文件接口

  struct stat {  
	dev_t     st_dev;         /* ID of device containing file */  
	ino_t     st_ino;         /* Inode number */  
	mode_t    st_mode;        /* File type and mode */  
	nlink_t   st_nlink;       /* Number of hard links */  
	uid_t     st_uid;         /* User ID of owner */  
	gid_t     st_gid;         /* Group ID of owner */  
	dev_t     st_rdev;        /* Device ID (if special file) */  
	off_t     st_size;        /* Total size, in bytes */  
	blksize_t st_blksize;     /* Block size for filesystem I/O */  
	blkcnt_t  st_blocks;      /* Number of 512B blocks allocated */   
	struct timespec st_atim;  /* Time of last access (read) */  
	struct timespec st_mtim;  /* Time of last modification (write) */  
	struct timespec st_ctim;  /* Time of last status change (property change) */
};
//st_mode是一个16位的整形数, 1-3表示其他人权限4-6表示组权限7-9表示拥有者权限10-12表示特殊权限13-16表示文件类型

struct timespec {  
	__kernel_time_t tv_sec;   /* seconds */  
	long            tv_nsec;  /* nanoseconds */
}

//常用配合函数
struct passwd getpwuid(uid_t uid)			//
struct group getgrgid(gid_t  gid)			//
struct tm* localtime(const time_t* timep)	//可来处理st_atim.tv_sec
  

  int stat(					//成功返回0, 失败返回-1设置errno, stat参数是一个传出参数
	const char *pathname, 
	struct stat *statbuf). 
int chmod(
	const char *path, 
	mode_t mode)
int access(
	const char *path , 
	int mode)				//R_OK(判断读权限)\W_OK(判断写权限)\X_OK(判断执行权限)\F_OK(判断文件存在)

int mkfifo(					//创建fifo管道文件.针对fifo管道, 使用open打开时若只读或只写打开会阻塞, 直到另一个进程或线程打开对应的写或读
	const char *pathname, 
	mode_t mode)
  

   struct flock {  
  ...  
  short l_type;    /* Type of lock: F_RDLCK, F_WRLCK, F_UNLCK */  
  short l_whence;  /* How to interpret l_start: SEEK_SET, SEEK_CUR, SEEK_END */  
  off_t l_start;   /* Starting offset for lock */  
  off_t l_len;     /* Number of bytes to lock */  
  pid_t l_pid;     /* PID of process blocking our lock(set by F_GETLK and F_OFD_GETLK) */  
};
  

  int open(//打开一个文件, 返回一个最小可用的文件描述符
	const char* path, 
	int flag): 				//是一个int型位图, 其中O_RDONLY、O_WRONLY和O_RDWD必选其一
							//- O_RDONLY: 只读打开
							//- O_WRONLY: 只写打开
							//- O_RDWD: 读写打开
							//- O_APPEND: 打开时文件指针指向文件末尾
							//- O_CREAT: 打开时文件不存在则创建, O_EXCL补充打开时文件存在, 返回-1并设置errno
							//- NO_BLOCK: 非阻塞文件描述符

int fcntl(//获取或设置文件描述符的标志位(即open函数中使用的那个)
	int fd, 
	int cmd,...): 			//文件描述符	
							//- F_GETFLAG
							//- F_SETFLAG
							//- F_SETLG
  

  struct dirent {
	ino_t          d_ino;       /* Inode number 目录项ino编号*/
	off_t          d_off;       /* Not an offset; see below 目录项偏移*/
	unsigned short d_reclen;    /* Length of this record 目录项的大小*/
	unsigned char  d_type;      /* Type of file; not supported by all filesystem types */
	char           d_name[256]; /* Null-terminated filename 目录项名称*/
};
  

  int mkdir(							//创建目录, mkdir命令默认给的是0777&~umask权限
	const char *pathname, 
	mode_t mode)
DIR *opendir(const char *name)		//
struct dirent *readdir(DIR *dirp):	//返回一个目录项结构体指针, 目录结尾返回NULL, 或错误返回NULL并设置errno  
int closedir(DIR *dirp): 			//关闭目录流指针
rewindir(DIR *dirp): 				//目录流指针指向开头
telldir(DIR *dirp): 				//返回目录流指针位置
seekdir(DIR *dirp): 				//指定目录流指针