apue初学--DIR

dir=opendir(dir_buf);
ptr=readdir(dir);//ptr为一个结构体 dirent
closedir(dir);
 
1.存储目录中的文件信息（文件名、扩展名等等）
#include <dirent.h>
struct dirent
{
   long d_ino; /inode number 索引节点号 
   off_t d_off; / offset to this dirent 在目录文件中的偏移
   unsigned short d_reclen;  /length of this d_name 文件名长
   unsigned char d_type; / the type of d_name 文件类型 
   char d_name [NAME_MAX+1]; /file name (null-terminated) 文件名，最长255字符 }

2.
struct __dirstream
   {
void *__fd; / `struct hurd_fd' pointer for descriptor.  
char *__data; / Directory block.  
int __entry_data; /Entry number `__data' corresponds to.  
char *__ptr; / Current pointer into the block.  
int __entry_ptr; /Entry number `__ptr' corresponds to.  
size_t __allocation; / Space allocated for the block.  
size_t __size; / Total valid data in the block.  
__libc_lock_define (, __lock) / Mutex lock for this structure.   
   };

typedef struct __dirstream DIR