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 $
40 .Nd UNIX-domain protocol family
47 protocol family is a collection of protocols
48 that provides local (on-machine) interprocess
49 communication through the normal
59 filesystem pathnames for addressing.
62 addresses are variable-length filesystem pathnames of
63 at most 104 characters.
67 .Bd -literal -offset indent
79 causes a socket file to be created in the filesystem.
82 removed when the socket is closed \(em
84 must be used to remove the file.
88 protocol family does not support broadcast addressing or any form
91 matching on incoming messages.
92 All addresses are absolute- or relative-pathnames
96 Normal filesystem access-control mechanisms are also
97 applied when referencing pathnames; e.g., the destination
106 protocol family is comprised of simple
107 transport protocols that support the
113 sockets also support the communication of
115 file descriptors through the use of the
124 Any valid descriptor may be sent in a message.
125 The file descriptor(s) to be passed are described using a
127 that is defined in the include file
128 .Aq Pa sys/socket.h .
129 The type of the message is
131 and the data portion of the messages is an array of integers
132 representing the file descriptors to be passed.
133 The number of descriptors being passed is defined
134 by the length field of the message;
135 the length field is the sum of the size of the header
136 plus the size of the array of file descriptors.
138 The received descriptor is a
140 of the sender's descriptor, as if it were created with a call to
142 Per-process descriptor flags, set with
146 passed to a receiver.
147 Descriptors that are awaiting delivery, or that are
148 purposely not received, are automatically closed by the system
149 when the destination socket is closed.
151 The effective credentials (i.e., the user ID and group list) of a
154 socket may be obtained using the
157 This may be used by a server to obtain and verify the credentials of
158 its client, and vice versa by the client to verify the credentials
160 These will arrive in the form of a filled in
163 .Aq Pa sys/ucred.h ) .
164 The credentials presented to the server (the
166 caller) are those of the client when it called
168 the credentials presented to the client (the
170 caller) are those of the server when it called
172 This mechanism is reliable; there is no way for either party to influence
173 the credentials presented to its peer except by calling the appropriate
178 under different effective credentials.
183 .%T "An Introductory 4.3 BSD Interprocess Communication Tutorial"
188 .%T "An Advanced 4.3 BSD Interprocess Communication Tutorial"