shell

说明：  实验一利用课本第9页程序1-5的框架，实现允许输入命令带参数的简单shell。原来的实现是不能够带参数的。输入命令所能带的参数个数，只受到系统键盘输入缓冲区长度（以及shell输入缓冲区长度）的限制，该缓冲区的缺省长度是4096个字节。
(Experiments using the framework of textbooks 9 program 1-5, simple shell allows the input command with parameters. The original implementation can not take parameters. Enter the command with the number of parameters can only be subject to the limitations of the system keyboard input buffer length (and the shell length of the input buffer), the default length of the buffer is 4096 bytes....)