ipcs - Reports Interprocess Communication (IPC) facility
status
ipcs [-a | -bcopt] [-mqs] [-C corefile] [-N namelist]
The ipcs command writes to the standard output information
about active Interprocess Communication (IPC) facilities.
Interfaces documented on this reference page conform to
industry standards as follows:
ipcs: XCU5.0
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
Same as specifying the -b, -c, -o, -p, and -t options.
Writes the maximum number of bytes in message queues, the
size of segments for shared memory, and the number of
semaphores in each semaphore set. Writes the username and
group name of the user that made the facility. Writes
report based on contents of file corefile instead of
/dev/kmem. Writes information about active shared memory
segments. Writes report based on contents of file
namelist instead of /vmunix. Writes the following usage
information: Number of messages on queue Total number of
bytes in message queues Number of processes attached to
shared memory segments Writes the following: Process number
of the last process to receive a message on message
queues Process number of the creating process Process number
of last process to attach or detach on shared memory
segments Writes information about active message queues.
Writes information about active semaphore set. Writes the
following: Time of the last control operation that changed
the access permissions for all facilities Time of the last
msgsnd() and last msgrcv() on message queues Time of the
last shmat() and last shmdt() on shared memory Time of the
last semop() on semaphore sets
If you do not specify any options, ipcs writes information
in a short form about currently active message queues,
shared memory segments, semaphores, remote queues, and
local queue headers.
Column Headings [Toc] [Back]
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.
The word all means that the heading always appears. The
flags only determine what information is provided for each
facility; they do not determine which facilities are
listed. Type of facility: Message queue Shared memory
segment Semaphore The identifier for the facility entry.
The key used as a parameter to the msgget(), semget() or
shemget() system calls to make the facility entry.
Note that the key of a shared memory segment is
changed to IPC_PRIVATE when the segment is removed.
This change remains in effect 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 can be: [Tru64 UNIX] If
the associated shared memory segment was locked.
If a process is waiting on a msgrcv() system call.
If a process is waiting on a msgsnd() system call.
If the associated shared memory segment was
removed. It disappears when the last process
attached to the segment detaches it. If 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 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: Read permission
is granted. Write permission is granted.
Alter permission is granted. The indicated permission
is not granted. The username of the owner of
the facility entry. The name of the group that
owns the facility entry. The username of the creator
of the facility entry. The group name of the
group of the creator of the facility entry.
Note that for the OWNER, GROUP, CREATOR, and
CGROUP, the user and group IDs display instead of
the usernames. 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 outstanding on
the associated message queue. The ID of the last
process that sent a message to the associated
queue. The ID of the last process that received a
message from the associated queue. The time when
the last message was sent to the associated queue.
The time when the last message was received from
the associated queue. The time when the associated
entry was created or changed. 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 entry. The process ID of the last
process to attach or detach the shared memory segment.
The time when the last attach was completed
to the associated shared memory segment. The time
when the last detach was completed on the associated
shared memory segment. The number of
semaphores in the set associated with the semaphore
entry. The time when the last semaphore operation
was completed on the set associated with the
semaphore entry.
Sample output from entering ipcs without options follows.
Message Queues:
T ID KEY MODE OWNER GROUP
q 4 0x41002ab4 --rw------- root system
Shared Memory:
T ID KEY MODE OWNER GROUP
m 0 0x3253bc5c --rw-rw-rw- root system
m 129 0 DLrw------- root daemon
Semaphores:
T ID KEY MODE OWNER GROUP
s 0 0x41002ab4 --ra------- root system
Output is formatted differently if the environment variable
CMD_ENV is set to the string svr4. For example:
IPC status from /dev/kmem as of Thu Mar 26 11:31:03 1998
T ID KEY MODE OWNER GROUP
Message Queues:
q 4 0x41002ab4 --rw------- root system
Shared Memory:
m 0 0x3253bc5c --rw-rw-rw- root system
m 129 0 DLrw------- root daemon
Semaphores:
s 0 0x41002ab4 --ra------- root system
Contains user information. Contains group information.
Commands: ipcrm(1)
Functions: msgrcv(2), msgsnd(2), semop(2), shmat(2),
shmdt(2)
ipcs(1)
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