How to read text file and compare string using C++ and execute blocks of code.

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Hi friends, please help me out. I need to read a text file that contains names along with another text(include,exclude) separated by a comma. I need to compare it with a user input for example name in the text file and name provided as user input should match. If they both match a bock of code to be executed else another block of code to be executed. I am posting my sample code.

What I have tried:

C++

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

using namespace std;

int main()
{

    fstream newfile;

    string query,user;
    cout<< "enter query\n";
    getline(cin,query);

    cout<< "enter username\n";
    getline(cin,user);

    newfile.open("users.txt",ios::in); 
    if (newfile.is_open()){ 
    string tp;
    while(getline(newfile, tp)){ 
         //cout << tp << "\n"; 
       if (tp.compare(user)!= string::npos)
         {
             cout << query<<"\n";
          //   found = true;
          break;
         }
         else
            {
                cout << "print something";
         }

      }
   }
      newfile.close();

My text file contains data as below

user1 , include
user2 , exclude
user3 , include

Note: When a user is provided as input and the file has the username along with include the if block should execute or else block should execute

Posted 20-Jul-20 8:18am

pooher

Updated 20-Jul-20 10:40am

CPallini

v2

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CPallini · Answer 1 · 2020-07-20T10:40:00

I would use a std::set to store 'included' users:

C++

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

using namespace std;

int main()
{
    set<string> included_user;

    string query,user;

    cout<< "enter query\n";
    getline(cin,query);

    cout<< "enter username\n";
    getline(cin,user);

    { // read the file and fill the set of 'included' users
      ifstream newfile( "users.txt");
      do
      {
        string name, comma, inclusion;
        newfile >> name >> comma >> inclusion;
        if ( inclusion == "include")
          included_user.insert(name);
      } while (newfile);
    }

    // conditiona execution here
    if (included_user.count(user) > 0)
    {
      cout << query<<"\n";
    }
    else
    {
      cout << "print something\n";
    }
}

Richard MacCutchan · Answer 2 · 2020-07-20T10:23:00

Solution 1

The string::compare function returns one of three values as described at basic_string Class | Microsoft Docs[^]. That is what you should be testing against.

[edit]
Also you need to extract the username from the text read from the file. If you compare "user1" to "user1 , include" it will never match.
[/edit]

Posted 20-Jul-20 10:23am

Richard MacCutchan

Updated 20-Jul-20 10:31am

v3

Comments

pooher 21-Jul-20 3:16am

Could you please let me post some code if possible as I am new in C++ and trying to find out answers