MSGGET(2) System Calls MSGGET(2)
msgget - get message queue
#include <sys/msg.h>
int msgget(key_t key, int msgflg);
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.
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.
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.
See attributes(7) for descriptions of the following attributes:
+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+
Intro(2), msgctl(2), msgrcv(2), msgsnd(2), setrctl(2), ftok(3C),
attributes(7), standards(7), rctladm(8)
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(8) and setrctl(2) for information about using resource
controls.
August 14, 2006 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(7) for descriptions of the following attributes:
+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+
SEE ALSO
Intro(2), msgctl(2), msgrcv(2), msgsnd(2), setrctl(2), ftok(3C),
attributes(7), standards(7), rctladm(8)
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(8) and setrctl(2) for information about using resource
controls.
August 14, 2006 MSGGET(2)