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CURLOPT_CHUNK_BGN_FUNCTION(3)       libcurl      CURLOPT_CHUNK_BGN_FUNCTION(3)

NAME
       CURLOPT_CHUNK_BGN_FUNCTION - callback before a transfer with FTP
       wildcard match

SYNOPSIS
       #include <curl/curl.h>

       struct curl_fileinfo {
         char *filename;
         curlfiletype filetype;
         time_t time;   /* always zero! */
         unsigned int perm;
         int uid;
         int gid;
         curl_off_t size;
         long int hardlinks;

         struct {
           /* If some of these fields is not NULL, it is a pointer to b_data. */
           char *time;
           char *perm;
           char *user;
           char *group;
           char *target; /* pointer to the target filename of a symlink */
         } strings;

         unsigned int flags;

         /* used internally */
         char *b_data;
         size_t b_size;
         size_t b_used;
       };

       long chunk_bgn_callback(const void *transfer_info, void *ptr,
                               int remains);

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CHUNK_BGN_FUNCTION,
                                 chunk_bgn_callback);

DESCRIPTION
       Pass a pointer to your callback function, which should match the
       prototype shown above.

       This callback function gets called by libcurl before a part of the
       stream is going to be transferred (if the transfer supports chunks).

       The transfer_info pointer will point to a curl_fileinfo struct with
       details about the file that is about to get transferred.

       This callback makes sense only when using the CURLOPT_WILDCARDMATCH(3)
       option for now.

       The target of transfer_info parameter is a "feature depended"
       structure. For the FTP wildcard download, the target is curl_fileinfo
       structure (see curl/curl.h).  The parameter ptr is a pointer given by
       CURLOPT_CHUNK_DATA(3). The parameter remains contains number of chunks
       remaining per the transfer. If the feature is not available, the
       parameter has zero value.

       Return CURL_CHUNK_BGN_FUNC_OK if everything is fine,
       CURL_CHUNK_BGN_FUNC_SKIP if you want to skip the concrete chunk or
       CURL_CHUNK_BGN_FUNC_FAIL to tell libcurl to stop if some error
       occurred.

DEFAULT
       NULL

PROTOCOLS
       FTP

EXAMPLE
       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);
       }

AVAILABILITY
       This was added in 7.21.0

RETURN VALUE
       Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION
       if not.

SEE ALSO
       CURLOPT_CHUNK_END_FUNCTION(3), CURLOPT_WILDCARDMATCH(3),

ibcurl 8.1.2                    April 26, 2023   CURLOPT_CHUNK_BGN_FUNCTION(3)