ipcs —
report System V interprocess communication facilities
  status
The ipcs program provides information on System V
  interprocess communication (IPC) facilities on the system.
The options are as follows:
  - -a
- Show the maximum amount of information possible when displaying active
      semaphores, message queues, and shared memory segments. (This is shorthand
      for specifying the -b,-c,-o,-p, and-toptions.)
- -b
- Show the maximum allowed sizes for active semaphores, message queues, and
      shared memory segments. The “maximum allowed size” is the
      maximum number of bytes in a message on a message queue, the size of a
      shared memory segment, or the number of semaphores in a set of
    semaphores.
- -c
- Show the creator's name and group for active semaphores, message queues,
      and shared memory segments.
- -m
- Display information about active shared memory segments.
- -o
- Show outstanding usage for active message queues, and shared memory
      segments. The “outstanding usage” is the number of messages
      in a message queue, or the number of processes attached to a shared memory
      segment.
- -p
- Show the process ID information for active semaphores, message queues, and
      shared memory segments. The “process ID information” is the
      last process to send a message to or receive a message from a message
      queue, the process that created a semaphore, or the last process to attach
      or detach a shared memory segment.
- -q
- Display information about active message queues.
- -s
- Display information about active semaphores.
- -t
- Show access times for active semaphores, message queues, and shared memory
      segments. The access times is the time of the last control operation on an
      IPC object, the last send or receive of a message, the last attach or
      detach of a shared memory segment, or the last operation on a
    semaphore.
- -M
- Display system information about shared memory.
- -Q
- Display system information about messages queues.
- -S
- Display system information about semaphores.
- -T
- Display system information about shared memory, message queues and
      semaphores. (This is shorthand for specifying the
      -M,-Q, and-Soptions.)
If none of the -M,
    -m, -Q,
    -q, -S,
    -s, or -T options are
    specified, information about all active IPC facilities is listed.
System data structures may change while ipcs is running;
  the output of ipcs is not guaranteed to be consistent.
This manual page is woefully incomplete, because it does not at all attempt to
  explain the information printed by ipcs.