NAME

ipcs − Reports Interprocess Communication (IPC) facility status

SYNOPSIS

ipcs [−a | −bcopt] [−mqs] [−C corefile] [−N namelist]

The ipcs command writes to the standard output information about active Interprocess Communication (IPC) facilities. 

FLAGS

−aSame as specifying the −b, −c, −o, −p and −t flags. 

−bWrites the maximum number of bytes in message queues, the size of segments for shared memory, and the number of semaphores in each semaphore set. 

−cWrites the username and group name of the user that made the facility. 

−C corefile
Writes report based on contents of file corefile instead of /dev/kmem. 

−mWrites information about active shared memory segments. 

−N namelist
Writes report based on contents of file namelist instead of /vmunix. 

−oWrites the following usage information:

       •Number of messages on queue

       •Total number of bytes in message queues

       •Number of processes attached to shared memory segments

−pWrites 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

−qWrites information about active message queues. 

−sWrites information about active semaphore set. 

−tWrites 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

DESCRIPTION

If you do not specify any flags, ipcs writes information in a short form about currently active message queues, shared memory segments, semaphores, remote queues, and local queue headers. 

Column Headings

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.  all means that the heading always appears.  These flags only determine what information is provided for each facility.  They do not determine which facilities are listed. 

T (all)Type of facility:

qMessage queue

mShared memory segment

sSemaphore

ID (all)The identifier for the facility entry. 

KEY (all)
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. 

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:

L[Digital]  If the associated shared memory segment was locked. 

RIf a process is waiting on a msgrcv() system call. 

SIf a process is waiting on a msgsnd() system call. 

DIf 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:

rRead permission is granted. 

wWrite permission is granted. 

aAlter permission is granted. 

−The indicated permission is not granted. 

OWNER (all)
The username of the owner of the facility entry.

GROUP (all)
The name of the group that owns the facility entry.

CREATOR (a,c)
The username of the creator of the facility entry.

CGROUP (a,c)
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. 

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.

LRPID (a,p)
The ID of the last process that received a message from the associated queue.

STIME (a,t)
The time when the last message was sent to the associated queue.

RTIME (a,t)
The time when the last message was received from the associated queue.

CTIME (a,t)
The time when the associated entry was created or changed.

NATTCH (a,o)
The number of processes attached 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 when the last semaphore operation was completed on the set associated with the semaphore entry.

EXAMPLES

Sample output from entering ipcs without flags follows. 

Message Queues:
T      ID        KEY     MODE         OWNER    GROUP
q       0 1090523774 ---rw-------      root   system
Shared Memory:
T      ID        KEY     MODE         OWNER    GROUP
m       0  844348508 ---rw-rw-rw-      root   system
m    2433          0 LD-rw-------      root   daemon
Semaphores:
T      ID        KEY     MODE         OWNER    GROUP
s       0 1090523774 ---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 Fri Mar  7 14:41:40 1997
T      ID        KEY     MODE         OWNER    GROUP
Message Queues:
q       0 1090523774 ---rw-------      root   system
Shared Memory:
m       0  844348508 ---rw-rw-rw-      root   system
m    2433          0 LD-rw-------      root   daemon
Semaphores:
s       0 1090523774 ---ra-------      root   system

FILES

/etc/passwdContains user information. 

/etc/groupContains group information. 

RELATED INFORMATION

Commands:  ipcrm(1). 

Functions: msgrcv(2), msgsnd(2), semop(2), shmat(2), shmdt(2).