setenv.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

/*
 * Copyright (c) 1987 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */

#ifndef lint
static	char	*sccsid = "@(#)setenv.c	4.1	(ULTRIX)	7/3/90";
#endif lint

/************************************************************************
 *									*
 *			Copyright (c) 1984,86 by			*
 *		Digital Equipment Corporation, Maynard, MA		*
 *			All rights reserved.				*
 *									*
 *   This software is furnished under a license and may be used and	*
 *   copied  only  in accordance with the terms of such license and	*
 *   with the  inclusion  of  the  above  copyright  notice.   This	*
 *   software  or  any  other copies thereof may not be provided or	*
 *   otherwise made available to any other person.  No title to and	*
 *   ownership of the software is hereby transferred.			*
 *									*
 *   This software is  derived  from  software  received  from  the	*
 *   University    of   California,   Berkeley,   and   from   Bell	*
 *   Laboratories.  Use, duplication, or disclosure is  subject  to	*
 *   restrictions  under  license  agreements  with  University  of	*
 *   California and with AT&T.						*
 *									*
 *   The information in this software is subject to change  without	*
 *   notice  and should not be construed as a commitment by Digital	*
 *   Equipment Corporation.						*
 *									*
 *   Digital assumes no responsibility for the use  or  reliability	*
 *   of its software on equipment which is not supplied by Digital.	*
 *									*
 ************************************************************************/
/************************************************************************
 *			Modification History				*
 ************************************************************************/
/*
 *	Jon Reeves, 1989-Sept-15
 *	Changed environ to __environ for ANSI compliance
 */

#include <sys/types.h>
#include <stdio.h>

/*
 * setenv(name,value,rewrite)
 *	Set the value of the environmental variable "name" to be
 *	"value".  If rewrite is set, replace any current value.
 */
setenv(name,value,rewrite)
	register char	*name,
			*value;
	int	rewrite;
{
	extern char	**__environ;
	static int	alloced;		/* if allocated space before */
	register char	*C;
	int	l_value,
		offset;
	char	*malloc(), *realloc(), *_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,
			    (u_int)(sizeof(char *) * (cnt + 2)));
			if (!__environ)
				return(-1);
		}
		else {				/* get new space */
			alloced = 1;		/* copy old entries into it */
			P = (char **)malloc((u_int)(sizeof(char *) *
			    (cnt + 2)));
			if (!P)
				return(-1);
			bcopy(__environ,P,cnt * sizeof(char *));
			__environ = P;
		}
		__environ[cnt + 1] = NULL;
		offset = cnt;
	}
	for (C = name;*C && *C != '=';++C);	/* no `=' in name */
	if (!(__environ[offset] =			/* name + `=' + value */
	    malloc((u_int)((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)
	char	*name;
{
	extern	char	**__environ;
	register char	**P;
	int	offset;

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