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.


     [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 ALSO
     socket(2), netintro(7)
     IRIX Network Programming Guide.


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