xref: /src/lib/libc/stdlib/getenv.c

/*	$NetBSD: getenv.c,v 1.17 2003/08/07 16:43:39 agc Exp $	*/

/*
 * Copyright (c) 1987, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)getenv.c	8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: getenv.c,v 1.17 2003/08/07 16:43:39 agc Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include "local.h"
#include "reentrant.h"

#ifdef _REENTRANT
rwlock_t __environ_lock = RWLOCK_INITIALIZER;
#endif
extern char **environ;

/*
 * getenv --
 *	Returns ptr to value associated with name, if any, else NULL.
 */
char *
getenv(name)
	const char *name;
{
	int offset;
	char *result;

	_DIAGASSERT(name != NULL);

	rwlock_rdlock(&__environ_lock);
	result = __findenv(name, &offset);
	rwlock_unlock(&__environ_lock);
	return (result);
}

/*
 * __findenv --
 *	Returns pointer to value associated with name, if any, else NULL.
 *	Sets offset to be the offset of the name/value combination in the
 *	environmental array, for use by setenv(3) and unsetenv(3).
 *	Explicitly removes '=' in argument name.
 *
 *	This routine *should* be a static; don't use it.
 */
char *
__findenv(name, offset)
	const char *name;
	int *offset;
{
	size_t len;
	const char *np;
	char **p, *c;

	if (name == NULL || environ == NULL)
		return (NULL);
	for (np = name; *np && *np != '='; ++np)
		continue;
	len = np - name;
	for (p = environ; (c = *p) != NULL; ++p)
		if (strncmp(c, name, len) == 0 && c[len] == '=') {
			*offset = p - environ;
			return (c + len + 1);
		}
	return (NULL);
}