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NN_RECV(3)			 nanomsg 1.0.0			    NN_RECV(3)

NAME
       nn_recv - receive a message

SYNOPSIS
       #include	<nanomsg/nn.h>

       int nn_recv (int	s, void	*buf, size_t len, int flags);

DESCRIPTION
       Receive a message from the socket s and store it	in the buffer
       referenced by the buf argument. Any bytes exceeding the length
       specified by the	len argument will be truncated.

       Alternatively, nanomsg can allocate the buffer for you. To do so, let
       the buf parameter be a pointer to a void* variable (pointer to pointer)
       to the receive buffer and set the len parameter to NN_MSG. If the call
       is successful the user is responsible for deallocating the message
       using the nn_freemsg(3) function.

       The flags argument is a combination of the flags	defined	below:

       NN_DONTWAIT
	   Specifies that the operation	should be performed in non-blocking
	   mode. If the	message	cannot be received straight away, the function
	   will	fail with errno	set to EAGAIN.

RETURN VALUE
       If the function succeeds	number of bytes	in the message is returned.
       Otherwise, -1 is	returned and errno is set to to	one of the values
       defined below.

ERRORS
       EBADF
	   The provided	socket is invalid.

       ENOTSUP
	   The operation is not	supported by this socket type.

       EFSM
	   The operation cannot	be performed on	this socket at the moment
	   because socket is not in the	appropriate state. This	error may
	   occur with socket types that	switch between several states.

       EAGAIN
	   Non-blocking	mode was requested and there's no message to receive
	   at the moment.

       EINTR
	   The operation was interrupted by delivery of	a signal before	the
	   message was received.

       ETIMEDOUT
	   Individual socket types may define their own	specific timeouts. If
	   such	timeout	is hit this error will be returned.

       ETERM
	   The library is terminating.

EXAMPLES
       Receiving a message into	a buffer allocated by the user
	   This	example	code will retrieve a message of	either 100 bytes or
	   less. If a larger message was sent it will be truncated to 100
	   bytes.

	   char	buf [100];
	   nbytes = nn_recv (s,	buf, sizeof (buf), 0);

       Receiving a message into	a buffer allocated by nanomsg
	   The following will get a message from the pipe with a buffer
	   allocated by	the system. It is large	enough to accommodate the
	   entire message. This	is a good way to get the entire	message
	   without truncating if the size of the message is unknown. It	is the
	   user's responsibility to call nn_freemsg(3) after processing	the
	   message.

	   void	*buf = NULL;
	   nbytes = nn_recv (s,	&amp;buf, NN_MSG, 0);

	   if (nbytes <	0) {
	       /* handle error */
	       ...
	   }
	   else	{
	       /* process message */
	       ...
	       nn_freemsg (buf);
	   }

       Note that this can be more efficient than manually allocating a buffer
       since it	is a zero-copy operation.

SEE ALSO
       nn_send(3) nn_recvmsg(3)	nn_socket(3) nanomsg(7)

AUTHORS
       Martin Sustrik <sustrik@250bpm.com>

				  2016-06-10			    NN_RECV(3)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | SEE ALSO | AUTHORS

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