How to read a specific line from a text file in c++?

[Nathan_22]

C++ program that displays on the screen item codes with corresponding
item descriptions and prices. It asks the user to enter the code of the item
purchased by a customer. It looks for a match of the item code stored in items.txt.

How to read a specific line from a text file in c++?

[rproffitt]

Seems simple.
In psuedo code:

1. Open file.
2. Loop
3. Read a line.
4. If match, close file, return result.
5. End of file? Close file, return not found.

[toneewa]

Here is a solution that you can use, that will do what you asked.

#include <fstream> 
#include <iostream>
#include <string>
#include <vector>
#include <iomanip>
#include <regex>
using namespace std;
int debug = 1;
int z = 0;
int ct = 0;
int match0 = 0;

int chr = 0;
string list[512];
int ver[512];

int input();
int next();
int main()
{
    //Joshua Haglund
    cout << "Item Check" << endl;
    input();
    return 0;
}

int input()
{
    ifstream file;
    file.open("items.txt");
    int endofline = 0;
    string lines = " ";
    string upc = " ";
    string product;
    string price;
    string qty;
    std::cout << "enter item code: ";
    bool status = false;
    bool found = false;

    while (1) {

        z = z + 1;
        upc = " ";
        std::cin >> upc;
        list[z] = upc; 
        ver[z] = status;

        while (file.good()) {


            while (file >> lines >> product >> price >> qty) {

                ver[z] = status;

                std::string s;
                s = lines;
                std::smatch m;
                std::regex e(upc);


                {
                    while (std::regex_search(s, m, e)) {
                        for (auto& x : m) {
                            s = m.suffix().str();
                            std::cout << " ";
                            std::cout << std::endl;
                            std::cout << ""; 
                            found = true;

                        }
                        if (found == true) {
                            std::cout << "" << std::endl;
                            std::cout << "-------------------------------------------------------------------------------" << std::endl;
                            std::cout << setw(15) << "UPC" << std::setw(20) << "Product" << std::setw(17) << "Price" << std::setw(20) << "Qty" << std::endl;
                            std::cout << "-------------------------------------------------------------------------------" << std::endl;
                            std::cout << setw(15) << upc << std::setw(20) << product << std::setw(17) << price << std::setw(20) << qty << std::endl;
                        }
                    }
                }
            }

            std::cout << "" << std::endl;

            //extra credit
            /*
            std::cout << "search history" << std::endl;
            for (ct = 0; ct <= z; ct++) {
                std::cout << list[ct] << " ";
            }
            */
            list[0] = upc;
            ver[0] = status;
            std::cout << "" << std::endl;

            if (found == false)
            {
                std::cout << "no item found." << std::endl;
            }
            file.close();
        }
        next();
    }
    return 0;
}
int next()
{
    std::cout << "" << std::endl;
    input();
    return 0;
}



items.txt
9000012345  Milk-2%         $3.49       20
9000012346  Milk-1%         $3.29       24
7000012347  Bread-White     $2.29       28
7000012348  Bread-Wheat     $2.99       12
#4011       Bananas         $0.49/lbs   14
#94012      Bananas-Organic $0.69/lbs   7



Item Check
enter item code: #4011


-------------------------------------------------------------------------------
            UPC             Product            Price                 Qty
-------------------------------------------------------------------------------
          #4011             Bananas        $0.49/lbs                  14

enter item code: 7000012348


-------------------------------------------------------------------------------
            UPC             Product            Price                 Qty
-------------------------------------------------------------------------------
     7000012348         Bread-Wheat            $2.99                  12