写一个脚本文件checkuser,该脚本运行时带一个用户名作为参数，具体要求如下：

1)如果命令行格式不符合要求，应有错误提示信息；

2)在/etc/passwd文件中查找是否有该用户，

如有，则输出“Found <user> in the /etc/passwd file.”

否则，输出“No such <user> on our system”

-Write a scr ipt file checkuser, the scr ipt run-time with a user name as a parameter, and specific requirements are as follows: 1) If the command-line format does not meet the requirements, there should be error message　2) in/etc/passwd file to check if there were any users, and if so, then the output " Found <user> in the/etc/passwd file. " Otherwise, output"　No such <user> on our system "