setenv.c

/*
 * Copyright (c) 1987 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. 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.
 */

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#ifndef HAVE_SETENV

#if defined(LIBC_SCCS) && !defined(lint)
/*static char *sccsid = "from: @(#)setenv.c	5.6 (Berkeley) 6/4/91";*/
static char *rcsid = "$Id: setenv.c,v 1.5 1996/09/04 22:10:42 sjg Exp $";
#endif /* LIBC_SCCS and not lint */

#include <stddef.h>
#include <stdlib.h>
#include <string.h>

/*
 * __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.
 */
static char *
__findenv(name, offset)
	register char *name;
	int *offset;
{
	extern char **environ;
	register int len;
	register char **P, *C;

	for (C = name, len = 0; *C && *C != '='; ++C, ++len);
	for (P = environ; *P; ++P)
		if (!strncmp(*P, name, len))
			if (*(C = *P + len) == '=') {
				*offset = P - environ;
				return(++C);
			}
	return(NULL);
}

/*
 * setenv --
 *	Set the value of the environmental variable "name" to be
 *	"value".  If rewrite is set, replace any current value.
 */
setenv(name, value, rewrite)
	register const char *name;
	register const char *value;
	int rewrite;
{
	extern char **environ;
	static int alloced;			/* if allocated space before */
	register char *C;
	int l_value, offset;
	char *__findenv();

	if (*value == '=')			/* no `=' in value */
		++value;
	l_value = strlen(value);
	if ((C = __findenv(name, &offset))) {	/* find if already exists */
		if (!rewrite)
			return (0);
		if (strlen(C) >= l_value) {	/* old larger; copy over */
			while (*C++ = *value++);
			return (0);
		}
	} else {					/* create new slot */
		register int	cnt;
		register char	**P;

		for (P = environ, cnt = 0; *P; ++P, ++cnt);
		if (alloced) {			/* just increase size */
			environ = (char **)realloc((char *)environ,
			    (size_t)(sizeof(char *) * (cnt + 2)));
			if (!environ)
				return (-1);
		}
		else {				/* get new space */
			alloced = 1;		/* copy old entries into it */
			P = (char **)malloc((size_t)(sizeof(char *) *
			    (cnt + 2)));
			if (!P)
				return (-1);
			bcopy(environ, P, cnt * sizeof(char *));
			environ = P;
		}
		environ[cnt + 1] = NULL;
		offset = cnt;
	}
	for (C = (char *)name; *C && *C != '='; ++C);	/* no `=' in name */
	if (!(environ[offset] =			/* name + `=' + value */
	    malloc((size_t)((int)(C - name) + l_value + 2))))
		return (-1);
	for (C = environ[offset]; (*C = *name++) && *C != '='; ++C)
		;
	for (*C++ = '='; *C++ = *value++; )
		;
	return (0);
}

/*
 * unsetenv(name) --
 *	Delete environmental variable "name".
 */
void
unsetenv(name)
	const char	*name;
{
	extern char **environ;
	register char **P;
	int offset;
	char *__findenv();

	while (__findenv(name, &offset))		/* if set multiple times */
		for (P = &environ[offset];; ++P)
			if (!(*P = *(P + 1)))
				break;
}
#endif