根据ID/Registration搜索和编辑.txt fstream文件

Question

我正在尝试从.txt中搜索特定的ID/注册，并相应地显示相应的信息。在这种情况下，我想根据应输入的相应注册号显示定价。

读写文件对我来说不是问题。网上有很多关于读写的信息，但根据ID/注册进行搜索和显示的信息不多。

#include <iostream>
#include <iomanip>
#include <fstream>
#include <cstdlib>
#include <string>
using namespace std;
int main()
{
    string line;
    double cost;
    string reg;
    ifstream in_stream;
    ofstream out_stream;
    char registration[10]; 
    //Open file
    in_stream.open("Fines.dat");
    //Error if opening fails
    if (in_stream.fail())
    {
        cout << "Input file could not open. " << endl;
        exit(1);
    }
    //Open out stream file
    out_stream.open("OutStandingFines.dat");
    //Error if opening fails
    if (out_stream.fail())
    {
        cout << "Output file opening failed.n";
        exit(1);
    }
    //Display original .dat file
    cout <<"Original .dat File" << endl;
    if(in_stream.is_open())
    {
        while(in_stream >> reg >> cost)
        {       
                cout << reg <<" " << cost << 'n';
        }
        in_stream.close();
    }
    else
    {
        cout <<"File is not open: " << endl;
    }

/////////////My problem is from here//////////////////////////
    //Enter the registration number you wish to search
    cout << "Please enter registration number: " << endl;
    cin >>registration;

//I must display all cost values that have the same registration number???????? I need help with this
/*
    for (int i = 0; i < 10; i++)
    {

                if( reg == registration)
                {   
                    cout << fixed << setw(2)<< setprecision(2) <<"R " << cost << 'n';
                    out_stream << fixed << setw(2)<< setprecision(2) << "R "<< cost << endl; //send back to .dat
                }

    }
*/


    in_stream.close();
    out_stream.close();
    system("pause");
    return(0);
}

Answer 1

好的，我设法得到了输出。我现在的问题是显示具有相同注册/ID的所有值。

由于某种原因，当我输入"ABC123"时，只显示fstream.txt中的最后一行。

input.txt包含以下信息

ABC123 400
DEC234 340
ABC123 500
GED345 600
ABC123 240
GEE600 120
GED345 230
GEE600 470
ABC123 120

---

#include <iostream>
#include <iomanip>
#include <fstream>
#include <cstdlib>
#include <string>
using namespace std;
int main()
{
    string line;
    double cost;
    string reg;
    ifstream in_stream;
    ofstream out_stream;
    string registration; 

    in_stream.open("Fines.dat");
    if (in_stream.fail())
    {
        cout << "Input file could not open. " << endl;
        exit(1);
    }
    out_stream.open("OutStandingFines.dat");
    if (out_stream.fail())
    {
        cout << "Output file opening failed.n";
        exit(1);
    }
    //Display original .dat file
    cout <<"Original .dat File" << endl;
    if(in_stream.is_open())
    {
        while(in_stream >> reg >> cost)
        {       
                cout << reg <<" " << cost << 'n';
        }
    }
    else
    {
        cout <<"File is not open: " << endl;
    }

    //Enter Registration here
    cout << "Please enter registration number: " << endl;
    cin >>registration;
    //compare and display all registration numbers that match
    cout <<"Fines: " << endl;
    if(out_stream.is_open())
    {
        while(reg == registration)
        {       

                cout << fixed << setw(2)<< setprecision(2) <<"R " << cost << 'n';
                out_stream << fixed << setw(2)<< setprecision(2) << "R "<< cost << endl; //send back to .dat
            exit(1);
        }
    }
    else
    {
        cout <<"File is not open: " << endl;
    }

    in_stream.close();
    out_stream.close();
    system("pause");
    return(0);
}