十一月九日

#include 
void *task1(void *arg)
{
	int fd1=-1;
	int fd2=-1;
	if((fd1=open("text.txt",O_RDONLY))==-1)
	{
		perror("open error");
		return NULL;
	}
	if((fd2=open("txt.txt",O_WRONLY))==-1)
	{
		perror("open error");
		return NULL;
	}
	int a=lseek(fd1,0,SEEK_END);
	char buf[1]="";
	lseek(fd1,0,SEEK_SET);
	while(1)
	{
		read(fd1,buf,sizeof(buf));
		write(fd2,buf,sizeof(buf));
		if(lseek(fd1,0,SEEK_CUR)>=a/2)
		{
			break;
		}
	}
	close(fd1);
	close(fd2);
	pthread_exit(NULL);
	return NULL;
}

void *task2(void *arg)
{
	int fd1=-1;
	int fd2=-1;
	if((fd1=open("text.txt",O_RDONLY))==-1)
	{
		perror("open error");
		return NULL;
	}
	if((fd2=open("txt.txt",O_WRONLY))==-1)
	{
		perror("open error");
		return NULL;
	}
	int a=lseek(fd1,0,SEEK_END);
	char buf[1]="";
	lseek(fd1,a/2,SEEK_SET);
	lseek(fd2,a/2,SEEK_SET);
	while(1)
	{
		if(read(fd1,buf,sizeof(buf))==0)
		{
			break;
		}
		write(fd2,buf,sizeof(buf));
	}
	close(fd1);
	close(fd2);
	pthread_exit(NULL);
	return NULL;
}




int main(int argc, const char *argv[])
{
	pthread_t tid=-1;
	pthread_t tid1=-1;
	int fd=-1;
	if(pthread_create(&tid,NULL,task1,NULL)!=0)
	{
		fprintf(stderr,"pthread_create error\n");
		return -1;
	}
	if(pthread_create(&tid1,NULL,task2,NULL)!=0)
	{
		fprintf(stderr,"pthread_create error\n");
		return -1;
	}

	pthread_join(tid,NULL);
	pthread_join(tid1,NULL);

	return 0;
}

先在主函数内定义两个线程号，并且创建两个线程，在定义两个文件拷贝函数，一个复制前半个，一个复制文件后半段