access.h

Linux 的最重要的特徵之一是它的为许多不同的文件系统的支持。这使其非常灵活从而与许多另外的操作系统可以很好的共存。linux采用的是树型结构。最上层是根目录

#include <stdio.h>
#include "structure.h"

unsigned int access(user_id,inode,mode)
unsigned int user_id;
struct inode *inode;
unsigned short mode;
{
	switch(mode)
	{
	case READ:
		if(inode->di_mode&ODIREAD) return 1;
		if((inode->di_mode&GDIREAD)&&
			(user[user_id].u_gid==inode->di_gid)) return 1;
		if((inode->di_mode&UDIREAD)&&
			(user[user_id].u_uid==inode->di_uid)) return 1;
		return 0;
	case WRITE:
		if(inode->di_mode&ODIWRITE) return 1;
		if((inode->di_mode&GDIWRITE)&&
			(user[user_id].u_gid==inode->di_gid)) return 1;
		if((inode->di_mode&UDIWRITE)&&
			(user[user_id].u_uid==inode->di_uid)) return 1;
		return 0;
	case EXICUTE:
		if(inode->di_mode&ODIEXICUTE) return 1;
		if((inode->di_mode&GDIEXICUTE)&&
			(user[user_id].u_gid==inode->di_gid)) return 1;
		if((inode->di_mode&UDIEXICUTE)&&
			(user[user_id].u_uid==inode->di_uid)) return 1;
		return 0;
default:
		return 1;
	}
}