path: root/usr/src/man/man2/msgget.2

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.TH MSGGET 2 "Aug 14, 2006"
.SH NAME
msgget \- get message queue
.SH SYNOPSIS
.LP
.nf
#include <sys/msg.h>

\fBint\fR \fBmsgget\fR(\fBkey_t\fR \fIkey\fR, \fBint\fR \fImsgflg\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBmsgget()\fR argument returns the message queue identifier associated
with \fIkey\fR.
.sp
.LP
A message queue identifier and associated message queue and data structure (see
\fBIntro\fR(2)) are created for \fIkey\fR if one of the following are true:
.RS +4
.TP
.ie t \(bu
.el o
\fIkey\fR is \fBIPC_PRIVATE\fR.
.RE
.RS +4
.TP
.ie t \(bu
.el o
\fIkey\fR does not already have a message queue identifier associated with it,
and (\fImsgflg\fR\fB&IPC_CREAT\fR) is true.
.RE
.sp
.LP
On creation, the data structure associated with the new message queue
identifier is initialized as follows:
.RS +4
.TP
.ie t \(bu
.el o
\fBmsg_perm.cuid\fR, \fBmsg_perm.uid\fR, \fBmsg_perm.cgid\fR, and
\fBmsg_perm.gid\fR are set to the effective user \fBID\fR and effective group
\fBID,\fR respectively, of the calling process.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The low-order 9 bits of \fBmsg_perm.mode\fR are set to the low-order 9 bits of
\fImsgflg\fR.
.RE
.RS +4
.TP
.ie t \(bu
.el o
\fBmsg_qnum\fR, \fBmsg_lspid\fR, \fBmsg_lrpid\fR, \fBmsg_stime\fR, and
\fBmsg_rtime\fR are set to 0.
.RE
.RS +4
.TP
.ie t \(bu
.el o
\fBmsg_ctime\fR is set to the current time.
.RE
.RS +4
.TP
.ie t \(bu
.el o
\fBmsg_qbytes\fR is set to the system limit. See NOTES.
.RE
.SH RETURN VALUES
.sp
.LP
Upon successful completion, a non-negative integer representing a message queue
identifier is returned. Otherwise, \fB\(mi1\fR is returned and \fBerrno\fR is
set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBmsgget()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEACCES\fR\fR
.ad
.RS 10n
A message queue identifier exists for \fIkey\fR, but operation permission (see
\fBIntro\fR(2)) as specified by the low-order 9 bits of \fImsgflg\fR would not
be granted.
.RE

.sp
.ne 2
.na
\fB\fBEEXIST\fR\fR
.ad
.RS 10n
A message queue identifier exists for \fIkey\fR but
(\fImsgflg\fR\fB&IPC_CREAT\fR) and (\fImsgflg\fR\fB&IPC_EXCL\fR) are both true.
.RE

.sp
.ne 2
.na
\fB\fBENOENT\fR\fR
.ad
.RS 10n
A message queue identifier does not exist for \fIkey\fR and
(\fImsgflg\fR\fB&IPC_CREAT\fR) is false.
.RE

.sp
.ne 2
.na
\fB\fBENOSPC\fR\fR
.ad
.RS 10n
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.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
.TE

.SH SEE ALSO
.sp
.LP
.BR Intro (2),
.BR msgctl (2),
.BR msgrcv (2),
.BR msgsnd (2),
.BR setrctl (2),
.BR ftok (3C),
.BR attributes (7),
.BR standards (7),
.BR rctladm (8)
.SH NOTES
.sp
.LP
The system-defined limit used to initialize \fBmsg_qbytes\fR is the minimum
enforced value of the calling process's \fBprocess.max-msg-qbytes\fR resource
control.
.sp
.LP
The system-imposed limit on the number of message queue identifiers is
maintained on a per-project basis using the \fBproject.max-msg-ids\fR resource
control. The \fBzone.max-msg-ids\fR resource control restricts the total amount
of message queue identifiers that can be allocated by a zone.
.sp
.LP
See \fBrctladm\fR(8) and \fBsetrctl\fR(2) for information about using resource
controls.