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SHMGET(2)		    BSD System Calls Manual		     SHMGET(2)

NAME
     shmget — get shared memory area identifier

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

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

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

     A shared memory segment is created if either key is equal to IPC_PRIVATE,
     or key does not have a shared memory segment identifier associated with
     it, and the IPC_CREAT bit is set in shmflg.

     If a new shared memory segment is created, the data structure associated
     with it (the shmid_ds structure, see shmctl(2)) is initialized as fol‐
     lows:

     ·	 shm_perm.cuid and shm_perm.uid are set to the effective uid of the
	 calling process.

     ·	 shm_perm.gid and shm_perm.cgid are set to the effective gid of the
	 calling process.

     ·	 shm_perm.mode is set to the lower 9 bits of shmflg.

     ·	 shm_lpid, shm_nattch, shm_atime, and shm_dtime are set to 0

     ·	 shm_ctime is set to the current time.

     ·	 shm_segsz is set to the value of size.

RETURN VALUES
     Upon successful completion a positive shared memory segment identifier is
     returned.	Otherwise, -1 is returned and the global variable errno is set
     to indicate the error.

ERRORS
     [EACESS]		A shared memory segment is already associated with key
			and the caller has no permission to access it.

     [EEXIST]		Both IPC_CREAT and IPC_EXCL are set in shmflg, and a
			shared memory segment is already associated with key.

     [ENOSPC]		A new shared memory indentifier could not be created
			because the system limit for the number of shared mem‐
			ory identifiers has been reached.

     [ENOENT]		IPC_CREAT was not set in shmflg and no shared memory
			segment associated with key was found.

     [ENOMEM]		There is not enough memory left to created a shared
			memory segment of the requested size.

SEE ALSO
     shmctl(2), shmat(2), shmdt(2)

BSD				August 17, 1995				   BSD
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