Retrieving response text from curl in cpp

Question

we need to receive response string from curl in CPP ,I tried following options but nothing worked.js uses xhr.responseText for this.I need to do in cpp.

 static size_t WriteCallback(void *contents, size_t size, size_t nmemb, void *userp)
{
    size_t realsize = size * nmemb;
    const char* sp = static_cast<const char*>(contents);
    readBuffer.append(sp, realsize);
    return realsize;
 }

CURLcode res;
char* http_error= new char[100];

readBuffer.clear();
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteCallback);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &readBuffer);
CURLcode code(CURLE_FAILED_INIT);
code = curl_easy_perform(curl);
cout <<  "Curl response msg CURLOPT_WRITEDATA: "<<curl_easy_strerror(code)<< " respose :"<<readBuffer;


res=curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &http_code) ;
cout <<  "Curl response msg: "<< curl_easy_strerror(res);

Perhaps you should use high-level library https://github.com/whoshuu/cpr — Sergei Nikulov, Jul 29 '16 at 10:29
there is no direct method for this like retrieving the http status code? — Ek1234, Jul 29 '16 at 11:51

huu · Accepted Answer · 2016-08-04T18:12:04.003

Change your WriteCallback function to this:

size_t WriteCallback(void* contents, size_t size, size_t nmemb, std::string* userp) {
    userp->append((char*) contents, size * nmemb);
    return size * nmemb;
}

Remember, you are passing in &readBuffer as the CURL_WRITEDATA option. This shows up as the fourth parameter in the WriteCallback. Since the type of &readBuffer is std::string*, you can use that as the signature in your callback.

Additionally, since it's a std::string* and not a std::string, you have to access append through the pointer, hence the -> instead of .. After curl_easy_perform, readBuffer should hold the response from the curl request.

To get the response code, you can grab that after making the request:

long http_code;
curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &http_code);

Hi..thanks for replying..inside userp->append((char*) ptr, size * nmemb); ptr is sp(contents)? — Ek1234, Aug 03 '16 at 11:41
Oops, mistyped it. I'll correct it. You're right, it's supposed to be contents. — huu, Aug 04 '16 at 18:11

Retrieving response text from curl in cpp

1 Answers1