关于ADDRESSBOOK 的编程，实现了通过ls，cd等操作对addressbook的增加，修改，查看-About ADDRESSBOOK programming, realized through the ls, cd addressbook and other operations on the increase, modify, view

创建一个进程，由子进程调用命令 ls，父进程等待子进程结束后退出，并以特定方式显示输出。-Create a process, called by the sub-process command ls, the parent process to wait for the end of child process exit, and display a particular way.

创建一个进程，由子进程调用命令 ls，父进程等待子进程结束后退出，并以特定方式显示输出。-Create a process, called by the sub-process command ls, the parent process to wait for the end of child process exit, and display a particular way.