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<<"\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;
}

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