1 .\" Copyright (c) 1991, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
12 .\" 3. All advertising materials mentioning features or use of this software
13 .\" must display the following acknowledgement:
14 .\" This product includes software developed by the University of
15 .\" California, Berkeley and its contributors.
16 .\" 4. Neither the name of the University nor the names of its contributors
17 .\" may be used to endorse or promote products derived from this software
18 .\" without specific prior written permission.
20 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 .\" @(#)unix.4 8.1 (Berkeley) 6/9/93
33 .\" $FreeBSD: src/share/man/man4/unix.4,v 1.3.2.4 2002/04/22 08:59:53 dd Exp $
34 .\" $DragonFly: src/share/man/man4/unix.4,v 1.3 2006/05/26 19:39:39 swildner Exp $
41 .Nd UNIX-domain protocol family
48 protocol family is a collection of protocols
49 that provides local (on-machine) interprocess
50 communication through the normal
61 filesystem pathnames for addressing.
64 addresses are variable-length filesystem pathnames of
65 at most 104 characters.
69 .Bd -literal -offset indent
81 causes a socket file to be created in the filesystem.
84 removed when the socket is closed \(em
86 must be used to remove the file.
90 protocol family does not support broadcast addressing or any form
93 matching on incoming messages.
94 All addresses are absolute- or relative-pathnames
98 Normal filesystem access-control mechanisms are also
99 applied when referencing pathnames; e.g., the destination
108 protocol family is comprised of simple
109 transport protocols that support the
119 sockets also support the communication of
121 file descriptors through the use of the
130 Any valid descriptor may be sent in a message.
131 The file descriptor(s) to be passed are described using a
133 that is defined in the include file
135 The type of the message is
137 and the data portion of the messages is an array of integers
138 representing the file descriptors to be passed.
139 The number of descriptors being passed is defined
140 by the length field of the message;
141 the length field is the sum of the size of the header
142 plus the size of the array of file descriptors.
144 The received descriptor is a
146 of the sender's descriptor, as if it were created with a call to
148 Per-process descriptor flags, set with
152 passed to a receiver.
153 Descriptors that are awaiting delivery, or that are
154 purposely not received, are automatically closed by the system
155 when the destination socket is closed.
157 The effective credentials (i.e., the user ID and group list) of a
160 socket may be obtained using the
163 This may be used by a server to obtain and verify the credentials of
164 its client, and vice versa by the client to verify the credentials
166 These will arrive in the form of a filled in
170 The credentials presented to the server (the
172 caller) are those of the client when it called
174 the credentials presented to the client (the
176 caller) are those of the server when it called
178 This mechanism is reliable; there is no way for either party to influence
179 the credentials presented to its peer except by calling the appropriate
184 under different effective credentials.
189 .%T "An Introductory 4.3 BSD Interprocess Communication Tutorial"
194 .%T "An Advanced 4.3 BSD Interprocess Communication Tutorial"