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mq_receive

Section: C Library Functions (3)
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NAME

mq_receive - Receives the oldest, highest-priority message from the message queue (P1003.1b)  

SYNOPSIS

#include <mqueue.h>

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

PARAMETERS

mqdes
Specifies a message queue by descriptor.
*msg_ptr
A pointer to a buffer to receive the message.
msg_len
Specifies the size of the receive buffer identified by the msg_ptr argument.
*msg_prio
A pointer to a location to receive the message priority.
 

DESCRIPTION

Receives the oldest, highest-priority message from the message queue. The message is removed from the queue and transferred to the buffer pointed to by the msg_ptr argument.

If the specified message queue is empty and the O_NONBLOCK flag is not set with the mqdes argument, the mq_receive function blocks until a message is put on the queue, or until the mq_receive function is interrupted by a signal. If more than one process is waiting to receive a message when a message arrives at an empty queue, the highest-priority process that has been waiting the longest is selected to receive the message. If the message queue is empty and the O_NONBLOCK flag is set, no message is removed from the queue, and an error is returned.  

RETURN VALUES

On successful completion, the function returns the length of the selected message.

Otherwise, the function returns the value -1 and sets errno to indicate the error. No message is removed from the queue.  

ERRORS

The mq_receive function fails under the following conditions:

[EAGAIN]
O_NONBLOCK was set in the message description associated with mqdes, and the specified message queue is empty.
[EBADF]
The mqdes argument is not a valid message queue descriptor open for reading.
[EBADMSG]
The implementation has detected a data corruption problem with the message.
[EFAULT]
Internal virtual memory error.
[EINTR]
The mq_receive function was interrupted by a signal.
[EMSGSIZE]
The specified message buffer size, msg_len is less than the message size attribute of the message queue.
 

RELATED INFORMATION

Functions: mq_send(3) delim off


 

Index

NAME
SYNOPSIS
PARAMETERS
DESCRIPTION
RETURN VALUES
ERRORS
RELATED INFORMATION

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Time: 02:42:27 GMT, October 02, 2010