通过C++处理文本文件 - 从文本文件中提取某个字符串

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

std::string extractStringFromFile(const std::string& filename, const std::string& searchString) {
    std::ifstream file(filename);
    std::string line;
    std::string result;

    if (file.is_open()) {
        while (std::getline(file, line)) {
            size_t found = line.find(searchString);
            if (found != std::string::npos) {
                result = line.substr(found + searchString.length());
                break;
            }
        }
        file.close();
    }
    return result;
}

int main() {
    std::string filename = "example.txt";
    std::string searchString = "target_string";
    std::string extractedString = extractStringFromFile(filename, searchString);

    if (!extractedString.empty()) {
        std::cout << "Extracted string: " << extractedString << std::endl;
    } else {
        std::cout << "String not found in the file." << std::endl;
    }

    return 0;
}