思维导图：

1.使用父子进程实现一个图片的拷贝

要求父进程拷贝前一部分

子进程拷贝后一部分

使用diff查看两个文件是否相同

#include <head.h>
int main(int argc, const char *argv[])
{
	int fd1=open("/home/ubuntu/3.6/xiaoxin.bmp",O_RDONLY);
	int fd2=open("/home/ubuntu/3.6/cp.bmp",O_WRONLY | O_CREAT | O_TRUNC,0644);
	struct stat st;
	if(stat("/home/ubuntu/3.6/xiaoxin.bmp",&st)==-1)
	{
		PRINT_ERROR("stat error");
	}
	if(fd1==0||fd2==0)
		PRINT_ERROR("open error");
	//获取文件大小
	off_t size=st.st_size;
	off_t half=size/2;
	pid_t pid=fork();
	if(pid>0)
	{
		char *buf=malloc(half);
		read(fd1,buf,half);
		write(fd2,buf,half);
		free(buf);
		close(fd2);
		wait(NULL);
		printf("parent done\n");
	}
	else if(pid==0)
	{
		char *buf=malloc(size-half);
		lseek(fd1,half,SEEK_SET);
		lseek(fd2,half,SEEK_SET);
		read(fd1,buf,size-half);
		write(fd2,buf,size-half);
		free(buf);
		close(fd1);
		close(fd2);
		printf("child done\n");
	}
	
	return 0;
}