在Linux系统的/etc目录下有这样一个文件passwd，该文件里包含系统中所有用户信息的记录，记录里包含每个用户的如下信息：用户名、密码、用户ID、组ID、用户全名、用户主目录和用户登录所用的shell。请设计一个脚本（shell）程序能实现增加、删除、查找和显示特定用户信息的功能。你们可以通过创建一些UNIX/LINUX shell 脚本文件来满足以上需求。-In the Linux system,/etc directory there is such a file passwd, this file contains all the user information system, records, record where each user that contains the following information: user name, password, user ID, group ID, user' s full name , the user' s home directory and the user logged in with the shell. Please design a scr ipt (shell) program enables to add, delete, search and display information on a specific user function. You can by creating a number of UNIX/LINUX shell scr ipt file to meet the above requirements.