为linux系统设计一个简单的二级文件系统-Linux system design for a simple two file system. Required to do the following:

(1) can be achieved following a few commands

read_file read the file

create_file create a file

　 create_dir create a directory

　del_file delete files

del_dir remove directory

　display_curdir displays the current directory list of files

display_dir into the specified directory

back_dir Back to a directory

display_sys show disk usage

copy_file copy files

move_file move files

rename_file Rename Files

append_file additional contents of the file

edit_file edit content of the document

remove_user Remove User

login Login

chomd Manage Users

add_user Add Users

see see user permissions

　(2) column directory to list the file name, physical address, protect code and file size

　(3) The source files can be read and write protection.