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
		       sufficient 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
		       identifiers 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 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.  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.

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

SunOS 5.10							    4 Sep 2003								 shmget(2)