cURL 保持打印传输到控制台？

Question

我的应用程序将打印响应主体保存到控制台。而我在代码中没有像 cout 或类似函数这样的函数。好奇怪。

#include <iostream>
#include <curl.h>

#pragma comment(lib, "libcurldll.lib");

int main() {
    CURL* curl = curl_easy_init();

    curl_easy_setopt(curl, CURLOPT_URL, "url");
    curl_easy_setopt(curl, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/75.0.3770.100 Safari/537.36");
    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);

    curl_easy_perform(curl);
    curl_easy_cleanup(curl);

    return 0;
}

Answer 1

根据 the documentation，libcurl 的默认行为是使用 fwrite.

将响应写出到 stdout

您需要像这样覆盖 CURLOPT_WRITEFUNCTION：

size_t my_write_callback(char *ptr, size_t size, size_t nmemb, void *userdata) {
    cout << "Received " << nmemb << " bytes" << endl;
    return nmemb;
}

curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, my_write_callback);

可以通过改变CURLOPT_WRITEDATA来控制userdata的值，默认等于stdout.

编辑：使用 std::string 作为内存缓冲区的简单示例：

size_t my_write_callback(char *ptr, size_t size, size_t nmemb, void *userdata) {
    static_cast<std::string*>(userdata)->append((char*) ptr, size * nmemb);
    return nmemb;
}

std::string buf;
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, my_write_callback);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &buf);
curl_easy_perform(curl);
// do something with buf

cURL 保持打印传输到控制台？

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