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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" /> |
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13 | <div class="pod"> |
13 | <div class="pod"> |
14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
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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="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li> |
29 | <ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li> |
30 | <li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - 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="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - 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</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> |
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="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - 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="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - 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> |
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322 | *)</code>), and you can stop watching for events at any time by calling the |
322 | *)</code>), and you can stop watching for events at any time by calling the |
323 | corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p> |
323 | corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p> |
324 | <p>As long as your watcher is active (has been started but not stopped) you |
324 | <p>As long as your watcher is active (has been started but not stopped) you |
325 | must not touch the values stored in it. Most specifically you must never |
325 | must not touch the values stored in it. Most specifically you must never |
326 | reinitialise it or call its set method.</p> |
326 | reinitialise it or call its set method.</p> |
327 | <p>You cna check whether an event is active by calling the <code>ev_is_active |
327 | <p>You can check whether an event is active by calling the <code>ev_is_active |
328 | (watcher *)</code> macro. To see whether an event is outstanding (but the |
328 | (watcher *)</code> macro. To see whether an event is outstanding (but the |
329 | callback for it has not been called yet) you cna use the <code>ev_is_pending |
329 | callback for it has not been called yet) you can use the <code>ev_is_pending |
330 | (watcher *)</code> macro.</p> |
330 | (watcher *)</code> macro.</p> |
331 | <p>Each and every callback receives the event loop pointer as first, the |
331 | <p>Each and every callback receives the event loop pointer as first, the |
332 | registered watcher structure as second, and a bitset of received events as |
332 | registered watcher structure as second, and a bitset of received events as |
333 | third argument.</p> |
333 | third argument.</p> |
334 | <p>The rceeived events usually include a single bit per event type received |
334 | <p>The received 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 |
336 | are:</p> |
336 | are:</p> |
337 | <dl> |
337 | <dl> |
338 | <dt><code>EV_READ</code></dt> |
338 | <dt><code>EV_READ</code></dt> |
339 | <dt><code>EV_WRITE</code></dt> |
339 | <dt><code>EV_WRITE</code></dt> |
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389 | |
389 | |
390 | </div> |
390 | </div> |
391 | <h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> |
391 | <h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> |
392 | <div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> |
392 | <div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> |
393 | <p>Each watcher has, by default, a member <code>void *data</code> that you can change |
393 | <p>Each watcher has, by default, a member <code>void *data</code> that you can change |
394 | and read at any time, libev will completely ignore it. This cna be used |
394 | and read at any time, libev will completely ignore it. This can be used |
395 | to associate arbitrary data with your watcher. If you need more data and |
395 | to associate arbitrary data with your watcher. If you need more data and |
396 | don't want to allocate memory and store a pointer to it in that data |
396 | don't want to allocate memory and store a pointer to it in that data |
397 | member, you can also "subclass" the watcher type and provide your own |
397 | member, you can also "subclass" the watcher type and provide your own |
398 | data:</p> |
398 | data:</p> |
399 | <pre> struct my_io |
399 | <pre> struct my_io |
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431 | <h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> |
431 | <h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> |
432 | <div id="code_ev_io_code_is_this_file_descrip-2"> |
432 | <div id="code_ev_io_code_is_this_file_descrip-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 |
434 | in each iteration of the event loop (This behaviour is called |
434 | in each iteration of the event loop (This behaviour is called |
435 | level-triggering because you keep receiving events as long as the |
435 | level-triggering because you keep receiving events as long as the |
436 | condition persists. Remember you cna stop the watcher if you don't want to |
436 | condition persists. Remember you can stop the watcher if you don't want to |
437 | act on the event and neither want to receive future events).</p> |
437 | act on the event and neither want to receive future events).</p> |
438 | <p>In general you can register as many read and/or write event watchers oer |
438 | <p>In general you can register as many read and/or write event watchers oer |
439 | fd as you want (as long as you don't confuse yourself). Setting all file |
439 | fd as you want (as long as you don't confuse yourself). Setting all file |
440 | descriptors to non-blocking mode is also usually a good idea (but not |
440 | descriptors to non-blocking mode is also usually a good idea (but not |
441 | required if you know what you are doing).</p> |
441 | required if you know what you are doing).</p> |
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505 | the timer, and again will automatically restart it if need be.</p> |
505 | the 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="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - 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</h2> |
511 | <div id="code_ev_periodic_code_to_cron_or_not-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 <code>ev_timer</code>'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) |
515 | but on wallclock time (absolute time). You can tell a periodic watcher |
515 | but on wallclock time (absolute time). You can tell a periodic watcher |
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603 | <div id="code_ev_signal_code_signal_me_when_a-2"> |
603 | <div id="code_ev_signal_code_signal_me_when_a-2"> |
604 | <p>Signal watchers will trigger an event when the process receives a specific |
604 | <p>Signal watchers will trigger an event when the process receives a specific |
605 | signal one or more times. Even though signals are very asynchronous, libev |
605 | signal one or more times. Even though signals are very asynchronous, libev |
606 | will try it's best to deliver signals synchronously, i.e. as part of the |
606 | will try it's best to deliver signals synchronously, i.e. as part of the |
607 | normal event processing, like any other event.</p> |
607 | normal event processing, like any other event.</p> |
608 | <p>You cna configure as many watchers as you like per signal. Only when the |
608 | <p>You can configure as many watchers as you like per signal. Only when the |
609 | first watcher gets started will libev actually register a signal watcher |
609 | first watcher gets started will libev actually register a signal watcher |
610 | with the kernel (thus it coexists with your own signal handlers as long |
610 | with the kernel (thus it coexists with your own signal handlers as long |
611 | as you don't register any with libev). Similarly, when the last signal |
611 | as you don't register any with libev). Similarly, when the last signal |
612 | watcher for a signal is stopped libev will reset the signal handler to |
612 | watcher for a signal is stopped libev will reset the signal handler to |
613 | SIG_DFL (regardless of what it was set to before).</p> |
613 | SIG_DFL (regardless of what it was set to before).</p> |
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630 | <dt>ev_child_set (ev_child *, int pid)</dt> |
630 | <dt>ev_child_set (ev_child *, int pid)</dt> |
631 | <dd> |
631 | <dd> |
632 | <p>Configures the watcher to wait for status changes of process <code>pid</code> (or |
632 | <p>Configures the watcher to wait for status changes of process <code>pid</code> (or |
633 | <i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look |
633 | <i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look |
634 | at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see |
634 | at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see |
635 | the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member |
635 | the status word (use the macros from <code>sys/wait.h</code> and see your systems |
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636 | <code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the |
636 | contains the pid of the process causing the status change.</p> |
637 | process causing the status change.</p> |
637 | </dd> |
638 | </dd> |
638 | </dl> |
639 | </dl> |
639 | |
640 | |
640 | </div> |
641 | </div> |
641 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> |
642 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> |
642 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
643 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
643 | <p>Idle watchers trigger events when there are no other I/O or timer (or |
644 | <p>Idle watchers trigger events when there are no other events are pending |
644 | periodic) events pending. That is, as long as your process is busy |
645 | (prepare, check and other idle watchers do not count). That is, as long |
645 | handling sockets or timeouts it will not be called. But when your process |
646 | as your process is busy handling sockets or timeouts (or even signals, |
646 | is idle all idle watchers are being called again and again - until |
647 | imagine) it will not be triggered. But when your process is idle all idle |
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648 | watchers are being called again and again, once per event loop iteration - |
647 | stopped, that is, or your process receives more events.</p> |
649 | until stopped, that is, or your process receives more events and becomes |
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650 | busy.</p> |
648 | <p>The most noteworthy effect is that as long as any idle watchers are |
651 | <p>The most noteworthy effect is that as long as any idle watchers are |
649 | active, the process will not block when waiting for new events.</p> |
652 | active, the process will not block when waiting for new events.</p> |
650 | <p>Apart from keeping your process non-blocking (which is a useful |
653 | <p>Apart from keeping your process non-blocking (which is a useful |
651 | effect on its own sometimes), idle watchers are a good place to do |
654 | effect on its own sometimes), idle watchers are a good place to do |
652 | "pseudo-background processing", or delay processing stuff to after the |
655 | "pseudo-background processing", or delay processing stuff to after the |
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661 | </dl> |
664 | </dl> |
662 | |
665 | |
663 | </div> |
666 | </div> |
664 | <h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> |
667 | <h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> |
665 | <div id="prepare_and_check_your_hooks_into_th-2"> |
668 | <div id="prepare_and_check_your_hooks_into_th-2"> |
666 | <p>Prepare and check watchers usually (but not always) are used in |
669 | <p>Prepare and check watchers are usually (but not always) used in tandem: |
667 | tandom. Prepare watchers get invoked before the process blocks and check |
670 | Prepare watchers get invoked before the process blocks and check watchers |
668 | watchers afterwards.</p> |
671 | afterwards.</p> |
669 | <p>Their main purpose is to integrate other event mechanisms into libev. This |
672 | <p>Their main purpose is to integrate other event mechanisms into libev. This |
670 | could be used, for example, to track variable changes, implement your own |
673 | could be used, for example, to track variable changes, implement your own |
671 | watchers, integrate net-snmp or a coroutine library and lots more.</p> |
674 | watchers, integrate net-snmp or a coroutine library and lots more.</p> |
672 | <p>This is done by examining in each prepare call which file descriptors need |
675 | <p>This is done by examining in each prepare call which file descriptors need |
673 | to be watched by the other library, registering <code>ev_io</code> watchers for them |
676 | to be watched by the other library, registering <code>ev_io</code> watchers for |
674 | and starting an <code>ev_timer</code> watcher for any timeouts (many libraries provide |
677 | them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries |
675 | just this functionality). Then, in the check watcher you check for any |
678 | provide just this functionality). Then, in the check watcher you check for |
676 | events that occured (by making your callbacks set soem flags for example) |
679 | any events that occured (by checking the pending status of all watchers |
677 | and call back into the library.</p> |
680 | and stopping them) and call back into the library. The I/O and timer |
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681 | callbacks will never actually be called (but must be valid neverthelles, |
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682 | because you never know, you know?).</p> |
678 | <p>As another example, the perl Coro module uses these hooks to integrate |
683 | <p>As another example, the Perl Coro module uses these hooks to integrate |
679 | coroutines into libev programs, by yielding to other active coroutines |
684 | coroutines into libev programs, by yielding to other active coroutines |
680 | during each prepare and only letting the process block if no coroutines |
685 | during each prepare and only letting the process block if no coroutines |
681 | are ready to run.</p> |
686 | are ready to run (its actually more complicated, it only runs coroutines |
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687 | with priority higher than the event loop and one lower priority once, |
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688 | using idle watchers to keep the event loop from blocking if lower-priority |
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689 | coroutines exist, thus mapping low-priority coroutines to idle/background |
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690 | tasks).</p> |
682 | <dl> |
691 | <dl> |
683 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
692 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
684 | <dt>ev_check_init (ev_check *, callback)</dt> |
693 | <dt>ev_check_init (ev_check *, callback)</dt> |
685 | <dd> |
694 | <dd> |
686 | <p>Initialises and configures the prepare or check watcher - they have no |
695 | <p>Initialises and configures the prepare or check watcher - they have no |
687 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
696 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
688 | macros, but using them is utterly, utterly pointless.</p> |
697 | macros, but using them is utterly, utterly and completely pointless.</p> |
689 | </dd> |
698 | </dd> |
690 | </dl> |
699 | </dl> |
691 | |
700 | |
692 | </div> |
701 | </div> |
693 | <h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
702 | <h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
694 | <div id="OTHER_FUNCTIONS_CONTENT"> |
703 | <div id="OTHER_FUNCTIONS_CONTENT"> |
695 | <p>There are some other fucntions of possible interest. Described. Here. Now.</p> |
704 | <p>There are some other functions of possible interest. Described. Here. Now.</p> |
696 | <dl> |
705 | <dl> |
697 | <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> |
706 | <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> |
698 | <dd> |
707 | <dd> |
699 | <p>This function combines a simple timer and an I/O watcher, calls your |
708 | <p>This function combines a simple timer and an I/O watcher, calls your |
700 | callback on whichever event happens first and automatically stop both |
709 | callback on whichever event happens first and automatically stop both |
701 | watchers. This is useful if you want to wait for a single event on an fd |
710 | watchers. This is useful if you want to wait for a single event on an fd |
702 | or timeout without havign to allocate/configure/start/stop/free one or |
711 | or timeout without havign to allocate/configure/start/stop/free one or |
703 | more watchers yourself.</p> |
712 | more watchers yourself.</p> |
704 | <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is |
713 | <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events |
705 | ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and <code>events</code> set |
714 | is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and |
706 | will be craeted and started.</p> |
715 | <code>events</code> set will be craeted and started.</p> |
707 | <p>If <code>timeout</code> is less than 0, then no timeout watcher will be |
716 | <p>If <code>timeout</code> is less than 0, then no timeout watcher will be |
708 | started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and repeat |
717 | started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and |
709 | = 0) will be started.</p> |
718 | repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of |
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719 | dubious value.</p> |
710 | <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and |
720 | <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets |
711 | gets passed an events set (normally a combination of <code>EV_ERROR</code>, <code>EV_READ</code>, |
721 | passed an events set like normal event callbacks (with a combination of |
712 | <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> value passed to <code>ev_once</code>:</p> |
722 | <code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> |
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723 | value passed to <code>ev_once</code>:</p> |
713 | <pre> static void stdin_ready (int revents, void *arg) |
724 | <pre> static void stdin_ready (int revents, void *arg) |
714 | { |
725 | { |
715 | if (revents & EV_TIMEOUT) |
726 | if (revents & EV_TIMEOUT) |
716 | /* doh, nothing entered */ |
727 | /* doh, nothing entered */; |
717 | else if (revents & EV_READ) |
728 | else if (revents & EV_READ) |
718 | /* stdin might have data for us, joy! */ |
729 | /* stdin might have data for us, joy! */; |
719 | } |
730 | } |
720 | |
731 | |
721 | ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); |
732 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
722 | |
733 | |
723 | </pre> |
734 | </pre> |
724 | </dd> |
735 | </dd> |
725 | <dt>ev_feed_event (loop, watcher, int events)</dt> |
736 | <dt>ev_feed_event (loop, watcher, int events)</dt> |
726 | <dd> |
737 | <dd> |
727 | <p>Feeds the given event set into the event loop, as if the specified event |
738 | <p>Feeds the given event set into the event loop, as if the specified event |
728 | has happened for the specified watcher (which must be a pointer to an |
739 | had happened for the specified watcher (which must be a pointer to an |
729 | initialised but not necessarily active event watcher).</p> |
740 | initialised but not necessarily started event watcher).</p> |
730 | </dd> |
741 | </dd> |
731 | <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> |
742 | <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> |
732 | <dd> |
743 | <dd> |
733 | <p>Feed an event on the given fd, as if a file descriptor backend detected it.</p> |
744 | <p>Feed an event on the given fd, as if a file descriptor backend detected |
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745 | the given events it.</p> |
734 | </dd> |
746 | </dd> |
735 | <dt>ev_feed_signal_event (loop, int signum)</dt> |
747 | <dt>ev_feed_signal_event (loop, int signum)</dt> |
736 | <dd> |
748 | <dd> |
737 | <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> |
749 | <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> |
738 | </dd> |
750 | </dd> |