IPCS(1) General Commands Manual IPCS(1)
ipcs - report interprocess communication facilities status
ipcs [ primitives ]
ipcs prints information about active interprocess communication facili-
ties as specified by the primitives shown below. If no primitives are
given, information is printed in short format for message queues,
shared memory, and semaphores that are currently active in the system.
Command - Line Primitives
If any of the primitives -m, -q, or -s are specified, information about
only indicated facilities is printed. If none of these are specified,
information about all three is printed.
-q Print information about active message queues.
-m Print information about active shared memory segments.
-s Print information about active semaphores.
-b Print the currently allowed size information. (Maximum
number of bytes in messages on queue for message queues,
size of segments for shared memory, and number of sema-
phores in each set for semaphores.) See below for the
meaning of columns in a listing.
-c Print creator's login name and group name. See below.
-o Print information on outstanding usage. (Number of mes-
sages on queue and total number of bytes in messages on
queue for message queues and number of processes
attached to shared memory segments.)
-p Print process number information. (Process ID of last
process to send a message and process ID of last process
to receive a message on message queues and process ID of
creating process and process ID of last process to
attach or detach on shared memory segments)See below.
-t Print time information. (Time of the last control oper-
ation that changed the access permissions for all facil-
ities. Time of last msgsnd and last msgrcv (see
msgop(2)) on message queues, last shmat and last shmdt
(see shmop(2)) on shared memory, last semop(2) on sema-
phores.) See below.
-a Use all display primitives. (This is a shorthand nota-
tion for -b, -c, -o, -p, and -t.)
-C corefile Use the file corefile in place of /dev/mem.
-N namelist The argument will be taken as the name of an alternate
filenamelist (/vmunix is the default).
The column headings and the meaning of the columns in an ipcs listing
are given below; the letters in parentheses indicate the primitives
that cause the corresponding heading to appear; all means that the
heading always appears. Note: these primitives only determine what
information is provided for each facility; they do not determine which
facilities will be listed.
T (all) Type of the facility:
q message queue
m shared memory segment
ID (all) The identifier for the facility entry.
KEY (all) 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.)
MODE (all) The facility access modes and flags: The mode consists
of 11 characters that are interpreted as follows:
The first two characters are:
R If a process is waiting on a msgrcv.
S If a process is waiting on a msgsnd.
D If the associated shared memory segment has
been removed. It will disappear when the
last process attached to the segment
C If the associated shared memory segment is
to be cleared when the first attach is exe-
- If the corresponding special flag is not
The next 9 characters are interpreted as three
sets of three bits each. The first set refers
to the owner's permissions; the next to permis-
sions of others in the user-group of the facil-
ity entry; and the last to all others. Within
each set, the first character indicates permis-
sion to read, the second character indicates
permission to write or alter the facility entry,
and the last character is currently unused.
The permissions are indicated as follows:
r If read permission is granted.
w If write permission is granted.
a If alter permission is granted.
-- If the indicated permission is not granted.
OWNER (all) The login name of the owner of the facility entry.
GROUP (all) The group name of the group of the owner of the facil-
CREATOR(a,c) The login name of the creator of the facility entry.
CGROUP (a,c) The group name of the group of the creator of the
CBYTES (a,o) The number of bytes in messages currently outstanding
on the associated message queue.
QNUM (a,o) The number of messages currently outstanding on the
associated message queue.
QBYTES (a,b) The maximum number of bytes allowed in messages out-
standing on the associated message queue.
LSPID (a,p) The process ID of the last process to send a message to
the associated queue.
LRPID (a,p) The process ID of the last process to receive a message
from the associated queue.
STIME (a,t) The time the last message was sent to the associated
RTIME (a,t) The time the last message was received from the associ-
CTIME (a,t) The time when the associated entry was created or
NATTCH (a,o) The number of processes attached to the associated
shared memory segment.
SEGSZ (a,b) The size of the associated shared memory segment.
CPID (a,p) The process ID of the creator of the shared memory
LPID (a,p) The process ID of the last process to attach or detach
the shared memory segment.
ATIME (a,t) The time the last attach was completed to the associ-
ated shared memory segment.
DTIME (a,t) The time the last detach was completed on the associ-
ated shared memory segment.
NSEMS (a,b) The number of semaphores in the set associated with the
OTIME (a,t) The time the last semaphore operation was completed on
the set associated with the semaphore entry.
/vmunix system namelist
/etc/passwd user names
/etc/group group names
ipcrm(1), msgop(2), semctl(2), semget(2), semop(2), shmctl(2),
Things can change while ipcs is running; the picture it gives is only a
close approximation to reality.
9 September 1987 IPCS(1)