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From: mark@ems.UUCP (Mark H. Colburn)
Newsgroups: comp.unix.questions
Subject: Re: access(2) question
Message-ID: <348@ems.UUCP>
Date: Thu, 2-Jul-87 18:27:11 EDT
Article-I.D.: ems.348
Posted: Thu Jul  2 18:27:11 1987
Date-Received: Sat, 4-Jul-87 08:41:45 EDT
References: <530@applix.UUCP> <1341@xanth.UUCP> <1027@killer.UUCP>
Reply-To: mark@ems.UUCP (Mark H. Colburn)
Organization: EMS/McGraw-Hill, Eden Pairie, MN
Lines: 50
Keywords: access permissions


	After all the discussion about an access call that uses EFFECTIVE
	user ids rather than real, including my own two cents worth, here
	is a copy of code that was written by one of the people here to
	resolve the exact problem that we have been talking about.

	The routine is called access in order to overlay the system access
	call when it is linked into the system, so that tempnam and tmpnam
	work as I wanted them to for the project.

	The code is trivial, but I thought that some of you might be
	interested.

/*
 * McGraw-Hill Demo System, Version 2.0
 * 
 * access.c - determine accessibility of a file using "effective" user ID.
 *
 * Author: Andrew C. Esh, EMS/McGraw-Hill	06/23/86
 *
 * HISTORY
 * 
 */

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

unsigned short	getuid();

access (path, amode)
char	*path;
int	amode;
{
	struct	stat	buf;
	int		tempmode = 0;

	if (stat(path, &buf) == -1) {
		return(-1);
	}
	if (geteuid() == buf.st_uid)
		tempmode = (buf.st_mode & 0x01c0) >> 6;
	if (getegid() == buf.st_gid)
		tempmode |= (buf.st_mode & 0x038) >> 3;
	tempmode |= buf.st_mode & 0x07;
	if ((amode & tempmode) != amode) {
		return(-1);
	}
	return(0);
}