1.\" $OpenBSD: socketpair.2,v 1.21 2018/04/08 18:46:43 schwarze Exp $ 2.\" $NetBSD: socketpair.2,v 1.5 1995/02/27 12:38:00 cgd Exp $ 3.\" 4.\" Copyright (c) 1983, 1991, 1993 5.\" The Regents of the University of California. 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.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)socketpair.2 8.1 (Berkeley) 6/4/93 32.\" 33.Dd $Mdocdate: April 8 2018 $ 34.Dt SOCKETPAIR 2 35.Os 36.Sh NAME 37.Nm socketpair 38.Nd create a pair of connected sockets 39.Sh SYNOPSIS 40.In sys/socket.h 41.Ft int 42.Fn socketpair "int domain" "int type" "int protocol" "int sv[2]" 43.Sh DESCRIPTION 44The 45.Fn socketpair 46call creates an unnamed pair of connected sockets. 47The descriptors used in referencing the new sockets 48are returned in 49.Fa sv Ns [0] 50and 51.Fa sv Ns [1] . 52The two sockets are indistinguishable. 53.Pp 54The only supported 55.Fa domain 56is 57.Dv AF_UNIX . 58Possible values for the 59.Fa type 60and 61.Fa protocol 62arguments are explained in the 63.Xr socket 2 64manual page. 65The only useful value for 66.Fa protocol 67is 0, which will let the system select an appropriate protocol 68for the requested socket 69.Fa type . 70.Pp 71Any combination of the following flags may additionally be used in the 72.Fa type 73argument: 74.Pp 75.Bl -tag -width "SOCK_NONBLOCKX" -offset indent -compact 76.It SOCK_CLOEXEC 77Set close-on-exec flag on both the new descriptors. 78.It SOCK_NONBLOCK 79Set non-blocking I/O mode on both the new sockets. 80.El 81.Sh RETURN VALUES 82.Rv -std 83.Sh ERRORS 84The call succeeds unless: 85.Bl -tag -width Er 86.It Bq Er EAFNOSUPPORT 87The specified address family is not supported on this machine. 88.It Bq Er EPROTONOSUPPORT 89The specified protocol is not supported on this machine. 90.It Bq Er EOPNOTSUPP 91The specified protocol does not support creation of socket pairs. 92.It Bq Er EPROTOTYPE 93The combination of the specified protocol and type is not supported. 94.It Bq Er EMFILE 95The per-process descriptor table is full. 96.It Bq Er ENFILE 97The system file table is full. 98.It Bq Er ENOBUFS 99Insufficient resources were available in the system 100to perform the operation. 101.It Bq Er EFAULT 102The address 103.Fa sv 104does not specify a valid part of the 105process address space. 106.El 107.Sh SEE ALSO 108.Xr pipe 2 , 109.Xr read 2 , 110.Xr socket 2 , 111.Xr write 2 112.Sh STANDARDS 113The 114.Fn socketpair 115function conforms to 116.St -p1003.1-2008 . 117The 118.Dv SOCK_CLOEXEC 119and 120.Dv SOCK_NONBLOCK 121flags are expected to conform to a future revision of that standard. 122.Sh HISTORY 123The 124.Fn socketpair 125function call appeared in 126.Bx 4.2 . 127Support for the 128.Dv SOCK_CLOEXEC 129and 130.Dv SOCK_NONBLOCK 131flags appeared in 132.Ox 5.7 . 133