How to timeout a libcurl C++ call and/or know when a timeout has happened in the call

Question

I'm trying to download remote html pages with my C++ program, however with some URLs a timeout occurs, but I don't know how to handle this, so the program will just hang indefinatly.

virtual void downloadpage(string pageaddress) {
    CURL *curl;
        CURLcode informationdownloaded;
        curl = curl_easy_init();
        if (curl) { 
            curl_easy_setopt(curl, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/525.13 (KHTML, like Gecko) Chrome/0.A.B.C Safari/525.13");
            curl_easy_setopt(curl, CURLOPT_URL, pageaddress.c_str());
            curl_easy_setopt(curl, CURLOPT_HEADER, 0);
            curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1);
            curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writepageinformation);
            curl_easy_setopt(curl, CURLOPT_WRITEDATA, &pageinformation);
            informationdownloaded = curl_easy_perform(curl);
            curl_easy_cleanup(curl);
    }
}

Here is my function for downloading the html source of a page into a string variable called "pageinformation" via the "writepageinformation" function.

Answer 1

informationdownloaded = curl_easy_perform(curl);

You can also specify timeout for your download

curl_easy_setopt(hCurl, CURLOPT_TIMEOUT, iTimeoutSeconds); // timeout for the URL to download

This is a blocked call until the entire file is downloaded. If you are interested to interrupt the blocked call (for signal to kill) install a progress callback, like below

curl_easy_setopt(hCurl, CURLOPT_NOPROGRESS, 0);
curl_easy_setopt(hCurl, CURLOPT_PROGRESSFUNCTION, progress_callback);
curl_easy_setopt(hCurl, CURLOPT_PROGRESSDATA, this);

static int progress_callback(void *clientp,
                           double dltotal,
                           double dlnow,
                           double ultotal,
                           double ulnow)
{
    CLASS &obj = *(CLASS*)clientp;


    if (obj.exit)
      return 1; // if u want the signal curl to unblock and return from curl_easy_perform

    return 0; // if u want the callback to continue
}