ipcs — show information on IPC facilities

Examples (TL;DR)


ipcs [options]


ipcs shows information on the inter-process communication facilities for which the calling process has read access. By default it shows information about all three resources: shared memory segments, message queues, and semaphore arrays.


-i, --id id

Show full details on just the one resource element identified by id. This option needs to be combined with one of the three resource options: -m, -q or -s.

-h, --help

Display help text and exit.

-V, --version

Display version information and exit.

Resource options

-m, --shmems

Write information about active shared memory segments.

-q, --queues

Write information about active message queues.

-s, --semaphores

Write information about active semaphore sets.

-a, --all

Write information about all three resources (default).

Output formats

Of these options only one takes effect: the last one specified.

-c, --creator

Show creator and owner.

-l, --limits

Show resource limits.

-p, --pid

Show PIDs of creator and last operator.

-t, --time

Write time information.  The time of the last control operation that changed the access permissions for all facilities, the time of the last msgsnd(2) and msgrcv(2) operations on message queues, the time of the last shmat(2) and shmdt(2) operations on shared memory, and the time of the last semop(2) operation on semaphores.

-u, --summary

Show status summary.


These affect only the -l (--limits) option.

-b, --bytes

Print sizes in bytes.


Print sizes in human-readable format.

See Also

ipcmk(1), ipcrm(1), msgrcv(2), msgsnd(2), semget(2), semop(2), shmat(2), shmdt(2), shmget(2)

Conforming to

The Linux ipcs utility is not fully compatible to the POSIX ipcs utility. The Linux version does not support the POSIX -a, -b and -o options, but does support the -l and -u options not defined by POSIX.  A portable application shall not use the -a, -b, -o, -l, and -u options.


Krishna Balasubramanian


The ipcs command is part of the util-linux package and is available from Linux Kernel Archive.

Referenced By

ipcmk(1), ipcrm(1), msgctl(2), proc(5), procenv(1), semctl(2), shmctl(2), sysvipc(7), x11vnc(1).

July 2014 util-linux