完成ls的如下功能

不带参数的ls：列出当前目录下的非隐藏（文件和目录名不以.开头）的文件和目录

ls -a：列出当前目录下的所有文件和目录

ls -l：以长列表形式列出当前目录下的非隐藏的文件和目录。每个文件或目录只要求列出如下信息：类型与权限、文件名、链接数、用户ID、组ID、字节大小、块数

ls 路径名：如果路径名代表一个存在的文件则显示该文件，否则提示出错；如果路径名字代表一个存在的目录则列出该目录中的文件

列出文件名和目录名时，要求可执行文件最后加上一个*号，目录名最后加上一个/号。

所提供的路径名可以包含“.”，“..”，“~”等特殊目录-completion of the following non-functional parameters of ls : listed in the current directory-hidden (files and directories were not. Beginning) of files and directories ls-a : listed in the current directory of all files and directories ls-l : in the long list of current directory listed under the non-hidden possession of files and directories. Each file or directory only asked to list the following information : the type and competence, file name, number of links, the user ID and group ID, byte size, a few blocks ls path : If a path representatives of the document showed documents suggest otherwise error; If representatives of a path name the presence of the directory lists the directory lists the file name and directory name, asked executable file with a * Finally, the last name of the