xref: /freebsd/share/man/man4/mqueuefs.4 (revision 1687d77197c01c6ffd5bb233c7a15c6ebb9319af)

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.Dd November 30, 2005
.Dt MQUEUEFS 4
.Os
.Sh NAME
.Nm mqueuefs
.Nd POSIX message queue file system
.Sh SYNOPSIS
To link into kernel:
.Pp
.Cd "options P1003_1B_MQUEUE"
.Pp
To load as a kernel loadable module:
.Pp
.Dl "kldload mqueuefs"
.Sh DESCRIPTION
The
.Nm
module will permit the
.Fx
kernel to support
.Tn POSIX
message queue.
The module contains system calls to manipulate
.Tn POSIX
message queues.
It also contains a file system to implement a view for all message queues of
the system.
This helps users to keep track of their message queues and make
it more easily usable without having to invent additional tools.
.Pp
The most common usage is as follows:
.Pp
.Dl "mount -t mqueuefs null /mnt/mqueue"
.Pp
where
.Pa /mnt/mqueue
is a mount point.
.Pp
It is possible to define an entry in
.Pa /etc/fstab
that looks similar to:
.Bd -literal
null	/mnt/mqueue	mqueuefs	rw	0	0
.Ed
.Pp
This will mount
.Nm
at the
.Pa /mnt/mqueue
mount point during system boot.
Using
.Pa /mnt/mqueue
as a permanent mount point is not advised as its intention
has always been to be a temporary mount point.
See
.Xr hier 7
for more information on
.Fx
directory layout.
.Pp
Some common tools can be used on the file system, e.g.:
.Xr cat 1 ,
.Xr chmod 1 ,
.Xr chown 8 ,
.Xr ls 1 ,
.Xr rm 1 ,
etc.
To use only the message queue system calls, it is not necessary for
user to mount the file system, just load the module or compile it
into the kernel.
Manually creating a file, for example,
.Dq Li "touch /mnt/mqueue/myqueue" ,
will create a message queue named
.Pa myqueue
in the kernel, default
message queue attributes will be applied to the queue.
It is not
advised to use this method to create a queue;
it is better to use the
.Xr mq_open 2
system call to create a queue as it
allows the user to specify different attributes.
.Pp
To see the queue's attributes, just read the file:
.Pp
.Dl "cat /mnt/mqueue/myqueue"
.Sh SEE ALSO
.Xr mq_open 2 ,
.Xr nmount 2 ,
.Xr unmount 2 ,
.Xr mount 8 ,
.Xr umount 8
.Sh AUTHORS
This manual page was written by
.An David Xu Aq Mt davidxu@FreeBSD.org .