freebsd-nq/lib/libc/sys/mq_setattr.2

.\" Copyright (c) 2005 David Xu <davidxu@FreeBSD.org>
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.\" Portions of this text are reprinted and reproduced in electronic form
.\" from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology --
.\" Portable Operating System Interface (POSIX), The Open Group Base
.\" Specifications Issue 6, Copyright (C) 2001-2004 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.
.\"
.\" $FreeBSD$
.\"
.Dd May 17, 2011
.Dt MQ_SETATTR 2
.Os
.Sh NAME
.Nm mq_setattr
.Nd "set message queue attributes (REALTIME)"
.Sh LIBRARY
.Lb librt
.Sh SYNOPSIS
.In mqueue.h
.Ft int
.Fo mq_setattr
.Fa "mqd_t mqdes"
.Fa "const struct mq_attr *restrict mqstat"
.Fa "struct mq_attr *restrict omqstat"
.Fc
.Sh DESCRIPTION
The
.Fn mq_setattr
system call sets attributes associated with the open message queue description
referenced by the message queue descriptor specified by
.Fa mqdes .
The message queue attributes corresponding to the following members defined
in the
.Vt mq_attr
structure will be set to the specified values upon successful completion of
.Fn mq_setattr :
.Bl -tag -width ".Va mq_flags"
.It Va mq_flags
The value of this member is zero or
.Dv O_NONBLOCK .
.El
.Pp
The values of the
.Va mq_maxmsg , mq_msgsize ,
and
.Va mq_curmsgs
members of the
.Vt mq_attr
structure are ignored by
.Fn mq_setattr .
.Sh RETURN VALUES
Upon successful completion, the function returns a value of zero and the
attributes of the message queue will have been changed as specified.
.Pp
Otherwise, the message queue attributes are unchanged, and the function
returns a value of \-1 and sets the global variable
.Va errno
to indicate the error.
.Sh ERRORS
The
.Fn mq_setattr
system call
will fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa mqdes
argument is not a valid message queue descriptor.
.El
.Sh SEE ALSO
.Xr mq_open 2 ,
.Xr mq_send 2 ,
.Xr mq_timedsend 2
.Sh STANDARDS
The
.Fn mq_setattr
system call conforms to
.St -p1003.1-2004 .
.Sh HISTORY
Support for
.Tn POSIX
message queues first appeared in
.Fx 7.0 .
.Sh COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology --
Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2004 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.