ipcs是Linux下显示进程间通信设施状态的工具。可以显示消息队列、共享内存和信号量的信息。对于程序员非常有用，普通的系统管理员一般用不到此指令。

ipcs shows information on the inter-process communication facilities for which the calling process has read access.By default it shows information about all three resources: shared memory segments, message queues, and semaphore arrays.
Without options, information shall be written in short format for message queues, shared memory segments, and semaphore sets that are currently active in the system. Otherwise, the information that is displayed is controlled by the options specified.

-q : Write information about active message queues.
-m : Write information about active shared memory segments.
-s : Write information about active semaphore sets.
 -a, --all         all (default)

------ Message Queues --------
key        msqid      owner      perms      used-bytes   messages    

root@52coder:~# ipcs -m

------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status      

root@52coder:~# ipcs -s

------ Semaphore Arrays --------
key        semid      owner      perms      nsems     

root@52coder:~# 

-c : Write creator’s user name and group name;.
-p : Write process number information. (Process ID of the last process to send a message and process ID of the last process to receive a message on message queues, process ID of the creating process, and process ID of the last process to attach or detach on shared memory segments.)
-t : Write time information. (Time of the last control operation that changed the access permissions for all facilities, time of the last msgsnd() and msgrcv() operations on message queues, time of the last shmat() and shmdt() operations on shared memory, and time of the last semop() operation on semaphores.)

root@52coder:~# ipcs -c

------ Message Queues Creators/Owners --------
msqid      perms      cuid       cgid       uid        gid       

------ Shared Memory Segment Creators/Owners --------
shmid      perms      cuid       cgid       uid        gid       

------ Semaphore Arrays Creators/Owners --------
semid      perms      cuid       cgid       uid        gid       

root@52coder:~# 
root@52coder:~# 
root@52coder:~# 
root@52coder:~# ipcs -p

------ Message Queues PIDs --------
msqid      owner      lspid      lrpid     

------ Shared Memory Creator/Last-op PIDs --------
shmid      owner      cpid       lpid      


root@52coder:~# ipcs -t

------ Message Queues Send/Recv/Change Times --------
msqid    owner      send                 recv                 change              

------ Shared Memory Attach/Detach/Change Times --------
shmid      owner      attached             detached             changed             

------ Semaphore Operation/Change Times --------
semid    owner      last-op                    last-changed              

root@52coder:~# 
root@52coder:~# ipcs --help

Usage:
 ipcs [resource-option...] [output-option]
 ipcs -m|-q|-s -i <id>

Show information on IPC facilities.

Options:
 -i, --id <id>  print details on resource identified by <id>
 -h, --help     display this help
 -V, --version  display version

Resource options:
 -m, --shmems      shared memory segments
 -q, --queues      message queues
 -s, --semaphores  semaphores
 -a, --all         all (default)

Output options:
 -t, --time        show attach, detach and change times
 -p, --pid         show PIDs of creator and last operator
 -c, --creator     show creator and owner
 -l, --limits      show resource limits
 -u, --summary     show status summary
     --human       show sizes in human-readable format
 -b, --bytes       show sizes in bytes

For more details see ipcs(1).