Using libcurl in loop C - c++

Question

I would like to dowload some page content of wikitionary. I use curl in a loop. The first iteration is ok but the others give me the same result as the first. What is missing/wrong?. Thank you. This is the loop:
std::string buffer;
size_t curl_write( void *ptr, size_t size, size_t nmemb, void *stream)
{
buffer.append((char*)ptr, size*nmemb);
return size*nmemb;
}
int main(int argc, char **argv)
{
CURL *curl = curl_easy_init();
string data;
data="http://fr.wiktionary.org/w/api.php?format=json&action=query&titles=";
//Page titles are read from local file. The code is not shown to make short.
while ( not_end_of_file){
//list_of_page_title is pages requested for the current iteration.
data=data+list_of_page_title+"prop=revisions&rvprop=content";
curl_easy_setopt(curl, CURLOPT_URL, data.c_str());
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, curl_write);
curl_easy_perform(curl);
curl_easy_reset(curl);
}
curl_easy_cleanup(curl);
return 0;
}
I am new to curl. May be many things are missed. Thank you for the help.

Answer 1

data=data+list_of_page_title will append the new title onto your previous URL instead of replacing the previous. By the end you'll have a gigantic URL full of garbage. The server is probably paying attention to the first title and ignoring the rest.
And this would be obvious if you just output your URL as the first step of debugging... "Am I requesting what I think I'm requesting?"

Answer 2

One problem is that you are not resetting your buffer variable.
while ( not_end_of_file){
buffer = ""; // reset buffer to empty string
//list_of_page_title is pages requested for the current iteration.
data="http://fr.wiktionary.org/w/api.php?format=json&action=query&titles=" +
list_of_page_title +
"prop=revisions&rvprop=content";
curl_easy_setopt(curl, CURLOPT_URL, data.c_str());
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, curl_write);
curl_easy_perform(curl);
curl_easy_reset(curl);
}
And as Peter points out your handling of the data variable has a very similar problem.