libc/stdlib/setenv.c

/*	$OpenBSD: setenv.c,v 1.9 2005/08/08 08:05:37 espie Exp $ */
/*
 * 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. 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 *offset);

extern char **environ;

/*
 * setenv --
 *	Set the value of the environmental variable "name" to be
 *	"value".  If rewrite is set, replace any current value.
 */
int
setenv(const char *name, const char *value, int rewrite)
{
	static char **lastenv;			/* last value of environ */
	char *C;
	int l_value, offset;

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

		for (P = environ; *P != NULL; P++)
			;
		cnt = P - environ;
        P = (char **)realloc(lastenv, sizeof(char *) * (cnt + 2));
		if (!P)
			return (-1);
		if (lastenv != environ)
			memcpy(P, environ, cnt * sizeof(char *));
		lastenv = environ = P;
		offset = cnt;
		environ[cnt + 1] = NULL;
	}
	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".
 */
int
unsetenv(const char *name)
{
	char **P;
	int offset;

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

        return 0;
}