实验4 信号处理（20分）

目的：

学习和掌握信号的处理方法，特别是sigaction，alarm，sigpending，sigsetjmp和siglongjmp等函数的使用。



要求：

1、编制具有简单执行时间限制功能的shell：

　　　　　　myshell [ -t <time> ]

这个测试程序的功能类似实验1，但是具有系统shell (在cs8服务器上是bash)的全部功能。<time>是测试程序允许用户命令执行的时间限制，默认值为无限制。当用户命令的执行时间限制到达时，测试程序终止用户命令的执行，转而接收下一个用户命令。

2、myshell只在前台运行。

3、按Ctrl-\键不是中断myshell程序的运行，而是中断当前用户命令的接收或终止当前用户命令的执行，转而接收下一个用户命令。

4、注意信号SIGALRM和SIGQUIT之间嵌套关系的处理。

-Signal Processing Experiment 4 (20 points)

purpose:

Learning and mastering signal processing methods, particularly the use of sigaction, alarm, sigpending, sigsetjmp and siglongjmp and other functions.



Claim:

1, the preparation of the execution time limit with a simple function of shell:

myshell [-t <time>]

This functional test procedures similar to Experiment 1, but with the system shell (on cs8 server is bash) for full functionality. <time> is the test program allows users to command execution time limit, the default value is unlimited. When the user commands the execution time limit is reached, test the program terminates user commands instead receive the next user command.

2, myshell only run in the foreground.

3. Press Ctrl- \ key is not interrupted run myshell program, but the current interruption receiving user commands or terminate execution of the current user commands instead receive the next user command.

4, deal with the relationship between nested at