CURLOPT_XFERINFOFUNCTION(3)curl_easy_setopt optionsCURLOPT_XFERINFOFUNCTION(3)

NAME
       CURLOPT_XFERINFOFUNCTION - callback to progress meter function

SYNOPSIS
       #include <curl/curl.h>

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

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

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

       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_XFERINFODATA(3), it is not used
       by  libcurl  but is only passed along from the application to the call-
       back.

       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
       Added in 7.32.0. This callback replaces CURLOPT_PROGRESSFUNCTION(3)

RETURN VALUE
       Returns CURLE_OK.

SEE ALSO
       CURLOPT_XFERINFODATA(3), CURLOPT_NOPROGRESS(3),

libcurl 7.54.0                 February 03, 2016   CURLOPT_XFERINFOFUNCTION(3)