作业

创建子父进程，子进程将1.txt内容拷贝到2.txt中，父进程将3.txt内容拷贝到4.txt中。

#include <myhead.h>
int main(int argc, const char *argv[])
{
	pid_t ID;
	ID = fork();
	if(ID > 0)
	{
		int fd1;
		fd1 = open("./3.txt",O_RDONLY);
		if( fd1 == -1)
		{
			perror("open");
			return -1;
		}
		int fd2;
		fd2 = open("./4.txt",O_WRONLY | O_CREAT | O_TRUNC,0664);
		if( fd2 == -1)
		{
			perror("open");
			return -1;
		}

		char buf[5];
		ssize_t len1;
		while((len1 = read(fd1,buf,sizeof(buf))) != 0)
		{
			write(fd2,buf,len1);
		}
		printf("拷贝成功\n");

		close(fd1);
		close(fd2);
	}
	else if(ID == 0)
	{
		int fd3;
		fd3 = open("./1.txt",O_RDONLY);
		if( fd3 == -1)
		{
			perror("open");
			return -1;
		}
		int fd4;
		fd4 = open("./2.txt",O_WRONLY | O_CREAT | O_TRUNC,0664);
		if( fd4 == -1)
		{
			perror("open");
			return -1;
		}

		char buff[5];
		ssize_t len2;
		while((len2 = read(fd3,buff,sizeof(buff))) != 0)
		{
			write(fd4,buff,len2);
		}
		printf("拷贝成功\n");

		close(fd3);
		close(fd4);
	}
	else
	{
		perror("fork");
		return -1;
	}
	while(1);
	return 0;
}

运行结果：

知识梳理