CURLOPT_WRITEFUNCTION: initial man page

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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 http://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_WRITEFUNCTION 3 "16 Jun 2014" "libcurl 7.37.0" "curl_easy_setopt options"
+.SH NAME
+CURLOPT_WRITEFUNCTION \- set callback for writing received data
+.SH SYNOPSIS
+.nf
+#include <curl/curl.h>
+
+size_t write_callback(char *ptr, size_t size, size_t nmemb, void *userdata);
+
+CURLcode curl_easy_setopt(CURL *handle, CURLOPT_WRITEFUNCTION, write_callback);
+.SH DESCRIPTION
+Pass a pointer to your callback function, as the prototype shows above.
+
+This callback function gets called by libcurl as soon as there is data
+received that needs to be saved.  \fIptr\fP points to the delivered data, and
+the size of that data is \fIsize\fP multiplied with \fInmemb\fP.
+
+The received data will not be zero terminated!
+
+Return the number of bytes actually taken care of. If that amount differs from
+the amount passed to your callback function, it'll signal an error condition
+to the library. This will cause the transfer to get aborted and return
+\fICURLE_WRITE_ERROR\fP.
+
+The callback function can return CURL_WRITEFUNC_PAUSE which then will cause
+writing to this connection to become paused. See \fIcurl_easy_pause(3)\fP for
+further details.
+
+This function may be called with zero bytes data if the transferred file is
+empty.
+
+Set this option to NULL to get the internal default function used instead of
+your callback. The internal default function will write the data to the FILE *
+given with \fICURLOPT_WRITEDATA(3)\fP.
+
+Set the \fIuserdata\fP argument with the \fICURLOPT_WRITEDATA(3)\fP option.
+
+The callback function will be passed as much data as possible in all invokes,
+but you cannot possibly make any assumptions. It may be one byte, it may be
+thousands. The maximum amount of body data that can be passed to the write
+callback is defined in the curl.h header file: CURL_MAX_WRITE_SIZE (the usual
+default is 16K). If you however have \fICURLOPT_HEADER(3)\fP set, which sends
+header data to the write callback, you can get up to
+\fICURL_MAX_HTTP_HEADER\fP bytes of header data passed into it. This usually
+means 100K.
+.SH PROTOCOLS
+For all protocols
+.SH AVAILABILITY
+Support for the CURL_WRITEFUNC_PAUSE return code was added in version 7.18.0.
+.SH EXAMPLE
+A common technique is to use this callback to store the incoming data into a
+dynamically growing allocated buffer. Like in the getinmemory example:
+http://curl.haxx.se/libcurl/c/getinmemory.html
+.SH "SEE ALSO"
+.BR CURLOPT_WRITEDATA "(3), " CURLOPT_READFUNCTION "(3), "