4 use vars qw($VERSION $XS_VERSION @ISA @EXPORT @EXPORT_OK $AUTOLOAD);
12 @EXPORT_OK = qw (usleep sleep ualarm alarm gettimeofday time tv_interval
13 getitimer setitimer nanosleep
14 ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF ITIMER_REALPROF
15 d_usleep d_ualarm d_gettimeofday d_getitimer d_setitimer
19 $XS_VERSION = $VERSION;
20 $VERSION = eval $VERSION;
24 ($constname = $AUTOLOAD) =~ s/.*:://;
25 die "&Time::HiRes::constant not defined" if $constname eq 'constant';
26 my ($error, $val) = constant($constname);
27 if ($error) { die $error; }
30 *$AUTOLOAD = sub { $val };
37 XSLoader::load('Time::HiRes', $XS_VERSION);
41 local @ISA = qw(DynaLoader);
42 bootstrap Time::HiRes $XS_VERSION;
45 # Preloaded methods go here.
48 # probably could have been done in C
50 $b = [gettimeofday()] unless defined($b);
51 (${$b}[0] - ${$a}[0]) + ((${$b}[1] - ${$a}[1]) / 1_000_000);
54 # Autoload methods go after =cut, and are processed by the autosplit program.
61 Time::HiRes - High resolution alarm, sleep, gettimeofday, interval timers
65 use Time::HiRes qw( usleep ualarm gettimeofday tv_interval nanosleep );
67 usleep ($microseconds);
68 nanosleep ($nanoseconds);
70 ualarm ($microseconds);
71 ualarm ($microseconds, $interval_microseconds);
74 ($seconds, $microseconds) = gettimeofday;
76 $elapsed = tv_interval ( $t0, [$seconds, $microseconds]);
77 $elapsed = tv_interval ( $t0, [gettimeofday]);
78 $elapsed = tv_interval ( $t0 );
80 use Time::HiRes qw ( time alarm sleep );
82 $now_fractions = time;
83 sleep ($floating_seconds);
84 alarm ($floating_seconds);
85 alarm ($floating_seconds, $floating_interval);
87 use Time::HiRes qw( setitimer getitimer
88 ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF ITIMER_REALPROF );
90 setitimer ($which, $floating_seconds, $floating_interval );
95 The C<Time::HiRes> module implements a Perl interface to the
96 C<usleep>, C<nanosleep>, C<ualarm>, C<gettimeofday>, and
97 C<setitimer>/C<getitimer> system calls, in other words, high
98 resolution time and timers. See the L</EXAMPLES> section below and the
99 test scripts for usage; see your system documentation for the
100 description of the underlying C<nanosleep> or C<usleep>, C<ualarm>,
101 C<gettimeofday>, and C<setitimer>/C<getitimer> calls.
103 If your system lacks C<gettimeofday()> or an emulation of it you don't
104 get C<gettimeofday()> or the one-argument form of C<tv_interval()>.
105 If your system lacks all of C<nanosleep()>, C<usleep()>, and
106 C<select()>, you don't get C<Time::HiRes::usleep()>,
107 C<Time::HiRes::nanosleep()>, or C<Time::HiRes::sleep()>. If your
108 system lacks both C<ualarm()> and C<setitimer()> you don't get
109 C<Time::HiRes::ualarm()> or C<Time::HiRes::alarm()>.
111 If you try to import an unimplemented function in the C<use> statement
112 it will fail at compile time.
114 If your subsecond sleeping is implemented with C<nanosleep()> instead
115 of C<usleep()>, you can mix subsecond sleeping with signals since
116 C<nanosleep()> does not use signals. This, however, is not portable,
117 and you should first check for the truth value of
118 C<&Time::HiRes::d_nanosleep> to see whether you have nanosleep, and
119 then carefully read your C<nanosleep()> C API documentation for any
122 Unless using C<nanosleep> for mixing sleeping with signals, give
123 some thought to whether Perl is the tool you should be using for
124 work requiring nanosecond accuracies.
126 The following functions can be imported from this module.
127 No functions are exported by default.
131 =item gettimeofday ()
133 In array context returns a two-element array with the seconds and
134 microseconds since the epoch. In scalar context returns floating
135 seconds like C<Time::HiRes::time()> (see below).
137 =item usleep ( $useconds )
139 Sleeps for the number of microseconds (millionths of a second)
140 specified. Returns the number of microseconds actually slept. Can
141 sleep for more than one second, unlike the C<usleep> system call. See
142 also C<Time::HiRes::usleep()> and C<Time::HiRes::sleep()>.
144 Do not expect usleep() to be exact down to one microsecond.
146 =item nanosleep ( $nanoseconds )
148 Sleeps for the number of nanoseconds (1e9ths of a second) specified.
149 Returns the number of nanoseconds actually slept (accurate only to
150 microseconds, the nearest thousand of them). Can sleep for more than
151 one second. See also C<Time::HiRes::sleep()> and
152 C<Time::HiRes::usleep()>.
154 Do not expect nanosleep() to be exact down to one nanosecond.
155 Getting even accuracy of one thousand nanoseconds is good.
157 =item ualarm ( $useconds [, $interval_useconds ] )
159 Issues a C<ualarm> call; the C<$interval_useconds> is optional and
160 will be zero if unspecified, resulting in C<alarm>-like behaviour.
162 Note that the interaction between alarms and sleeps is unspecified.
166 tv_interval ( $ref_to_gettimeofday [, $ref_to_later_gettimeofday] )
168 Returns the floating seconds between the two times, which should have
169 been returned by C<gettimeofday()>. If the second argument is omitted,
170 then the current time is used.
174 Returns a floating seconds since the epoch. This function can be
175 imported, resulting in a nice drop-in replacement for the C<time>
176 provided with core Perl; see the L</EXAMPLES> below.
178 B<NOTE 1>: This higher resolution timer can return values either less
179 or more than the core C<time()>, depending on whether your platform
180 rounds the higher resolution timer values up, down, or to the nearest second
181 to get the core C<time()>, but naturally the difference should be never
182 more than half a second.
184 B<NOTE 2>: Since Sunday, September 9th, 2001 at 01:46:40 AM GMT, when
185 the C<time()> seconds since epoch rolled over to 1_000_000_000, the
186 default floating point format of Perl and the seconds since epoch have
187 conspired to produce an apparent bug: if you print the value of
188 C<Time::HiRes::time()> you seem to be getting only five decimals, not
189 six as promised (microseconds). Not to worry, the microseconds are
190 there (assuming your platform supports such granularity in the first
191 place). What is going on is that the default floating point format of
192 Perl only outputs 15 digits. In this case that means ten digits
193 before the decimal separator and five after. To see the microseconds
194 you can use either C<printf>/C<sprintf> with C<"%.6f">, or the
195 C<gettimeofday()> function in list context, which will give you the
196 seconds and microseconds as two separate values.
198 =item sleep ( $floating_seconds )
200 Sleeps for the specified amount of seconds. Returns the number of
201 seconds actually slept (a floating point value). This function can
202 be imported, resulting in a nice drop-in replacement for the C<sleep>
203 provided with perl, see the L</EXAMPLES> below.
205 Note that the interaction between alarms and sleeps is unspecified.
207 =item alarm ( $floating_seconds [, $interval_floating_seconds ] )
209 The C<SIGALRM> signal is sent after the specified number of seconds.
210 Implemented using C<ualarm()>. The C<$interval_floating_seconds> argument
211 is optional and will be zero if unspecified, resulting in C<alarm()>-like
212 behaviour. This function can be imported, resulting in a nice drop-in
213 replacement for the C<alarm> provided with perl, see the L</EXAMPLES> below.
215 B<NOTE 1>: With some combinations of operating systems and Perl
216 releases C<SIGALRM> restarts C<select()>, instead of interrupting it.
217 This means that an C<alarm()> followed by a C<select()> may together
218 take the sum of the times specified for the the C<alarm()> and the
219 C<select()>, not just the time of the C<alarm()>.
221 Note that the interaction between alarms and sleeps is unspecified.
223 =item setitimer ( $which, $floating_seconds [, $interval_floating_seconds ] )
225 Start up an interval timer: after a certain time, a signal arrives,
226 and more signals may keep arriving at certain intervals. To disable
227 an "itimer", use C<$floating_seconds> of zero. If the
228 C<$interval_floating_seconds> is set to zero (or unspecified), the
229 timer is disabled B<after> the next delivered signal.
231 Use of interval timers may interfere with C<alarm()>, C<sleep()>,
232 and C<usleep()>. In standard-speak the "interaction is unspecified",
233 which means that I<anything> may happen: it may work, it may not.
235 In scalar context, the remaining time in the timer is returned.
237 In list context, both the remaining time and the interval are returned.
239 There are usually three or four interval timers available: the
240 C<$which> can be C<ITIMER_REAL>, C<ITIMER_VIRTUAL>, C<ITIMER_PROF>, or
241 C<ITIMER_REALPROF>. Note that which ones are available depends: true
242 UNIX platforms usually have the first three, but (for example) Win32
243 and Cygwin have only C<ITIMER_REAL>, and only Solaris seems to have
244 C<ITIMER_REALPROF> (which is used to profile multithreaded programs).
246 C<ITIMER_REAL> results in C<alarm()>-like behaviour. Time is counted in
247 I<real time>; that is, wallclock time. C<SIGALRM> is delivered when
250 C<ITIMER_VIRTUAL> counts time in (process) I<virtual time>; that is,
251 only when the process is running. In multiprocessor/user/CPU systems
252 this may be more or less than real or wallclock time. (This time is
253 also known as the I<user time>.) C<SIGVTALRM> is delivered when the
256 C<ITIMER_PROF> counts time when either the process virtual time or when
257 the operating system is running on behalf of the process (such as I/O).
258 (This time is also known as the I<system time>.) (The sum of user
259 time and system time is known as the I<CPU time>.) C<SIGPROF> is
260 delivered when the timer expires. C<SIGPROF> can interrupt system calls.
262 The semantics of interval timers for multithreaded programs are
263 system-specific, and some systems may support additional interval
264 timers. See your C<setitimer()> documentation.
266 =item getitimer ( $which )
268 Return the remaining time in the interval timer specified by C<$which>.
270 In scalar context, the remaining time is returned.
272 In list context, both the remaining time and the interval are returned.
273 The interval is always what you put in using C<setitimer()>.
279 use Time::HiRes qw(usleep ualarm gettimeofday tv_interval);
281 $microseconds = 750_000;
282 usleep $microseconds;
284 # signal alarm in 2.5s & every .1s thereafter
285 ualarm 2_500_000, 100_000;
287 # get seconds and microseconds since the epoch
288 ($s, $usec) = gettimeofday;
290 # measure elapsed time
291 # (could also do by subtracting 2 gettimeofday return values)
292 $t0 = [gettimeofday];
293 # do bunch of stuff here
294 $t1 = [gettimeofday];
296 $t0_t1 = tv_interval $t0, $t1;
298 $elapsed = tv_interval ($t0, [gettimeofday]);
299 $elapsed = tv_interval ($t0); # equivalent code
302 # replacements for time, alarm and sleep that know about
306 $now_fractions = Time::HiRes::time;
307 Time::HiRes::sleep (2.5);
308 Time::HiRes::alarm (10.6666666);
310 use Time::HiRes qw ( time alarm sleep );
311 $now_fractions = time;
315 # Arm an interval timer to go off first at 10 seconds and
316 # after that every 2.5 seconds, in process virtual time
318 use Time::HiRes qw ( setitimer ITIMER_VIRTUAL time );
320 $SIG{VTALRM} = sub { print time, "\n" };
321 setitimer(ITIMER_VIRTUAL, 10, 2.5);
325 In addition to the perl API described above, a C API is available for
326 extension writers. The following C functions are available in the
330 --------------- ----------------------
331 Time::NVtime double (*)()
332 Time::U2time void (*)(UV ret[2])
334 Both functions return equivalent information (like C<gettimeofday>)
335 but with different representations. The names C<NVtime> and C<U2time>
336 were selected mainly because they are operating system independent.
337 (C<gettimeofday> is Unix-centric, though some platforms like Win32 and
338 VMS have emulations for it.)
340 Here is an example of using C<NVtime> from C:
342 double (*myNVtime)(); /* Returns -1 on failure. */
343 SV **svp = hv_fetch(PL_modglobal, "Time::NVtime", 12, 0);
344 if (!svp) croak("Time::HiRes is required");
345 if (!SvIOK(*svp)) croak("Time::NVtime isn't a function pointer");
346 myNVtime = INT2PTR(double(*)(), SvIV(*svp));
347 printf("The current time is: %f\n", (*myNVtime)());
351 =head2 negative time not invented yet
353 You tried to use a negative time argument.
355 =head2 internal error: useconds < 0 (unsigned ... signed ...)
357 Something went horribly wrong-- the number of microseconds that cannot
358 become negative just became negative. Maybe your compiler is broken?
362 Notice that the core C<time()> maybe rounding rather than truncating.
363 What this means is that the core C<time()> may be reporting the time
364 as one second later than C<gettimeofday()> and C<Time::HiRes::time()>.
366 Adjusting the system clock (either manually or by services like ntp)
367 may cause problems, especially for long running programs that assume
368 a monotonously increasing time (note that all platforms do not adjust
369 time as gracefully as UNIX ntp does). For example in Win32 (and derived
370 platforms like Cygwin and MinGW) the Time::HiRes::time() may temporarily
371 drift off from the system clock (and the original time()) by up to 0.5
372 seconds. Time::HiRes will notice this eventually and recalibrate.
376 L<BSD::Resource>, L<Time::TAI64>.
380 D. Wegscheid <wegscd@whirlpool.com>
381 R. Schertler <roderick@argon.org>
382 J. Hietaniemi <jhi@iki.fi>
383 G. Aas <gisle@aas.no>
385 =head1 COPYRIGHT AND LICENSE
387 Copyright (c) 1996-2002 Douglas E. Wegscheid. All rights reserved.
389 Copyright (c) 2002,2003,2004,2005 Jarkko Hietaniemi. All rights reserved.
391 This program is free software; you can redistribute it and/or modify
392 it under the same terms as Perl itself.