后面的代码模拟二级目录结构的文件系统。用户可以创建文件、打开文件、关闭文件、删除文件、读文件、写文件、查询用户目录。设置有主文件目录和用户文件目录。每个用户一个主文件目录，每个用户可以创建多个用户文件。-The code behind the simulation of the secondary file system directory structure. Users can create files, open files, close files, delete files, read files, write files, query the user directory. Setting a master file directory and user directory. A master file directory for each user, each user can create multiple user profiles.