http://blog.csdn.net/zhangchao3322218/article/details/7930857

#include  <iostream>
#include  <fstream>
#include  < string >

using   namespace  std;
 
void  OutPutAnEmptyLine()//输出空行
{
cout<< "\n" ;
}

//读取方式: 逐词读取, 词之间用空格区分
void  ReadDataFromFileWBW()
{
cout<<"逐词读取, 词之间用空格区分"<<endl;
ifstream fin( "data.txt" );  
string  s;  
while ( fin >> s ) 
    {
cout <<  "Read from file: "  << s << endl;  
     }
}

//读取方式: 逐行读取, 将行读入字符数组, 行之间用回车换行区分
void  ReadDataFromFileLBLIntoCharArray()
{
cout<<"逐行读取, 将行读入字符数组, 行之间用回车换行区分"<<endl;
ifstream fin( "data.txt" ); 
const   int  LINE_LENGTH =  100 ; 
char  str[LINE_LENGTH];  
while ( fin.getline(str,LINE_LENGTH) )
{    
cout <<  "Read from file: "  << str << endl;
}
}

//读取方式: 逐行读取, 将行读入字符串, 行之间用回车换行区分
//相比较上种方法，该种方法比较灵活，推荐使用
void  ReadDataFromFileLBLIntoString()
{
cout<<"逐行读取, 将行读入字符串, 行之间用回车换行区分"<<endl;
ifstream fin( "data.txt" );  
string  s;  
while ( getline(fin,s) )
{    
cout <<  "Read from file: "  << s << endl; 
}
}

//带错误检测的读取方式
void  ReadDataWithErrChecking()
{
    string  filename =  "dataFUNNY.txt" ;  
    ifstream fin( filename.c_str());  
    if ( !fin ) 
    {   
cout <<  "Error opening "  << filename <<  " for input"  << endl;   
exit(- 1 );  
    }
}

int  main()
{
ReadDataFromFileWBW();  //逐词读入字符串 
OutPutAnEmptyLine();  //输出空行

ReadDataFromFileLBLIntoCharArray();  //逐词读入字符数组
OutPutAnEmptyLine();  //输出空行

ReadDataFromFileLBLIntoString();  //逐词读入字符串
OutPutAnEmptyLine();  //输出空行

ReadDataWithErrChecking();  //带检测的读取
return   0 ;
}