sys_un.h(0p) — Linux manual page
sys_un.h(0P) POSIX Programmer's Manual sys_un.h(0P)
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(0p)), 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(0p), sys_socket.h(0p)
The System Interfaces volume of POSIX.1‐2017, bind(3p),
socket(3p), socketpair(3p)
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 .