shmdt(2) [osf1 man page]

shmdt(2)							System Calls Manual							  shmdt(2)

NAME

       shmdt - Detaches a shared memory region

SYNOPSIS

       #include <sys/shm.h>

       int shmdt(
	       const void *addr);

       Application developers may want to specify #include statements for <sys/types.h> and
	<sys/ipc.h>  before the one for <sys/shm.h> if programs are being developed for multiple platforms. The additional #include statements are
       not required on Tru64 UNIX systems or by ISO or X/Open standards, but may be required on other vendors' systems that conform to these stan-
       dards.

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       shmdt():  XPG4, XPG4-UNIX

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

PARAMETERS

       Specifies  the  starting  virtual  address for the shared memory region to be detached.	This is the address returned by a previous shmat()
       call.

DESCRIPTION

       The shmdt() function detaches the shared memory region at the address specified by the addr  parameter.	 Other	instances  of  the  region
       attached at other addresses are unaffected.

RETURN VALUES

       Upon  successful completion, the shmdt() function decrements the value of shm_nattach in the data structure associated with the shared mem-
       ory ID of the attached shared memory segment and returns 0 (zero).  Upon failure,  the  shared  memory  segment	is  not  detached,  -1	is
       returned, and errno is set to indicate the error.

ERRORS

       The  shmdt()  function  sets  errno  to the specified values for the following conditions: The addr parameter does not specify the starting
       address of a shared memory region.

RELATED INFORMATION

       Functions: shmat(2), shmctl(2), shmget(2)

       Data structures: shmid_ds(4)

       Standards: standards(5) delim off

																	  shmdt(2)

SHMAT(2)						      BSD System Calls Manual							  SHMAT(2)

NAME

     shmat, shmdt -- map/unmap shared memory

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <sys/shm.h>

     void *
     shmat(int shmid, const void *shmaddr, int shmflg);

     int
     shmdt(const void *shmaddr);

DESCRIPTION

     shmat() maps the shared memory segment associated with the shared memory identifier shmid into the address space of the calling process.  The
     address at which the segment is mapped is determined by the shmaddr parameter.  If it is equal to 0, the system will pick an address itself.
     Otherwise, an attempt is made to map the shared memory segment at the address shmaddr specifies.  If SHM_RND is set in shmflg, the system
     will round the address down to a multiple of SHMLBA bytes (SHMLBA is defined in <sys/shm.h>).

     A shared memory segment can be mapped read-only by specifying the SHM_RDONLY flag in shmflg.

     shmdt() unmaps the shared memory segment that is currently mapped at shmaddr from the calling process' address space.  shmaddr must be a
     value returned by a prior shmat() call.  A shared memory segment will remain in existence until it is removed by a call to shmctl(2) with the
     IPC_RMID command.

RETURN VALUES

     shmat() returns the address at which the shared memory segment has been mapped into the calling process' address space when successful,
     shmdt() returns 0 on successful completion.  Otherwise, a value of -1 is returned, and the global variable errno is set to indicate the
     error.

ERRORS

     shmat() will fail if:

     [EACCES]		The calling process has no permission to access this shared memory segment.

     [ENOMEM]		There is not enough available data space for the calling process to map the shared memory segment.

     [EINVAL]		shmid is not a valid shared memory identifier.

			shmaddr specifies an illegal address.

     [EMFILE]		The number of shared memory segments has reached the system-wide limit.

     shmdt() will fail if:

     [EINVAL]		shmaddr is not the start address of a mapped shared memory segment.

SEE ALSO

     ipcrm(1), ipcs(1), mmap(2), shmctl(2), shmget(2)

STANDARDS

     The shmat and shmdt system calls conform to X/Open System Interfaces and Headers Issue 5 (``XSH5'').

HISTORY

     Shared memory segments appeared in the first release of AT&T System V UNIX.

BSD
								   June 17, 2002							       BSD