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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
       posix_typed_mem_open — open a typed memory object (ADVANCED REALTIME)


SYNOPSIS
       #include <sys/mman.h>

       int posix_typed_mem_open(const char *name, int oflag, int tflag);


DESCRIPTION
       The  posix_typed_mem_open()  function  shall  establish  a  connection  between  the  typed memory object
       specified by the string pointed to by  name  and  a  file  descriptor.  It  shall  create  an  open  file
       description  that  refers  to the typed memory object and a file descriptor that refers to that open file
       description. The file descriptor shall be  allocated  as  described  in  Section  2.14,  File  Descriptor
       Allocation  and  can  be  used by other functions to refer to that typed memory object. It is unspecified
       whether the name appears in the file system and is visible to other  functions  that  take  pathnames  as
       arguments.  The  name  argument  conforms  to  the  construction  rules  for  a pathname, except that the
       interpretation of <slash> characters other than the leading <slash> character in name is  implementation-
       defined,  and that the length limits for the name argument are implementation-defined and need not be the
       same as the pathname limits {PATH_MAX} and {NAME_MAX}.  If name begins with the <slash>  character,  then
       processes calling posix_typed_mem_open() with the same value of name shall refer to the same typed memory
       object. If name does not begin with the <slash> character, the effect is implementation-defined.

       Each typed memory object supported in a system shall be identified by a name which specifies not only its
       associated  typed memory pool, but also the path or port by which it is accessed. That is, the same typed
       memory pool accessed via several different ports shall have several different  corresponding  names.  The
       binding between names and typed memory objects is established in an implementation-defined manner. Unlike
       shared memory objects, there is no way within POSIX.1‐2008 for a program to create a typed memory object.

       The value of tflag shall determine how the typed memory object behaves when subsequently mapped by  calls
       to mmap().  At most, one of the following flags defined in <sys/mman.h> may be specified:

       POSIX_TYPED_MEM_ALLOCATE
             Allocate on mmap().

       POSIX_TYPED_MEM_ALLOCATE_CONTIG
             Allocate contiguously on mmap().

       POSIX_TYPED_MEM_MAP_ALLOCATABLE
             Map on mmap(), without affecting allocatability.

       If  tflag  has  the  flag  POSIX_TYPED_MEM_ALLOCATE  specified,  any  subsequent call to mmap() using the
       returned file descriptor shall result in allocation and mapping of typed memory from the specified  typed
       memory  pool.  The  allocated  memory may be a contiguous previously unallocated area of the typed memory
       pool or several non-contiguous previously unallocated areas  (mapped  to  a  contiguous  portion  of  the
       process  address  space). If tflag has the flag POSIX_TYPED_MEM_ALLOCATE_CONTIG specified, any subsequent
       call to mmap() using the returned file descriptor shall result in allocation  and  mapping  of  a  single
       contiguous  previously  unallocated area of the typed memory pool (also mapped to a contiguous portion of
       the  process  address  space).  If  tflag   has   none   of   the   flags   POSIX_TYPED_MEM_ALLOCATE   or
       POSIX_TYPED_MEM_ALLOCATE_CONTIG  specified,  any  subsequent  call  to  mmap()  using  the  returned file
       descriptor shall map an application-chosen area from the specified  typed  memory  pool  such  that  this
       mapped  area  becomes  unavailable  for allocation until unmapped by all processes. If tflag has the flag
       POSIX_TYPED_MEM_MAP_ALLOCATABLE specified,  any  subsequent  call  to  mmap()  using  the  returned  file
       descriptor shall map an application-chosen area from the specified typed memory pool without an effect on
       the availability of that area for allocation; that is, mapping such an object leaves  each  byte  of  the
       mapped area unallocated if it was unallocated prior to the mapping or allocated if it was allocated prior
       to  the  mapping.  Appropriate  privileges  to  specify  the  POSIX_TYPED_MEM_MAP_ALLOCATABLE  flag   are
       implementation-defined.

       If  successful,  posix_typed_mem_open()  shall return a file descriptor for the typed memory object.  The
       open file description is new, and therefore the file  descriptor  shall  not  share  it  with  any  other
       processes.  It  is  unspecified  whether  the  file  offset  is  set. The FD_CLOEXEC file descriptor flag
       associated with the new file descriptor shall be cleared.

       The behavior of msync(), ftruncate(), and all file  operations  other  than  mmap(),  posix_mem_offset(),
       posix_typed_mem_get_info(),  fstat(),  dup(),  dup2(),  and  close(),  is  unspecified when passed a file
       descriptor connected to a typed memory object by this function.

       The file status flags of the open file description  shall  be  set  according  to  the  value  of  oflag.
       Applications shall specify exactly one of the three access mode values described below and defined in the
       <fcntl.h> header, as the value of oflag.

       O_RDONLY    Open for read access only.

       O_WRONLY    Open for write access only.

       O_RDWR      Open for read or write access.


RETURN VALUE
       Upon successful completion, the posix_typed_mem_open()  function  shall  return  a  non-negative  integer
       representing the file descriptor. Otherwise, it shall return -1 and set errno to indicate the error.


ERRORS
       The posix_typed_mem_open() function shall fail if:

       EACCES The typed memory object exists and the permissions specified by oflag are denied.

       EINTR  The posix_typed_mem_open() operation was interrupted by a signal.

       EINVAL The flags specified in tflag are invalid (more than one of POSIX_TYPED_MEM_ALLOCATE,
              POSIX_TYPED_MEM_ALLOCATE_CONTIG, or POSIX_TYPED_MEM_MAP_ALLOCATABLE is specified).

       EMFILE All file descriptors available to the process are currently open.

       ENFILE Too many file descriptors are currently open in the system.

       ENOENT The named typed memory object does not exist.

       EPERM  The caller lacks appropriate privileges to specify the POSIX_TYPED_MEM_MAP_ALLOCATABLE flag in the
              tflag argument.

       The posix_typed_mem_open() function may fail if:

       ENAMETOOLONG
              The  length  of the name argument exceeds {_POSIX_PATH_MAX} on systems that do not support the XSI
              option or exceeds {_XOPEN_PATH_MAX} on XSI systems, or has a pathname  component  that  is  longer
              than   {_POSIX_NAME_MAX}   on  systems  that  do  not  support  the  XSI  option  or  longer  than
              {_XOPEN_NAME_MAX} on XSI systems.

       The following sections are informative.


EXAMPLES
       None.


APPLICATION USAGE
       None.


RATIONALE
       None.


FUTURE DIRECTIONS
       None.


SEE ALSO
       Section 2.14, File Descriptor Allocation, close(), dup(), exec, fcntl(),  fstat(),  ftruncate(),  mmap(),
       msync(), posix_mem_offset(), posix_typed_mem_get_info(), umask()

       The Base Definitions volume of POSIX.1‐2017, <fcntl.h>, <sys_mman.h>


       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 .