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+.\" **************************************************************************
+.\" *                                  _   _ ____  _
+.\" *  Project                     ___| | | |  _ \| |
+.\" *                             / __| | | | |_) | |
+.\" *                            | (__| |_| |  _ <| |___
+.\" *                             \___|\___/|_| \_\_____|
+.\" *
+.\" * Copyright (C) 1998 - 2014, Daniel Stenberg, <daniel@haxx.se>, 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.haxx.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_PROGRESSFUNCTION 3 "17 Jun 2014" "libcurl 7.37.0" "curl_easy_setopt options"
+.SH NAME
+CURLOPT_PROGRESSFUNCTION \- callback to progress meter function
+.SH 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);
+.SH DESCRIPTION
+Pass a pointer to your callback function, which should match the prototype
+shown above.
+
+We encourage users to use the newer \fICURLOPT_XFERINFOFUNCTION(3)\fP 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.
+
+\fIclientp\fP is the pointer set with \fICURLOPT_PROGRESSDATA(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.
+
+Returning a 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.haxx.se/libcurl/c/progressfunc.html
+.SH AVAILABILITY
+Always
+.SH RETURN VALUE
+Returns CURLE_OK.
+.SH "SEE ALSO"
+.BR CURLOPT_VERBOSE "(3), " CURLOPT_NOPROGRESS "(3), "