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Revision 1.172 by root, Thu Jul 17 15:21:02 2008 UTC vs.
Revision 1.195 by root, Wed Mar 25 17:33:11 2009 UTC

6 6
7=head1 SYNOPSIS 7=head1 SYNOPSIS
8 8
9 use AnyEvent; 9 use AnyEvent;
10 10
11 my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { 11 my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { ... });
12 ...
13 });
14 12
15 my $w = AnyEvent->timer (after => $seconds, cb => sub { 13 my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
14 my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
15
16 print AnyEvent->now; # prints current event loop time
17 print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
18
19 my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
20
21 my $w = AnyEvent->child (pid => $pid, cb => sub {
22 my ($pid, $status) = @_;
16 ... 23 ...
17 }); 24 });
18 25
19 my $w = AnyEvent->condvar; # stores whether a condition was flagged 26 my $w = AnyEvent->condvar; # stores whether a condition was flagged
20 $w->send; # wake up current and all future recv's 27 $w->send; # wake up current and all future recv's
21 $w->recv; # enters "main loop" till $condvar gets ->send 28 $w->recv; # enters "main loop" till $condvar gets ->send
29 # use a condvar in callback mode:
30 $w->cb (sub { $_[0]->recv });
22 31
23=head1 INTRODUCTION/TUTORIAL 32=head1 INTRODUCTION/TUTORIAL
24 33
25This manpage is mainly a reference manual. If you are interested 34This manpage is mainly a reference manual. If you are interested
26in a tutorial or some gentle introduction, have a look at the 35in a tutorial or some gentle introduction, have a look at the
331=head2 CHILD PROCESS WATCHERS 340=head2 CHILD PROCESS WATCHERS
332 341
333You can also watch on a child process exit and catch its exit status. 342You can also watch on a child process exit and catch its exit status.
334 343
335The child process is specified by the C<pid> argument (if set to C<0>, it 344The child process is specified by the C<pid> argument (if set to C<0>, it
336watches for any child process exit). The watcher will trigger as often 345watches for any child process exit). The watcher will triggered only when
337as status change for the child are received. This works by installing a 346the child process has finished and an exit status is available, not on
338signal handler for C<SIGCHLD>. The callback will be called with the pid 347any trace events (stopped/continued).
339and exit status (as returned by waitpid), so unlike other watcher types, 348
340you I<can> rely on child watcher callback arguments. 349The callback will be called with the pid and exit status (as returned by
350waitpid), so unlike other watcher types, you I<can> rely on child watcher
351callback arguments.
352
353This watcher type works by installing a signal handler for C<SIGCHLD>,
354and since it cannot be shared, nothing else should use SIGCHLD or reap
355random child processes (waiting for specific child processes, e.g. inside
356C<system>, is just fine).
341 357
342There is a slight catch to child watchers, however: you usually start them 358There is a slight catch to child watchers, however: you usually start them
343I<after> the child process was created, and this means the process could 359I<after> the child process was created, and this means the process could
344have exited already (and no SIGCHLD will be sent anymore). 360have exited already (and no SIGCHLD will be sent anymore).
345 361
381The instrument to do that is called a "condition variable", so called 397The instrument to do that is called a "condition variable", so called
382because they represent a condition that must become true. 398because they represent a condition that must become true.
383 399
384Condition variables can be created by calling the C<< AnyEvent->condvar 400Condition variables can be created by calling the C<< AnyEvent->condvar
385>> method, usually without arguments. The only argument pair allowed is 401>> method, usually without arguments. The only argument pair allowed is
402
386C<cb>, which specifies a callback to be called when the condition variable 403C<cb>, which specifies a callback to be called when the condition variable
387becomes true. 404becomes true, with the condition variable as the first argument (but not
405the results).
388 406
389After creation, the condition variable is "false" until it becomes "true" 407After creation, the condition variable is "false" until it becomes "true"
390by calling the C<send> method (or calling the condition variable as if it 408by calling the C<send> method (or calling the condition variable as if it
391were a callback, read about the caveats in the description for the C<< 409were a callback, read about the caveats in the description for the C<<
392->send >> method). 410->send >> method).
448 466
449 my $done = AnyEvent->condvar; 467 my $done = AnyEvent->condvar;
450 my $delay = AnyEvent->timer (after => 5, cb => $done); 468 my $delay = AnyEvent->timer (after => 5, cb => $done);
451 $done->recv; 469 $done->recv;
452 470
471Example: Imagine an API that returns a condvar and doesn't support
472callbacks. This is how you make a synchronous call, for example from
473the main program:
474
475 use AnyEvent::CouchDB;
476
477 ...
478
479 my @info = $couchdb->info->recv;
480
481And this is how you would just ste a callback to be called whenever the
482results are available:
483
484 $couchdb->info->cb (sub {
485 my @info = $_[0]->recv;
486 });
487
453=head3 METHODS FOR PRODUCERS 488=head3 METHODS FOR PRODUCERS
454 489
455These methods should only be used by the producing side, i.e. the 490These methods should only be used by the producing side, i.e. the
456code/module that eventually sends the signal. Note that it is also 491code/module that eventually sends the signal. Note that it is also
457the producer side which creates the condvar in most cases, but it isn't 492the producer side which creates the condvar in most cases, but it isn't
590=item $bool = $cv->ready 625=item $bool = $cv->ready
591 626
592Returns true when the condition is "true", i.e. whether C<send> or 627Returns true when the condition is "true", i.e. whether C<send> or
593C<croak> have been called. 628C<croak> have been called.
594 629
595=item $cb = $cv->cb ([new callback]) 630=item $cb = $cv->cb ($cb->($cv))
596 631
597This is a mutator function that returns the callback set and optionally 632This is a mutator function that returns the callback set and optionally
598replaces it before doing so. 633replaces it before doing so.
599 634
600The callback will be called when the condition becomes "true", i.e. when 635The callback will be called when the condition becomes "true", i.e. when
790=item L<AnyEvent::IGS> 825=item L<AnyEvent::IGS>
791 826
792A non-blocking interface to the Internet Go Server protocol (used by 827A non-blocking interface to the Internet Go Server protocol (used by
793L<App::IGS>). 828L<App::IGS>).
794 829
795=item L<Net::IRC3> 830=item L<AnyEvent::IRC>
796 831
797AnyEvent based IRC client module family. 832AnyEvent based IRC client module family (replacing the older Net::IRC3).
798 833
799=item L<Net::XMPP2> 834=item L<Net::XMPP2>
800 835
801AnyEvent based XMPP (Jabber protocol) module family. 836AnyEvent based XMPP (Jabber protocol) module family.
802 837
822=cut 857=cut
823 858
824package AnyEvent; 859package AnyEvent;
825 860
826no warnings; 861no warnings;
827use strict; 862use strict qw(vars subs);
828 863
829use Carp; 864use Carp;
830 865
831our $VERSION = 4.22; 866our $VERSION = 4.341;
832our $MODEL; 867our $MODEL;
833 868
834our $AUTOLOAD; 869our $AUTOLOAD;
835our @ISA; 870our @ISA;
836 871
969# to support binding more than one watcher per filehandle (they usually 1004# to support binding more than one watcher per filehandle (they usually
970# allow only one watcher per fd, so we dup it to get a different one). 1005# allow only one watcher per fd, so we dup it to get a different one).
971sub _dupfh($$$$) { 1006sub _dupfh($$$$) {
972 my ($poll, $fh, $r, $w) = @_; 1007 my ($poll, $fh, $r, $w) = @_;
973 1008
974 require Fcntl;
975
976 # cygwin requires the fh mode to be matching, unix doesn't 1009 # cygwin requires the fh mode to be matching, unix doesn't
977 my ($rw, $mode) = $poll eq "r" ? ($r, "<") 1010 my ($rw, $mode) = $poll eq "r" ? ($r, "<")
978 : $poll eq "w" ? ($w, ">") 1011 : $poll eq "w" ? ($w, ">")
979 : Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'"; 1012 : Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
980 1013
988 1021
989package AnyEvent::Base; 1022package AnyEvent::Base;
990 1023
991# default implementation for now and time 1024# default implementation for now and time
992 1025
993use Time::HiRes (); 1026BEGIN {
1027 if (eval "use Time::HiRes (); time (); 1") {
1028 *_time = \&Time::HiRes::time;
1029 # if (eval "use POSIX (); (POSIX::times())...
1030 } else {
1031 *_time = sub { time }; # epic fail
1032 }
1033}
994 1034
995sub time { Time::HiRes::time } 1035sub time { _time }
996sub now { Time::HiRes::time } 1036sub now { _time }
997 1037
998# default implementation for ->condvar 1038# default implementation for ->condvar
999 1039
1000sub condvar { 1040sub condvar {
1001 bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar:: 1041 bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
1002} 1042}
1003 1043
1004# default implementation for ->signal 1044# default implementation for ->signal
1005 1045
1006our %SIG_CB; 1046our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
1047
1048sub _signal_exec {
1049 while (%SIG_EV) {
1050 sysread $SIGPIPE_R, my $dummy, 4;
1051 for (keys %SIG_EV) {
1052 delete $SIG_EV{$_};
1053 $_->() for values %{ $SIG_CB{$_} || {} };
1054 }
1055 }
1056}
1007 1057
1008sub signal { 1058sub signal {
1009 my (undef, %arg) = @_; 1059 my (undef, %arg) = @_;
1010 1060
1061 unless ($SIGPIPE_R) {
1062 if (AnyEvent::WIN32) {
1063 ($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
1064 AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
1065 AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
1066 } else {
1067 pipe $SIGPIPE_R, $SIGPIPE_W;
1068 require Fcntl;
1069 fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
1070 fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
1071 }
1072
1073 $SIGPIPE_R
1074 or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
1075
1076 $SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
1077 }
1078
1011 my $signal = uc $arg{signal} 1079 my $signal = uc $arg{signal}
1012 or Carp::croak "required option 'signal' is missing"; 1080 or Carp::croak "required option 'signal' is missing";
1013 1081
1014 $SIG_CB{$signal}{$arg{cb}} = $arg{cb}; 1082 $SIG_CB{$signal}{$arg{cb}} = $arg{cb};
1015 $SIG{$signal} ||= sub { 1083 $SIG{$signal} ||= sub {
1016 $_->() for values %{ $SIG_CB{$signal} || {} }; 1084 syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
1085 undef $SIG_EV{$signal};
1017 }; 1086 };
1018 1087
1019 bless [$signal, $arg{cb}], "AnyEvent::Base::Signal" 1088 bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"
1020} 1089}
1021 1090
1140 1209
1141# undocumented/compatibility with pre-3.4 1210# undocumented/compatibility with pre-3.4
1142*broadcast = \&send; 1211*broadcast = \&send;
1143*wait = \&_wait; 1212*wait = \&_wait;
1144 1213
1214=head1 ERROR AND EXCEPTION HANDLING
1215
1216In general, AnyEvent does not do any error handling - it relies on the
1217caller to do that if required. The L<AnyEvent::Strict> module (see also
1218the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
1219checking of all AnyEvent methods, however, which is highly useful during
1220development.
1221
1222As for exception handling (i.e. runtime errors and exceptions thrown while
1223executing a callback), this is not only highly event-loop specific, but
1224also not in any way wrapped by this module, as this is the job of the main
1225program.
1226
1227The pure perl event loop simply re-throws the exception (usually
1228within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
1229$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
1230so on.
1231
1232=head1 ENVIRONMENT VARIABLES
1233
1234The following environment variables are used by this module or its
1235submodules:
1236
1237=over 4
1238
1239=item C<PERL_ANYEVENT_VERBOSE>
1240
1241By default, AnyEvent will be completely silent except in fatal
1242conditions. You can set this environment variable to make AnyEvent more
1243talkative.
1244
1245When set to C<1> or higher, causes AnyEvent to warn about unexpected
1246conditions, such as not being able to load the event model specified by
1247C<PERL_ANYEVENT_MODEL>.
1248
1249When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1250model it chooses.
1251
1252=item C<PERL_ANYEVENT_STRICT>
1253
1254AnyEvent does not do much argument checking by default, as thorough
1255argument checking is very costly. Setting this variable to a true value
1256will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
1257check the arguments passed to most method calls. If it finds any problems
1258it will croak.
1259
1260In other words, enables "strict" mode.
1261
1262Unlike C<use strict>, it is definitely recommended ot keep it off in
1263production. Keeping C<PERL_ANYEVENT_STRICT=1> in your environment while
1264developing programs can be very useful, however.
1265
1266=item C<PERL_ANYEVENT_MODEL>
1267
1268This can be used to specify the event model to be used by AnyEvent, before
1269auto detection and -probing kicks in. It must be a string consisting
1270entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1271and the resulting module name is loaded and if the load was successful,
1272used as event model. If it fails to load AnyEvent will proceed with
1273auto detection and -probing.
1274
1275This functionality might change in future versions.
1276
1277For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1278could start your program like this:
1279
1280 PERL_ANYEVENT_MODEL=Perl perl ...
1281
1282=item C<PERL_ANYEVENT_PROTOCOLS>
1283
1284Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1285for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1286of auto probing).
1287
1288Must be set to a comma-separated list of protocols or address families,
1289current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1290used, and preference will be given to protocols mentioned earlier in the
1291list.
1292
1293This variable can effectively be used for denial-of-service attacks
1294against local programs (e.g. when setuid), although the impact is likely
1295small, as the program has to handle conenction and other failures anyways.
1296
1297Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1298but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1299- only support IPv4, never try to resolve or contact IPv6
1300addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1301IPv6, but prefer IPv6 over IPv4.
1302
1303=item C<PERL_ANYEVENT_EDNS0>
1304
1305Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1306for DNS. This extension is generally useful to reduce DNS traffic, but
1307some (broken) firewalls drop such DNS packets, which is why it is off by
1308default.
1309
1310Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1311EDNS0 in its DNS requests.
1312
1313=item C<PERL_ANYEVENT_MAX_FORKS>
1314
1315The maximum number of child processes that C<AnyEvent::Util::fork_call>
1316will create in parallel.
1317
1318=back
1319
1145=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE 1320=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1146 1321
1147This is an advanced topic that you do not normally need to use AnyEvent in 1322This is an advanced topic that you do not normally need to use AnyEvent in
1148a module. This section is only of use to event loop authors who want to 1323a module. This section is only of use to event loop authors who want to
1149provide AnyEvent compatibility. 1324provide AnyEvent compatibility.
1182 1357
1183I<rxvt-unicode> also cheats a bit by not providing blocking access to 1358I<rxvt-unicode> also cheats a bit by not providing blocking access to
1184condition variables: code blocking while waiting for a condition will 1359condition variables: code blocking while waiting for a condition will
1185C<die>. This still works with most modules/usages, and blocking calls must 1360C<die>. This still works with most modules/usages, and blocking calls must
1186not be done in an interactive application, so it makes sense. 1361not be done in an interactive application, so it makes sense.
1187
1188=head1 ENVIRONMENT VARIABLES
1189
1190The following environment variables are used by this module:
1191
1192=over 4
1193
1194=item C<PERL_ANYEVENT_VERBOSE>
1195
1196By default, AnyEvent will be completely silent except in fatal
1197conditions. You can set this environment variable to make AnyEvent more
1198talkative.
1199
1200When set to C<1> or higher, causes AnyEvent to warn about unexpected
1201conditions, such as not being able to load the event model specified by
1202C<PERL_ANYEVENT_MODEL>.
1203
1204When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1205model it chooses.
1206
1207=item C<PERL_ANYEVENT_STRICT>
1208
1209AnyEvent does not do much argument checking by default, as thorough
1210argument checking is very costly. Setting this variable to a true value
1211will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
1212check the arguments passed to most method calls. If it finds any problems
1213it will croak.
1214
1215In other words, enables "strict" mode.
1216
1217Unlike C<use strict> it is definitely recommended ot keep it off in
1218production.
1219
1220=item C<PERL_ANYEVENT_MODEL>
1221
1222This can be used to specify the event model to be used by AnyEvent, before
1223auto detection and -probing kicks in. It must be a string consisting
1224entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1225and the resulting module name is loaded and if the load was successful,
1226used as event model. If it fails to load AnyEvent will proceed with
1227auto detection and -probing.
1228
1229This functionality might change in future versions.
1230
1231For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1232could start your program like this:
1233
1234 PERL_ANYEVENT_MODEL=Perl perl ...
1235
1236=item C<PERL_ANYEVENT_PROTOCOLS>
1237
1238Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1239for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1240of auto probing).
1241
1242Must be set to a comma-separated list of protocols or address families,
1243current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1244used, and preference will be given to protocols mentioned earlier in the
1245list.
1246
1247This variable can effectively be used for denial-of-service attacks
1248against local programs (e.g. when setuid), although the impact is likely
1249small, as the program has to handle connection errors already-
1250
1251Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1252but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1253- only support IPv4, never try to resolve or contact IPv6
1254addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1255IPv6, but prefer IPv6 over IPv4.
1256
1257=item C<PERL_ANYEVENT_EDNS0>
1258
1259Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1260for DNS. This extension is generally useful to reduce DNS traffic, but
1261some (broken) firewalls drop such DNS packets, which is why it is off by
1262default.
1263
1264Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1265EDNS0 in its DNS requests.
1266
1267=item C<PERL_ANYEVENT_MAX_FORKS>
1268
1269The maximum number of child processes that C<AnyEvent::Util::fork_call>
1270will create in parallel.
1271
1272=back
1273 1362
1274=head1 EXAMPLE PROGRAM 1363=head1 EXAMPLE PROGRAM
1275 1364
1276The following program uses an I/O watcher to read data from STDIN, a timer 1365The following program uses an I/O watcher to read data from STDIN, a timer
1277to display a message once per second, and a condition variable to quit the 1366to display a message once per second, and a condition variable to quit the
1471watcher. 1560watcher.
1472 1561
1473=head3 Results 1562=head3 Results
1474 1563
1475 name watchers bytes create invoke destroy comment 1564 name watchers bytes create invoke destroy comment
1476 EV/EV 400000 244 0.56 0.46 0.31 EV native interface 1565 EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1477 EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers 1566 EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1478 CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal 1567 CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1479 Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation 1568 Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1480 Event/Event 16000 516 31.88 31.30 0.85 Event native interface 1569 Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1481 Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers 1570 Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
1482 Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour 1571 Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1483 Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers 1572 Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1484 POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event 1573 POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1485 POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select 1574 POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1486 1575
1487=head3 Discussion 1576=head3 Discussion
1488 1577
1489The benchmark does I<not> measure scalability of the event loop very 1578The benchmark does I<not> measure scalability of the event loop very
1490well. For example, a select-based event loop (such as the pure perl one) 1579well. For example, a select-based event loop (such as the pure perl one)
1692watchers, as the management overhead dominates. 1781watchers, as the management overhead dominates.
1693 1782
1694=back 1783=back
1695 1784
1696 1785
1786=head1 SIGNALS
1787
1788AnyEvent currently installs handlers for these signals:
1789
1790=over 4
1791
1792=item SIGCHLD
1793
1794A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
1795emulation for event loops that do not support them natively. Also, some
1796event loops install a similar handler.
1797
1798=item SIGPIPE
1799
1800A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
1801when AnyEvent gets loaded.
1802
1803The rationale for this is that AnyEvent users usually do not really depend
1804on SIGPIPE delivery (which is purely an optimisation for shell use, or
1805badly-written programs), but C<SIGPIPE> can cause spurious and rare
1806program exits as a lot of people do not expect C<SIGPIPE> when writing to
1807some random socket.
1808
1809The rationale for installing a no-op handler as opposed to ignoring it is
1810that this way, the handler will be restored to defaults on exec.
1811
1812Feel free to install your own handler, or reset it to defaults.
1813
1814=back
1815
1816=cut
1817
1818$SIG{PIPE} = sub { }
1819 unless defined $SIG{PIPE};
1820
1821
1697=head1 FORK 1822=head1 FORK
1698 1823
1699Most event libraries are not fork-safe. The ones who are usually are 1824Most event libraries are not fork-safe. The ones who are usually are
1700because they rely on inefficient but fork-safe C<select> or C<poll> 1825because they rely on inefficient but fork-safe C<select> or C<poll>
1701calls. Only L<EV> is fully fork-aware. 1826calls. Only L<EV> is fully fork-aware.

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