IPCS Example 1: List all the IPC facility

ipcs command with -a option lists all the IPC facilities which has read access for the current process. It provides details about message queue, semaphore and shared memory.

# ipcs -a

—— Shared Memory Segments ——–
key shmid owner perms bytes nattch status
0xc616cc44 1056800768 oracle 660 4096 0
0x0103f577 323158020 root 664 966 1
0x0000270f 325713925 root 666 1 2

—— Semaphore Arrays ——–
key semid owner perms nsems
0x0103eefd 0 root 664 1
0x0103eefe 32769 root 664 1
0x4b0d4514 1094844418 oracle 660 204

—— Message Queues ——–
key msqid owner perms used-bytes messages
0x000005a4 32768 root 644 0 0

All the IPC facility has unique key and identifier, which is used to identify an IPC facility.
IPCS Example 2: List all the Message Queue

ipcs with option -q, lists only message queues for which the current process has read access.

$ ipcs -q

—— Message Queues ——–
key msqid owner perms used-bytes messages
0x000005a4 32768 root 644 0 0

IPCS Example 3. List all the Semaphores

ipcs -s option is used to list the accessible semaphores.

# ipcs -s

—— Semaphore Arrays ——–
key semid owner perms nsems
0x0103eefd 0 root 664 1
0x0103eefe 32769 root 664 1
0x4b0d4514 1094844418 oracle 660 204

IPCS Example 4. List all the Shared Memory

ipcs -m option with ipcs command lists the shared memories.

# ipcs -m

—— Shared Memory Segments ——–
key shmid owner perms bytes nattch status
0xc616cc44 1056800768 oracle 660 4096 0
0x0103f577 323158020 root 664 966 1
0x0000270f 325713925 root 666 1 2

IPCS Example 5. Detailed information about an IPC facility

ipcs -i option provides detailed information about an ipc facility.

# ipcs -q -i 32768

Message Queue msqid=32768
uid=0 gid=0 cuid=0 cgid=0 mode=0644
cbytes=0 qbytes=65536 qnum=0 lspid=0 lrpid=0
send_time=Not set
rcv_time=Not set
change_time=Thu Aug 5 13:30:22 2010

Option -i with -q provides information about a particular message queue. Option -i with -s provides semaphore details. Option -i with -m provides details about a shared memory.
IPCS Example 6. Lists the Limits for IPC facility

ipcs -l option gives the system limits for each ipc facility.

# ipcs -m -l

—— Shared Memory Limits ——–
max number of segments = 4096
max seg size (kbytes) = 67108864
max total shared memory (kbytes) = 17179869184
min seg size (bytes) = 1

The above command gives the limits for shared memory. -l can be combined with -q and -s to view the limits for message queue and semaphores respectively.

Single option -l gives the limits for all three IPC facilities.

# ipcs -l

IPCS Example 7. List Creator and Owner Details for IPC Facility

ipcs -c option lists creator userid and groupid and owner userid and group id. This option can be combined with -m, -s and -q to view the creator details for specific IPC facility.

# ipcs -m -c

—— Shared Memory Segment Creators/Owners ——–
shmid perms cuid cgid uid gid
1056800768 660 oracle oinstall oracle oinstall
323158020 664 root root root root
325713925 666 root root root root

IPCS Example 8. Process ids that accessed IPC facility recently

ipcs -p option displays creator id, and process id which accessed the corresponding ipc facility very recently.

# ipcs -m -p

—— Shared Memory Creator/Last-op ——–
shmid owner cpid lpid
1056800768 oracle 16764 5389
323158020 root 2354 2354
325713925 root 20666 20668

-p also can be combined with -m,-s or -q.
IPCS Example 9. Last Accessed Time

ipcs -t option displays last operation time in each ipc facility. This option can also be combined with -m, -s or -q to print for specific type of ipc facility. For message queue, -t option displays last sent and receive time, for shared memory it displays last attached (portion of memory) and detached timestamp and for semaphore it displays last operation and changed time details.

# ipcs -s -t

—— Semaphore Operation/Change Times ——–
semid owner last-op last-changed
0 root Thu Aug 5 12:46:52 2010 Tue Jul 13 10:39:41 2010
32769 root Thu Aug 5 11:59:10 2010 Tue Jul 13 10:39:41 2010
1094844418 oracle Thu Aug 5 13:52:59 2010 Thu Aug 5 13:52:59 2010

IPCS Example 10. Status of current usage

ipcs with -u command displays current usage for all the IPC facility. This option can be combined with a specific option to display the status for a particular IPC facility.

# ipcs -u

—— Shared Memory Status ——–
segments allocated 30
pages allocated 102
pages resident 77
pages swapped 0
Swap performance: 0 attempts 0 successes

—— Semaphore Status ——–
used arrays = 49
allocated semaphores = 252

—— Messages: Status ——–
allocated queues = 1
used headers = 0
used space = 0 bytes