shmget(2)							   System Calls 							 shmget(2)

NAME

       shmget - get shared memory segment identifier

SYNOPSIS

       #include <sys/types.h>
       #include <sys/ipc.h>
       #include <sys/shm.h>

       int shmget(key_t key, size_t size, int shmflg);

DESCRIPTION

       The shmget() function returns the shared memory identifier associated with key.

       A  shared  memory  identifier and associated data structure and shared memory segment of at least size bytes (see Intro(2)) are created for
       key if one of the following are true:

	   o	  The key argument is equal to IPC_PRIVATE.

	   o	  The key argument does not already have a shared memory identifier associated with it, and (shmflg&IPC_CREAT) is true.

       Upon creation, the data structure associated with the new shared memory identifier is initialized as follows:

	   o	  The values of shm_perm.cuid, shm_perm.uid, shm_perm.cgid, and shm_perm.gid are set equal to the effective user ID and  effective
		  group ID, respectively, of the calling process.

	   o	  The access permission bits of shm_perm.mode are set equal to the access permission bits of shmflg. shm_segsz is set equal to the
		  value of size.

	   o	  The values of shm_lpid, shm_nattch shm_atime, and shm_dtime are set equal to 0.

	   o	  The shm_ctime is set equal to the current time.

       Shared memory segments must be explicitly removed after the last reference to them has been removed.

RETURN VALUES

       Upon successful completion, a non-negative integer representing a shared memory identifier is returned. Otherwise, -1 is returned and errno
       is set to indicate the error.

ERRORS

       The shmget() function will fail if:

       EACCES	 A  shared memory identifier exists for key but operation permission (see Intro(2)) as specified by the low-order 9 bits of shmflg
		 would not be granted.

       EEXIST	 A shared memory identifier exists for key but both (shmflg&IPC_CREAT) and (shmflg&IPC_EXCL) are true.

       EINVAL	 The size argument is less than the system-imposed minimum or greater than the system-imposed maximum. See NOTES.

		 A shared memory identifier exists for key but the size of the segment associated with it is less than size and size is not  equal
		 to 0.

       ENOENT	 A shared memory identifier does not exist for key and (shmflg&IPC_CREAT) is false.

       ENOMEM	 A  shared memory identifier and associated shared memory segment are to be created but the amount of available memory is not suf-
		 ficient to fill the request.

       ENOSPC	 A shared memory identifier is to be created but the system-imposed limit on the maximum number of allowed shared  memory  identi-
		 fiers system-wide would be exceeded. See NOTES.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       rctladm(1M), Intro(2), setrctl(2), shmctl(2), shmop(2), ftok(3C), getpagesize(3C), attributes(5), standards(5)

NOTES

       The  project.max-shm-memory  resource  control  restricts the total amount of shared memory a project can allocate. The zone.max-shm-memory
       resource control restricts the total amount of shared memory that can be allocated by a zone. The system-imposed maximum on the size  of  a
       shared  memory  segment	is therefore a	function of the sizes of any other shared memory segments the calling project might have allocated
       that are still in use, as well as any other shared memory segments allocated and still in use by processes in  the  zone.   For	accounting
       purposes, segment sizes are rounded up to the nearest multiple of the system page size. See getpagesize(3C).

       The  system-imposed  limit  on  the  number of shared memory identifiers is maintained on a per-project basis using the project.max-shm-ids
       resource control. The zone.max-shm-ids resource control restricts the total number of shared memory identifiers that can be allocated by  a
       zone.

       See rctladm(1M) and setrctl(2) for information about using resource controls.

SunOS 5.11							    14 Aug 2006 							 shmget(2)