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4<head> 4<head>
5 <title>libev</title> 5 <title>libev</title>
6 <meta name="description" content="Pod documentation for libev" /> 6 <meta name="description" content="Pod documentation for libev" />
7 <meta name="inputfile" content="&lt;standard input&gt;" /> 7 <meta name="inputfile" content="&lt;standard input&gt;" />
8 <meta name="outputfile" content="&lt;standard output&gt;" /> 8 <meta name="outputfile" content="&lt;standard output&gt;" />
9 <meta name="created" content="Mon Nov 12 09:29:10 2007" /> 9 <meta name="created" content="Mon Nov 12 09:32:26 2007" />
10 <meta name="generator" content="Pod::Xhtml 1.57" /> 10 <meta name="generator" content="Pod::Xhtml 1.57" />
11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> 11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
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24<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> 24<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
25<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> 25<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
26</ul> 26</ul>
27</li> 27</li>
28<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 28<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
29<ul><li><a href="#struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</a></li> 29<ul><li><a href="#code_ev_io_code_is_my_file_descripto"><code>ev_io</code> - is my file descriptor readable or writable</a></li>
30<li><a href="#struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</a></li> 30<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li>
31<li><a href="#ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</a></li> 31<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron it</a></li>
32<li><a href="#ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</a></li> 32<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li>
33<li><a href="#ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</a></li> 33<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li>
34<li><a href="#ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</a></li> 34<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li>
35<li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li> 35<li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li>
36</ul> 36</ul>
37</li> 37</li>
38<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 38<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
39<li><a href="#AUTHOR">AUTHOR</a> 39<li><a href="#AUTHOR">AUTHOR</a>
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161 <p>The flags argument can be used to specify special behaviour or specific 161 <p>The flags argument can be used to specify special behaviour or specific
162backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p> 162backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p>
163 <p>It supports the following flags:</p> 163 <p>It supports the following flags:</p>
164 <p> 164 <p>
165 <dl> 165 <dl>
166 <dt>EVFLAG_AUTO</dt> 166 <dt><code>EVFLAG_AUTO</code></dt>
167 <dd> 167 <dd>
168 <p>The default flags value. Use this if you have no clue (it's the right 168 <p>The default flags value. Use this if you have no clue (it's the right
169thing, believe me).</p> 169thing, believe me).</p>
170 </dd> 170 </dd>
171 <dt>EVFLAG_NOENV</dt> 171 <dt><code>EVFLAG_NOENV</code></dt>
172 <dd> 172 <dd>
173 <p>If this flag bit is ored into the flag value (or the program runs setuid 173 <p>If this flag bit is ored into the flag value (or the program runs setuid
174or setgid) then libev will <i>not</i> look at the environment variable 174or setgid) then libev will <i>not</i> look at the environment variable
175<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 175<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
176override the flags completely if it is found in the environment. This is 176override the flags completely if it is found in the environment. This is
177useful to try out specific backends to test their performance, or to work 177useful to try out specific backends to test their performance, or to work
178around bugs.</p> 178around bugs.</p>
179 </dd> 179 </dd>
180 <dt>EVMETHOD_SELECT (portable select backend)</dt> 180 <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt>
181 <dt>EVMETHOD_POLL (poll backend, available everywhere except on windows)</dt> 181 <dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt>
182 <dt>EVMETHOD_EPOLL (linux only)</dt> 182 <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt>
183 <dt>EVMETHOD_KQUEUE (some bsds only)</dt> 183 <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt>
184 <dt>EVMETHOD_DEVPOLL (solaris 8 only)</dt> 184 <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt>
185 <dt>EVMETHOD_PORT (solaris 10 only)</dt> 185 <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt>
186 <dd> 186 <dd>
187 <p>If one or more of these are ored into the flags value, then only these 187 <p>If one or more of these are ored into the flags value, then only these
188backends will be tried (in the reverse order as given here). If one are 188backends will be tried (in the reverse order as given here). If one are
189specified, any backend will do.</p> 189specified, any backend will do.</p>
190 </dd> 190 </dd>
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288</div> 288</div>
289<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 289<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
290<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 290<div id="ANATOMY_OF_A_WATCHER_CONTENT">
291<p>A watcher is a structure that you create and register to record your 291<p>A watcher is a structure that you create and register to record your
292interest in some event. For instance, if you want to wait for STDIN to 292interest in some event. For instance, if you want to wait for STDIN to
293become readable, you would create an ev_io watcher for that:</p> 293become readable, you would create an <code>ev_io</code> watcher for that:</p>
294<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 294<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
295 { 295 {
296 ev_io_stop (w); 296 ev_io_stop (w);
297 ev_unloop (loop, EVUNLOOP_ALL); 297 ev_unloop (loop, EVUNLOOP_ALL);
298 } 298 }
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333third argument.</p> 333third argument.</p>
334<p>The rceeived events usually include a single bit per event type received 334<p>The rceeived events usually include a single bit per event type received
335(you can receive multiple events at the same time). The possible bit masks 335(you can receive multiple events at the same time). The possible bit masks
336are:</p> 336are:</p>
337<dl> 337<dl>
338 <dt>EV_READ</dt> 338 <dt><code>EV_READ</code></dt>
339 <dt>EV_WRITE</dt> 339 <dt><code>EV_WRITE</code></dt>
340 <dd> 340 <dd>
341 <p>The file descriptor in the ev_io watcher has become readable and/or 341 <p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
342writable.</p> 342writable.</p>
343 </dd> 343 </dd>
344 <dt>EV_TIMEOUT</dt> 344 <dt><code>EV_TIMEOUT</code></dt>
345 <dd>
346 <p>The ev_timer watcher has timed out.</p>
347 </dd> 345 <dd>
348 <dt>EV_PERIODIC</dt> 346 <p>The <code>ev_timer</code> watcher has timed out.</p>
349 <dd> 347 </dd>
350 <p>The ev_periodic watcher has timed out.</p> 348 <dt><code>EV_PERIODIC</code></dt>
351 </dd> 349 <dd>
352 <dt>EV_SIGNAL</dt> 350 <p>The <code>ev_periodic</code> watcher has timed out.</p>
353 <dd> 351 </dd>
352 <dt><code>EV_SIGNAL</code></dt>
353 <dd>
354 <p>The signal specified in the ev_signal watcher has been received by a thread.</p> 354 <p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
355 </dd>
356 <dt>EV_CHILD</dt>
357 <dd> 355 </dd>
356 <dt><code>EV_CHILD</code></dt>
357 <dd>
358 <p>The pid specified in the ev_child watcher has received a status change.</p> 358 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
359 </dd>
360 <dt>EV_IDLE</dt>
361 <dd> 359 </dd>
360 <dt><code>EV_IDLE</code></dt>
361 <dd>
362 <p>The ev_idle watcher has determined that you have nothing better to do.</p> 362 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
363 </dd>
364 <dt>EV_PREPARE</dt>
365 <dt>EV_CHECK</dt>
366 <dd> 363 </dd>
364 <dt><code>EV_PREPARE</code></dt>
365 <dt><code>EV_CHECK</code></dt>
366 <dd>
367 <p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts 367 <p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts
368to gather new events, and all ev_check watchers are invoked just after 368to gather new events, and all <code>ev_check</code> watchers are invoked just after
369<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 369<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
370received events. Callbacks of both watcher types can start and stop as 370received events. Callbacks of both watcher types can start and stop as
371many watchers as they want, and all of them will be taken into account 371many watchers as they want, and all of them will be taken into account
372(for example, a ev_prepare watcher might start an idle watcher to keep 372(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
373<code>ev_loop</code> from blocking).</p> 373<code>ev_loop</code> from blocking).</p>
374 </dd> 374 </dd>
375 <dt>EV_ERROR</dt> 375 <dt><code>EV_ERROR</code></dt>
376 <dd> 376 <dd>
377 <p>An unspecified error has occured, the watcher has been stopped. This might 377 <p>An unspecified error has occured, the watcher has been stopped. This might
378happen because the watcher could not be properly started because libev 378happen because the watcher could not be properly started because libev
379ran out of memory, a file descriptor was found to be closed or any other 379ran out of memory, a file descriptor was found to be closed or any other
380problem. You best act on it by reporting the problem and somehow coping 380problem. You best act on it by reporting the problem and somehow coping
… …
426<div id="WATCHER_TYPES_CONTENT"> 426<div id="WATCHER_TYPES_CONTENT">
427<p>This section describes each watcher in detail, but will not repeat 427<p>This section describes each watcher in detail, but will not repeat
428information given in the last section.</p> 428information given in the last section.</p>
429 429
430</div> 430</div>
431<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2> 431<h2 id="code_ev_io_code_is_my_file_descripto"><code>ev_io</code> - is my file descriptor readable or writable</h2>
432<div id="struct_ev_io_is_my_file_descriptor_r-2"> 432<div id="code_ev_io_code_is_my_file_descripto-2">
433<p>I/O watchers check whether a file descriptor is readable or writable 433<p>I/O watchers check whether a file descriptor is readable or writable
434in each iteration of the event loop (This behaviour is called 434in each iteration of the event loop (This behaviour is called
435level-triggering because you keep receiving events as long as the 435level-triggering because you keep receiving events as long as the
436condition persists. Remember you cna stop the watcher if you don't want to 436condition persists. Remember you cna stop the watcher if you don't want to
437act on the event and neither want to receive future events).</p> 437act on the event and neither want to receive future events).</p>
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448EVMETHOD_POLL).</p> 448EVMETHOD_POLL).</p>
449<dl> 449<dl>
450 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 450 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
451 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 451 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
452 <dd> 452 <dd>
453 <p>Configures an ev_io watcher. The fd is the file descriptor to rceeive 453 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
454events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 454events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ |
455EV_WRITE</code> to receive the given events.</p> 455EV_WRITE</code> to receive the given events.</p>
456 </dd> 456 </dd>
457</dl> 457</dl>
458 458
459</div> 459</div>
460<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2> 460<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
461<div id="struct_ev_timer_relative_and_optiona-2"> 461<div id="code_ev_timer_code_relative_and_opti-2">
462<p>Timer watchers are simple relative timers that generate an event after a 462<p>Timer watchers are simple relative timers that generate an event after a
463given time, and optionally repeating in regular intervals after that.</p> 463given time, and optionally repeating in regular intervals after that.</p>
464<p>The timers are based on real time, that is, if you register an event that 464<p>The timers are based on real time, that is, if you register an event that
465times out after an hour and youreset your system clock to last years 465times out after an hour and youreset your system clock to last years
466time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because 466time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
… …
497value), or reset the running timer to the repeat value.</p> 497value), or reset the running timer to the repeat value.</p>
498 <p>This sounds a bit complicated, but here is a useful and typical 498 <p>This sounds a bit complicated, but here is a useful and typical
499example: Imagine you have a tcp connection and you want a so-called idle 499example: Imagine you have a tcp connection and you want a so-called idle
500timeout, that is, you want to be called when there have been, say, 60 500timeout, that is, you want to be called when there have been, say, 60
501seconds of inactivity on the socket. The easiest way to do this is to 501seconds of inactivity on the socket. The easiest way to do this is to
502configure an ev_timer with after=repeat=60 and calling ev_timer_again each 502configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each
503time you successfully read or write some data. If you go into an idle 503time you successfully read or write some data. If you go into an idle
504state where you do not expect data to travel on the socket, you can stop 504state where you do not expect data to travel on the socket, you can stop
505the timer, and again will automatically restart it if need be.</p> 505the timer, and again will automatically restart it if need be.</p>
506 </dd> 506 </dd>
507</dl> 507</dl>
508 508
509</div> 509</div>
510<h2 id="ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</h2> 510<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron it</h2>
511<div id="ev_periodic_to_cron_or_not_to_cron_i-2"> 511<div id="code_ev_periodic_code_to_cron_or_not-2">
512<p>Periodic watchers are also timers of a kind, but they are very versatile 512<p>Periodic watchers are also timers of a kind, but they are very versatile
513(and unfortunately a bit complex).</p> 513(and unfortunately a bit complex).</p>
514<p>Unlike ev_timer's, they are not based on real time (or relative time) 514<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
515but on wallclock time (absolute time). You can tell a periodic watcher 515but on wallclock time (absolute time). You can tell a periodic watcher
516to trigger &quot;at&quot; some specific point in time. For example, if you tell a 516to trigger &quot;at&quot; some specific point in time. For example, if you tell a
517periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 517periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now ()
518+ 10.&gt;) and then reset your system clock to the last year, then it will 518+ 10.&gt;) and then reset your system clock to the last year, then it will
519take a year to trigger the event (unlike an ev_timer, which would trigger 519take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
520roughly 10 seconds later and of course not if you reset your system time 520roughly 10 seconds later and of course not if you reset your system time
521again).</p> 521again).</p>
522<p>They can also be used to implement vastly more complex timers, such as 522<p>They can also be used to implement vastly more complex timers, such as
523triggering an event on eahc midnight, local time.</p> 523triggering an event on eahc midnight, local time.</p>
524<dl> 524<dl>
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553 <p>This doesn't mean there will always be 3600 seconds in between triggers, 553 <p>This doesn't mean there will always be 3600 seconds in between triggers,
554but only that the the callback will be called when the system time shows a 554but only that the the callback will be called when the system time shows a
555full hour (UTC), or more correct, when the system time is evenly divisible 555full hour (UTC), or more correct, when the system time is evenly divisible
556by 3600.</p> 556by 3600.</p>
557 <p>Another way to think about it (for the mathematically inclined) is that 557 <p>Another way to think about it (for the mathematically inclined) is that
558ev_periodic will try to run the callback in this mode at the next possible 558<code>ev_periodic</code> will try to run the callback in this mode at the next possible
559time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 559time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
560 </dd> 560 </dd>
561 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 561 <dt>* manual reschedule mode (reschedule_cb = callback)</dt>
562 <dd> 562 <dd>
563 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 563 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
… …
595program when the crontabs have changed).</p> 595program when the crontabs have changed).</p>
596 </dd> 596 </dd>
597</dl> 597</dl>
598 598
599</div> 599</div>
600<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2> 600<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
601<div id="ev_signal_signal_me_when_a_signal_ge-2"> 601<div id="code_ev_signal_code_signal_me_when_a-2">
602<p>Signal watchers will trigger an event when the process receives a specific 602<p>Signal watchers will trigger an event when the process receives a specific
603signal one or more times. Even though signals are very asynchronous, libev 603signal one or more times. Even though signals are very asynchronous, libev
604will try it's best to deliver signals synchronously, i.e. as part of the 604will try it's best to deliver signals synchronously, i.e. as part of the
605normal event processing, like any other event.</p> 605normal event processing, like any other event.</p>
606<p>You cna configure as many watchers as you like per signal. Only when the 606<p>You cna configure as many watchers as you like per signal. Only when the
… …
617of the <code>SIGxxx</code> constants).</p> 617of the <code>SIGxxx</code> constants).</p>
618 </dd> 618 </dd>
619</dl> 619</dl>
620 620
621</div> 621</div>
622<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2> 622<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
623<div id="ev_child_wait_for_pid_status_changes-2"> 623<div id="code_ev_child_code_wait_for_pid_stat-2">
624<p>Child watchers trigger when your process receives a SIGCHLD in response to 624<p>Child watchers trigger when your process receives a SIGCHLD in response to
625some child status changes (most typically when a child of yours dies).</p> 625some child status changes (most typically when a child of yours dies).</p>
626<dl> 626<dl>
627 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 627 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
628 <dt>ev_child_set (ev_child *, int pid)</dt> 628 <dt>ev_child_set (ev_child *, int pid)</dt>
… …
634contains the pid of the process causing the status change.</p> 634contains the pid of the process causing the status change.</p>
635 </dd> 635 </dd>
636</dl> 636</dl>
637 637
638</div> 638</div>
639<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2> 639<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
640<div id="ev_idle_when_you_ve_got_nothing_bett-2"> 640<div id="code_ev_idle_code_when_you_ve_got_no-2">
641<p>Idle watchers trigger events when there are no other I/O or timer (or 641<p>Idle watchers trigger events when there are no other I/O or timer (or
642periodic) events pending. That is, as long as your process is busy 642periodic) events pending. That is, as long as your process is busy
643handling sockets or timeouts it will not be called. But when your process 643handling sockets or timeouts it will not be called. But when your process
644is idle all idle watchers are being called again and again - until 644is idle all idle watchers are being called again and again - until
645stopped, that is, or your process receives more events.</p> 645stopped, that is, or your process receives more events.</p>
… …
666watchers afterwards.</p> 666watchers afterwards.</p>
667<p>Their main purpose is to integrate other event mechanisms into libev. This 667<p>Their main purpose is to integrate other event mechanisms into libev. This
668could be used, for example, to track variable changes, implement your own 668could be used, for example, to track variable changes, implement your own
669watchers, integrate net-snmp or a coroutine library and lots more.</p> 669watchers, integrate net-snmp or a coroutine library and lots more.</p>
670<p>This is done by examining in each prepare call which file descriptors need 670<p>This is done by examining in each prepare call which file descriptors need
671to be watched by the other library, registering ev_io watchers for them 671to be watched by the other library, registering <code>ev_io</code> watchers for them
672and starting an ev_timer watcher for any timeouts (many libraries provide 672and starting an <code>ev_timer</code> watcher for any timeouts (many libraries provide
673just this functionality). Then, in the check watcher you check for any 673just this functionality). Then, in the check watcher you check for any
674events that occured (by making your callbacks set soem flags for example) 674events that occured (by making your callbacks set soem flags for example)
675and call back into the library.</p> 675and call back into the library.</p>
676<p>As another example, the perl Coro module uses these hooks to integrate 676<p>As another example, the perl Coro module uses these hooks to integrate
677coroutines into libev programs, by yielding to other active coroutines 677coroutines into libev programs, by yielding to other active coroutines
… …
698callback on whichever event happens first and automatically stop both 698callback on whichever event happens first and automatically stop both
699watchers. This is useful if you want to wait for a single event on an fd 699watchers. This is useful if you want to wait for a single event on an fd
700or timeout without havign to allocate/configure/start/stop/free one or 700or timeout without havign to allocate/configure/start/stop/free one or
701more watchers yourself.</p> 701more watchers yourself.</p>
702 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is 702 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is
703ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set 703ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and <code>events</code> set
704will be craeted and started.</p> 704will be craeted and started.</p>
705 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 705 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
706started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat 706started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and repeat
707= 0) will be started.</p> 707= 0) will be started.</p>
708 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and 708 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and
709gets passed an events set (normally a combination of EV_ERROR, EV_READ, 709gets passed an events set (normally a combination of <code>EV_ERROR</code>, <code>EV_READ</code>,
710EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p> 710<code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> value passed to <code>ev_once</code>:</p>
711<pre> static void stdin_ready (int revents, void *arg) 711<pre> static void stdin_ready (int revents, void *arg)
712 { 712 {
713 if (revents &amp; EV_TIMEOUT) 713 if (revents &amp; EV_TIMEOUT)
714 /* doh, nothing entered */ 714 /* doh, nothing entered */
715 else if (revents &amp; EV_READ) 715 else if (revents &amp; EV_READ)

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