标准IO库

ifstream由istream派生而来，从文件中读取；ofstream由ostream派生而来，写到文件中去；fstream由iostream派生而来，读写文件；

#include "stdafx.h"
#include <fstream>
#include <iostream>
#include <string>
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
    ifstream infile;
    ofstream outfile;
    string filename = "D:/Program Files/C++_CODE/streamtest/Debug/201204.txt";//注意路径
    string print;
    infile.open(filename.c_str());//打开文件
    if(!infile) //检查是否打开
    {
     cout<<"open file is error!"<<endl;
     return -1;
    }
    else
    {
        while(!infile.eof())
     {
        getline(infile,print);//读内容
        cout<<"Today I want to say : "<<print.c_str()<<endl;
     }
     infile.close(); //关闭文件
     infile.clear(); //清除流状态
    }
    string rfilename="D:/Program Files/C++_CODE/streamtest/Debug/201204_R.txt";
    outfile.open(rfilename.c_str());
    if(!outfile)
    {
     cout<<"open file is error!"<<endl;
     return -1;
    }
    else
    {
     outfile<<"I hate you!";//往打开的文件中写内容
     outfile.close();
    }
    return 0;
}