.\" ************************************************************************** .\" * _ _ ____ _ .\" * Project ___| | | | _ \| | .\" * / __| | | | |_) | | .\" * | (__| |_| | _ <| |___ .\" * \___|\___/|_| \_\_____| .\" * .\" * Copyright (C) 1998 - 2020, Daniel Stenberg, , et al. .\" * .\" * This software is licensed as described in the file COPYING, which .\" * you should have received as part of this distribution. The terms .\" * are also available at https://curl.se/docs/copyright.html. .\" * .\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell .\" * copies of the Software, and permit persons to whom the Software is .\" * furnished to do so, under the terms of the COPYING file. .\" * .\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY .\" * KIND, either express or implied. .\" * .\" ************************************************************************** .\" .TH CURLOPT_XFERINFOFUNCTION 3 "November 04, 2020" "libcurl 7.74.0" "curl_easy_setopt options" .SH NAME CURLOPT_XFERINFOFUNCTION \- callback to progress meter function .SH SYNOPSIS #include 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); .SH DESCRIPTION Pass a pointer to your callback function, which should match the prototype 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. \fIclientp\fP is the pointer set with \fICURLOPT_XFERINFODATA(3)\fP, 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. \fIdltotal\fP is the total number of bytes libcurl expects to download in this transfer. \fIdlnow\fP is the number of bytes downloaded so far. \fIultotal\fP is the total number of bytes libcurl expects to upload in this transfer. \fIulnow\fP 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 \fICURLE_ABORTED_BY_CALLBACK\fP. 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. \fICURLOPT_NOPROGRESS(3)\fP must be set to 0 to make this function actually get called. .SH DEFAULT By default, libcurl has an internal progress meter. That's rarely wanted by users. .SH PROTOCOLS All .SH EXAMPLE https://curl.se/libcurl/c/progressfunc.html .SH AVAILABILITY Added in 7.32.0. This callback replaces \fICURLOPT_PROGRESSFUNCTION(3)\fP .SH RETURN VALUE Returns CURLE_OK. .SH "SEE ALSO" .BR CURLOPT_XFERINFODATA "(3), " CURLOPT_NOPROGRESS "(3), "