如何从头到尾读取文本文件。 C++

Posted 2023-03-06

【中文标题】如何从头到尾读取文本文件。 C++

【英文标题】：How to read a text file from the beginning up to a certain point. C++

【发布时间】：2020-04-12 18:56:25

【问题描述】：

所以我正在为一个讨论随机访问文件的课程做一些工作。其中一个问题（选项 3）要求我们创建一个代码，该代码获取一个文本文件，并从头到尾读取并显示其内容（这将由用户给出）。在用户给出输入后，我将如何设置代码以停止阅读？ 到目前为止，这是我的代码

#include <iostream>
#include <fstream>
#include <stdlib.h>
#include <string>
#include <iomanip>

using namespace std;

int main() 
  char filename[]="file.txt"; 
  char content[10];
  ifstream inFile;
  int choice;
  int option;
  l1: cout << "Choose an option to decide what you want to do with the file." << endl;
  cout << "Option 1: Beginning to End."<< endl;
  cout << "Option 2: End to Beginning."<< endl;
  cout << "Option 3: Beginning to Certain Point."<< endl;
  cout << "Option 4: Certain Point to Certain Point. "<< endl;
  cin >> choice;

  if (choice==1)

  inFile.open(filename);
  if(inFile.fail())
    
         cout << "file named can not be found \n";
         system("pause");
         exit(1);
    
    inFile>>content;
    while(inFile.good()) 
    
     cout <<content<< ' ' <<endl;
     inFile>>content;
     
        inFile.close();

    cout << "Do you want to go again? 1 for Yes and 2 for No."<< endl;
    cin >> option;
    if (option== 1)
    
      goto l1;
    
    else
    
      terminate();
    
  

  if (choice==2)

    inFile.open(filename);
    if(inFile.fail())
    
         cout << "file named can not be found \n";
         system("pause");
         exit(1);
    

    char c;
    std::ifstream myFile(filename,std::ios::ate);
    std::streampos size = myFile.tellg();
    for(int i=1;i<=size;i++)
        myFile.seekg(-i,std::ios::end);
        myFile.get(c);
        printf("%c",c);
    
    cout << "Do you want to go again? 1 for Yes and 2 for No."<< endl;
    cin >> option;
    if (option== 1)
    
      goto l1;
    
    else
    
      terminate();
    
  

  if (choice==3)

    inFile.open(filename);
    if(inFile.fail())
        
         cout << "file named can not be found \n";
         system("pause");
         exit(1);
        







  


  

【参考方案1】：

最简单的方法是获取他们想要停止读取的字符或行号并计数到该值。 类似的东西

int amount_read = 0;
int amount_to_be_read;
cin >> amount_to_be_read;

inFile>>content;
while(inFile.good() && amount_read < amount_to_be_read) 

    cout <<content<< ' ' <<endl;
    inFile>>content;
    amount_read++;

inFile.close();