I made the write callback create the file the first time it gets called so

#include <curl/types.h>

#include <curl/easy.h>

/* to make this work under windows, use the win32-functions from the

   win32socket.c file as well */

/*

 * This is an example showing how to get a single file from an FTP server.

 * It delays the actual destination file creation until the first write

 * callback so that it won't create an empty file in case the remote file

 * doesn't exist or something else fails.

 */

struct FtpFile {

  char *filename;

  FILE *stream;

};

int my_fwrite(void *buffer, size_t size, size_t nmemb, void *stream)

{

  struct FtpFile *out=(struct FtpFile *)stream;

  if(out && !out->stream) {

    /* open file for writing */

    out->stream=fopen(out->filename, "wb");

    if(!out->stream)

      return -1; /* failure, can't open file to write */

  }

  return fwrite(buffer, size, nmemb, out->stream);

}

int main(int argc, char **argv)

int main(void)

{

  CURL *curl;

  CURLcode res;

  FILE *ftpfile;

  struct FtpFile ftpfile={

    "curl.tar.gz", /* name to store the file as if succesful */

    NULL

  };

  /* local file name to store the file as */

  ftpfile = fopen("curl.tar.gz", "wb"); /* b is binary for win */

  curl_global_init(CURL_GLOBAL_DEFAULT);

  curl = curl_easy_init();

  if(curl) {

    /* Get curl 7.7 from sunet.se's FTP site: */

    /* Get curl 7.9.2 from sunet.se's FTP site: */

    curl_easy_setopt(curl, CURLOPT_URL,

                     "ftp://ftp.sunet.se/pub/www/utilities/curl/curl-7.7.tar.gz");

    curl_easy_setopt(curl, CURLOPT_FILE, ftpfile);

                     "ftp://ftp.sunet.se/pub/www/utilities/curl/curl-7.9.2.tar.gz");

    /* Define our callback to get called when there's data to be written */

    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, my_fwrite);

    /* Set a pointer to our struct to pass to the callback */

    curl_easy_setopt(curl, CURLOPT_FILE, &ftpfile);

    /* Switch on full protocol/debug output */

    curl_easy_setopt(curl, CURLOPT_VERBOSE, TRUE);

    res = curl_easy_perform(curl);

    /* always cleanup */

    curl_easy_cleanup(curl);

    if(CURLE_OK != res) {

      /* we failed */

      fprintf(stderr, "curl told us %d\n", res);

    }

  }

  fclose(ftpfile); /* close the local file */

  if(ftpfile.stream)

    fclose(ftpfile.stream); /* close the local file */

  curl_global_cleanup();

  return 0;

}