使用ifstream和getline读取文件内容[c++]

 转自：http://hi.baidu.com/xaioxain/blog/item/f08d3a4c5003c2ffd72afce3.html

假设有一个叫 data.txt 的文件, 它包含以下内容:

Fry: One Jillion dollars.
[Everyone gasps.]
Auctioneer: Sir, that's not a number.
数据读取， 测试 。

以下就是基于 data.txt 的数据读取操作:

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

using namespace std;

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

// 读取方式: 逐词读取, 词之间用空格区分
// read data from the file, W ord B y W ord
// when used in this manner, we'll get space-delimited bits of text from the file
// but all of the whitespace that separated words (including newlines) was lost.
void ReadDataFromFileWBW()
{
     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
// If we were interested in preserving whitespace,
// we could read the file in L ine-B y-L ine using the I/O getline() function.
void ReadDataFromFileLBLIntoCharArray()
{
     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
// If you want to avoid reading into character arrays,
// you can use the C++ string getline() function to read lines into strings
void ReadDataFromFileLBLIntoString()
{
     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
// Simply evaluating an I/O object in a boolean context will return false
// if any errors have occurred
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 ;
}

输出结果为:

Read from file: Fry:
Read from file: One
Read from file: Jillion
Read from file: dollars.
Read from file: [Everyone
Read from file: gasps.]
Read from file: Auctioneer:
Read from file: Sir,
Read from file: that's
Read from file: not
Read from file: a
Read from file: number.
Read from file: 数据读取，
Read from file: 测试
Read from file: 。

Read from file: Fry: One Jillion dollars.
Read from file: [Everyone gasps.]
Read from file: Auctioneer: Sir, that's not a number.
Read from file: 数据读取， 测试 。

Read from file: Fry: One Jillion dollars.
Read from file: [Everyone gasps.]
Read from file: Auctioneer: Sir, that's not a number.
Read from file: 数据读取， 测试 。

Error opening dataFUNNY.txt for input
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