ipcs
PURPOSE
Reports inter-process communication facility status.
SYNOPSIS
ipcs [ options ]
DESCRIPTION
The ipcs command writes to the standard output informa-
tion about active inter-process communication facilities.
If you do not specify any flags, ipcs writes information
in a short form about currently active message queues,
shared memory segments, semaphores, remote queues, and
local queue headers.
The column headings and the meaning of the columns in an
ipcs listing follow. The letters in parentheses indicate
the flags that cause the corresponding heading to appear.
all means that the heading always appears. These flags
only determine what information is provided for each
facility. They do not determine which facilities will be
listed.
T (all) Type of facility:
q message queue
Q message queue resides on a remote node
m shared memory segment
s semaphore.
ID (all) The identifier for the facility entry.
KEY (all) The key used as a parameter to msgget,
semget, or shemget to make the facility entry.
Note: The key of a shared memory segment is
changed to IPC_PRIVATE when the segment is
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 inter-
preted as follows:
The first two characters can be:
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 disappears when the last
process attached to the segment detaches it.
C if the associated shared memory segment is to
be cleared when the first attach is run
- if the corresponding special flag is not set.
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 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 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 name of the group that owns the
facility entry.
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 facility entry.
Note: For the OWNER, GROUP, CREATOR, and CGROUP,
the user and group IDs display instead of the
login names.
CBYTES (a,o) The number of bytes in messages currently
outstanding on the associated message queue.
QNUM (a,o) The number of messages currently out-
standing on the associated message queue.
QBYTES (a,b) The maximum number of bytes allowed in
messages outstanding on the associated message
queue.
LSPID (a,p) The ID of the last process that sent a
message to the associated queue. If the last
message sent was from a process in a node other
than the node which holds the queue, then LSPID
is the PID of the kernel process which actually
placed the message on the queue, not the PID of
the sending process.
LRPID (a,p) The ID of the last process that received a
message from the associated queue. If the last
message received was from a process in a node
other than the node which holds the queue, then
LRPID is the PID of the kernel process which
actually received the message on the queue, not
the PID of the receiving process.
STIME (a,t) The time when the last message was sent to
the associated queue. For remote queues, this is
the server time. No attempt is made to compen-
sate for any clock skew between the local clock
and the server clock.
RTIME (a,t) The time when the last message was
received from the associated queue. For remote
queues, this is the server time. No attempt is
made to compensate for any clock skew between the
local clock and the server clock.
CTIME (a,t) The time when the associated entry was
created or changed. For remote queues, this is
the server time. No attempt is made to compen-
sate for any clock skew between the local clock
and the server clock.
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 entry.
LPID (a,p) The process ID of the last process to
attach or detach the shared memory segment.
ATIME (a,t) The time when the last attach was com-
pleted to the associated shared memory segment.
DTIME (a,t) The time the last detach was completed on
the associated shared memory segment.
NSEMS (a,b) The number of semaphores in the set asso-
ciated with the semaphore entry.
OTIME (a,t) The time the last semaphore operation was
completed on the set associated with the
semaphore entry.
FLAGS
-a Uses the -b, -c, -o, -p and -t flags.
-b Writes the maximum number of bytes in
messages on queue for message queues, the
size of segments for shared memory, and
the number of semaphores in each
semaphores set.
-c Writes the login name and group name of
the user that made the facility.
-Ccorefile Uses the file corefile in place of
/dev/kmem. corefile is a memory image
file produced by the Ctrl-(left)Alt-End
key sequence.
-m Writes information about active shared
memory segments.
-Nkernel-image Uses the specified kernel-image (/unix is
the default).
-o Writes the following usage information:
o Number of messages on queue
o Total number of bytes in messages in
queue for message queues
o Number of processes attached to
shared memory segments.
-p Writes the following:
o Process number of the last process to
receive a message on message queues
o Process number of the creating
process
o Process number of last process to
attach or detach on shared memory
segments.
-q Writes information about active message
queues.
-s Writes information about active semaphore
set.
-t Writes the following:
o Time of the last control operation
that changed the access permissions
for all facilities
o Time of the last msgsnd and last
msgrcv on message queues
o Time of the last shmat and last shmdt
on shared memory
o Time of the last semop on semaphore
sets.
FILES
/unix System kernel image.
/dev/kmem Memory.
/etc/passwd User names.
/etc/group Group names.
RELATED INFORMATION
The ipcs, msgrcv, msgsnd, semop, shmat, and shmdt system
calls in AIX Operating System Technical Reference.
The discussion of generating core files in Problem Deter-
mination Guide.