IO作业day4

xmind

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 pid = fork();

	if(pid == 0)
	{
		int fp1 = open("./2.txt",O_WRONLY|O_CREAT|O_TRUNC,0644);
		if(fp1 == -1)
		{
			perror("open fp1");
			return -1;
		}
		int fp2 = open("./1.txt",O_RDONLY);
		if(fp2 == -1)
		{
			perror("open fp2");
			return -1;
		}
		char s[100];
		while(1)
		{
			int p = read(fp2,s,sizeof(s));
			if(p==0)
			{
				break;
			}
			write(fp1,s,p);
		}
		close(fp1);
		close(fp2);
	}
	else if(pid > 0)
	{
		int fp3 = open("./4.txt",O_WRONLY|O_CREAT|O_TRUNC,0644);
		if(fp3 == -1)
		{
			perror("open fp3");
			return -1;
		}
		int fp4 = open("./3.txt",O_RDONLY);
		if(fp4 == -1)
		{
			perror("open fp4");
			return -1;
		}
		char a[100];
		while(1)
		{

			int p = read(fp4,a,sizeof(a));
			if(p==0)
			{
				break;
			}
			write(fp3,a,p);
		}
		close(fp3);
		close(fp4);
	}

	else
	{
		perror("fork");
		return -1;
	}

	return 0;
}