c++如何显示字符串搜索关键字及其确切的行号？

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

void searchKeyword(const std::string& filename, const std::string& keyword) {
    std::ifstream file(filename);
    std::string line;
    int lineNum = 1;

    while (std::getline(file, line)) {
        if (line.find(keyword) != std::string::npos) {
            std::cout << "Keyword found at line " << lineNum << ": " << line << std::endl;
        }
        lineNum++;
    }

    file.close();
}

int main() {
    std::string filename = "example.txt";
    std::string keyword = "search";
    searchKeyword(filename, keyword);
    
    return 0;
}