day3 2/20

1> 使用多进程完成两个文件的拷贝，父进程拷贝前一半，子进程拷贝后一半，父进程回收子进程的资源

#include<myhead.h>
int main(int argc, const char *argv[])
{
	int fd1=-1,fd2=-1;
	if((fd1=open("./ggb.bmp",O_RDONLY,0664))==-1)
	{
		perror("open error");
		return -1;
	}

	if((fd2=open("./ggb1.bmp",O_WRONLY|O_CREAT|O_TRUNC,0664))==-1)
	{
		perror("open error");
		return -1;
	}
	int maxsize=lseek(fd1,0,SEEK_END);//fd1的光标最大值
	char buf[5];
	pid_t pid=-1;
	pid=fork();
	if(pid>0)
	{
		int loca=0;
		lseek(fd1,loca,SEEK_SET);
		lseek(fd2,loca,SEEK_SET);

		while(loca<(maxsize/2))
		{
			int rew=read(fd1,buf,sizeof(buf));
			if(rew<=0)
				break;

			write(fd2,buf,rew);
			loca=lseek(fd1,0,SEEK_CUR);
		}

	}
	else if(pid==0)
	{
		lseek(fd1,0,SEEK_SET);
		lseek(fd2,0,SEEK_SET);
		int loca=maxsize/2;
		while(loca<maxsize)
		{
			int rew=read(fd1,buf,sizeof(buf));
			if(rew<0)
				break;

			write(fd2,buf,rew);
			loca=lseek(fd1,0,SEEK_CUR);

		}
		exit(EXIT_SUCCESS);
	}
	else if(pid<0)
	{
		perror("fork error");
		return -1;
	}
	int loca=maxsize/2;
	lseek(fd1,loca,SEEK_SET);

	while(loca<maxsize)
	{
		int rew=read(fd1,buf,sizeof(buf));
		if(rew<=0)
			break;
		write(fd2,buf,rew);
		loca=lseek(fd1,0,SEEK_CUR);
	}

	wait(NULL);

	close(fd1);
	close(fd2);
	return 0;
}

2>思维导图