Copyright (c) 1991 The Regents of the University of California.
All rights reserved.

%sccs.include.redist.man%

@(#)unix.4 6.1 (Berkeley) 03/12/91

C 5 unix - UNIX\c -domain protocol family #include <sys/types.h>

#include <sys/un.h>

2.94 went to 2.6, 3.64 to 3.30
.. 3.5i went to 3.8i
.. The UNIX\c -domain protocol family is a collection of protocols that provides local (on-machine) interprocess communication through the normal socket (2) mechanisms. The UNIX\c -domain family supports the SOCK_STREAM and SOCK_DGRAM socket types and uses filesystem pathnames for addressing. UNIX\c -domain addresses are variable-length filesystem pathnames of at most 104 characters. The include file < sys/un.h > defines this address:

._f
struct sockaddr_un {
 u_char sun_len;
 u_char sun_family;
 char sun_path[104];
};

Binding a name to a UNIX\c -domain socket with bind (2) causes a socket file to be created in the filesystem. This file is not removed when the socket is closed\(em\c unlink (2) must be used to remove the file.

The UNIX\c -domain protocol family does not support broadcast addressing or any form of \*(lqwildcard\*(rq matching on incoming messages. All addresses are absolute- or relative-pathnames of other UNIX\c -domain sockets. Normal filesystem access-control mechanisms are also applied when referencing pathnames; e.g., the destination of a connect (2) or sendto (2) must be writable.

The UNIX\c -domain protocol family is comprised of simple transport protocols that support the SOCK_STREAM and SOCK_DGRAM abstractions. SOCK_STREAM sockets also support the communication of X file descriptors through the use of the msg_accrights field in the msg argument to sendmsg (2) and recvmsg (2). Any valid descriptor may be sent in a message. The received descriptor is a duplicate of the sender's descriptor, as if it were created with a call to dup (2). Per-process descriptor flags, set with fcntl (2), are not passed to a receiver. Descriptors that are awaiting delivery, or that are purposely not received, are automatically closed by the system when the destination socket is closed. socket(2), intro(4)

An Introductory 4.3BSD Interprocess Communication Tutorial (PS1:7).

An Advanced 4.3BSD Interprocess Communication Tutorial (PS1:8).