说明：  本实验是setitimer定时器实验。Linux下经常使用的定时器函数有两种：alarm和setitimer。如果定时要求不是非常精确的话，用alarm( )和signal( )配合就足够了。如果定时要求精确的话，可以使用setitimer函数。 开发环境 Redhat9.0
(This experiment is setitimer timer experiment. Often used under Linux, there are two timer functions: alarm and setitimer. If you are not very precise timing requirements, then use the alarm () and signal () with sufficient. If the precise timing requirements, you can use the setitimer function. Redhat9.0 Development Environment)