c ++：逐行读取文件 [英] c++: Reading a file line by line

问题描述

我遇到了下面的代码来完成这个任务：

我想知道是否有一个C ++方法打开一个文件， / p>

  #include< iostream> 
 #include< fstream> 
 using namespace std; 
 
 int main（）{
 ifstream myfile; 
 myfile.open（example.txt）; 
 return 0; 
} 
  

我鼓励不要使用任何C函数或命令。

事情是，我的example.txt是一个字符串形式，使用str.c_str（）是一个C函数，所以我想我有两种方法解决问题。

有没有另一种方式从文件逐行读取输入？也许使用将接受一个字符串作为文件路径的参数的东西？有没有C ++的做事方式？ ：）

或者，是否有另一种方法将字符串转换为const char *，这是myfile.open（）函数需要什么？

非常感谢！

编辑：我缺乏实​​用性和研究，所以我认为c_str ，而不是。我很抱歉。因为它没有找到我的答案。

解决方案

C ++ 11的 fstream 构造函数接受 string 。在大多数情况下，您想使用 fstream 的构造函数，而不是 .open（） - 您保存一行和一个函数调用。

要逐行读取文件，您应该使用 std :: getline（） 。

string :: c_str（）仍然是C ++函数，而不是C一个，以及 fstream 的构造函数 const char * 。大多数（如果不是全部，我不是100％肯定）C标准库函数也包括在C ++标准中。

I'm wondering if there's a C++ way of opening a file and reading the input line by line.

I encountered the following code that accomplishes the task:

#include <iostream>
#include <fstream>
using namespace std;

int main () {
  ifstream myfile;
  myfile.open ("example.txt");
  return 0;
}

I'm encouraged to not use any C functions or commands.

The thing is, my "example.txt" is in the form of a string, and using str.c_str() is a C function, so I guess I have two ways to solve the issue.

Is there another way to read input from a file line by line? Perhaps using something that will accept a string as a parameter for the filepath? Is there a C++ way of doing things? :)

Or, is there another way to convert the string in to a const char *, which is what the myfile.open() function needs?

Many thanks in advance!

EDIT: My lack of practivity and research led me to think c_str() was a C function, and it isn't. My apologies. Since it isn't I have found my answer.

解决方案

C++11's fstream constructor accepts string. In most cases, you want to use fstream's constructor, rather than .open() - you save one line and one function call.

For reading the file line-by-line, you should use std::getline().

Also note that string::c_str() is still C++ function, not C one, as well as fstream's constructor taking const char *. Most of (if not all, I'm not 100% sure) C standard library function are also included in C++ standard.

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