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  • 使用ifstream和getline读取文件内容[c++]

    转载:http://www.cnblogs.com/JCSU/articles/1190685.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<<"
    ";
    }
    
    //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;
    }
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  • 原文地址:https://www.cnblogs.com/qianwen/p/3842688.html
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