利用映射的关系实现父子进程间的通信，子进程可以映射，为什么父进程映射失败了？

#include
#include
#include
#include
#include
#include
#include

int main()
{
char buf[5]={'0'};
int fd=open("hello.c",O_RDWR|O_CREAT,0666);
if(fd<0)
{
printf("open is erroe\r\n");
return -1;

}
write(fd,buf,5);


pid_t pid = fork();//建立子进程
if(pid < 0)
{

    printf("fork is error\r\n");
    return -1;
}else if(pid ==0)//child
{
    sleep(1);
    char * p = mmap(NULL,5, PROT_READ| PROT_WRITE , MAP_SHARED,fd,0);
    if(p == (char *)-1)
    {
    printf(" child mmap is error\r\n");
    return -1;
    }


    printf("This is child \r\n");
    puts(p);    
   //取消映射
    munmap(p,5);

}else{
char * p = mmap(NULL,5,PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED,fd,0);    
if(p == (char *)-1);
{
    printf(" father mmap is error\r\n");
    return -1;
}
 mencpy(p,"hello",5);

}

return 0;

}

被吃掉的头文件........
#include
#include
#include
#include
#include
#include
#include