IO day3

 创建一个父子进程，父进程拷贝文件的前一部分，子进程拷贝文件的后一部分

#include <25head.h>

int main(int argc, const char *argv[])
{
	int fd = open("22", O_RDONLY);
	if(-1==fd)
		ERR_MSG("open error");
	off_t size = lseek(fd, 0, SEEK_END);
	lseek(fd, 0, SEEK_SET);

	pid_t pid =fork();
	if(pid>0)
	{
		int fd1 = open("33", O_WRONLY | O_CREAT | O_TRUNC, 0777);
		if(-1==fd1)
			ERR_MSG("open error");

		off_t s=0;
		while(s<size/2)
		{
			char a;
			read(fd,&a,1);
			write(fd1,&a,1);
			s++;
		}
		close(fd1);
	}
	else if(pid==0)
	{
		sleep(1);
		int fd1 = open("33", O_WRONLY | O_APPEND);
		if(-1==fd1)
			ERR_MSG("open error");

		off_t s=size/2;
		lseek(fd, s, SEEK_SET);
		while(s<=size)
		{
			char a;
			read(fd,&a,1);
			write(fd1,&a,1);
			s++;
		}
		close(fd1);
	}
	else
		ERR_MSG("fork error");
	close(fd);
	return 0;
}