1》打开目录 opendir

        #include <sys/types.h>

        #include <dirent.h>

        DIR *opendir(const char *name);

        形参：name：要打开的目录的路径/名字

        返回值：成功DIR *类型的目录流指针

        失败：返回NULL

2》关闭目录  closedir

        #include <sys/types.h>

        #include <dirent.h>

        int closedir(DIR *dirp);

        形参：opendir的返回值

        返回值：returns 0 on success.On error, -1 is returned

3》readdir -- 读取目录信息

        #include <dirent.h>

        struct dirent *readdir(DIR *dirp);

        形参：dirp：opendir打开获取到的目录流指针

        返回值：

        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 [255]; /* file name (null-terminated) 文件名，最长255字符 */

        }