c++ IO操作

记录一下c++的几种IO类，方便以后写代码时查阅。
iostream 用于读写流，fstream用于读写文件，sstream用于从string类中读写数据

iostream类

常用的操作是cin和cout

#include <iostream>

using namespace std;

int main() { 

	int info;
	cin >> info;
	cout << info;
	return 0;
}

fstream类

上述三种类型都属于fstream类，使用时需要加fstream

ifstream使用

#include <iostream>
#include <fstream>
#include <string>
using namespace std;


void ReadDataBySpace(const char * file) { 
	ifstream rd(file);
	string s;
	while (rd >> s) { 
		cout << "info:" << s << endl;
	}
	
}



void ReadDataByLine(const char* file) { 
	ifstream rd(file);
	char s[1024];
	while (rd.getline(s,1024)) { 
		cout << "info:" << s << endl;
	}
}

int main() { 
	string file = "text.txt";
	ReadDataBySpace(file.c_str());
	ReadDataByLine(file.c_str());
	return 0;
}

ofstream使用

#include <iostream>
#include <fstream>
#include <string>
using namespace std;


int main() { 
	string wfile = "write.txt";
	string rfile = "text.txt";
	ofstream out(wfile.c_str());
	ifstream in(rfile.c_str());
	if (!out.is_open()) { 
		cout << "open write.txt failed" << endl;
	}
	if (!in.is_open()) { 
		cout << "open text.txt failed " << endl;
	}
	char s[1024] = { 0};
	while (in.getline(s,1024)) { 
		out << s << endl;;
	}
	in.close();
	out.close();

	return 0;
}

sstream

一般用于类型转换

#include <iostream>
#include <sstream>
#include <string>

using namespace std;


int main() { 
	stringstream ss;
	string info = "1234";
// int x = 0;
// ss << info;
// ss >> x;
// cout << "x:" << x << endl;
	int m = 9999;
	ss << m;
	ss >> info;
	cout << "info:" << info << endl;


	return 0;
}