80  */
     81 char *
     82 __findenv(name, offset)
     83 	const char *name;
     84 	int *offset;
     85 {
     86 	size_t len;
     87 	const char *np;
     88 	char **p, *c;
     89 
     90 	if (name == NULL || environ == NULL)
     91 		return (NULL);
     92 	for (np = name; *np && *np != '='; ++np)
     93 		continue;
     94 	len = np - name;
     95 	for (p = environ; (c = *p) != NULL; ++p)
     96 		if (strncmp(c, name, len) == 0 && c[len] == '=') {
     97 			*offset = p - environ;
     98 			return (c + len + 1);
     99 		}
    100 	return (NULL);
    101 }
    102