getenv.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

/*
 * Copyright (c) 1987 Regents of the University of California.
 * This file may be freely redistributed provided that this
 * notice remains attached.
 */

#ifndef lint
static	char	*sccsid = "@(#)getenv.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 <stdio.h>

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

	return(_findenv(name,&offset));
}

/*
 * _findenv(name,offset) --
 *	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)
	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);
}