mirror of https://github.com/mkerrisk/man-pages
126 lines
4.2 KiB
Plaintext
126 lines
4.2 KiB
Plaintext
|
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
|
||
|
.TH "MSGGET" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
|
||
|
.\" msgget
|
||
|
.SH NAME
|
||
|
msgget \- get the XSI message queue identifier
|
||
|
.SH SYNOPSIS
|
||
|
.LP
|
||
|
\fB#include <sys/msg.h>
|
||
|
.br
|
||
|
.sp
|
||
|
int msgget(key_t\fP \fIkey\fP\fB, int\fP \fImsgflg\fP\fB); \fP
|
||
|
\fB
|
||
|
.br
|
||
|
\fP
|
||
|
.SH DESCRIPTION
|
||
|
.LP
|
||
|
The \fImsgget\fP() function operates on XSI message queues (see the
|
||
|
Base Definitions volume of IEEE\ Std\ 1003.1-2001,
|
||
|
Section 3.224, Message Queue). It is unspecified whether this function
|
||
|
interoperates with the realtime interprocess communication facilities
|
||
|
defined in \fIRealtime\fP .
|
||
|
.LP
|
||
|
The \fImsgget\fP() function shall return the message queue identifier
|
||
|
associated with the argument \fIkey\fP.
|
||
|
.LP
|
||
|
A message queue identifier, associated message queue, and data structure
|
||
|
(see \fI<sys/msg.h>\fP), shall be created for the argument \fIkey\fP
|
||
|
if one of the following is
|
||
|
true:
|
||
|
.IP " *" 3
|
||
|
The argument \fIkey\fP is equal to IPC_PRIVATE.
|
||
|
.LP
|
||
|
.IP " *" 3
|
||
|
The argument \fIkey\fP does not already have a message queue identifier
|
||
|
associated with it, and (\fImsgflg\fP & IPC_CREAT)
|
||
|
is non-zero.
|
||
|
.LP
|
||
|
.LP
|
||
|
Upon creation, the data structure associated with the new message
|
||
|
queue identifier shall be initialized as follows:
|
||
|
.IP " *" 3
|
||
|
\fBmsg_perm.cuid\fP, \fBmsg_perm.uid\fP, \fBmsg_perm.cgid\fP, and
|
||
|
\fBmsg_perm.gid\fP shall be set equal to the effective
|
||
|
user ID and effective group ID, respectively, of the calling process.
|
||
|
.LP
|
||
|
.IP " *" 3
|
||
|
The low-order 9 bits of \fBmsg_perm.mode\fP shall be set equal to
|
||
|
the low-order 9 bits of \fImsgflg\fP.
|
||
|
.LP
|
||
|
.IP " *" 3
|
||
|
\fBmsg_qnum\fP, \fBmsg_lspid\fP, \fBmsg_lrpid\fP, \fBmsg_stime\fP,
|
||
|
and \fBmsg_rtime\fP shall be set equal to 0.
|
||
|
.LP
|
||
|
.IP " *" 3
|
||
|
\fBmsg_ctime\fP shall be set equal to the current time.
|
||
|
.LP
|
||
|
.IP " *" 3
|
||
|
\fBmsg_qbytes\fP shall be set equal to the system limit.
|
||
|
.LP
|
||
|
.SH RETURN VALUE
|
||
|
.LP
|
||
|
Upon successful completion, \fImsgget\fP() shall return a non-negative
|
||
|
integer, namely a message queue identifier. Otherwise,
|
||
|
it shall return -1 and set \fIerrno\fP to indicate the error.
|
||
|
.SH ERRORS
|
||
|
.LP
|
||
|
The \fImsgget\fP() function shall fail if:
|
||
|
.TP 7
|
||
|
.B EACCES
|
||
|
A message queue identifier exists for the argument \fIkey\fP, but
|
||
|
operation permission as specified by the low-order 9 bits of
|
||
|
\fImsgflg\fP would not be granted; see \fIXSI Interprocess Communication\fP
|
||
|
\&.
|
||
|
.TP 7
|
||
|
.B EEXIST
|
||
|
A message queue identifier exists for the argument \fIkey\fP but ((\fImsgflg\fP
|
||
|
& IPC_CREAT) && (\fImsgflg\fP
|
||
|
& IPC_EXCL)) is non-zero.
|
||
|
.TP 7
|
||
|
.B ENOENT
|
||
|
A message queue identifier does not exist for the argument \fIkey\fP
|
||
|
and (\fImsgflg\fP & IPC_CREAT) is 0.
|
||
|
.TP 7
|
||
|
.B 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.
|
||
|
.sp
|
||
|
.LP
|
||
|
\fIThe following sections are informative.\fP
|
||
|
.SH EXAMPLES
|
||
|
.LP
|
||
|
None.
|
||
|
.SH APPLICATION USAGE
|
||
|
.LP
|
||
|
The POSIX Realtime Extension defines alternative interfaces for interprocess
|
||
|
communication (IPC). Application developers who
|
||
|
need to use IPC should design their applications so that modules using
|
||
|
the IPC routines described in \fIXSI Interprocess Communication\fP
|
||
|
can be easily modified to use the alternative
|
||
|
interfaces.
|
||
|
.SH RATIONALE
|
||
|
.LP
|
||
|
None.
|
||
|
.SH FUTURE DIRECTIONS
|
||
|
.LP
|
||
|
None.
|
||
|
.SH SEE ALSO
|
||
|
.LP
|
||
|
\fIXSI Interprocess Communication\fP , \fIRealtime\fP , \fImq_close\fP()
|
||
|
, \fImq_getattr\fP() , \fImq_notify\fP() , \fImq_open\fP() , \fImq_receive\fP()
|
||
|
, \fImq_send\fP() , \fImq_setattr\fP() , \fImq_unlink\fP() , \fImsgctl\fP()
|
||
|
, \fImsgrcv\fP() ,
|
||
|
\fImsgsnd\fP() , the Base Definitions volume of IEEE\ Std\ 1003.1-2001,
|
||
|
\fI<sys/msg.h>\fP
|
||
|
.SH COPYRIGHT
|
||
|
Portions of this text are reprinted and reproduced in electronic form
|
||
|
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
|
||
|
-- Portable Operating System Interface (POSIX), The Open Group Base
|
||
|
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
|
||
|
Electrical and Electronics Engineers, Inc and The Open Group. In the
|
||
|
event of any discrepancy between this version and the original IEEE and
|
||
|
The Open Group Standard, the original IEEE and The Open Group Standard
|
||
|
is the referee document. The original Standard can be obtained online at
|
||
|
http://www.opengroup.org/unix/online.html .
|