实验3

#include <stdio.h>

#include <stdlib.h>

#include <sys/types.h>

#include <unistd.h>

#include <sys/wait.h>

int main(void)

{

int child1, child2, child;

//创建子进程1

child1 = fork();

if(child1 == -1){//子进程1的出错处理

printf("Child1 fork error\n");

exit(1);

}  

else if(child1 == 0) //fork创建进程返回值为0说明现在是子进程

{

printf("In child1: execute 'ls-l'\n");

if(execlp("ls", "ls","-l", NULL) < 0) //该函数的最后一个参数必须为NULL

{

printf("Child1 execlp error\n");

}

}  

else{

child2 = fork();//在父进程中创建子进程2，然后等待两个子进程的退出

if (child2 == -1){//子进程2的出错处理

printf("Child2 fork error\n");

exit(1);

}

else if(child2 == 0){//在子进程2中使其暂停5s

printf("In child2: sleep for 5seconds and then exit\n");

sleep(5);

exit(0);

}

printf("In father process:\n");

child = waitpid(child1, NULL, 0); /* 阻塞式等待 */

if (child == child1){

printf("Get child1 exitcode\n");

}

else{

printf("Error occured!\n");

}

do{

child = waitpid(child2, NULL, WNOHANG);/* 非阻塞式等待 */

if (child == 0){ //由于子进程2未结束，waitpid()不阻塞而立即返回0，若结束，则返回子进程2的pid：child2，waitpid阻塞

printf("The child2 process has notexited!\n");

sleep(1);

}

} while (child == 0);

if(child == child2){

printf("Get child2 exitcode\n");

}

else{

printf("Error occured!\n");

}

}

exit(0);

}

quot;child1 noticed that child2 has exited");

 

     closelog();//关闭日志服务

     while(1)

     {

        sleep(10);

     }

   }

}