用c++写一个代码根据输入的基因名字从ENA官网上下载对应的Project号并输出为txt文件

以下是一个使用C++编写的代码示例，用于根据输入的基因名从ENA官网下载对应的Project号，并将结果输出为txt文件。

#include <iostream>
#include <fstream>
#include <string>
#include <curl/curl.h>

// 回调函数，用于处理下载的数据
size_t WriteCallback(void* contents, size_t size, size_t nmemb, std::string* output) {
    size_t totalSize = size * nmemb;
    output->append((char*)contents, totalSize);
    return totalSize;
}

// 根据基因名从ENA官网获取Project号
std::string getProjectNumber(const std::string& geneName) {
    std::string url = "https://www.ebi.ac.uk/ena/data/search?query=" + geneName;
    std::string response;

    CURL* curl = curl_easy_init();
    if (curl) {
        curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteCallback);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, &response);
        CURLcode res = curl_easy_perform(curl);
        curl_easy_cleanup(curl);

        if (res != CURLE_OK) {
            std::cerr << "Failed to download data from ENA." << std::endl;
            return "";
        }
    } else {
        std::cerr << "Failed to initialize CURL." << std::endl;
        return "";
    }

    // 从下载的数据中提取Project号
    size_t startPos = response.find("studyId\":\"");
    if (startPos == std::string::npos) {
        std::cerr << "Failed to find Project number in the response." << std::endl;
        return "";
    }
    startPos += 10;
    size_t endPos = response.find("\"", startPos);
    if (endPos == std::string::npos) {
        std::cerr << "Failed to find Project number in the response." << std::endl;
        return "";
    }

    return response.substr(startPos, endPos - startPos);
}

int main() {
    std::string geneName;
    std::cout << "Enter gene name: ";
    std::cin >> geneName;

    std::string projectNumber = getProjectNumber(geneName);
    if (!projectNumber.empty()) {
        std::ofstream outputFile("project_number.txt");
        if (outputFile.is_open()) {
            outputFile << projectNumber;
            outputFile.close();
            std::cout << "Project number saved to project_number.txt" << std::endl;
        } else {
            std::cerr << "Failed to open output file." << std::endl;
        }
    }

    return 0;
}

请确保已安装libcurl库，并在编译时链接该库。编译命令可以使用以下命令：

g++ -o download_project_number download_project_number.cpp -lcurl

运行程序后，将提示输入基因名字。程序将从ENA官网下载对应的Project号，并将结果保存在名为"project_number.txt"的文本文件中。