# zmq_getmsgopt(3) Manual Page

## NAME

zmq_getmsgopt - retrieve message option

## SYNOPSIS

int zmq_getmsgopt (zmq_msg_t *message, int option_name, void *option_value, size_t *option_len);

## DESCRIPTION

The zmq_getmsgopt() function shall retrieve the value for the option specified by the option_name argument for the message pointed to by the message argument, and store it in the buffer pointed to by the option_value argument. The option_len argument is the size in bytes of the buffer pointed to by option_value; upon successful completion zmq_getsockopt() shall modify the option_len argument to indicate the actual size of the option value stored in the buffer.

The following options can be retrieved with the zmq_getmsgopt() function:

ZMQ_MORE

  Indicates that there are more message parts to follow after the message.

## RETURN VALUE

The zmq_getmsgopt() function shall return zero if successful. Otherwise it shall return `-1` and set errno to one of the values defined below.

## ERRORS

EINVAL

  The requested option option_name is unknown, or the requested option_size or option_value is invalid, or the size of the buffer pointed to by option_value, as specified by option_len, is insufficient for storing the option value.

## EXAMPLE

Receiving a multi-part message

    zmq_msg_t part;
    int more;
    size_t more_size = sizeof (more);
    while (true) {
        /* Create an empty 0MQ message to hold the message part */
        int rc = zmq_msg_init (&part);
        assert (rc == 0);
        /* Block until a message is available to be received from socket */
        rc = zmq_recvmsg (socket, &part, 0);
        assert (rc != -1);
        rc = getmsgopt (&part, ZMQ_MORE, &more, &more_size);
        assert (rc == 0);
        if (more) {
          fprintf (stderr, "more\n");
        }
        else {
          fprintf (stderr, "end\n");
          break;
        }
        zmq_msg_close (part);
    }

## SEE ALSO

zmq_msg_data(3) zmq_msg_init(3) zmq_msg_init_size(3) zmq_msg_init_data(3) zmq_msg_close(3) zmq(7)

## AUTHORS

The ØMQ documentation was written by Chuck Remes <cremes@mac.com>.