4 use vars qw($VERSION $XS_VERSION @ISA @EXPORT @EXPORT_OK $AUTOLOAD);
9 @ISA = qw(Exporter DynaLoader);
12 @EXPORT_OK = qw (usleep sleep ualarm alarm gettimeofday time tv_interval
13 getitimer setitimer nanosleep clock_gettime clock_getres
15 CLOCK_HIGHRES CLOCK_MONOTONIC CLOCK_PROCESS_CPUTIME_ID
16 CLOCK_REALTIME CLOCK_SOFTTIME CLOCK_THREAD_CPUTIME_ID
17 CLOCK_TIMEOFDAY CLOCKS_PER_SEC
18 ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF ITIMER_REALPROF
20 d_usleep d_ualarm d_gettimeofday d_getitimer d_setitimer
21 d_nanosleep d_clock_gettime d_clock_getres
22 d_clock d_clock_nanosleep);
25 $XS_VERSION = $VERSION;
26 $VERSION = eval $VERSION;
30 ($constname = $AUTOLOAD) =~ s/.*:://;
31 # print "AUTOLOAD: constname = $constname ($AUTOLOAD)\n";
32 die "&Time::HiRes::constant not defined" if $constname eq 'constant';
33 my ($error, $val) = constant($constname);
34 # print "AUTOLOAD: error = $error, val = $val\n";
36 my (undef,$file,$line) = caller;
37 die "$error at $file line $line.\n";
41 *$AUTOLOAD = sub { $val };
49 if (($i eq 'clock_getres' && !&d_clock_getres) ||
50 ($i eq 'clock_gettime' && !&d_clock_gettime) ||
51 ($i eq 'clock_nanosleep' && !&d_clock_nanosleep) ||
52 ($i eq 'clock' && !&d_clock) ||
53 ($i eq 'nanosleep' && !&d_nanosleep) ||
54 ($i eq 'usleep' && !&d_usleep) ||
55 ($i eq 'ualarm' && !&d_ualarm)) {
57 Carp::croak("Time::HiRes::$i(): unimplemented in this platform");
60 Time::HiRes->export_to_level(1, $this, @_);
63 bootstrap Time::HiRes;
65 # Preloaded methods go here.
68 # probably could have been done in C
70 $b = [gettimeofday()] unless defined($b);
71 (${$b}[0] - ${$a}[0]) + ((${$b}[1] - ${$a}[1]) / 1_000_000);
74 # Autoload methods go after =cut, and are processed by the autosplit program.
81 Time::HiRes - High resolution alarm, sleep, gettimeofday, interval timers
85 use Time::HiRes qw( usleep ualarm gettimeofday tv_interval nanosleep
86 clock_gettime clock_getres clock_nanosleep clock );
88 usleep ($microseconds);
89 nanosleep ($nanoseconds);
91 ualarm ($microseconds);
92 ualarm ($microseconds, $interval_microseconds);
95 ($seconds, $microseconds) = gettimeofday;
97 $elapsed = tv_interval ( $t0, [$seconds, $microseconds]);
98 $elapsed = tv_interval ( $t0, [gettimeofday]);
99 $elapsed = tv_interval ( $t0 );
101 use Time::HiRes qw ( time alarm sleep );
103 $now_fractions = time;
104 sleep ($floating_seconds);
105 alarm ($floating_seconds);
106 alarm ($floating_seconds, $floating_interval);
108 use Time::HiRes qw( setitimer getitimer
109 ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF ITIMER_REALPROF );
111 setitimer ($which, $floating_seconds, $floating_interval );
114 $realtime = clock_gettime(CLOCK_REALTIME);
115 $resolution = clock_getres(CLOCK_REALTIME);
117 clock_nanosleep(CLOCK_REALTIME, 1.5);
118 clock_nanosleep(CLOCK_REALTIME, time() + 10, TIMER_ABSTIME);
120 my $ticktock = clock();
124 The C<Time::HiRes> module implements a Perl interface to the
125 C<usleep>, C<nanosleep>, C<ualarm>, C<gettimeofday>, and
126 C<setitimer>/C<getitimer> system calls, in other words, high
127 resolution time and timers. See the L</EXAMPLES> section below and the
128 test scripts for usage; see your system documentation for the
129 description of the underlying C<nanosleep> or C<usleep>, C<ualarm>,
130 C<gettimeofday>, and C<setitimer>/C<getitimer> calls.
132 If your system lacks C<gettimeofday()> or an emulation of it you don't
133 get C<gettimeofday()> or the one-argument form of C<tv_interval()>.
134 If your system lacks all of C<nanosleep()>, C<usleep()>,
135 C<select()>, and C<poll>, you don't get C<Time::HiRes::usleep()>,
136 C<Time::HiRes::nanosleep()>, or C<Time::HiRes::sleep()>.
137 If your system lacks both C<ualarm()> and C<setitimer()> you don't get
138 C<Time::HiRes::ualarm()> or C<Time::HiRes::alarm()>.
140 If you try to import an unimplemented function in the C<use> statement
141 it will fail at compile time.
143 If your subsecond sleeping is implemented with C<nanosleep()> instead
144 of C<usleep()>, you can mix subsecond sleeping with signals since
145 C<nanosleep()> does not use signals. This, however, is not portable,
146 and you should first check for the truth value of
147 C<&Time::HiRes::d_nanosleep> to see whether you have nanosleep, and
148 then carefully read your C<nanosleep()> C API documentation for any
151 If you are using C<nanosleep> for something else than mixing sleeping
152 with signals, give some thought to whether Perl is the tool you should
153 be using for work requiring nanosecond accuracies.
155 The following functions can be imported from this module.
156 No functions are exported by default.
160 =item gettimeofday ()
162 In array context returns a two-element array with the seconds and
163 microseconds since the epoch. In scalar context returns floating
164 seconds like C<Time::HiRes::time()> (see below).
166 =item usleep ( $useconds )
168 Sleeps for the number of microseconds (millionths of a second)
169 specified. Returns the number of microseconds actually slept. Can
170 sleep for more than one second, unlike the C<usleep> system call. Can
171 also sleep for zero seconds, which often works like a I<thread yield>.
172 See also C<Time::HiRes::usleep()>, C<Time::HiRes::sleep()>, and
173 C<Time::HiRes::clock_nanosleep()>.
175 Do not expect usleep() to be exact down to one microsecond.
177 =item nanosleep ( $nanoseconds )
179 Sleeps for the number of nanoseconds (1e9ths of a second) specified.
180 Returns the number of nanoseconds actually slept (accurate only to
181 microseconds, the nearest thousand of them). Can sleep for more than
182 one second. Can also sleep for zero seconds, which often works like a
183 I<thread yield>. See also C<Time::HiRes::sleep()>,
184 C<Time::HiRes::usleep()>, and C<Time::HiRes::clock_nanosleep()>.
186 Do not expect nanosleep() to be exact down to one nanosecond.
187 Getting even accuracy of one thousand nanoseconds is good.
189 =item ualarm ( $useconds [, $interval_useconds ] )
191 Issues a C<ualarm> call; the C<$interval_useconds> is optional and
192 will be zero if unspecified, resulting in C<alarm>-like behaviour.
194 Note that the interaction between alarms and sleeps is unspecified.
198 tv_interval ( $ref_to_gettimeofday [, $ref_to_later_gettimeofday] )
200 Returns the floating seconds between the two times, which should have
201 been returned by C<gettimeofday()>. If the second argument is omitted,
202 then the current time is used.
206 Returns a floating seconds since the epoch. This function can be
207 imported, resulting in a nice drop-in replacement for the C<time>
208 provided with core Perl; see the L</EXAMPLES> below.
210 B<NOTE 1>: This higher resolution timer can return values either less
211 or more than the core C<time()>, depending on whether your platform
212 rounds the higher resolution timer values up, down, or to the nearest second
213 to get the core C<time()>, but naturally the difference should be never
214 more than half a second. See also L</clock_getres>, if available
217 B<NOTE 2>: Since Sunday, September 9th, 2001 at 01:46:40 AM GMT, when
218 the C<time()> seconds since epoch rolled over to 1_000_000_000, the
219 default floating point format of Perl and the seconds since epoch have
220 conspired to produce an apparent bug: if you print the value of
221 C<Time::HiRes::time()> you seem to be getting only five decimals, not
222 six as promised (microseconds). Not to worry, the microseconds are
223 there (assuming your platform supports such granularity in the first
224 place). What is going on is that the default floating point format of
225 Perl only outputs 15 digits. In this case that means ten digits
226 before the decimal separator and five after. To see the microseconds
227 you can use either C<printf>/C<sprintf> with C<"%.6f">, or the
228 C<gettimeofday()> function in list context, which will give you the
229 seconds and microseconds as two separate values.
231 =item sleep ( $floating_seconds )
233 Sleeps for the specified amount of seconds. Returns the number of
234 seconds actually slept (a floating point value). This function can
235 be imported, resulting in a nice drop-in replacement for the C<sleep>
236 provided with perl, see the L</EXAMPLES> below.
238 Note that the interaction between alarms and sleeps is unspecified.
240 =item alarm ( $floating_seconds [, $interval_floating_seconds ] )
242 The C<SIGALRM> signal is sent after the specified number of seconds.
243 Implemented using C<ualarm()>. The C<$interval_floating_seconds> argument
244 is optional and will be zero if unspecified, resulting in C<alarm()>-like
245 behaviour. This function can be imported, resulting in a nice drop-in
246 replacement for the C<alarm> provided with perl, see the L</EXAMPLES> below.
248 B<NOTE 1>: With some combinations of operating systems and Perl
249 releases C<SIGALRM> restarts C<select()>, instead of interrupting it.
250 This means that an C<alarm()> followed by a C<select()> may together
251 take the sum of the times specified for the the C<alarm()> and the
252 C<select()>, not just the time of the C<alarm()>.
254 Note that the interaction between alarms and sleeps is unspecified.
256 =item setitimer ( $which, $floating_seconds [, $interval_floating_seconds ] )
258 Start up an interval timer: after a certain time, a signal arrives,
259 and more signals may keep arriving at certain intervals. To disable
260 an "itimer", use C<$floating_seconds> of zero. If the
261 C<$interval_floating_seconds> is set to zero (or unspecified), the
262 timer is disabled B<after> the next delivered signal.
264 Use of interval timers may interfere with C<alarm()>, C<sleep()>,
265 and C<usleep()>. In standard-speak the "interaction is unspecified",
266 which means that I<anything> may happen: it may work, it may not.
268 In scalar context, the remaining time in the timer is returned.
270 In list context, both the remaining time and the interval are returned.
272 There are usually three or four interval timers available: the
273 C<$which> can be C<ITIMER_REAL>, C<ITIMER_VIRTUAL>, C<ITIMER_PROF>, or
274 C<ITIMER_REALPROF>. Note that which ones are available depends: true
275 UNIX platforms usually have the first three, but (for example) Win32
276 and Cygwin have only C<ITIMER_REAL>, and only Solaris seems to have
277 C<ITIMER_REALPROF> (which is used to profile multithreaded programs).
279 C<ITIMER_REAL> results in C<alarm()>-like behaviour. Time is counted in
280 I<real time>; that is, wallclock time. C<SIGALRM> is delivered when
283 C<ITIMER_VIRTUAL> counts time in (process) I<virtual time>; that is,
284 only when the process is running. In multiprocessor/user/CPU systems
285 this may be more or less than real or wallclock time. (This time is
286 also known as the I<user time>.) C<SIGVTALRM> is delivered when the
289 C<ITIMER_PROF> counts time when either the process virtual time or when
290 the operating system is running on behalf of the process (such as I/O).
291 (This time is also known as the I<system time>.) (The sum of user
292 time and system time is known as the I<CPU time>.) C<SIGPROF> is
293 delivered when the timer expires. C<SIGPROF> can interrupt system calls.
295 The semantics of interval timers for multithreaded programs are
296 system-specific, and some systems may support additional interval
297 timers. See your C<setitimer()> documentation.
299 =item getitimer ( $which )
301 Return the remaining time in the interval timer specified by C<$which>.
303 In scalar context, the remaining time is returned.
305 In list context, both the remaining time and the interval are returned.
306 The interval is always what you put in using C<setitimer()>.
308 =item clock_gettime ( $which )
310 Return as seconds the current value of the POSIX high resolution timer
311 specified by C<$which>. All implementations that support POSIX high
312 resolution timers are supposed to support at least the C<$which> value
313 of C<CLOCK_REALTIME>, which is supposed to return results close to the
314 results of C<gettimeofday>, or the number of seconds since 00:00:00:00
315 January 1, 1970 Greenwich Mean Time (GMT). Do not assume that
316 CLOCK_REALTIME is zero, it might be one, or something else.
317 Another potentially useful (but not available everywhere) value is
318 C<CLOCK_MONOTONIC>, which guarantees a monotonically increasing time
319 value (unlike time(), which can be adjusted). See your system
320 documentation for other possibly supported values.
322 =item clock_getres ( $which )
324 Return as seconds the resolution of the POSIX high resolution timer
325 specified by C<$which>. All implementations that support POSIX high
326 resolution timers are supposed to support at least the C<$which> value
327 of C<CLOCK_REALTIME>, see L</clock_gettime>.
329 =item clock_nanosleep ( $which, $seconds, $flags = 0)
331 Sleeps for the number of seconds (1e9ths of a second) specified.
332 Returns the number of seconds actually slept. The $which is the
333 "clock id", as with clock_gettime() and clock_getres(). The flags
334 default to zero but C<TIMER_ABSTIME> can specified (must be exported
335 explicitly) which means that C<$nanoseconds> is not a time interval
336 (as is the default) but instead an absolute time. Can sleep for more
337 than one second. Can also sleep for zero seconds, which often works
338 like a I<thread yield>. See also C<Time::HiRes::sleep()>,
339 C<Time::HiRes::usleep()>, and C<Time::HiRes::nanosleep()>.
341 Do not expect clock_nanosleep() to be exact down to one nanosecond.
342 Getting even accuracy of one thousand nanoseconds is good.
346 Return as seconds the I<process time> (user + system time) spent by
347 the process since the first call to clock() (the definition is B<not>
348 "since the start of the process", though if you are lucky these times
349 may be quite close to each other, depending on the system). What this
350 means is that you probably need to store the result of your first call
351 to clock(), and subtract that value from the following results of clock().
353 The time returned also includes the process times of the terminated
354 child processes for which wait() has been executed. This value is
355 somewhat like the second value returned by the times() of core Perl,
356 but not necessarily identical. Note that due to backward
357 compatibility limitations the returned value may wrap around at about
358 2147 seconds or at about 36 minutes.
364 use Time::HiRes qw(usleep ualarm gettimeofday tv_interval);
366 $microseconds = 750_000;
367 usleep($microseconds);
369 # signal alarm in 2.5s & every .1s thereafter
370 ualarm(2_500_000, 100_000);
372 # get seconds and microseconds since the epoch
373 ($s, $usec) = gettimeofday();
375 # measure elapsed time
376 # (could also do by subtracting 2 gettimeofday return values)
377 $t0 = [gettimeofday];
378 # do bunch of stuff here
379 $t1 = [gettimeofday];
381 $t0_t1 = tv_interval $t0, $t1;
383 $elapsed = tv_interval ($t0, [gettimeofday]);
384 $elapsed = tv_interval ($t0); # equivalent code
387 # replacements for time, alarm and sleep that know about
391 $now_fractions = Time::HiRes::time;
392 Time::HiRes::sleep (2.5);
393 Time::HiRes::alarm (10.6666666);
395 use Time::HiRes qw ( time alarm sleep );
396 $now_fractions = time;
400 # Arm an interval timer to go off first at 10 seconds and
401 # after that every 2.5 seconds, in process virtual time
403 use Time::HiRes qw ( setitimer ITIMER_VIRTUAL time );
405 $SIG{VTALRM} = sub { print time, "\n" };
406 setitimer(ITIMER_VIRTUAL, 10, 2.5);
408 use Time::HiRes qw( clock_gettime clock_getres CLOCK_REALTIME );
409 # Read the POSIX high resolution timer.
410 my $high = clock_getres(CLOCK_REALTIME);
411 # But how accurate we can be, really?
412 my $reso = clock_getres(CLOCK_REALTIME);
414 use Time::HiRes qw( clock_nanosleep TIMER_ABSTIME );
415 clock_nanosleep(CLOCK_REALTIME, 1e6);
416 clock_nanosleep(CLOCK_REALTIME, 2e9, TIMER_ABSTIME);
418 use Time::HiRes qw( clock );
419 my $clock0 = clock();
421 my $clock1 = clock();
422 my $clockd = $clock1 - $clock0;
426 In addition to the perl API described above, a C API is available for
427 extension writers. The following C functions are available in the
431 --------------- ----------------------
432 Time::NVtime double (*)()
433 Time::U2time void (*)(pTHX_ UV ret[2])
435 Both functions return equivalent information (like C<gettimeofday>)
436 but with different representations. The names C<NVtime> and C<U2time>
437 were selected mainly because they are operating system independent.
438 (C<gettimeofday> is Unix-centric, though some platforms like Win32 and
439 VMS have emulations for it.)
441 Here is an example of using C<NVtime> from C:
443 double (*myNVtime)(); /* Returns -1 on failure. */
444 SV **svp = hv_fetch(PL_modglobal, "Time::NVtime", 12, 0);
445 if (!svp) croak("Time::HiRes is required");
446 if (!SvIOK(*svp)) croak("Time::NVtime isn't a function pointer");
447 myNVtime = INT2PTR(double(*)(), SvIV(*svp));
448 printf("The current time is: %f\n", (*myNVtime)());
452 =head2 negative time not invented yet
454 You tried to use a negative time argument.
456 =head2 internal error: useconds < 0 (unsigned ... signed ...)
458 Something went horribly wrong-- the number of microseconds that cannot
459 become negative just became negative. Maybe your compiler is broken?
463 Notice that the core C<time()> maybe rounding rather than truncating.
464 What this means is that the core C<time()> may be reporting the time
465 as one second later than C<gettimeofday()> and C<Time::HiRes::time()>.
467 Adjusting the system clock (either manually or by services like ntp)
468 may cause problems, especially for long running programs that assume
469 a monotonously increasing time (note that all platforms do not adjust
470 time as gracefully as UNIX ntp does). For example in Win32 (and derived
471 platforms like Cygwin and MinGW) the Time::HiRes::time() may temporarily
472 drift off from the system clock (and the original time()) by up to 0.5
473 seconds. Time::HiRes will notice this eventually and recalibrate.
474 Note that since Time::HiRes 1.77 the clock_gettime(CLOCK_MONOTONIC)
475 might help in this (in case your system supports CLOCK_MONOTONIC).
479 Perl modules L<BSD::Resource>, L<Time::TAI64>.
481 Your system documentation for C<clock_gettime>, C<clock_settime>,
482 C<gettimeofday>, C<getitimer>, C<setitimer>, C<ualarm>.
486 D. Wegscheid <wegscd@whirlpool.com>
487 R. Schertler <roderick@argon.org>
488 J. Hietaniemi <jhi@iki.fi>
489 G. Aas <gisle@aas.no>
491 =head1 COPYRIGHT AND LICENSE
493 Copyright (c) 1996-2002 Douglas E. Wegscheid. All rights reserved.
495 Copyright (c) 2002, 2003, 2004, 2005 Jarkko Hietaniemi. All rights reserved.
497 This program is free software; you can redistribute it and/or modify
498 it under the same terms as Perl itself.