使用ifstream和getline读取文件内容

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, Word By Word


//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 Line-By-Line 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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