**************************************************************************
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* Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
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* furnished to do so, under the terms of the COPYING file.
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CURLOPT_CHUNK_DATA - custom pointer to the FTP chunk callbacks #include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CHUNK_DATA, void *pointer); Pass a pointer that will be untouched by libcurl and passed as the ptr argument to the CURLOPT_CHUNK_BGN_FUNCTION(3) and CURLOPT_CHUNK_END_FUNCTION(3). NULL FTP

static long file_is_coming(struct curl_fileinfo *finfo,
 struct callback_data *data,
 int remains)
{
 printf("%3d %40s %10luB ", remains, finfo->filename,
 (unsigned long)finfo->size);

 switch(finfo->filetype) {
 case CURLFILETYPE_DIRECTORY:
 printf(" DIR\n");
 break;
 case CURLFILETYPE_FILE:
 printf("FILE ");
 break;
 default:
 printf("OTHER\n");
 break;
 }

 if(finfo->filetype == CURLFILETYPE_FILE) {
 /* do not transfer files >= 50B */
 if(finfo->size > 50) {
 printf("SKIPPED\n");
 return CURL_CHUNK_BGN_FUNC_SKIP;
 }

 data->output = fopen(finfo->filename, "wb");
 if(!data->output) {
 return CURL_CHUNK_BGN_FUNC_FAIL;
 }
 }

 return CURL_CHUNK_BGN_FUNC_OK;
}

int main()
{
 /* data for callback */
 struct callback_data callback_info;

 /* callback is called before download of concrete file started */
 curl_easy_setopt(curl, CURLOPT_CHUNK_BGN_FUNCTION, file_is_coming);
 curl_easy_setopt(curl, CURLOPT_CHUNK_DATA, &callback_info);
}

Added in 7.21.0 Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not. CURLOPT_CHUNK_BGN_FUNCTION "(3), " CURLOPT_WILDCARDMATCH "(3), "