.\" **************************************************************************
.\" *                                  _   _ ____  _
.\" *  Project                     ___| | | |  _ \| |
.\" *                             / __| | | | |_) | |
.\" *                            | (__| |_| |  _ <| |___
.\" *                             \___|\___/|_| \_\_____|
.\" *
.\" * Copyright (C) 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.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.
.\" *
.\" * SPDX-License-Identifier: curl
.\" *
.\" **************************************************************************
.\"
.TH CURLOPT_UPLOAD_BUFFERSIZE 3 "December 04, 2023" "ibcurl 8.5.0" libcurl

.SH NAME
CURLOPT_UPLOAD_BUFFERSIZE \- upload buffer size
.SH SYNOPSIS
.nf
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_UPLOAD_BUFFERSIZE, long size);
.fi
.SH DESCRIPTION
Pass a long specifying your preferred \fIsize\fP (in bytes) for the upload
buffer in libcurl. It makes libcurl uses a larger buffer that gets passed to
the next layer in the stack to get sent off. In some setups and for some
protocols, there is a huge performance benefit of having a larger upload
buffer.

This is just treated as a request, not an order. You cannot be guaranteed to
actually get the given size.

The upload buffer size is by default 64 kilobytes. The maximum buffer size
allowed to be set is 2 megabytes. The minimum buffer size allowed to be set is
16 kilobytes.

The upload buffer is allocated on-demand - so if the handle is not used for
upload, this buffer is not allocated at all.

DO NOT set this option on a handle that is currently used for an active
transfer as that may lead to unintended consequences.
.SH DEFAULT
65536 bytes
.SH PROTOCOLS
All
.SH EXAMPLE
.nf
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    curl_easy_setopt(curl, CURLOPT_URL, "sftp://example.com/foo.bin");

    /* ask libcurl to allocate a larger upload buffer */
    curl_easy_setopt(curl, CURLOPT_UPLOAD_BUFFERSIZE, 120000L);

    res = curl_easy_perform(curl);

    curl_easy_cleanup(curl);
  }
}
.fi
.SH AVAILABILITY
Added in 7.62.0.
.SH RETURN VALUE
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
.SH "SEE ALSO"
.BR CURLOPT_BUFFERSIZE (3),
.BR CURLOPT_READFUNCTION (3),
.BR CURLOPT_TCP_NODELAY (3)