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| | % posix-mq-rb(1) posix-mq-rb User Manual
% Ruby POSIX MQ hackers <ruby-posix-mq@bogomips.org>
% Jan 1, 2010
# NAME
posix-mq-rb - command-line interface for POSIX message queues
# SYNOPSIS
MQUEUE=/name posix-mq-rb COMMAND [*OPTIONS*] [*ARGUMENTS*]
# DESCRIPTION
A command-line interface for manipulating POSIX message queues. It is
useful for testing and debugging applications using POSIX message
queues.
# COMMANDS
*create* - create a new message queue
*attr* - output attributes of the message queue
*send* - insert a message into the queue from stdin or the command-line
*receive* - take a message from the queue and outputs it to stdout
*wait* - sleep until a message is available in the queue
*unlink* - unlink the message queue
# CREATE USAGE
The *create* command accepts the following options:
-x, \--exclusive
: This causes queue creation to fail if the queue exists.
-m, \--mode MODE
: The MODE to open the file under, the actual mode of the queue
will be AND-ed with the current umask (like open(2)).
-c, \--maxmsg COUNT
: The maximum messages in the queue. The default and limit of this
value is system-dependent. This must be specified if \--msgsize is
also specified.
-s, \--msgsize BYTES
: The maximum size of an individual message. The default and limit of
this value is system-dependent. This must be specified if \--maxmsg
is also specified.
# ATTR USAGE
The *attr* command takes no special options nor command-line arguments.
The output format of this command is suitable for "eval" in
shell scripts. Sample output is below:
flags=0
maxmsg=10
msgsize=8192
curmsgs=3
See mq_getattr(3) for information on the meaning of the fields.
# SEND USAGE
The *send* command will read a message from standard input if no
command-line arguments are given. If command-line arguments are
given, each argument is considered its own message and will be
inserted into the queue separately.
The following command-line arguments are accepted:
-n, \--nonblock
: Exit immediately with error if the message queue is full.
Normally posix-mq-rb(1) will block until the queue is writable or
interrupted. This may not be used in conjunction with \--timeout .
-t, \--timeout SECONDS
: Timeout and exit with error after SECONDS if the message queue is full.
This may not be used in conjunction with \--nonblock.
-p, \--priority PRIORITY
: Specify an integer PRIORITY, this value should be 0 through 31
(inclusive) for portability across POSIX-compliant systems.
The default priority is 0.
# RECEIVE USAGE
The *receive* command will output message to standard output. It will
read a message from standard input if no command-line arguments are
given. If command-line arguments are given, each argument is considered
its own message and will be inserted into the queue separately.
The following command-line arguments are accepted:
-n, \--nonblock
: Exit immediately with error if the message queue is empty.
Normally posix-mq-rb(1) will block until the queue is readable or
interrupted. This may not be used in conjunction with \--timeout .
-t, \--timeout SECONDS
: Timeout and exit with error after SECONDS if the message queue is empty.
This may not be used in conjunction with \--nonblock.
-p, \--priority
: Output the priority of the received message to stderr in the following
format:
priority=3
The priority is an unsigned integer.
# WAIT USAGE
The *wait* command will cause posix-mq-rb(1) to sleep until a message is
available in the queue. Only one process may wait on an empty queue,
posix-mq-rb(1) will exit with an error if there is another waiting process.
It takes no arguments and accepts the following options:
-t, \--timeout SECONDS
: Timeout and exit with error after SECONDS if the message queue is empty.
# UNLINK USAGE
The *unlink* command prevents further opening and use of the current
queue. Existing processes with the queue open may continue to operate
on the queue indefinitely. If a new queue is created with the same
name, the created queue is a different queue from the unlinked queue.
See mq_unlink(3) for more information.
# GENERAL OPTIONS
-q
: Do not show warning/error messages, suitable for scripting.
\-h, \--help
: Show summary usage
# ENVIRONMENT
All commands rely on the MQUEUE environment variable. The value
of MQUEUE should always be prefixed with a slash ("/") for
portability.
# DIAGNOSTICS
Exit status is normally 0. Exit status is 2 if a timeout occurs, 1 for
all other errors.
Under FreeBSD, the mq_* system calls are not available unless you load
the mqueuefs(5) kernel module:
kldload mqueuefs
# SEE ALSO
* [mq_overview(7)][1]
* [mqueuefs(5)][2]
[1]: http://kernel.org/doc/man-pages/online/pages/man7/mq_overview.7.html
[2]: http://freebsd.org/cgi/man.cgi?query=mqueuefs
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