#include <sys/types.h>

 #include <stdio.h>

 #include <unistd.h>

 #include <fcntl.h>

 #include <string.h>

 #include <stdlib.h>

 int main()

 {

     pid_t pid;

     int fd;//文件描述符

     int i=;

     int status;

     char *ch1 = "nihao";

     char *ch2 = "china";

     char *ch3 = "yes";

     if((fd=open("test.txt",O_RDWR|O_CREAT,))==-)//不存在就创建

     {

         perror("parent open");

         exit(EXIT_FAILURE);

     }

     //父进程向文件写入数据

     if(write(fd,ch1,strlen(ch1))==-)

     {

         perror("parent open");

         exit(EXIT_FAILURE);

     }

     //创建新进程

     if((pid=fork())==-)

     {

         perror("fock");

         exit(EXIT_FAILURE);

     }

     else if(pid==)

     {

         i=;

         printf("in child\n");//打印i的值 以与父进程进行区别

         printf("i=%d\n",i);

         if(write(fd,ch2,strlen(ch2))==-)//写文件 与父进程共享

         {

             perror("child write");

             return ;

         }

     }else

         {

             sleep();//等待子进程先完成

             printf("in parent\n");

             printf("i=%d\n",i);

             if(write(fd,ch3,sizeof(ch3))==-)

             {

                 perror("parent,write");

             }

             wait(&status);

             return ;

         }

     return ;

 }