ipcs - report inter-process communication facilities status
ipcs [ options ]
ipcs prints certain information about active inter-process communication
facilities for which the calling process has read access. Without
options, information is printed in short format for message queues,
shared memory, and semaphores that are currently active in the system.
Otherwise, the information that is displayed is controlled by the
-q Print information about active message queues.
-m Print information about active shared memory segments.
-s Print information about active semaphores.
If any of the options -q, -m, or -s are specified, information about only
those indicated will be printed. If none of these three are specified,
information about all three will be printed subject to these options:
-b Print biggest allowable size information. (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 Print creator's login name and group name. See below.
-o Print information on outstanding usage. (Number of messages 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
-t Print time information. (Time of the last control operation that
changed the access permissions for all facilities. Time of last
msgsnd and last msgrcv on message queues, last shmat and last shmdt
on shared memory, last semop(2) on semaphores.) See below.
-a Use all print options. (This is a shorthand notation for -b, -c,
-o, -p, and -t.)
Use the file corefile in place of /dev/kmem.
The argument will be taken as the name of an alternate namelist
(/unix 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 options that cause
the corresponding heading to appear; all means that the heading always
appears. Note that these options only determine what information is
provided for each facility; they do not determine which facilities will
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, semget, or shmget
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 detaches it;
C if the associated shared memory segment is to be
cleared when the first attach is executed;
- 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 group name of the group of the owner of the facility
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
outstanding 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
CTIME (a,t) The time when the associated entry was created or
NATTCH (a,o) The number of processes attached to the associated shared
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 the last attach was completed 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 associated with the
OTIME (a,t) The time the last semaphore operation was completed on
the set associated with the semaphore entry.
/unix system namelist
/etc/passwd user names
/etc/group group names
msgop(2), semop(2), shmop(2)
Things can change while ipcs is running; the picture it gives is only a
close approximation to reality.
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