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

int main()
{
    std::string filename = "example";
    std::ifstream file( filename + ".txt" );

    if( file.good() )
    {
        std::string keyword;

        std::cout << "Podaj wyraz do wyszukania: ";
        std::cin >> keyword;

        std::string line;
        while( std::getline( file, line ) )
        {
            if( line.find( keyword ) != std::string::npos )
            {
                std::cout << line << '\n';
            }
        }
    }
    else
    {
        std::cerr << "Nie mozna otworzyc pliku: " << filename << '\n';
    }

    file.close();

    return 0;
}