1.\" $OpenBSD: BIO_s_null.3,v 1.10 2023/04/11 16:58:43 schwarze Exp $ 2.\" full merge up to: OpenSSL e9b77246 Jan 20 19:58:49 2017 +0100 3.\" 4.\" This file was written by Dr. Stephen Henson <steve@openssl.org>. 5.\" Copyright (c) 2000 The OpenSSL Project. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in 16.\" the documentation and/or other materials provided with the 17.\" distribution. 18.\" 19.\" 3. All advertising materials mentioning features or use of this 20.\" software must display the following acknowledgment: 21.\" "This product includes software developed by the OpenSSL Project 22.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 23.\" 24.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 25.\" endorse or promote products derived from this software without 26.\" prior written permission. For written permission, please contact 27.\" openssl-core@openssl.org. 28.\" 29.\" 5. Products derived from this software may not be called "OpenSSL" 30.\" nor may "OpenSSL" appear in their names without prior written 31.\" permission of the OpenSSL Project. 32.\" 33.\" 6. Redistributions of any form whatsoever must retain the following 34.\" acknowledgment: 35.\" "This product includes software developed by the OpenSSL Project 36.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" 37.\" 38.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 39.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 40.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 41.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 42.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 43.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 44.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 45.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 46.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 47.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 48.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 49.\" OF THE POSSIBILITY OF SUCH DAMAGE. 50.\" 51.Dd $Mdocdate: April 11 2023 $ 52.Dt BIO_S_NULL 3 53.Os 54.Sh NAME 55.Nm BIO_s_null 56.\" .Nm BIO_s_log is intentionally undocumented because it is unused 57.Nd null data sink 58.Sh SYNOPSIS 59.In openssl/bio.h 60.Ft const BIO_METHOD * 61.Fo BIO_s_null 62.Fa void 63.Fc 64.Sh DESCRIPTION 65.Fn BIO_s_null 66returns the null sink BIO method. 67Data written to the null sink is discarded, reads return EOF. 68.Pp 69A null sink BIO behaves in a similar manner to the 70.Xr null 4 71device. 72.Pp 73A null BIO can be placed on the end of a chain to discard any data 74passed through it. 75.Pp 76A null sink is useful if, for example, an application wishes 77to digest some data by writing through a digest bio 78but not send the digested data anywhere. 79Since a BIO chain must normally include a source/sink BIO, 80this can be achieved by adding a null sink BIO to the end of the chain. 81.Sh RETURN VALUES 82.Fn BIO_s_null 83returns the null sink BIO method. 84.Pp 85When called on a null sink BIO object, 86.Xr BIO_method_type 3 87returns the constant 88.Dv BIO_TYPE_NULL 89and 90.Xr BIO_method_name 3 91returns a pointer to the static string 92.Qq NULL , 93not to be confused with a NUL string nor with a 94.Dv NULL 95pointer. 96.Sh SEE ALSO 97.Xr BIO_new 3 98.Sh HISTORY 99.Fn BIO_s_null 100first appeared in SSLeay 0.6.0 and has been available since 101.Ox 2.4 . 102