如何在C ++中从文本文件中进行多次搜索？ [英] How Do I Do Multiple Searches From A Text File In C++?

问题描述

所以，这是我试图编写的程序 - 用户将有机会输入字符串，字符串将与存储在文本文件中的字符串匹配。什么时候，我试过它，它工作正常，并没有显示任何问题。现在，我想扭曲程序一点，并希望给用户多次机会从数据库中搜索一个单词。这是程序开始向我显示错误的地方。我将程序放在一个循环中，并尝试给用户两次搜索数据库中的单词。问题是当我运行程序时，它只在第二次第一次工作，其余时间不在数据库中搜索单词。我不知道问题出在哪里。请任何人都可以建议我。这是我的代码。

我正在寻找的文本文件包含以下内容（Hello World，嘿）。

So, this is the program i tried to write- The user will be given a chance to enter a string and the string will be matched with the string stored in a text file. When, i tried it, it worked fine and showed no problems. Now, i wanted to twist the program a bit and wanted to give the user multiple chances to search for a word from the database. This is where the program started showing me errors. I placed the program in a loop and tried to give the user two times to search for a word in the database. The problem is when i run the program, it only works for the first time the second time and the remaining times it doesn't search for the word in the database. I don't know where the problem is. Please can anyone suggest me anything. Here is my code.
My text file which i am looking for contains the following (Hello World, Hey).

#include <iostream>
#include <fstream>
#include <string>

using namespace std;


int main()
{

  string search,line;
  ifstream read;

  int i =0;

  while(i<2)
  {
    read.open("type.txt");

  cout<<"Enter the word to search"<<endl;
  cin>>search;

  size_t pos;
  if(read.is_open())
  {
	  while (getline(read,line))
	  {
		   pos = line.find(search);
			   if(pos != string::npos)
			  {
				  

				  cout<<line<<endl;
				  
				  

			   }
	  }

	  




	  }

  i++;



  }







  system("pause");







  }

推荐答案

while循环应测试ifstream是否为eof或使用good（）时出错。 getline只返回文件流而不是布尔表达式。

The while loop should test if the ifstream is at eof or an error using good(). getline only returns the file stream not a boolean expression.

int main()
{
string _search;
string line;
ifstream read;

int i =0;
    while(i++<2)
    {
        cout<<"Enter the word to search"<<endl;
        cin>>_search;
        read.open("type.txt");
        size_t pos,i=0;
        if(read.is_open())
        {
            while (read.good())
            {
                i++;
                getline(read,line);
                pos = line.find(_search);
                if(pos != string::npos)
                {
                   cout<<i<<": "<<line<<endl;
                }
                else
                {
                    cout<<"Not found"<<endl;
                }

            }
            read.close();
        }

    }
}

#include <iostream>
#include <fstream>
#include <string>

using namespace std;
 

int main()
{
 
  string search,line;
  ifstream read;
 
  int i =0;
 
  while(i<2)
  {
    read.open("type.txt");
 
  cout<<"Enter the word to search"<<endl;
  cin>>search;
 
  size_t pos;
  if(read.is_open())
  {
	  while (getline(read,line))
	  {
		   pos = line.find(search);
			   if(pos != string::npos)
			  {
				  
 
				  cout<<line<<endl;
				  
				  read.close();
 
			   }
	  }
 
	  
 

 

	  }
 
  i++;
 

 
  }
 

 

 

 
  system("pause");
 

 

 

 
  }

这篇关于如何在C ++中从文本文件中进行多次搜索？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！