ipcs(1)
NAME
ipcs − report inter-process communication facilities status
SYNTAX
ipcs [ options ]
DESCRIPTION
The ipcs command prints information about active inter-process communication facilities. Without options, information is printed in short format for message queues, and semaphores that are currently active in the system. Otherwise, the information that is displayed is controlled by the following options:
−q
Print information about active message queues.
−s
Print information about active semaphores.
If either of the options −q or −s is specified, information about only those indicated will be printed. If neither of these is specified, information about both will be printed.
−b
Print biggest allowable size information. (Maximum number of bytes in messages on queue for message queues, 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).
−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).
−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 semop(2) on semaphores.) See below.
−a
Use all print options. (This is a shorthand notation for −b, −c, −o, −p, and −t.)
−C corefile
Use the file corefile in place of /dev/kmem.
−N namelist
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 be listed.
T (all) Type of the facility:
q message queue;
s semaphore.
ID (all) The identifier for the facility entry.
KEY (all) The key used as an argument to msgget or semget, to create the facility entry.
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;
− 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 entry.
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 facility entry.
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 queue.
RTIME (a,t) The time the last message was received from the associated queue.
CTIME (a,t) The time when the associated entry was created or changed.
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.
RESTRICTIONS
Things can change while ipcs is running. The picture it gives is only a close approximation to reality.
FILES
/unixsystem namelist
/dev/kmemmemory
/etc/passwduser names
/etc/groupgroup names