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+.\" **************************************************************************
+.\" *                                  _   _ ____  _
+.\" *  Project                     ___| | | |  _ \| |
+.\" *                             / __| | | | |_) | |
+.\" *                            | (__| |_| |  _ <| |___
+.\" *                             \___|\___/|_| \_\_____|
+.\" *
+.\" * Copyright (C) 1998 - 2017, 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_HEADERDATA 3 "17 Jun 2014" "libcurl 7.37.0" "curl_easy_setopt options"
+.SH NAME
+CURLOPT_HEADERDATA \- pointer to pass to header callback
+.SH SYNOPSIS
+#include <curl/curl.h>
+
+CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HEADERDATA, void *pointer);
+.SH DESCRIPTION
+Pass a \fIpointer\fP to be used to write the header part of the received data
+to.
+
+If \fICURLOPT_WRITEFUNCTION(3)\fP or \fICURLOPT_HEADERFUNCTION(3)\fP is used,
+\fIpointer\fP will be passed in to the respective callback.
+
+If neither of those options are set, \fIpointer\fP must be a valid FILE * and
+it will be used by a plain fwrite() to write headers to.
+.SH DEFAULT
+NULL
+.SH PROTOCOLS
+All
+.SH EXAMPLE
+.nf
+struct my_info {
+  int shoesize;
+  char *secret;
+};
+
+static size_t header_callback(char *buffer, size_t size,
+                              size_t nitems, void *userdata)
+{
+  struct my_info *i = (struct my_info *)userdata;
+
+  /* now this callback can access the my_info struct */
+
+  return nitems * size;
+}
+
+CURL *curl = curl_easy_init();
+if(curl) {
+  struct my_info my = { 10, "the cookies are in the cupboard" };
+  curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
+
+  curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, header_callback);
+
+  /* pass in custom data to the callback */
+  curl_easy_setopt(curl, CURLOPT_HEADERDATA, &my);
+
+  curl_easy_perform(curl);
+}
+.fi
+.SH AVAILABILITY
+Always
+.SH RETURN VALUE
+Returns CURLE_OK
+.SH "SEE ALSO"
+.BR CURLOPT_HEADERFUNCTION "(3), " CURLOPT_WRITEFUNCTION "(3), "