os hw3 sol ? I'm not sure it is the solution or not.

os3.cpp

#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <signal.h>
#include <fcntl.h>
using namespace std;
class rika
{
public:
	string err_msg_filename;
	int err_msg_fd;
	rika() { err_msg_filename = "Y_msg"; err_msg_fd = -1;}
	int init() { err_msg_fd = open(err_msg_filename.c_str(), O_WRONLY | O_NONBLOCK); }

	int overwrite_stderr()
	{
		dup2(err_msg_fd, 2);
		close(err_msg_fd);
	}
};
class yozora
{
public:
	int fd[1000][2], fd_max;
	int err_msg_fd;

	int create(int m)
	{
		fd_max = m;
		for (int i = 0; i < fd_max; i++) pipe(fd[i]);
	}
	int clear()
	{
		for (int i = 0; i < fd_max; i++)
		{
			close(fd[i][0]);
			close(fd[i][1]);
		}
	}
	int clear_stdio(int no)
	{
		close(fd[no][0]);
		close(fd[no+1][1]);
	}
	int overwrite_stdin(int no) { dup2(fd[no][0], 0); }
	int overwrite_stdout(int no) { dup2(fd[no+1][1], 1); }

};
class sena
{
public:
	vector<string> cmd_ary;
	vector<int> cmd_spliter;
	int cmd_size;
	int parse(string q)
	{
		cmd_ary.clear();
		cmd_spliter.clear();
		cmd_spliter.push_back(-1);
		istringstream ssin(q);
		string tmp;
		while (ssin >> tmp)
		{
			cmd_ary.push_back(tmp);
			if (tmp == "|") cmd_spliter.push_back(cmd_ary.size() - 1);
		}
		cmd_spliter.push_back(cmd_ary.size());
		cmd_size = cmd_spliter.size()-1;
	}
	int exec(int no)
	{
		char* ary_tmp[1000] = {0};
		for (int i = cmd_spliter[no] + 1, j = 0; i < cmd_spliter[no+1]; i++, j++)
		{
			ary_tmp[j] = (char*)(cmd_ary[i].c_str());
		}
		execvp(ary_tmp[0], ary_tmp);
	}
};
int kobato(string cmd)
{
	sena a;
	yozora b;
	a.parse(cmd);
	b.create(a.cmd_size);

	for (int i = 0; i < a.cmd_size; i++)
	{
		int pid;
		if (pid = fork())
		{
			b.clear_stdio(i);
			waitpid(-1, 0, 0);
		}
		else
		{
			if (i != 0) b.overwrite_stdin(i);
			if (i != a.cmd_size - 1) b.overwrite_stdout(i);
			b.clear();
			a.exec(i);
		}
	}	
}

void handler(int sig_no)
{
	cout << endl << "Bye Bye~" << endl;
	exit(0);
}
int main()
{
	string cmd;
	if (signal(SIGINT, handler) == SIG_ERR)
	{
		perror("Can't set SIGUSR1: \n");
		exit(1);
	}
	cout << "Yuki.N > ";
	rika err_msg;
	err_msg.init();
	while (getline(cin, cmd))
	{
		if (fork())
		{
			waitpid(-1, 0, 0);
			cout << "Yuki.N > ";
		}
		else
		{
			err_msg.overwrite_stderr();
			kobato(cmd);
		}
	}
}