5 如何获取文件系统目录下文件名

ls的源代码如下，不需要看懂，只需要直接调用，不就可以打印目录下的所有文件了吗？

void ls(const char *pathname)
{
    struct stat stat;
    int length;
    char *fullpath, *path;

    fullpath = NULL;
    if (pathname == NULL)
    {
#ifdef DFS_USING_WORKDIR
        /* open current working directory */
        path = rt_strdup(working_directory);
#else
        path = rt_strdup("/");
#endif
        if (path == NULL)
            return ; /* out of memory */
    }
    else
    {
        path = (char *)pathname;
    }

    /* list directory */
    if (dfs_file_open(&fd, path, O_DIRECTORY) == 0)
    {
        rt_kprintf("Directory %s:\n", path);
        do
        {
            memset(&dirent, 0, sizeof(struct dirent));
            length = dfs_file_getdents(&fd, &dirent, sizeof(struct dirent));
            if (length > 0)
            {
                memset(&stat, 0, sizeof(struct stat));

                /* build full path for each file */
                fullpath = dfs_normalize_path(path, dirent.d_name);
                if (fullpath == NULL)
                    break;

                if (dfs_file_stat(fullpath, &stat) == 0)
                {
                    rt_kprintf("%-20s", dirent.d_name);
                    if (S_ISDIR(stat.st_mode))
                    {
                        rt_kprintf("%-25s\n", "<DIR>");
                    }
                    else
                    {
                        rt_kprintf("%-25lu\n", stat.st_size);
                    }
                }
                else
                    rt_kprintf("BAD file: %s\n", dirent.d_name);
                rt_free(fullpath);
            }
        }
        while (length > 0);

        dfs_file_close(&fd);
    }
    else
    {
        rt_kprintf("No such directory\n");
    }
    if (pathname == NULL)
        rt_free(path);
}