ipcs - report inter-process communication facilities status
ipcs [-aAbcimopqst] [-D mtype]
The ipcs utility prints information about active inter-
process communication facilities. The information that is
displayed is controlled by the options supplied. Without
options, information is printed in short format for message
queues, shared memory, and semaphores that are currently
active in the system.
The following options are supported:
-m Prints information about active shared memory seg-
-q Prints information about active message queues.
-s Prints information about active semaphores.
If -m, -q, or -s are specified, information about only those
indicated is printed. If none of these three is specified,
information about all three is printed subject to these
-a Uses all XCU5 print options. (This is a shorthand
notation for -b, -c, -o, -p, and -t.)
-A Uses all print options. (This is a shorthand notation
for -b, -c, -i, -o, -p, and -t.)
-b Prints information on biggest allowable size: maximum
number of bytes in messages on queue for message
queues, size of segments for shared memory, and number
of semaphores in each set for semaphores. See below
for meaning of columns in a listing.
-c Prints creator's login name and group name. See below.
Displays, in hexadecimal and ASCII, the contents of
all messages of type mtype found on any message queue
that the user invoking ipcs has permission to read. If
mtype is 0, all messages are displayed. If mtype is
negative, all messages with type less than or equal to
the absolute value of mtype are displayed. (See
msgrcv(2) and msgsnap(2)).
-i Prints number of ISM attaches to shared memory seg-
-o Prints information on outstanding usage: number of
messages on queue and total number of bytes in mes-
sages on queue for message queues and number of
processes attached to shared memory segments.
-p Prints process number information: process ID of last
process to send a message, process ID of last process
to receive a message on message queues, process ID of
creating process, and process ID of last process to
attach or detach on shared memory segments. See below.
-t Prints time information: time of the last control
operation that changed the access permissions for all
facilities, time of last msgsnd(2) and last msgrcv(2)
on message queues, time of last shmat(2) and last
shmdt(2 ) on shared memory (see shmop(2)), time of
last semop(2) on semaphores. See below.
The column headings and the meaning of the columns in an
ipcs listing are given below. The letters in parentheses
indicate the options that cause the corresponding heading to
appear. "all" means that the heading always appears. Note:
These options only determine what information is provided
for each facility; they do not determine which facilities
Type of the facility:
q message queue
m shared memory segment
The identifier for the facility entry.
The key used as an argument to msgget(2), semget(2),
or shmget(2) to create the facility entry. (Note: The
key of a shared memory segment is changed to
IPC_PRIVATE when the segment has been removed until
all processes attached to the segment detach it.)
The facility access modes and flags: The mode consists
of 11 characters that are interpreted as follows. The
first two characters are:
R A process is waiting on a msgrcv(2).
S A process is waiting on a msgsnd(2).
D The associated shared memory segment has been
removed. It will disappear when the last process
attached to the segment detaches it. (Note: If
the shared memory segment identifier is removed
via an IPC_RMID call to shmctl(2) before the
process has detached from the segment with
shmdt(2), the segment is no longer visible to
ipcs and it will not appear in the ipcs output.)
C The associated shared memory segment is to be
cleared when the first attach is executed.
- The corresponding special flag is not set.
The next nine characters are interpreted as three sets of
three bits each. The first set refers to the owner's permis-
sions; the next to permissions of others in the user-group
of the facility entry; and the last to all others. Within
each set, the first character indicates permission to read,
the second character indicates permission to write or alter
the facility entry, and the last character is currently
The permissions are indicated as follows:
r Read permission is granted.
w Write permission is granted.
a Alter permission is granted.
- The indicated permission is not granted.
The login name of the owner of the facility entry.
The group name of the group of the owner of the facil-
The login name of the creator of the facility entry.
The group name of the group of the creator of the
The number of bytes in messages currently outstanding
on the associated message queue.
The number of messages currently outstanding on the
associated message queue.
The maximum number of bytes allowed in messages out-
standing on the associated message queue.
The process ID of the last process to send a message
to the associated queue.
The process ID of the last process to receive a mes-
sage from the associated queue.
The time the last message was sent to the associated
The time the last message was received from the asso-
The time when the associated entry was created or
The number of ISM attaches to the associated shared
The number of processes attached to the associated
shared memory segment.
The size of the associated shared memory segment.
The process ID of the creator of the shared memory
The process ID of the last process to attach or detach
the shared memory segment.
The time the last attach was completed to the associ-
ated shared memory segment.
The time the last detach was completed on the associ-
ated shared memory segment.
The number of semaphores in the set associated with
the semaphore entry.
The time the last semaphore operation was completed on
the set associated with the semaphore entry.
See environ(5) for descriptions of the following environment
variables that affect the execution of ipcs: LANG, LC_ALL,
LC_CTYPE, LC_MESSAGES, and NLSPATH.
TZ Determine the timezone for the time strings written by
See attributes(5) for descriptions of the following attri-
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| Availability | SUNWipc |
| Interface Stability | Standard |
ipcrm(1), msgget(2), msgids(2), msgrcv(2), msgsnap(2),
msgsnd(2), semget(2), semids(2), semop(2), shmctl(2),
shmget(2), shmids(2), shmop(2), attributes(5), environ( 5),
Things can change while ipcs is running. The information it
gives is guaranteed to be accurate only when it was
Man(1) output converted with