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" + note + "</div>"; spans[i].innerHTML = "[<a id='_footnoteref_" + n + "' href='#_footnote_" + n + "' title='View footnote' class='footnote'>" + n + "</a>]"; var id =spans[i].getAttribute("id"); if (id != null) refs["#"+id] = n; } } if (n == 0) noteholder.parentNode.removeChild(noteholder); else { // Process footnoterefs. for (i=0; i<spans.length; i++) { if (spans[i].className == "footnoteref") { var href = spans[i].getElementsByTagName("a")[0].getAttribute("href"); href = href.match(/#.*/)[0]; // Because IE return full URL. n = refs[href]; spans[i].innerHTML = "[<a href='#_footnote_" + n + "' title='View footnote' class='footnote'>" + n + "</a>]"; } } } } } /*]]>*/ </script> </head> <body> <div id="header"> <h1> zmq_poll(3) Manual Page </h1> <h2>NAME</h2> <div class="sectionbody"> <p>zmq_poll - input/output multiplexing </p> </div> </div> <div id="content"> <h2 id="_synopsis">SYNOPSIS</h2> <div class="sectionbody"> <div class="paragraph"><p><strong>int zmq_poll (zmq_pollitem_t <em>*items</em>, int <em>nitems</em>, long <em>timeout</em>);</strong></p></div> </div> <h2 id="_description">DESCRIPTION</h2> <div class="sectionbody"> <div class="paragraph"><p>The <em>zmq_poll()</em> function provides a mechanism for applications to multiplex input/output events in a level-triggered fashion over a set of sockets. Each member of the array pointed to by the <em>items</em> argument is a <strong>zmq_pollitem_t</strong> structure. The <em>nitems</em> argument specifies the number of items in the <em>items</em> array. The <strong>zmq_pollitem_t</strong> structure is defined as follows:</p></div> <div class="literalblock"> <div class="content"> <pre><tt>typedef struct { void <em>*socket</em>; int <em>fd</em>; short <em>events</em>; short <em>revents</em>; } zmq_pollitem_t;</tt></pre> </div></div> <div class="paragraph"><p>For each <strong>zmq_pollitem_t</strong> item, <em>zmq_poll()</em> shall examine either the ØMQ socket referenced by <em>socket</em> <strong>or</strong> the standard socket specified by the file descriptor <em>fd</em>, for the event(s) specified in <em>events</em>. If both <em>socket</em> and <em>fd</em> are set in a single <strong>zmq_pollitem_t</strong>, the ØMQ socket referenced by <em>socket</em> shall take precedence and the value of <em>fd</em> shall be ignored.</p></div> <div class="admonitionblock"> <table><tr> <td class="icon"> <div class="title">Note</div> </td> <td class="content">All ØMQ sockets passed to the <em>zmq_poll()</em> function must share the same ØMQ <em>context</em> and must belong to the thread calling <em>zmq_poll()</em>.</td> </tr></table> </div> <div class="paragraph"><p>For each <strong>zmq_pollitem_t</strong> item, <em>zmq_poll()</em> shall first clear the <em>revents</em> member, and then indicate any requested events that have occurred by setting the bit corresponding to the event condition in the <em>revents</em> member.</p></div> <div class="paragraph"><p>If none of the requested events have occurred on any <strong>zmq_pollitem_t</strong> item, <em>zmq_poll()</em> shall wait <em>timeout</em> microseconds for an event to occur on any of the requested items. If the value of <em>timeout</em> is <tt>0</tt>, <em>zmq_poll()</em> shall return immediately. If the value of <em>timeout</em> is <tt>-1</tt>, <em>zmq_poll()</em> shall block indefinitely until a requested event has occurred on at least one <strong>zmq_pollitem_t</strong>. The resolution of <em>timeout</em> is 1 millisecond.</p></div> <div class="paragraph"><p>The <em>events</em> and <em>revents</em> members of <strong>zmq_pollitem_t</strong> are bit masks constructed by OR’ing a combination of the following event flags:</p></div> <div class="dlist"><dl> <dt class="hdlist1"> <strong>ZMQ_POLLIN</strong> </dt> <dd> <p> For ØMQ sockets, at least one message may be received from the <em>socket</em> without blocking. For standard sockets this is equivalent to the <em>POLLIN</em> flag of the <em>poll()</em> system call and generally means that at least one byte of data may be read from <em>fd</em> without blocking. </p> </dd> <dt class="hdlist1"> <strong>ZMQ_POLLOUT</strong> </dt> <dd> <p> For ØMQ sockets, at least one message may be sent to the <em>socket</em> without blocking. For standard sockets this is equivalent to the <em>POLLOUT</em> flag of the <em>poll()</em> system call and generally means that at least one byte of data may be written to <em>fd</em> without blocking. </p> </dd> <dt class="hdlist1"> <strong>ZMQ_POLLERR</strong> </dt> <dd> <p> For standard sockets, this flag is passed through <em>zmq_poll()</em> to the underlying <em>poll()</em> system call and generally means that some sort of error condition is present on the socket specified by <em>fd</em>. For ØMQ sockets this flag has no effect if set in <em>events</em>, and shall never be returned in <em>revents</em> by <em>zmq_poll()</em>. </p> </dd> </dl></div> <div class="admonitionblock"> <table><tr> <td class="icon"> <div class="title">Note</div> </td> <td class="content">The <em>zmq_poll()</em> function may be implemented or emulated using operating system interfaces other than <em>poll()</em>, and as such may be subject to the limits of those interfaces in ways not defined in this documentation.</td> </tr></table> </div> </div> <h2 id="_return_value">RETURN VALUE</h2> <div class="sectionbody"> <div class="paragraph"><p>Upon successful completion, the <em>zmq_poll()</em> function shall return the number of <strong>zmq_pollitem_t</strong> structures with events signaled in <em>revents</em> or <tt>0</tt> if no events have been signaled. Upon failure, <em>zmq_poll()</em> shall return <tt>-1</tt> and set <em>errno</em> to one of the values defined below.</p></div> </div> <h2 id="_errors">ERRORS</h2> <div class="sectionbody"> <div class="dlist"><dl> <dt class="hdlist1"> <strong>ETERM</strong> </dt> <dd> <p> At least one of the members of the <em>items</em> array refers to a <em>socket</em> whose associated ØMQ <em>context</em> was terminated. </p> </dd> <dt class="hdlist1"> <strong>EFAULT</strong> </dt> <dd> <p> The provided <em>items</em> was not valid (NULL). </p> </dd> <dt class="hdlist1"> <strong>EINTR</strong> </dt> <dd> <p> The operation was interrupted by delivery of a signal before any events were available. </p> </dd> </dl></div> </div> <h2 id="_example">EXAMPLE</h2> <div class="sectionbody"> <div class="listingblock"> <div class="title">Polling indefinitely for input events on both a ØMQ socket and a standard socket.</div> <div class="content"> <pre><tt>zmq_pollitem_t items [2]; /* First item refers to 0MQ socket 'socket' */ items[0].socket = socket; items[0].events = ZMQ_POLLIN; /* Second item refers to standard socket 'fd' */ items[1].socket = NULL; items[1].fd = fd; items[1].events = ZMQ_POLLIN; /* Poll for events indefinitely */ int rc = zmq_poll (items, 2, -1); assert (rc >= 0); /* Returned events will be stored in items[].revents */</tt></pre> </div></div> </div> <h2 id="_see_also">SEE ALSO</h2> <div class="sectionbody"> <div class="paragraph"><p><a href="zmq_socket.html">zmq_socket(3)</a> <a href="zmq_send.html">zmq_send(3)</a> <a href="zmq_recv.html">zmq_recv(3)</a> <a href="zmq.html">zmq(7)</a></p></div> <div class="paragraph"><p>Your operating system documentation for the <em>poll()</em> system call.</p></div> </div> <h2 id="_authors">AUTHORS</h2> <div class="sectionbody"> <div class="paragraph"><p>This ØMQ manual page was written by Martin Sustrik <<a href="mailto:sustrik@250bpm.com">sustrik@250bpm.com</a>> and Martin Lucina <<a href="mailto:mato@kotelna.sk">mato@kotelna.sk</a>>.</p></div> </div> </div> <div id="footnotes"><hr /></div> <div id="footer"> <div id="footer-text"> ØMQ 2.1.10<br /> Last updated 2011-08-23 16:01:49 CDT </div> </div> </body> </html>