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SHMGET(2) BSD System Calls Manual SHMGET(2)
shmget -- get shared memory area identifier
shmget(key_t key, int size, int shmflg);
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
If a new shared memory segment is created, the data structure associated with it (the
shmid_ds structure, see shmctl(2)) is initialized as follows:
o shm_perm.cuid and shm_perm.uid are set to the effective uid of the calling process.
o shm_perm.gid and shm_perm.cgid are set to the effective gid of the calling process.
o shm_perm.mode is set to the lower 9 bits of shmflg.
o shm_lpid, shm_nattch, shm_atime, and shm_dtime are set to 0
o shm_ctime is set to the current time.
o shm_segsz is set to the value of size.
Upon successful completion a positive shared memory segment identifier is returned. Other-
wise, -1 is returned and the global variable errno is set to indicate the error.
[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 seg-
ment is already associated with key.
[ENOSPC] A new shared memory indentifier could not be created because the system
limit for the number of shared memory 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
shmctl(2), shmat(2), shmdt(2)
BSD August 17, 1995 BSD
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