NAME

       CURLOPT_PROGRESSFUNCTION - progress meter callback

SYNOPSIS

       #include <curl/curl.h>

       int progress_callback(void *clientp,
                             double dltotal,
                             double dlnow,
                             double ultotal,
                             double ulnow);

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROGRESSFUNCTION,
                                 progress_callback);

DESCRIPTION

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

       This    option    is    deprecated   and   we   encourage   users   to   use   the   newer
       CURLOPT_XFERINFOFUNCTION(3) instead, if you can.

       This function gets called by libcurl instead of its internal equivalent  with  a  frequent
       interval.  While  data  is  being  transferred  it  is invoked frequently, and during slow
       periods like when nothing is being transferred it can slow down  to  about  one  call  per
       second.

       clientp  is the pointer set with CURLOPT_PROGRESSDATA(3), it is not used by libcurl but is
       only passed along from the application to the callback.

       The callback gets told how much data libcurl is about to transfer and has transferred,  in
       number  of bytes. dltotal is the total number of bytes libcurl expects to download in this
       transfer. dlnow is the number of bytes downloaded so far. ultotal is the total  number  of
       bytes libcurl expects to upload in this transfer. ulnow is the number of bytes uploaded so
       far.

       Unknown/unused argument values passed to the callback are be set to zero (like if you only
       download  data,  the upload size remains 0). Many times the callback is called one or more
       times first, before it knows the data sizes so a program must be made to handle that.

       If your callback function returns CURL_PROGRESSFUNC_CONTINUE it causes libcurl to continue
       executing the default progress function.

       Returning any other non-zero value from this callback makes libcurl abort the transfer and
       return CURLE_ABORTED_BY_CALLBACK.

       If you transfer data with the multi interface, this function is not called during  periods
       of idleness unless you call the appropriate libcurl function that performs transfers.

       CURLOPT_NOPROGRESS(3) must be set to 0 to make this function actually get called.

DEFAULT

       NULL. libcurl has an internal progress meter. That is rarely wanted by users.

PROTOCOLS

       This functionality affects all supported protocols

EXAMPLE

       struct progress {
         char *private;
         size_t size;
       };

       static size_t progress_callback(void *clientp,
                                       double dltotal,
                                       double dlnow,
                                       double ultotal,
                                       double ulnow)
       {
         struct progress *memory = clientp;
         printf("private: %p\n", memory->private);

         /* use the values */

         return 0; /* all is good */
       }

       int main(void)
       {
         struct progress data;

         CURL *curl = curl_easy_init();
         if(curl) {
           /* pass struct to callback  */
           curl_easy_setopt(curl, CURLOPT_PROGRESSDATA, &data);
           curl_easy_setopt(curl, CURLOPT_PROGRESSFUNCTION, progress_callback);

           curl_easy_perform(curl);
         }
       }

DEPRECATED

       Deprecated since 7.32.0.

AVAILABILITY

       Added in curl 7.1

RETURN VALUE

       Returns CURLE_OK.

SEE ALSO

       CURLOPT_NOPROGRESS(3), CURLOPT_VERBOSE(3), CURLOPT_XFERINFOFUNCTION(3)