shmctl(2)

Place the current value of each member of the data structure associated with shmid into the structure pointed to by buf. The contents of this structure are defined in glossary(9).

Set the value of the following members of the data structure associated with shmid to the corresponding value found in the structure pointed to by buf:

This cmd can only be executed by a process that has an effective user ID equal to either that of a user having appropriate privileges or to the value of either shm_perm.uid or shm_perm.cuid in the data structure associated with shmid.

This cmd cannot be executed on a shared memory segment that has been created with relaxed isolation.

Remove the shared memory identifier specified by shmid from the system and destroy the shared memory segment and data structure associated with it. If the segment is attached to one or more processes, then the segment key is changed to IPC_PRIVATE and the segment is marked removed. The segment disappears when the last attached process detaches it. This cmd can only be executed by a process that has an effective user ID equal to either that of a user with appropriate privileges or to the value of either shm_perm.uid or shm_perm.cuid in the data structure associated with shmid.

Lock the shared memory segment specified by shmid in memory. This cmd can only be executed by a process that either has an effective user ID equal to that of a user having appropriate privileges or has an effective user ID equal to the value of either shm_perm.uid or shm_perm.cuid in the data structure associated with shmid and has the PRIV_MLOCK privilege (see getprivgrp(2)).

Unlock the shared memory segment specified by shmid. This cmd can only be executed by a process that either has an effective user ID equal to a user having appropriate privileges or has an effective user ID equal to the value of either shm_perm.uid or shm_perm.cuid in the data structure associated with shmid and has the PRIV_MLOCK privilege (see getprivgrp(2)).

Successful completion.

Failure. errno is set to indicate the error.

cmd is equal to IPC_STAT and Read operation permission is denied to the calling process (see shared memory operation permissions in glossary(9)).

buf points to an illegal address. The reliable detection of this error is implementation dependent.

cmd is equal to SHM_UNLOCK and the shared-memory segment specified by shmid is not locked in memory.

shmid is not a valid shared memory identifier.

cmd is not a valid command, or the command contains invalid parameters.

cmd is equal to SHM_LOCK and there is not sufficient lockable memory to fill the request.

cmd is equal to IPC_STAT. The attached process count of a shared memory object is too large for the field in the data structure provided by the application. Recompile the application with the latest /usr/include/sys/ipc.h file to resolve this issue.

cmd is equal to IPC_RMID, IPC_SET, SHM_LOCK, or SHM_UNLOCK and the effective user ID of the calling process is not equal to that of a user having appropriate privileges and it is not equal to the value of either shm_perm.uid or shm_perm.cuid in the data structure associated with shmid.

cmd is equal to IPC_SET and the shared memory segment has relaxed isolation.

cmd is equal to SHM_LOCK or SHM_UNLOCK and the effective user ID of the calling process is not equal to that of a user having appropriate privileges and the calling process does not have the PRIV_MLOCK privilege (see getprivgrp(2)).