MSGGET(2) System Calls MSGGET(2)


NAME


msgget - get message queue

SYNOPSIS


#include <sys/msg.h>

int msgget(key_t key, int msgflg);


DESCRIPTION


The msgget() argument returns the message queue identifier associated
with key.


A message queue identifier and associated message queue and data
structure (see Intro(2)) are created for key if one of the following are
true:

o key is IPC_PRIVATE.

o key does not already have a message queue identifier
associated with it, and (msgflg&IPC_CREAT) is true.


On creation, the data structure associated with the new message queue
identifier is initialized as follows:

o msg_perm.cuid, msg_perm.uid, msg_perm.cgid, and msg_perm.gid
are set to the effective user ID and effective group ID,
respectively, of the calling process.

o The low-order 9 bits of msg_perm.mode are set to the low-order
9 bits of msgflg.

o msg_qnum, msg_lspid, msg_lrpid, msg_stime, and msg_rtime are
set to 0.

o msg_ctime is set to the current time.

o msg_qbytes is set to the system limit. See NOTES.

RETURN VALUES


Upon successful completion, a non-negative integer representing a message
queue identifier is returned. Otherwise, -1 is returned and errno is set
to indicate the error.

ERRORS


The msgget() function will fail if:

EACCES
A message queue identifier exists for key, but operation
permission (see Intro(2)) as specified by the low-order 9 bits
of msgflg would not be granted.


EEXIST
A message queue identifier exists for key but
(msgflg&IPC_CREAT) and (msgflg&IPC_EXCL) are both true.


ENOENT
A message queue identifier does not exist for key and
(msgflg&IPC_CREAT) is false.


ENOSPC
A message queue identifier is to be created but the system-
imposed limit on the maximum number of allowed message queue
identifiers system wide would be exceeded. See NOTES.


ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+

SEE ALSO


rctladm(1M), Intro(2), msgctl(2), msgrcv(2), msgsnd(2), setrctl(2),
ftok(3C), attributes(5), standards(5)

NOTES


The system-defined limit used to initialize msg_qbytes is the minimum
enforced value of the calling process's process.max-msg-qbytes resource
control.


The system-imposed limit on the number of message queue identifiers is
maintained on a per-project basis using the project.max-msg-ids resource
control. The zone.max-msg-ids resource control restricts the total amount
of message queue identifiers that can be allocated by a zone.


See rctladm(1M) and setrctl(2) for information about using resource
controls.


August 14, 2006 MSGGET(2)