Question

I’m trying to make a callback function, and then write the content retrieved into a file using libcurl. The program works nicely in Linux and Windows, however, the fopen operation fails in solarix_x86. myvector contains a list of url files to be copied, and PATH_SEPARATOR is a macro which formats the string path, depending on the platform (Unix, Windows).

  vector<string>::iterator it;

  for( it=myvector.begin() ; it < myvector.end(); it++ ){
      string dest = "/home/files/" + PATH_SEPARATOR + *it // PATH_SEPARATOR IS A MACRO
      curl_easy_setopt(curl, CURLOPT_URL, it->c_str());
      curl_easy_setopt(curl, CURL_WRITEFUNCTION, write_data);

      file = fopen(dest.c_str(), "w+b");
      if(file == NULL){
          throw std::runtime_error("FILE IS NULL, CAN'T OPEN\n");
      }

      curl_easy_setopt(curl, CURLOPT_WRITEDATA, file);
      curl_easy_perform(curl);
      fclose(file);
  }

And function write_data:

static size_t write_data(void *ptr, size_t size, size_t nmemb, void *stream){
     size_t written = fwrite(ptr, size, nmemb, (FILE*)stream);
     return written;
}

I’m suspecting is something related to the "w+b" flag…. Any thoughts?

************ UPDATE **********

errno=2.

Answer 1

Don’t confuse characters and character arrays: You want "w+b". Mind the quotation marks.

A good (or ‘properly operated’) compiler should have warned you about the fact that you are using a “multibyte character constant” (namely your 'w+b'), which is an obscure feature of C++ that almost never makes sense.