C++ 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:

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#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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