Merge commit 'e988fee1679536137b87d10e939eff5c1f27c8ab' as 'libs/libzmq'

libs/libzmq/doc/zmq_recv.txt

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+zmq_recv(3)
+===========
+
+
+NAME
+----
+zmq_recv - receive a message part from a socket
+
+
+SYNOPSIS
+--------
+*int zmq_recv (void '*socket', void '*buf', size_t 'len', int 'flags');*
+
+
+DESCRIPTION
+-----------
+The _zmq_recv()_ function shall receive a message from the socket referenced
+by the 'socket' argument and store it in the buffer referenced by the 'buf'
+argument. Any bytes exceeding the length specified by the 'len' argument shall
+be truncated. If there are no messages available on the specified 'socket'
+the _zmq_recv()_ function shall block until the request can be satisfied.
+The 'flags' argument is a combination of the flags defined below: The 'buf'
+argument may be null if len is zero.
+
+*ZMQ_DONTWAIT*::
+Specifies that the operation should be performed in non-blocking mode. If there
+are no messages available on the specified 'socket', the _zmq_recv()_
+function shall fail with 'errno' set to EAGAIN.
+
+
+Multi-part messages
+~~~~~~~~~~~~~~~~~~~
+A 0MQ message is composed of 1 or more message parts. 0MQ ensures atomic
+delivery of messages: peers shall receive either all _message parts_ of a
+message or none at all. The total number of message parts is unlimited except
+by available memory.
+
+An application that processes multi-part messages must use the _ZMQ_RCVMORE_
+linkzmq:zmq_getsockopt[3] option after calling _zmq_recv()_ to determine if
+there are further parts to receive.
+
+RETURN VALUE
+------------
+The _zmq_recv()_ function shall return number of bytes in the message
+if successful. Note that the value can exceed the value of the 'len' parameter
+in case the message was truncated. If not successful the function shall return
+`-1` and set 'errno' to one of the values defined below.
+
+
+ERRORS
+------
+*EAGAIN*::
+Either the timeout set via the socket-option ZMQ_RCVTIMEO (see linkzmq:zmq_setsockopt[3])
+has been reached (flag ZMQ_DONTWAIT not set) without being able to read a message
+from the socket or there are no messages available at the moment (flag ZMQ_DONTWAIT set)
+and the operation would block.
+*ENOTSUP*::
+The _zmq_recv()_ operation is not supported by this socket type.
+*EFSM*::
+The _zmq_recv()_ operation cannot be performed on this socket at the moment
+due to the socket not being in the appropriate state.  This error may occur with
+socket types that switch between several states, such as ZMQ_REP.  See the
+_messaging patterns_ section of linkzmq:zmq_socket[3] for more information.
+*ETERM*::
+The 0MQ 'context' associated with the specified 'socket' was terminated.
+*ENOTSOCK*::
+The provided 'socket' was invalid.
+*EINTR*::
+The operation was interrupted by delivery of a signal before a message was
+available.
+
+
+EXAMPLE
+-------
+.Receiving a message from a socket
+----
+char buf [256];
+nbytes = zmq_recv (socket, buf, 256, 0);
+assert (nbytes != -1);
+----
+
+
+SEE ALSO
+--------
+linkzmq:zmq_send[3]
+linkzmq:zmq_getsockopt[3]
+linkzmq:zmq_setsockopt[3]
+linkzmq:zmq_socket[7]
+linkzmq:zmq[7]
+
+
+AUTHORS
+-------
+This page was written by the 0MQ community. To make a change please
+read the 0MQ Contribution Policy at <http://www.zeromq.org/docs:contributing>.