c++获取txt文件中的一行数据

Question

我想从一个 txt 文件中读取数据，但我无法获取它。我是 C++ 的新手。这是我的代码，但它不起作用。我用了 getline(),

 ifstream inFile;
 string sPassWord;
 inFile.open("QdatPassWordconfig.config");
 inFile.seekg(0,ios::end);
 int length=inFile.tellg();

  if (inFile.is_open())
  {
      while (!inFile.eof())
      {
              getline(inFile,sPassWord);
               cout<<sPassWord<<endl;
      }

         cout<<"get data from txt file"<<endl;
         // here ,I cannot read data from file
         cout<<sPassWord<<endl;
  }

 if(!inFile.is_open() || length==0)
  {
      cout<<"file is create or write"<<endl;
      sPassWord="BdsWUjT26";
      ofstream outFile;
      outFile.open("QdatPassWordconfig.config");
      outFile<<sPassWord<<endl;
      outFile.close();
  }
   inFile.close();
  cout<<sPassWord<<endl;

Answer 1

不清楚您是在尝试读取文件的第一行、文件的最后一行还是文件的所有行。这里是每种可能性的程序片段:

读取文件的第一行:

// UNTESTED
{
  ifstream inFile("QdatPassWordconfig.config");
  string sPassWord;
  if(std::getline(inFile, sPassWord)) {
    std::cout << "Password is: " << sPassWord << "\n";
  } else {
    std::cout << "No password available.\n"
  }
}

读取文件的所有行:

// TESTED
#include <iostream>
#include <fstream>
#include <string>

int main ()
{
  std::ifstream inFile("QdatPassWordconfig.config");
  std::string sPassWord;
  while(std::getline(inFile, sPassWord)) {
    std::cout << "Password is: " << sPassWord << "\n";
  }
}

读取文件的最后一行:

// UNTESTED
{
  ifstream inFile("QdatPassWordconfig.config");
  string sPassWord;
  int lineCount = 0;
  while(std::getline(inFile, sPassWord)) {
    lineCount++;
  }
  if(lineCount) {
    std::cout << "Password is: " << sPassWord << "\n";
  } else {
    std::cout << "No password available.\n";
  }
}