CURLOPT_XFERINFOFUNCTION - callback to progress meter function
int progress_callback(void *clientp,
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_XFERINFOFUNCTION,
Pass a pointer to your callback function, which should match the prototype shown
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.
is the pointer set with CURLOPT_XFERINFODATA(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
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.
must be set to 0 to make this function actually get
By default, libcurl has an internal progress meter. That's rarely wanted by
Added in 7.32.0. This callback replaces CURLOPT_PROGRESSFUNCTION(3)