UNIX(7F)UNIX(7F)NAME
unix - UNIX-domain protocol family
SYNOPSIS
#include <sys/types.h>
#include <sys/un.h>
DESCRIPTION
The UNIX-domain protocol family is a collection of protocols that
provides local (on-machine) interprocess communication through the normal
socket(2) mechanisms. The UNIX-domain family supports the SOCK_STREAM
and SOCK_DGRAM socket types and uses filesystem pathnames for addressing.
ADDRESSING
UNIX-domain addresses are variable-length filesystem pathnames of at most
108 characters. The include file <sys/un.h> defines this address:
struct sockaddr_un {
short sun_family;
char sun_path[108];
};
Binding a name to a UNIX-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 - unlink(2) must be used to remove the file.
The UNIX-domain does not support broadcast addressing or any form of
"wildcard" matching on incoming messages. All addresses are absolute- or
relative-pathnames of other UNIX-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.
PROTOCOLS
The UNIX-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 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.
DIAGNOSTICS
The bind(2) and connect(2) socket operations may fail with one of the
following errors returned:
[ENOTDIR] A component of the path prefix is not a directory.
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UNIX(7F)UNIX(7F)
[ENOENT] The named file does not exist.
[EACCES] Search permission is denied for a component of the
path prefix.
[ENAMETOOLONG] The length of path exceeds {PATH_MAX}, or a pathname
component is longer than {NAME_MAX}.
[ELOOP] Too many symbolic links were encountered in
translating the pathname.
SEE ALSOsocket(2), netintro(7)
IRIX Network Programming Guide.
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