xref: /xsrc/external/mit/xedit/dist/lisp/getenv.c

/*	$OpenBSD: getenv.c,v 1.10 2010/08/23 22:31:50 millert 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 <stdlib.h>
#include <string.h>

char *__findenv(const char *name, int len, int *offset);

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

	if (name == NULL || environ == NULL)
		return (NULL);
	for (p = environ + *offset; (cp = *p) != NULL; ++p) {
		for (np = name, i = len; i && *cp; i--)
			if (*cp++ != *np++)
				break;
		if (i == 0 && *cp++ == '=') {
			*offset = p - environ;
			return (cp);
		}
	}
	return (NULL);
}

/*
 * getenv --
 *	Returns ptr to value associated with name, if any, else NULL.
 */
char *
getenv(const char *name)
{
	int offset = 0;
	const char *np;

	for (np = name; *np && *np != '='; ++np)
		;
	return (__findenv(name, (int)(np - name), &offset));
}