进程挂起函数pause

探讨一下pause函数的用法： 1 #include<stdio.h>
 2 #include<signal.h>
 3 #include<unistd.h>
 4 void signhand(int signo)
 5 {
 6         int i;
 7         for(i=0;i<10;i++)
 8         {
 9                 printf("signhand number is %d\n",i);
10                 sleep(1);
11         }
12 }
13 int main()
14 {
15         int i;
16         signal(SIGALRM,signhand);
17         alarm(3);
18         pause();  //进程挂起
19         for(i=0;i<10;i++)
20         {
21                 printf("main number is %d\n",i);
22                 sleep(1);
23         }
24         return 0;
25 }

程序运行结果：(其实程序是执行到pause后等待信号的触发，信号触发后，执行信号函数，执行信号函数完毕后，返回主函数继续执行！)

signhand number is 0
signhand number is 1
signhand number is 2
signhand number is 3
signhand number is 4
signhand number is 5
signhand number is 6
signhand number is 7
signhand number is 8
signhand number is 9
main number is 0
main number is 1
main number is 2
main number is 3
main number is 4
main number is 5
main number is 6
main number is 7
main number is 8
main number is 9

再看一个牛X的程序：我们设置在10s后，进程向自身发送SIGALRM信号

 1 #include<stdio.h>
 2 #include<signal.h>
 3 #include<unistd.h>
 4 void signhand(int signo)
 5 {
 6         int i;
 7         for(i=0;i<5;i++)
 8         {
 9                 printf("signhand number is %d\n",i);
10                 sleep(1);
11         }
12 }
13 int main()
14 {
15         int i;
16         signal(SIGALRM,signhand);
17         alarm(10);
18         for(i=0;i<5;i++)
19         {
20                 printf("main number is %d\n",i);
21                 sleep(1);
22         }
23         return 0;
24 }

该程序的运行结果如下：

1 main number is 0
2 main number is 1
3 main number is 2
4 main number is 3
5 main number is 4

可以看到该函数没有触发信号函数的，在主函数运行过程中根本没有信号的相关操作！