waitpid传入参数

 1 #include<stdio.h>
 2 #include<stdlib.h>
 3 #include<unistd.h>
 4 int main()
 5 {
 6     pid_t pid,pr;
 7     pid =fork();
 8     int status;
 9     if(pid<0)
10     {
11         printf("Fork failed!\n");
12         exit(1);
13     }
14     else if(pid==0)
15     {
16         printf("This child process with pid of %d.\n",getpid());
17         exit(3);
18     }
19     else
20     {
21         do{
22             pr=waitpid(pid,&status,WNOHANG);//如果子进程没有结束，那么父进程中的pr=0l;如果子进程结束，那么父进程中的pr值等于子进程的pid
23             if(pr==0)
24             {
25                 printf("No child exited!\n");
26                 sleep(1);
27             }
28         }while(pr==0);
29
30         if(pr==pid)
31         {
32
33             if(WIFEXITED(status))
34             {
35                 printf("The child process success %d\n%d\n",pr,WEXITSTATUS(status));
36             }
37             else
38             {
39                 printf("ERROR!\n");
40             }
41         }
42         else
43         {
44             printf("Error!\n");
45         }
46
47     return 0;
48     }
49
50 }

程序运行结果：

1 No child exited!
2 This child process with pid of 7333.
3 The child process success 7333
4 3