如何读取和写入C ++中的文本文件？ [英] How to read and write to a text file in C++?

问题描述

嘿大家，我刚刚开始学习C ++，我想知道如何读写一个文本文件。我看到很多例子，但他们都很难理解/跟随，他们有各种各样。我希望有人在这里可以帮助。我是一个初学者，所以我需要明确的指示。这里是我想要做的一个例子：

  #include< iostream> 
 #include< fstream> 
 using namespace std; 
 string usreq，usr，yn，usrenter; 
 int start（）
 {
 cout<< Welcome ...
 int main（）
 {
 cout< 这是你第一次使用TEST< endl; 
 cin>> yn; 
 if（yn ==y）
 {
 ofstream iusrfile; 
 ofstream ousrfile; 
 iusrfile.open（usrfile.txt，w）; 
 iusrfile>> ; 
 cout<< iusrfile; 
 iusrfile.close（）; 
 cout<< 请输入您的用户名。\\\
; 
 cin>>用户
 if（usrenter == usr）
 {
 start（）; 
} 
} 
 else 
 {
 cout< 不是注册的用户名。 
} 
 
 return 0; 
 
} 
  

解决方案

需要：

  #include< iostream> 
 #include< fstream> 
  

声明输入文件流：

  ifstream in（in.txt）; 
  

声明输出文件流：

  ofstream out（out.txt）; 
  

如果要对文件名使用变量而不是硬编码， p>

  string file_name =my_file.txt; 
 ifstream in2（file_name.c_str（））; 
 

从文件读入变量（假设文件中有2个int变量）：

  int num1，num2; 
在>> num1>> num2; 
  

或从文件中读取一行时间：

  string行; 
 while（getline（in，line））{
 //使用行
执行某些操作
  

将变量写回文件：

  out< num1<< num2; 
  

关闭文件：

  in.close（）; 
 out.close（）; 
  




Hey everyone, I have just started to learn C++ and I wanted to know how to read and write to a text file. I have seen many examples but they have all been hard to understand/follow and they have all varied. I was hoping that someone here could help. I am a total beginner so I need clear instructions. Here is an example of what i'm trying to do:

#include <iostream>
#include <fstream>
using namespace std;
string usreq, usr, yn, usrenter;
int start ()
{
    cout << "Welcome..."
int main ()
{
    cout << "Is this your first time using TEST" << endl;
    cin >> yn;
    if (yn == "y")
        {
            ofstream iusrfile;
            ofstream ousrfile;
            iusrfile.open("usrfile.txt", "w");
            iusrfile >> usr;
            cout << iusrfile;
            iusrfile.close();
            cout << "Please type your Username. \n";
            cin >> usrenter;
            if (usrenter == usr)
            {
            start ();
            }
        }
    else
        {
            cout << "THAT IS NOT A REGISTERED USERNAME.";
        }

    return 0;

}

解决方案

Header files needed:

#include <iostream>
#include <fstream>

declare input file stream:

ifstream in("in.txt");

declare output file stream:

ofstream out("out.txt");

if you want to use variable for a file name, instead of hardcoding it, use this:

string file_name = "my_file.txt";
ifstream in2(file_name.c_str());

reading from file into variables (assume file has 2 int variables in):

int num1,num2;
in >> num1 >> num2;

or, reading a line a time from file:

string line;
while(getline(in,line)){
//do something with the line
}

write variables back to the file:

out << num1 << num2;

close the files:

in.close();
out.close();

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