Message queues. More...

#include "FreeRTOS_POSIX/time.h"

Data Structures
struct	mq_attr
	Message queue attributes. More...

Typedefs
typedef void *	mqd_t
	Message queue descriptor.

Functions
int	mq_close (mqd_t mqdes)
	Close a message queue. More...

int	mq_getattr (mqd_t mqdes, struct mq_attr *mqstat)
	Get message queue attributes. More...

mqd_t	mq_open (const char name, int oflag, mode_t mode, struct mq_attr attr)
	Open a message queue. More...

ssize_t	mq_receive (mqd_t mqdes, char msg_ptr, size_t msg_len, unsigned int msg_prio)
	Receive a message from a message queue. More...

int	mq_send (mqd_t mqdes, const char *msg_ptr, size_t msg_len, unsigned msg_prio)
	Send a message to a message queue. More...

ssize_t	mq_timedreceive (mqd_t mqdes, char msg_ptr, size_t msg_len, unsigned msg_prio, const struct timespec *abstime)
	Receive a message from a message queue with timeout. More...

int	mq_timedsend (mqd_t mqdes, const char msg_ptr, size_t msg_len, unsigned msg_prio, const struct timespec abstime)
	Send a message to a message queue with timeout. More...

int	mq_unlink (const char *name)
	Remove a message queue. More...

Detailed Description

Message queues.

http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/mqueue.h.html

Function Documentation

◆ mq_close()

int mq_close ( mqd_t mqdes )

Close a message queue.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_close.html

Return values

0	- Upon successful completion
-1	- A error occurred. errno is also set.

Side Effects:: Possible errno values
EBADF - The mqdes argument is not a valid message queue descriptor.

◆ mq_getattr()

int mq_getattr	(	mqd_t	mqdes,
		struct mq_attr *	mqstat
	)

Get message queue attributes.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_getattr.html

Return values

0	- Upon successful completion
-1	- A error occurred. errno is also set.

Side Effects:: Possible errno values
DBADF - The mqdes argument is not a valid message queue descriptor.

◆ mq_open()

mqd_t mq_open	(	const char *	name,
		int	oflag,
		mode_t	mode,
		struct mq_attr *	attr
	)

Open a message queue.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_open.html

Note: Supported name pattern: leading <slash> character in name is always required; the maximum length (excluding null-terminator) of the name argument can be NAME_MAX. The default value of NAME_MAX in FreeRTOS_POSIX_portable_default.h is 64, which can be overwritten by user.; mode argument is not supported.; Supported oflags: O_RDWR, O_CREAT, O_EXCL, and O_NONBLOCK.

Return values

Message	queue descriptor – Upon successful completion
(mqd_t)	- 1 – An error occurred. errno is also set.

Side Effects:: Possible errno values
EINVAL - name argument is invalid (not following name pattern), OR if O_CREAT is specified in oflag with attr argument not NULL and either mq_maxmsg or mq_msgsize is equal to or less than zero, OR either O_CREAT or O_EXCL is not set and a queue with the same name is unlinked but pending to be removed.
EEXIST - O_CREAT and O_EXCL are set and the named message queue already exists.
ENOSPC - There is insufficient space for the creation of the new message queue.
ENOENT - O_CREAT is not set and the named message queue does not exist.

◆ mq_receive()

ssize_t mq_receive	(	mqd_t	mqdes,
		char *	msg_ptr,
		size_t	msg_len,
		unsigned int *	msg_prio
	)

Receive a message from a message queue.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_receive.html

Note: msg_prio argument is not supported. Messages are not checked for corruption.

Return values

The	length of the selected message in bytes - Upon successful completion. The message is removed from the queue
-1	- An error occurred. errno is also set.

Side Effects:: Possible errno values
EBADF - The mqdes argument is not a valid message queue descriptor open for reading.
EMSGSIZE - The specified message buffer size, msg_len, is less than the message size attribute of the message queue.
ETIMEDOUT - The O_NONBLOCK flag was not set when the message queue was opened, but no message arrived on the queue before the specified timeout expired.
EAGAIN - O_NONBLOCK was set in the message description associated with mqdes, and the specified message queue is empty.

◆ mq_send()

int mq_send	(	mqd_t	mqdes,
		const char *	msg_ptr,
		size_t	msg_len,
		unsigned	msg_prio
	)

Send a message to a message queue.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_send.html

Note: msg_prio argument is not supported.

Return values

0	- Upon successful completion.
-1	- An error occurred. errno is also set.

Side Effects:: Possible errno values
EBADF - The mqdes argument is not a valid message queue descriptor open for writing.
EMSGSIZE - The specified message length, msg_len, exceeds the message size attribute of the message queue, OR insufficient memory for the message to be sent.
ETIMEDOUT - The O_NONBLOCK flag was not set when the message queue was opened, but the timeout expired before the message could be added to the queue.
EAGAIN - The O_NONBLOCK flag is set in the message queue description associated with mqdes, and the specified message queue is full.

◆ mq_timedreceive()

ssize_t mq_timedreceive	(	mqd_t	mqdes,
		char *	msg_ptr,
		size_t	msg_len,
		unsigned *	msg_prio,
		const struct timespec *	abstime
	)

Receive a message from a message queue with timeout.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_timedreceive.html

Note: msg_prio argument is not supported. Messages are not checked for corruption.

Return values

The	length of the selected message in bytes - Upon successful completion. The message is removed from the queue
-1	- An error occurred. errno is also set.

Side Effects:: Possible errno values
EBADF - The mqdes argument is not a valid message queue descriptor open for reading.
EMSGSIZE - The specified message buffer size, msg_len, is less than the message size attribute of the message queue.
EINVAL - The process or thread would have blocked, and the abstime parameter specified a nanoseconds field value less than zero or greater than or equal to 1000 million.
ETIMEDOUT - The O_NONBLOCK flag was not set when the message queue was opened, but no message arrived on the queue before the specified timeout expired.
EAGAIN - O_NONBLOCK was set in the message description associated with mqdes, and the specified message queue is empty.

◆ mq_timedsend()

int mq_timedsend	(	mqd_t	mqdes,
		const char *	msg_ptr,
		size_t	msg_len,
		unsigned	msg_prio,
		const struct timespec *	abstime
	)

Send a message to a message queue with timeout.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_timedsend.html

Note: msg_prio argument is not supported.

Return values

0	- Upon successful completion.
-1	- An error occurred. errno is also set.

Side Effects:: Possible errno values
EBADF - The mqdes argument is not a valid message queue descriptor open for writing.
EMSGSIZE - The specified message length, msg_len, exceeds the message size attribute of the message queue, OR insufficient memory for the message to be sent.
EINVAL - The process or thread would have blocked, and the abstime parameter specified a nanoseconds field value less than zero or greater than or equal to 1000 million.
ETIMEDOUT - The O_NONBLOCK flag was not set when the message queue was opened, but the timeout expired before the message could be added to the queue.
EAGAIN - The O_NONBLOCK flag is set in the message queue description associated with mqdes, and the specified message queue is full.

◆ mq_unlink()

int mq_unlink ( const char * name )

Remove a message queue.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_unlink.html

Return values

0	- Upon successful completion.
-1	- An error occurred. errno is also set.

Side Effects:: Possible errno values
EINVAL - name argument is invalid. Refer to requirements on name argument in mq_open().
ENOENT - The named message queue does not exist.

Data Structures

Typedefs

Functions

Detailed Description

Function Documentation

◆ mq_close()

◆ mq_getattr()

◆ mq_open()

◆ mq_receive()

◆ mq_send()

◆ mq_timedreceive()

◆ mq_timedsend()

◆ mq_unlink()