struct dirent
{
    long d_ino;                 /* inode number 索引節(jié)點(diǎn)號 */
    off_t d_off;                /* offset to this dirent 在目錄文件中的偏移 */
    unsigned short d_reclen;    /* length of this d_name 文件名長 */
    unsigned char d_type;        /* the type of d_name 文件類型 */   
    char d_name [NAME_MAX+1];   /* file name (null-terminated) 文件名，最長255字符 */
}

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;

#include <sys/types.h>
#include <dirent.h>
#include <unistd.h>
#include <stdio.h>

int main(){
    DIR    *dir;
    struct    dirent    *ptr;
    dir = opendir("."); ///open the dir

    while((ptr = readdir(dir)) != NULL) ///read the list of this dir
    {
        #ifdef _WIN32
            printf("d_name: %s\n", ptr->d_name);
        #endif
        #ifdef __linux
            printf("d_type:%d d_name: %s\n", ptr->d_type,ptr->d_name);
        #endif
    }
    closedir(dir);
    return 0;
}