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Revision 1.6 by root, Thu Nov 1 17:32:39 2007 UTC vs.
Revision 1.16 by root, Fri Dec 7 18:11:23 2007 UTC

… …
9 9
10 my $w = EV::timer 2, 0, sub { 10 my $w = EV::timer 2, 0, sub {
11 warn "is called after 2s"; 11 warn "is called after 2s";
12 }; 12 };
13 13
14 my $w = EV::timer 2, 1, sub { 14 my $w = EV::timer 2, 2, sub {
15 warn "is called roughly every 2s (repeat = 1)"; 15 warn "is called roughly every 2s (repeat = 2)";
16 }; 16 };
17 17
18 undef $w; # destroy event watcher again 18 undef $w; # destroy event watcher again
19 19
20 my $w = EV::periodic 0, 60, sub { 20 my $w = EV::periodic 0, 60, 0, sub {
21 warn "is called every minute, on the minute, exactly"; 21 warn "is called every minute, on the minute, exactly";
22 }; 22 };
23 23
24 # IO 24 # IO
25 25
26 my $w = EV::io *STDIN, EV::READ, sub { 26 my $w = EV::io *STDIN, EV::READ, sub {
27 my ($w, $revents) = @_; # all callbacks get the watcher object and event mask 27 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
28 warn "stdin is readable, you entered: ", <STDIN>; 28 warn "stdin is readable, you entered: ", <STDIN>;
29 }; 29 };
30 30
31 # SIGNALS 31 # SIGNALS
32 32
33 my $w = EV::signal 'QUIT', sub { 33 my $w = EV::signal 'QUIT', sub {
34 warn "sigquit received\n"; 34 warn "sigquit received\n";
35 }; 35 };
36 36
37 my $w = EV::signal 3, sub {
38 warn "sigquit received (this is GNU/Linux, right?)\n";
39 };
40
41 # CHILD/PID STATUS CHANGES 37 # CHILD/PID STATUS CHANGES
42 38
43 my $w = EV::child 666, sub { 39 my $w = EV::child 666, sub {
44 my ($w, $revents, $status) = @_; 40 my ($w, $revents) = @_;
41 my $status = $w->rstatus;
42 };
43
44 # STAT CHANGES
45 my $w = EV::stat "/etc/passwd", 10, sub {
46 my ($w, $revents) = @_;
47 warn $w->path, " has changed somehow.\n";
45 }; 48 };
46 49
47 # MAINLOOP 50 # MAINLOOP
48 EV::loop; # loop until EV::loop_done is called 51 EV::loop; # loop until EV::unloop is called or all watchers stop
49 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled 52 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled
50 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block 53 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block
51 54
52DESCRIPTION 55DESCRIPTION
53 This module provides an interface to libev 56 This module provides an interface to libev
54 (<http://software.schmorp.de/pkg/libev.html>). 57 (<http://software.schmorp.de/pkg/libev.html>). While the documentation
58 below is comprehensive, one might also consult the documentation of
59 libev itself (<http://cvs.schmorp.de/libev/ev.html>) for more subtle
60 details on watcher semantics or some discussion on the available
61 backends, or how to force a specific backend with "LIBEV_FLAGS", or just
62 about in any case because it has much more detailed information.
55 63
56BASIC INTERFACE 64BASIC INTERFACE
57 $EV::DIED 65 $EV::DIED
58 Must contain a reference to a function that is called when a 66 Must contain a reference to a function that is called when a
59 callback throws an exception (with $@ containing thr error). The 67 callback throws an exception (with $@ containing thr error). The
… …
67 $time = EV::now 75 $time = EV::now
68 Returns the time the last event loop iteration has been started. 76 Returns the time the last event loop iteration has been started.
69 This is the time that (relative) timers are based on, and refering 77 This is the time that (relative) timers are based on, and refering
70 to it is usually faster then calling EV::time. 78 to it is usually faster then calling EV::time.
71 79
72 $method = EV::ev_method 80 $method = EV::method
73 Returns an integer describing the backend used by libev 81 Returns an integer describing the backend used by libev
74 (EV::METHOD_SELECT or EV::METHOD_EPOLL). 82 (EV::METHOD_SELECT or EV::METHOD_EPOLL).
75 83
76 EV::loop [$flags] 84 EV::loop [$flags]
77 Begin checking for events and calling callbacks. It returns when a 85 Begin checking for events and calling callbacks. It returns when a
78 callback calls EV::loop_done. 86 callback calls EV::unloop.
79 87
80 The $flags argument can be one of the following: 88 The $flags argument can be one of the following:
81 89
82 0 as above 90 0 as above
83 EV::LOOP_ONESHOT block at most once (wait, but do not loop) 91 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
84 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) 92 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
85 93
86 EV::loop_done [$how] 94 EV::unloop [$how]
87 When called with no arguments or an argument of 1, makes the 95 When called with no arguments or an argument of EV::UNLOOP_ONE,
88 innermost call to EV::loop return. 96 makes the innermost call to EV::loop return.
89 97
90 When called with an agrument of 2, all calls to EV::loop will return 98 When called with an argument of EV::UNLOOP_ALL, all calls to
91 as fast as possible. 99 EV::loop will return as fast as possible.
92 100
93 WATCHER 101 $count = EV::loop_count
102 Return the number of times the event loop has polled for new events.
103 Sometiems useful as a generation counter.
104
105 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
106 This function rolls together an I/O and a timer watcher for a single
107 one-shot event without the need for managing a watcher object.
108
109 If $fh_or_undef is a filehandle or file descriptor, then $events
110 must be a bitset containing either "EV::READ", "EV::WRITE" or
111 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
112 wait for. If you do not want to wait for some I/O event, specify
113 "undef" for $fh_or_undef and 0 for $events).
114
115 If timeout is "undef" or negative, then there will be no timeout.
116 Otherwise a EV::timer with this value will be started.
117
118 When an error occurs or either the timeout or I/O watcher triggers,
119 then the callback will be called with the received event set (in
120 general you can expect it to be a combination of "EV:ERROR",
121 "EV::READ", "EV::WRITE" and "EV::TIMEOUT").
122
123 EV::once doesn't return anything: the watchers stay active till
124 either of them triggers, then they will be stopped and freed, and
125 the callback invoked.
126
127 WATCHER OBJECTS
94 A watcher is an object that gets created to record your interest in some 128 A watcher is an object that gets created to record your interest in some
95 event. For instance, if you want to wait for STDIN to become readable, 129 event. For instance, if you want to wait for STDIN to become readable,
96 you would create an EV::io watcher for that: 130 you would create an EV::io watcher for that:
97 131
98 my $watcher = EV::io *STDIN, EV::READ, sub { 132 my $watcher = EV::io *STDIN, EV::READ, sub {
… …
106 received events. 140 received events.
107 141
108 Each watcher type has its associated bit in revents, so you can use the 142 Each watcher type has its associated bit in revents, so you can use the
109 same callback for multiple watchers. The event mask is named after the 143 same callback for multiple watchers. The event mask is named after the
110 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE, 144 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
111 EV::periodic sets EV::PERIODIC and so on, with the exception of IO 145 EV::periodic sets EV::PERIODIC and so on, with the exception of I/O
112 events (which can set both EV::READ and EV::WRITE bits), and EV::timer 146 events (which can set both EV::READ and EV::WRITE bits), and EV::timer
113 (which uses EV::TIMEOUT). 147 (which uses EV::TIMEOUT).
114 148
115 In the rare case where one wants to create a watcher but not start it at 149 In the rare case where one wants to create a watcher but not start it at
116 the same time, each constructor has a variant with a trailing "_ns" in 150 the same time, each constructor has a variant with a trailing "_ns" in
117 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on. 151 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
118 152
119 Please note that a watcher will automatically be stopped when the 153 Please note that a watcher will automatically be stopped when the
120 watcher object is returned, so you *need* to keep the watcher objects 154 watcher object is destroyed, so you *need* to keep the watcher objects
121 returned by the constructors. 155 returned by the constructors.
122 156
123 WATCHER TYPES 157 Also, all methods changing some aspect of a watcher (->set, ->priority,
124 Now lets move to the existing watcher types and asociated methods. 158 ->fh and so on) automatically stop and start it again if it is active,
159 which means pending events get lost.
125 160
126 The following methods are available for all watchers. Then followes a 161 COMMON WATCHER METHODS
127 description of each watcher constructor (EV::io, EV::timer, 162 This section lists methods common to all watchers.
128 EV::periodic, EV::signal, EV::child, EV::idle, EV::prepare and
129 EV::check), followed by any type-specific methods (if any).
130 163
131 $w->start 164 $w->start
132 Starts a watcher if it isn't active already. Does nothing to an 165 Starts a watcher if it isn't active already. Does nothing to an
133 already active watcher. By default, all watchers start out in the 166 already active watcher. By default, all watchers start out in the
134 active state (see the description of the "_ns" variants if you need 167 active state (see the description of the "_ns" variants if you need
135 stopped watchers). 168 stopped watchers).
136 169
137 $w->stop 170 $w->stop
138 Stop a watcher if it is active. Also clear any pending events 171 Stop a watcher if it is active. Also clear any pending events
139 (events that have been received but that didn't yet result in a 172 (events that have been received but that didn't yet result in a
140 callback invocation), regardless of wether the watcher was active or 173 callback invocation), regardless of whether the watcher was active
141 not. 174 or not.
142 175
143 $bool = $w->is_active 176 $bool = $w->is_active
144 Returns true if the watcher is active, false otherwise. 177 Returns true if the watcher is active, false otherwise.
178
179 $current_data = $w->data
180 $old_data = $w->data ($new_data)
181 Queries a freely usable data scalar on the watcher and optionally
182 changes it. This is a way to associate custom data with a watcher:
183
184 my $w = EV::timer 60, 0, sub {
185 warn $_[0]->data;
186 };
187 $w->data ("print me!");
145 188
146 $current_cb = $w->cb 189 $current_cb = $w->cb
147 $old_cb = $w->cb ($new_cb) 190 $old_cb = $w->cb ($new_cb)
148 Queries the callback on the watcher and optionally changes it. You 191 Queries the callback on the watcher and optionally changes it. You
149 cna do this at any time. 192 can do this at any time without the watcher restarting.
193
194 $current_priority = $w->priority
195 $old_priority = $w->priority ($new_priority)
196 Queries the priority on the watcher and optionally changes it.
197 Pending watchers with higher priority will be invoked first. The
198 valid range of priorities lies between EV::MAXPRI (default 2) and
199 EV::MINPRI (default -2). If the priority is outside this range it
200 will automatically be normalised to the nearest valid priority.
201
202 The default priority of any newly-created watcher is 0.
203
204 Note that the priority semantics have not yet been fleshed out and
205 are subject to almost certain change.
150 206
151 $w->trigger ($revents) 207 $w->trigger ($revents)
152 Call the callback *now* with the given event mask. 208 Call the callback *now* with the given event mask.
153 209
210 $previous_state = $w->keepalive ($bool)
211 Normally, "EV::loop" will return when there are no active watchers
212 (which is a "deadlock" because no progress can be made anymore).
213 This is convinient because it allows you to start your watchers (and
214 your jobs), call "EV::loop" once and when it returns you know that
215 all your jobs are finished (or they forgot to register some watchers
216 for their task :).
217
218 Sometimes, however, this gets in your way, for example when you the
219 module that calls "EV::loop" (usually the main program) is not the
220 same module as a long-living watcher (for example a DNS client
221 module written by somebody else even). Then you might want any
222 outstanding requests to be handled, but you would not want to keep
223 "EV::loop" from returning just because you happen to have this
224 long-running UDP port watcher.
225
226 In this case you can clear the keepalive status, which means that
227 even though your watcher is active, it won't keep "EV::loop" from
228 returning.
229
230 The initial value for keepalive is true (enabled), and you cna
231 change it any time.
232
233 Example: Register an I/O watcher for some UDP socket but do not keep
234 the event loop from running just because of that watcher.
235
236 my $udp_socket = ...
237 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
238 $udp_watcher->keepalive (0);
239
240 WATCHER TYPES
241 Each of the following subsections describes a single watcher type.
242
243 I/O WATCHERS - is this file descriptor readable or writable?
154 $w = EV::io $fileno_or_fh, $eventmask, $callback 244 $w = EV::io $fileno_or_fh, $eventmask, $callback
155 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 245 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
156 As long as the returned watcher object is alive, call the $callback 246 As long as the returned watcher object is alive, call the $callback
157 when the events specified in $eventmask. 247 when at least one of events specified in $eventmask occurs.
158 248
159 The $eventmask can be one or more of these constants ORed together: 249 The $eventmask can be one or more of these constants ORed together:
160 250
161 EV::READ wait until read() wouldn't block anymore 251 EV::READ wait until read() wouldn't block anymore
162 EV::WRITE wait until write() wouldn't block anymore 252 EV::WRITE wait until write() wouldn't block anymore
… …
174 264
175 $current_eventmask = $w->events 265 $current_eventmask = $w->events
176 $old_eventmask = $w->events ($new_eventmask) 266 $old_eventmask = $w->events ($new_eventmask)
177 Returns the previously set event mask and optionally set a new one. 267 Returns the previously set event mask and optionally set a new one.
178 268
269 TIMER WATCHERS - relative and optionally repeating timeouts
179 $w = EV::timer $after, $repeat, $callback 270 $w = EV::timer $after, $repeat, $callback
180 $w = EV::timer_ns $after, $repeat, $callback 271 $w = EV::timer_ns $after, $repeat, $callback
181 Calls the callback after $after seconds. If $repeat is non-zero, the 272 Calls the callback after $after seconds (which may be fractional).
182 timer will be restarted (with the $repeat value as $after) after the 273 If $repeat is non-zero, the timer will be restarted (with the
183 callback returns. 274 $repeat value as $after) after the callback returns.
184 275
185 This means that the callback would be called roughly after $after 276 This means that the callback would be called roughly after $after
186 seconds, and then every $repeat seconds. "Roughly" because the time 277 seconds, and then every $repeat seconds. The timer does his best not
187 of callback processing is not taken into account, so the timer will 278 to drift, but it will not invoke the timer more often then once per
188 slowly drift. If that isn't acceptable, look at EV::periodic. 279 event loop iteration, and might drift in other cases. If that isn't
280 acceptable, look at EV::periodic, which can provide long-term stable
281 timers.
189 282
190 The timer is based on a monotonic clock, that is if somebody is 283 The timer is based on a monotonic clock, that is, if somebody is
191 sitting in front of the machine while the timer is running and 284 sitting in front of the machine while the timer is running and
192 changes the system clock, the timer will nevertheless run (roughly) 285 changes the system clock, the timer will nevertheless run (roughly)
193 the same time. 286 the same time.
194 287
195 The "timer_ns" variant doesn't start (activate) the newly created 288 The "timer_ns" variant doesn't start (activate) the newly created
196 watcher. 289 watcher.
197 290
198 $w->set ($after, $repeat) 291 $w->set ($after, $repeat)
199 Reconfigures the watcher, see the constructor above for details. Can 292 Reconfigures the watcher, see the constructor above for details. Can
200 be at any time. 293 be called at any time.
201 294
202 $w->again 295 $w->again
203 Similar to the "start" method, but has special semantics for 296 Similar to the "start" method, but has special semantics for
204 repeating timers: 297 repeating timers:
205 298
299 If the timer is active and non-repeating, it will be stopped.
300
206 If the timer is active and repeating, reset the timeout to occur 301 If the timer is active and repeating, reset the timeout to occur
207 $repeat seconds after now. 302 $repeat seconds after now.
208 303
209 If the timer is active and non-repeating, it will be stopped.
210
211 If the timer is in active and repeating, start it. 304 If the timer is inactive and repeating, start it using the repeat
305 value.
212 306
213 Otherwise do nothing. 307 Otherwise do nothing.
214 308
215 This behaviour is useful when you have a timeout for some IO 309 This behaviour is useful when you have a timeout for some IO
216 operation. You create a timer object with the same value for $after 310 operation. You create a timer object with the same value for $after
217 and $repeat, and then, in the read/write watcher, run the "again" 311 and $repeat, and then, in the read/write watcher, run the "again"
218 method on the timeout. 312 method on the timeout.
219 313
314 PERIODIC WATCHERS - to cron or not to cron?
220 $w = EV::periodic $at, $interval, $callback 315 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
221 $w = EV::periodic_ns $at, $interval, $callback 316 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
222 Similar to EV::timer, but the time is given as an absolute point in 317 Similar to EV::timer, but is not based on relative timeouts but on
223 time ($at), plus an optional $interval. 318 absolute times. Apart from creating "simple" timers that trigger
319 "at" the specified time, it can also be used for non-drifting
320 absolute timers and more complex, cron-like, setups that are not
321 adversely affected by time jumps (i.e. when the system clock is
322 changed by explicit date -s or other means such as ntpd). It is also
323 the most complex watcher type in EV.
224 324
225 If the $interval is zero, then the callback will be called at the 325 It has three distinct "modes":
226 time $at if that is in the future, or as soon as possible if it is
227 in the past. It will not automatically repeat.
228 326
229 If the $interval is nonzero, then the watcher will always be 327 * absolute timer ($interval = $reschedule_cb = 0)
230 scheduled to time out at the next "$at + N * $interval" time. 328 This time simply fires at the wallclock time $at and doesn't
329 repeat. It will not adjust when a time jump occurs, that is, if
330 it is to be run at January 1st 2011 then it will run when the
331 system time reaches or surpasses this time.
231 332
232 This can be used to schedule a callback to run at very regular 333 * non-repeating interval timer ($interval > 0, $reschedule_cb = 0)
233 intervals, as long as the processing time is less then the interval 334 In this mode the watcher will always be scheduled to time out at
234 (otherwise obviously events will be skipped). 335 the next "$at + N * $interval" time (for some integer N) and
336 then repeat, regardless of any time jumps.
235 337
338 This can be used to create timers that do not drift with respect
339 to system time:
340
341 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
342
343 That doesn't mean there will always be 3600 seconds in between
344 triggers, but only that the the clalback will be called when the
345 system time shows a full hour (UTC).
346
236 Another way to think about it (for the mathematically inclined) is 347 Another way to think about it (for the mathematically inclined)
237 that EV::periodic will try to run the callback at the next possible 348 is that EV::periodic will try to run the callback in this mode
238 time where "$time = $at (mod $interval)", regardless of any time 349 at the next possible time where "$time = $at (mod $interval)",
239 jumps. 350 regardless of any time jumps.
240 351
241 This periodic timer is based on "wallclock time", that is, if the 352 * manual reschedule mode ($reschedule_cb = coderef)
242 clock changes ("ntp", "date -s" etc.), then the timer will 353 In this mode $interval and $at are both being ignored. Instead,
243 nevertheless run at the specified time. This means it will never 354 each time the periodic watcher gets scheduled, the reschedule
244 drift (it might jitter, but it will not drift). 355 callback ($reschedule_cb) will be called with the watcher as
356 first, and the current time as second argument.
357
358 *This callback MUST NOT stop or destroy this or any other
359 periodic watcher, ever*. If you need to stop it, return 1e30 and
360 stop it afterwards.
361
362 It must return the next time to trigger, based on the passed
363 time value (that is, the lowest time value larger than to the
364 second argument). It will usually be called just before the
365 callback will be triggered, but might be called at other times,
366 too.
367
368 This can be used to create very complex timers, such as a timer
369 that triggers on each midnight, local time (actually 24 hours
370 after the last midnight, to keep the example simple. If you know
371 a way to do it correctly in about the same space (without
372 requiring elaborate modules), drop me a note :):
373
374 my $daily = EV::periodic 0, 0, sub {
375 my ($w, $now) = @_;
376
377 use Time::Local ();
378 my (undef, undef, undef, $d, $m, $y) = localtime $now;
379 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
380 }, sub {
381 print "it's midnight or likely shortly after, now\n";
382 };
245 383
246 The "periodic_ns" variant doesn't start (activate) the newly created 384 The "periodic_ns" variant doesn't start (activate) the newly created
247 watcher. 385 watcher.
248 386
249 $w->set ($at, $interval) 387 $w->set ($at, $interval, $reschedule_cb)
250 Reconfigures the watcher, see the constructor above for details. Can 388 Reconfigures the watcher, see the constructor above for details. Can
251 be at any time. 389 be called at any time.
252 390
391 $w->again
392 Simply stops and starts the watcher again.
393
394 SIGNAL WATCHERS - signal me when a signal gets signalled!
253 $w = EV::signal $signal, $callback 395 $w = EV::signal $signal, $callback
254 $w = EV::signal_ns $signal, $callback 396 $w = EV::signal_ns $signal, $callback
255 Call the callback when $signal is received (the signal can be 397 Call the callback when $signal is received (the signal can be
256 specified by number or by name, just as with kill or %SIG). 398 specified by number or by name, just as with "kill" or %SIG).
257 399
258 EV will grab the signal for the process (the kernel only allows one 400 EV will grab the signal for the process (the kernel only allows one
259 component to receive a signal at a time) when you start a signal 401 component to receive a signal at a time) when you start a signal
260 watcher, and removes it again when you stop it. Perl does the same 402 watcher, and removes it again when you stop it. Perl does the same
261 when you add/remove callbacks to %SIG, so watch out. 403 when you add/remove callbacks to %SIG, so watch out.
… …
265 The "signal_ns" variant doesn't start (activate) the newly created 407 The "signal_ns" variant doesn't start (activate) the newly created
266 watcher. 408 watcher.
267 409
268 $w->set ($signal) 410 $w->set ($signal)
269 Reconfigures the watcher, see the constructor above for details. Can 411 Reconfigures the watcher, see the constructor above for details. Can
270 be at any time. 412 be called at any time.
271 413
414 $current_signum = $w->signal
415 $old_signum = $w->signal ($new_signal)
416 Returns the previously set signal (always as a number not name) and
417 optionally set a new one.
418
419 CHILD WATCHERS - watch out for process status changes
272 $w = EV::child $pid, $callback 420 $w = EV::child $pid, $callback
273 $w = EV::child_ns $pid, $callback 421 $w = EV::child_ns $pid, $callback
274 Call the callback when a status change for pid $pid (or any pid if 422 Call the callback when a status change for pid $pid (or any pid if
275 $pid is 0) has been received. More precisely: when the process 423 $pid is 0) has been received. More precisely: when the process
276 receives a SIGCHLD, EV will fetch the outstanding exit/wait status 424 receives a "SIGCHLD", EV will fetch the outstanding exit/wait status
277 for all changed/zombie children and call the callback. 425 for all changed/zombie children and call the callback.
278 426
279 Unlike all other callbacks, this callback will be called with an 427 It is valid (and fully supported) to install a child watcher after a
280 additional third argument which is the exit status. See the 428 child has exited but before the event loop has started its next
281 "waitpid" function for details. 429 iteration (for example, first you "fork", then the new child process
430 might exit, and only then do you install a child watcher in the
431 parent for the new pid).
282 432
433 You can access both exit (or tracing) status and pid by using the
434 "rstatus" and "rpid" methods on the watcher object.
435
283 You can have as many pid watchers per pid as you want. 436 You can have as many pid watchers per pid as you want, they will all
437 be called.
284 438
285 The "child_ns" variant doesn't start (activate) the newly created 439 The "child_ns" variant doesn't start (activate) the newly created
286 watcher. 440 watcher.
287 441
288 $w->set ($pid) 442 $w->set ($pid)
289 Reconfigures the watcher, see the constructor above for details. Can 443 Reconfigures the watcher, see the constructor above for details. Can
290 be at any time. 444 be called at any time.
291 445
446 $current_pid = $w->pid
447 $old_pid = $w->pid ($new_pid)
448 Returns the previously set process id and optionally set a new one.
449
450 $exit_status = $w->rstatus
451 Return the exit/wait status (as returned by waitpid, see the waitpid
452 entry in perlfunc).
453
454 $pid = $w->rpid
455 Return the pid of the awaited child (useful when you have installed
456 a watcher for all pids).
457
458 STAT WATCHERS - did the file attributes just change?
459 $w = EV::stat $path, $interval, $callback
460 $w = EV::stat_ns $path, $interval, $callback
461 Call the callback when a file status change has been detected on
462 $path. The $path does not need to exist, changing from "path exists"
463 to "path does not exist" is a status change like any other.
464
465 The $interval is a recommended polling interval for systems where
466 OS-supported change notifications don't exist or are not supported.
467 If you use 0 then an unspecified default is used (which is highly
468 recommended!), which is to be expected to be around five seconds
469 usually.
470
471 This watcher type is not meant for massive numbers of stat watchers,
472 as even with OS-supported change notifications, this can be
473 resource-intensive.
474
475 The "stat_ns" variant doesn't start (activate) the newly created
476 watcher.
477
478 ... = $w->stat
479 This call is very similar to the perl "stat" built-in: It stats
480 (using "lstat") the path specified in the watcher and sets perls
481 stat cache (as well as EV's idea of the current stat values) to the
482 values found.
483
484 In scalar context, a boolean is return indicating success or failure
485 of the stat. In list context, the same 13-value list as with stat is
486 returned (except that the blksize and blocks fields are not
487 reliable).
488
489 In the case of an error, errno is set to "ENOENT" (regardless of the
490 actual error value) and the "nlink" value is forced to zero (if the
491 stat was successful then nlink is guaranteed to be non-zero).
492
493 See also the next two entries for more info.
494
495 ... = $w->attr
496 Just like "$w->stat", but without the initial stat'ing: this returns
497 the values most recently detected by EV. See the next entry for more
498 info.
499
500 ... = $w->prev
501 Just like "$w->stat", but without the initial stat'ing: this returns
502 the previous set of values, before the change.
503
504 That is, when the watcher callback is invoked, "$w->prev" will be
505 set to the values found *before* a change was detected, while
506 "$w->attr" returns the values found leading to the change detection.
507 The difference (if any) between "prev" and "attr" is what triggered
508 the callback.
509
510 If you did something to the filesystem object and do not want to
511 trigger yet another change, you can call "stat" to update EV's idea
512 of what the current attributes are.
513
514 $w->set ($path, $interval)
515 Reconfigures the watcher, see the constructor above for details. Can
516 be called at any time.
517
518 $current_path = $w->path
519 $old_path = $w->path ($new_path)
520 Returns the previously set path and optionally set a new one.
521
522 $current_interval = $w->interval
523 $old_interval = $w->interval ($new_interval)
524 Returns the previously set interval and optionally set a new one.
525 Can be used to query the actual interval used.
526
527 IDLE WATCHERS - when you've got nothing better to do...
292 $w = EV::idle $callback 528 $w = EV::idle $callback
293 $w = EV::idle_ns $callback 529 $w = EV::idle_ns $callback
294 Call the callback when there are no pending io, timer/periodic, 530 Call the callback when there are no other pending watchers of the
295 signal or child events, i.e. when the process is idle. 531 same or higher priority (excluding check, prepare and other idle
532 watchers of the same or lower priority, of course). They are called
533 idle watchers because when the watcher is the highest priority
534 pending event in the process, the process is considered to be idle
535 at that priority.
536
537 If you want a watcher that is only ever called when *no* other
538 events are outstanding you have to set the priority to "EV::MINPRI".
296 539
297 The process will not block as long as any idle watchers are active, 540 The process will not block as long as any idle watchers are active,
298 and they will be called repeatedly until stopped. 541 and they will be called repeatedly until stopped.
299 542
543 For example, if you have idle watchers at priority 0 and 1, and an
544 I/O watcher at priority 0, then the idle watcher at priority 1 and
545 the I/O watcher will always run when ready. Only when the idle
546 watcher at priority 1 is stopped and the I/O watcher at priority 0
547 is not pending with the 0-priority idle watcher be invoked.
548
300 The "idle_ns" variant doesn't start (activate) the newly created 549 The "idle_ns" variant doesn't start (activate) the newly created
301 watcher. 550 watcher.
302 551
552 PREPARE WATCHERS - customise your event loop!
303 $w = EV::prepare $callback 553 $w = EV::prepare $callback
304 $w = EV::prepare_ns $callback 554 $w = EV::prepare_ns $callback
305 Call the callback just before the process would block. You can still 555 Call the callback just before the process would block. You can still
306 create/modify any watchers at this point. 556 create/modify any watchers at this point.
307 557
308 See the EV::check watcher, below, for explanations and an example. 558 See the EV::check watcher, below, for explanations and an example.
309 559
310 The "prepare_ns" variant doesn't start (activate) the newly created 560 The "prepare_ns" variant doesn't start (activate) the newly created
311 watcher. 561 watcher.
312 562
563 CHECK WATCHERS - customise your event loop even more!
313 $w = EV::check $callback 564 $w = EV::check $callback
314 $w = EV::check_ns $callback 565 $w = EV::check_ns $callback
315 Call the callback just after the process wakes up again (after it 566 Call the callback just after the process wakes up again (after it
316 has gathered events), but before any other callbacks have been 567 has gathered events), but before any other callbacks have been
317 invoked. 568 invoked.
… …
328 # do nothing unless active 579 # do nothing unless active
329 $dispatcher->{_event_queue_h} 580 $dispatcher->{_event_queue_h}
330 or return; 581 or return;
331 582
332 # make the dispatcher handle any outstanding stuff 583 # make the dispatcher handle any outstanding stuff
584 ... not shown
333 585
334 # create an IO watcher for each and every socket 586 # create an I/O watcher for each and every socket
335 @snmp_watcher = ( 587 @snmp_watcher = (
336 (map { EV::io $_, EV::READ, sub { } } 588 (map { EV::io $_, EV::READ, sub { } }
337 keys %{ $dispatcher->{_descriptors} }), 589 keys %{ $dispatcher->{_descriptors} }),
590
591 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
592 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
593 0, sub { },
338 ); 594 );
339
340 # if there are any timeouts, also create a timer
341 push @snmp_watcher, EV::timer $event->[Net::SNMP::Dispatcher::_TIME] - EV::now, 0, sub { }
342 if $event->[Net::SNMP::Dispatcher::_ACTIVE];
343 }; 595 };
344 596
345 The callbacks are irrelevant, the only purpose of those watchers is 597 The callbacks are irrelevant (and are not even being called), the
346 to wake up the process as soon as one of those events occurs (socket 598 only purpose of those watchers is to wake up the process as soon as
347 readable, or timer timed out). The corresponding EV::check watcher 599 one of those events occurs (socket readable, or timer timed out).
348 will then clean up: 600 The corresponding EV::check watcher will then clean up:
349 601
350 our $snmp_check = EV::check sub { 602 our $snmp_check = EV::check sub {
351 # destroy all watchers 603 # destroy all watchers
352 @snmp_watcher = (); 604 @snmp_watcher = ();
353 605
354 # make the dispatcher handle any new stuff 606 # make the dispatcher handle any new stuff
607 ... not shown
355 }; 608 };
356 609
357 The callbacks of the created watchers will not be called as the 610 The callbacks of the created watchers will not be called as the
358 watchers are destroyed before this cna happen (remember EV::check 611 watchers are destroyed before this cna happen (remember EV::check
359 gets called first). 612 gets called first).
360 613
361 The "check_ns" variant doesn't start (activate) the newly created 614 The "check_ns" variant doesn't start (activate) the newly created
362 watcher. 615 watcher.
363 616
617 FORK WATCHERS - the audacity to resume the event loop after a fork
618 Fork watchers are called when a "fork ()" was detected. The invocation
619 is done before the event loop blocks next and before "check" watchers
620 are being called, and only in the child after the fork.
621
622 $w = EV::fork $callback
623 $w = EV::fork_ns $callback
624 Call the callback before the event loop is resumed in the child
625 process after a fork.
626
627 The "fork_ns" variant doesn't start (activate) the newly created
628 watcher.
629
630PERL SIGNALS
631 While Perl signal handling (%SIG) is not affected by EV, the behaviour
632 with EV is as the same as any other C library: Perl-signals will only be
633 handled when Perl runs, which means your signal handler might be invoked
634 only the next time an event callback is invoked.
635
636 The solution is to use EV signal watchers (see "EV::signal"), which will
637 ensure proper operations with regards to other event watchers.
638
639 If you cannot do this for whatever reason, you can also force a watcher
640 to be called on every event loop iteration by installing a "EV::check"
641 watcher:
642
643 my $async_check = EV::check sub { };
644
645 This ensures that perl shortly gets into control for a short time, and
646 also ensures slower overall operation.
647
364THREADS 648THREADS
365 Threads are not supported by this in any way. Perl pseudo-threads is 649 Threads are not supported by this module in any way. Perl pseudo-threads
366 evil stuff and must die. 650 is evil stuff and must die. As soon as Perl gains real threads I will
651 work on thread support for it.
652
653FORK
654 Most of the "improved" event delivering mechanisms of modern operating
655 systems have quite a few problems with fork(2) (to put it bluntly: it is
656 not supported and usually destructive). Libev makes it possible to work
657 around this by having a function that recreates the kernel state after
658 fork in the child.
659
660 On non-win32 platforms, this module requires the pthread_atfork
661 functionality to do this automatically for you. This function is quite
662 buggy on most BSDs, though, so YMMV. The overhead for this is quite
663 negligible, because everything the function currently does is set a flag
664 that is checked only when the event loop gets used the next time, so
665 when you do fork but not use EV, the overhead is minimal.
666
667 On win32, there is no notion of fork so all this doesn't apply, of
668 course.
367 669
368SEE ALSO 670SEE ALSO
369 L<EV::DNS>, L<EV::AnyEvent>. 671 EV::ADNS (asynchronous dns), Glib::EV (makes Glib/Gtk2 use EV as event
672 loop), Coro::EV (efficient coroutines with EV).
370 673
371AUTHOR 674AUTHOR
372 Marc Lehmann <schmorp@schmorp.de> 675 Marc Lehmann <schmorp@schmorp.de>
373 http://home.schmorp.de/ 676 http://home.schmorp.de/
374 677

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