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.

       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 will be called 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 will 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 will be set to zero (like if you
       only download data, the upload size will remain 0). Many times the callback will be 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  will  cause  libcurl  to
       continue executing the default progress function.

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

       If you transfer data with the multi interface, this function will  not  be  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

       By default, libcurl has an internal progress meter. That is rarely wanted by users.

PROTOCOLS

       All

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 = (struct progress *)clientp;

          /* use the values */

          return 0; /* all is good */
        }

        struct progress data;

        /* pass struct to callback  */
        curl_easy_setopt(curl_handle, CURLOPT_PROGRESSDATA, &data);

        curl_easy_setopt(curl_handle, CURLOPT_PROGRESSFUNCTION, progress_callback);

AVAILABILITY

       Always

RETURN VALUE

       Returns CURLE_OK.

SEE ALSO

       CURLOPT_VERBOSE(3), CURLOPT_NOPROGRESS(3),