PROLOG

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

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 .