IPCS
Section: User Commands (1)
Updated: July 2014
Page Index
NAME
ipcs - show information on IPC facilities
SYNOPSIS
ipcs
[options]
DESCRIPTION
ipcs
shows information on System V inter-process communication facilities.
By default it shows information about all three resources:
shared memory segments, message queues, and semaphore arrays.
OPTIONS
- -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.
Representation
These affect only the
-l (
--limits) option.
- -b, --bytes
-
Print sizes in bytes.
- --human
-
Print sizes in human-readable format.
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.
NOTES
The current implementation of
ipcs
obtains information about available IPC resources by parsing the files in
/proc/sysvipc.
Before util-linux version v2.23, an alternate mechanism was used: the
IPC_STAT
command of
msgctl(2),
semctl(2),
and
shmctl(2).
This mechanism is also used in later util-linux versions in the case where
/proc
is unavailable.
A limitation of the
IPC_STAT
mechanism is that it can only be used to retrieve information about
IPC resources for which the user has read permission.
AUTHORS
Krishna Balasubramanian
SEE ALSO
ipcmk(1),
ipcrm(1),
msgrcv(2),
msgsnd(2),
semget(2),
semop(2),
shmat(2),
shmdt(2),
shmget(2),
sysvipc(7)
AVAILABILITY
The ipcs command is part of the util-linux package and is available from
Linux Kernel Archive