sys_un.h(3)                POSIX Programmer's Manual               sys_un.h(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NAME
       sys/un.h -- definitions for UNIX domain sockets

SYNOPSIS
       #include <sys/un.h>

DESCRIPTION
       The <sys/un.h> header shall define the sockaddr_un structure, which
       shall include at least the following members:


           sa_family_t  sun_family  Address family.
           char         sun_path[]  Socket pathname.

       The sockaddr_un structure is used to store addresses for UNIX domain
       sockets.  Pointers to this type shall be cast by applications to struct
       sockaddr ** for use with socket functions.

       The <sys/un.h> header shall define the sa_family_t type as described in
       <sys/socket.h>.

       The following sections are informative.

APPLICATION USAGE
       The size of sun__path has intentionally been left undefined. This is
       because different implementations use different sizes. For example, 4.3
       BSD uses a size of 108, and 4.4 BSD uses a size of 104. Since most
       implementations originate from BSD versions, the size is typically in
       the range 92 to 108.

       Applications should not assume a particular length for sun__path or
       assume that it can hold {_POSIX_PATH_MAX} bytes (256).

       Although applications are required to initialize all members (including
       any non-standard ones) of a sockaddr_in6 structure (see
       <netinet_in.h>), the same is not required for the sockaddr_un
       structure, since historically many applications only initialized the
       standard members. Despite this, applications are encouraged to
       initialize sockaddr_un structures in a manner similar to the required
       initialization of sockaddr_in6 structures.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       <netinet_in.h>, <sys_socket.h>

       The System Interfaces volume of POSIX.1-2017, bind(), socket(),
       socketpair()

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  In the event of any discrepancy between this version and the
       original IEEE and The Open Group Standard, the original IEEE and The
       Open Group Standard is the referee document. The original Standard can
       be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                          sys_un.h(3)
