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researchv10 Dan Cross

.ds ZZ DEVELOPMENT PACKAGE
.TH MSGGET 3L "630 MTG"
.XE "msgget()"
.SH NAME
msgget \- get message queue
.SH SYNOPSIS
.B #include <message.h>
.sp
.B long msgget (key, msgflg)
.br
.B long key;
.br
.B int msgflg;
.SH DESCRIPTION
.I Msgget
returns the message queue identifier associated with
.IR key .
.PP
A message queue identifier and associated message queue and
data structure are created for
.I key
if one of the following is true:
.PP
.RS 6
.I Key
is equal to \fBIPC_PRIVATE\fR.
.PP
.I Key
does not already have a message queue identifier
associated with it, and
.RI ( msgflg
& 
.BR IPC_CREAT )
is ``true''.
.PP
.RE
Upon creation, the data structure associated with the new
message queue identifier is initialized as follows:
.PP
.RS 6
.BR Msg_qnum ,
.BR msg_curbytes ,
.BR msg_list ,
.BR msg_lspid ,
.BR msg_lrpid ,
.BR msg_stime ,
and
.B msg_rtime
are set equal to 0.
.sp
.B Msg_ctime
is set equal to the current time
.RI ( realtime ).
.sp
.B Msg_qbytes
is set equal to
.BR MAX_QBYTES .
.sp
.B State
is set to
.RB ( msgflg
&
.BR NO_SAVE ).
.sp
.B Cid
is set to the calling process's id
.RI ( P ).
.sp
.B Name
is set to
.IR key .
.RE
.PP
If
.I state
is ``true'', the message queue will be deleted when the process
.I cid
is deleted.
.PP
.I Msgget
will fail if one or more of the following are true:
.sp
.RS 6
A message queue identifier does not exist for
.I key
and
.RI ( msgflg
&
.BR IPC_CREAT )
is ``false''.
.sp
A message queue identifier is to be created
but there isn't enough memory.
.sp
A message queue identifier exists for
.I key
but (
.RI [ msgflg
&
.BR IPC_CREAT ]
&& 
.RI [ msgflg
&
.BR IPC_EXCL ]
) is ``true''.
.PP
.RE
.PP
Each message queue identifier that \fImsgget\fR returns is added to 
a list maintained for the application.
This list defines which message queues constitute the MSG resource when
using the \fIwait\fR(MSG) and \fIown\fR(MSG) functions.
.PP
.SS Return Value
Upon successful completion, a non-negative long, namely a
message queue identifier (pointer to msqid_ds structure), is returned.
Otherwise, a value of -1 is returned.
.PP
.SH SEE ALSO
msgctl(3L), msgop(3L), realtime(3R), resources(3R), structures(3R).

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