NAME

       CURLOPT_PROGRESSFUNCTION - callback to progress meter function

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 very 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.

       Returning a 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's rarely wanted by users.

PROTOCOLS

       All

EXAMPLE

       https://curl.haxx.se/libcurl/c/progressfunc.html

AVAILABILITY

       Always

RETURN VALUE

       Returns CURLE_OK.

SEE ALSO

       CURLOPT_VERBOSE(3), CURLOPT_NOPROGRESS(3),

libcurl 7.58.0                                  February 03, 2016                    CURLOPT_PROGRESSFUNCTION(3)