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AIX Version 4.3 Commands Reference, Volume 3

ipcs Command

Purpose

Reports interprocess communication facility status.

Syntax

ipcs [-m] [-q] [-s] [-a | -b -c -o -p -t] [-CCoreFile] [-N Kernel ]

Description

The ipcs command writes to the standard output information about active interprocess communication facilities. If you do not specify any flags, the ipcs command 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 command listing follow. The letters in parentheses indicate the flags that cause the corresponding heading to appear. The designator all means the heading is always displayed. These flags only determine what information is provided for each facility. They do not determine which facilities are listed.

T (all) the type of facility. There are three facility types:
q message queue
m shared memory segment
s semaphore
ID (all) the identifier for the facility entry.
KEY (all) the key used as a parameter to the msgget subroutine, the semget subroutine, or the shmget subroutine 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 from it.
MODE (all) the facility access modes and flags. The mode consists of 11 characters that are interpreted as follows:

The first two characters can be the following:

R If a process is waiting on a msgrcv system call.
S If a process is waiting on a msgsnd system call.
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 nine characters are interpreted as three sets of 3 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 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 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 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 that holds the queue, LSPID is the PID of the kernel process that 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 that holds the queue, LRPID is the PID of the kernel process that 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 compensate for time-zone differences 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 time-zone differences 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 compensate for any time-zone differences between the local clock and the server clock.
NATTCH (a,o) The current number of attaches 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 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 semaphore entry.
OTIME (a,t) The time the last semaphore operation was completed on the set associated with the semaphore entry.

This command supports multibyte character sets.

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 specified by the CoreFile parameter in place of the /dev/mem file. The CoreFile parameter is a memory image file produced by the Ctrl-(left)Alt-End key sequence.
-m Writes information about active shared memory segments.
-NKernel Uses the specified Kernel (the /usr/lib/boot/unix file is the default).
-o Writes the following usage information:
  • Number of messages on queue
  • Total number of bytes in messages in queue for message queues
  • Number of processes attached to shared memory segments
-p 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
-q Writes information about active message queues.
-s Writes information about active semaphore set.
-t Writes the following:
  • Time of the last control operation that changed the access permissions for all facilities
  • Time of the last msgsnd and msgrcv on message queues
  • Time of the last shmat and shmdt on shared memory
  • Time of the last semop on semaphore sets

Example

Example output from entering ipcs without flags:

IPC status from /dev/mem as of Mon Aug 14 15:03:46 1989
T    ID         KEY        MODE       OWNER     GROUP
Message Queues:
q       0    0x00010381 -Rrw-rw-rw-   root      system
q   65537    0x00010307 -Rrw-rw-rw-   root      system
q   65538    0x00010311 -Rrw-rw-rw-   root      system
q   65539    0x0001032f -Rrw-rw-rw-   root      system
q   65540    0x0001031b -Rrw-rw-rw-   root      system
q   65541    0x00010339--rw-rw-rw-    root      system
q       6    0x0002fe03 -Rrw-rw-rw-   root      system
Shared Memory:
m   65537    0x00000000 DCrw-------   root      system
m  720898    0x00010300 -Crw-rw-rw-   root      system
m   65539    0x00000000 DCrw-------   root      system
Semaphores:
s  131072    0x4d02086a --ra-ra----   root      system
s   65537    0x00000000 --ra-------   root      system
s 1310722    0x000133d0 --ra-------   7003      30720

Files

/usr/lib/boot/unix Specifies the system kernel image.
/dev/mem Specifies memory.
/etc/passwd Specifies user names.
/etc/group Specifies group names.
/usr/include/sys/ipc.h Contains the header file.

Related Information

The ipcrm command.

The msgrcv subroutine, msgsnd subroutine, semop subroutine, shmat subroutine, shmdt subroutine.

Commands Overview in AIX Version 4.3 System User's Guide: Operating System and Devices.

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