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mq_receive(3)
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)

Index for Section 3

Alphabetical listing for M

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