| 1 | package Time::HiRes; |
| 2 | |
| 3 | use strict; |
| 4 | use vars qw($VERSION $XS_VERSION @ISA @EXPORT @EXPORT_OK $AUTOLOAD); |
| 5 | |
| 6 | require Exporter; |
| 7 | require DynaLoader; |
| 8 | |
| 9 | @ISA = qw(Exporter DynaLoader); |
| 10 | |
| 11 | @EXPORT = qw( ); |
| 12 | @EXPORT_OK = qw (usleep sleep ualarm alarm gettimeofday time tv_interval |
| 13 | getitimer setitimer nanosleep clock_gettime clock_getres |
| 14 | clock clock_nanosleep |
| 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 |
| 19 | TIMER_ABSTIME |
| 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); |
| 23 | |
| 24 | $VERSION = '1.86'; |
| 25 | $XS_VERSION = $VERSION; |
| 26 | $VERSION = eval $VERSION; |
| 27 | |
| 28 | sub AUTOLOAD { |
| 29 | my $constname; |
| 30 | ($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 = $val\n"; |
| 35 | if ($error) { |
| 36 | my (undef,$file,$line) = caller; |
| 37 | die "$error at $file line $line.\n"; |
| 38 | } |
| 39 | { |
| 40 | no strict 'refs'; |
| 41 | *$AUTOLOAD = sub { $val }; |
| 42 | } |
| 43 | goto &$AUTOLOAD; |
| 44 | } |
| 45 | |
| 46 | sub import { |
| 47 | my $this = shift; |
| 48 | for my $i (@_) { |
| 49 | if (($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)) { |
| 56 | require Carp; |
| 57 | Carp::croak("Time::HiRes::$i(): unimplemented in this platform"); |
| 58 | } |
| 59 | } |
| 60 | Time::HiRes->export_to_level(1, $this, @_); |
| 61 | } |
| 62 | |
| 63 | bootstrap Time::HiRes; |
| 64 | |
| 65 | # Preloaded methods go here. |
| 66 | |
| 67 | sub tv_interval { |
| 68 | # probably could have been done in C |
| 69 | my ($a, $b) = @_; |
| 70 | $b = [gettimeofday()] unless defined($b); |
| 71 | (${$b}[0] - ${$a}[0]) + ((${$b}[1] - ${$a}[1]) / 1_000_000); |
| 72 | } |
| 73 | |
| 74 | # Autoload methods go after =cut, and are processed by the autosplit program. |
| 75 | |
| 76 | 1; |
| 77 | __END__ |
| 78 | |
| 79 | =head1 NAME |
| 80 | |
| 81 | Time::HiRes - High resolution alarm, sleep, gettimeofday, interval timers |
| 82 | |
| 83 | =head1 SYNOPSIS |
| 84 | |
| 85 | use Time::HiRes qw( usleep ualarm gettimeofday tv_interval nanosleep |
| 86 | clock_gettime clock_getres clock_nanosleep clock ); |
| 87 | |
| 88 | usleep ($microseconds); |
| 89 | nanosleep ($nanoseconds); |
| 90 | |
| 91 | ualarm ($microseconds); |
| 92 | ualarm ($microseconds, $interval_microseconds); |
| 93 | |
| 94 | $t0 = [gettimeofday]; |
| 95 | ($seconds, $microseconds) = gettimeofday; |
| 96 | |
| 97 | $elapsed = tv_interval ( $t0, [$seconds, $microseconds]); |
| 98 | $elapsed = tv_interval ( $t0, [gettimeofday]); |
| 99 | $elapsed = tv_interval ( $t0 ); |
| 100 | |
| 101 | use Time::HiRes qw ( time alarm sleep ); |
| 102 | |
| 103 | $now_fractions = time; |
| 104 | sleep ($floating_seconds); |
| 105 | alarm ($floating_seconds); |
| 106 | alarm ($floating_seconds, $floating_interval); |
| 107 | |
| 108 | use Time::HiRes qw( setitimer getitimer |
| 109 | ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF ITIMER_REALPROF ); |
| 110 | |
| 111 | setitimer ($which, $floating_seconds, $floating_interval ); |
| 112 | getitimer ($which); |
| 113 | |
| 114 | $realtime = clock_gettime(CLOCK_REALTIME); |
| 115 | $resolution = clock_getres(CLOCK_REALTIME); |
| 116 | |
| 117 | clock_nanosleep(CLOCK_REALTIME, 1.5); |
| 118 | clock_nanosleep(CLOCK_REALTIME, time() + 10, TIMER_ABSTIME); |
| 119 | |
| 120 | my $ticktock = clock(); |
| 121 | |
| 122 | =head1 DESCRIPTION |
| 123 | |
| 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. |
| 131 | |
| 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()>. |
| 139 | |
| 140 | If you try to import an unimplemented function in the C<use> statement |
| 141 | it will fail at compile time. |
| 142 | |
| 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 |
| 149 | peculiarities. |
| 150 | |
| 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. |
| 154 | |
| 155 | The following functions can be imported from this module. |
| 156 | No functions are exported by default. |
| 157 | |
| 158 | =over 4 |
| 159 | |
| 160 | =item gettimeofday () |
| 161 | |
| 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). |
| 165 | |
| 166 | =item usleep ( $useconds ) |
| 167 | |
| 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()>. |
| 174 | |
| 175 | Do not expect usleep() to be exact down to one microsecond. |
| 176 | |
| 177 | =item nanosleep ( $nanoseconds ) |
| 178 | |
| 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()>. |
| 185 | |
| 186 | Do not expect nanosleep() to be exact down to one nanosecond. |
| 187 | Getting even accuracy of one thousand nanoseconds is good. |
| 188 | |
| 189 | =item ualarm ( $useconds [, $interval_useconds ] ) |
| 190 | |
| 191 | Issues a C<ualarm> call; the C<$interval_useconds> is optional and |
| 192 | will be zero if unspecified, resulting in C<alarm>-like behaviour. |
| 193 | |
| 194 | Note that the interaction between alarms and sleeps is unspecified. |
| 195 | |
| 196 | =item tv_interval |
| 197 | |
| 198 | tv_interval ( $ref_to_gettimeofday [, $ref_to_later_gettimeofday] ) |
| 199 | |
| 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. |
| 203 | |
| 204 | =item time () |
| 205 | |
| 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. |
| 209 | |
| 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 |
| 215 | in your system. |
| 216 | |
| 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. |
| 230 | |
| 231 | =item sleep ( $floating_seconds ) |
| 232 | |
| 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. |
| 237 | |
| 238 | Note that the interaction between alarms and sleeps is unspecified. |
| 239 | |
| 240 | =item alarm ( $floating_seconds [, $interval_floating_seconds ] ) |
| 241 | |
| 242 | The C<SIGALRM> signal is sent after the specified number of seconds. |
| 243 | Implemented using C<ualarm()>. The C<$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. |
| 247 | |
| 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()>. |
| 253 | |
| 254 | Note that the interaction between alarms and sleeps is unspecified. |
| 255 | |
| 256 | =item setitimer ( $which, $floating_seconds [, $interval_floating_seconds ] ) |
| 257 | |
| 258 | Start up an interval timer: after a certain time, a signal arrives, |
| 259 | and more signals may keep arriving at certain intervals. To disable |
| 260 | an "itimer", use C<$floating_seconds> of zero. If the |
| 261 | C<$interval_floating_seconds> is set to zero (or unspecified), the |
| 262 | timer is disabled B<after> the next delivered signal. |
| 263 | |
| 264 | Use of interval timers may interfere with C<alarm()>, C<sleep()>, |
| 265 | and C<usleep()>. In standard-speak the "interaction is unspecified", |
| 266 | which means that I<anything> may happen: it may work, it may not. |
| 267 | |
| 268 | In scalar context, the remaining time in the timer is returned. |
| 269 | |
| 270 | In list context, both the remaining time and the interval are returned. |
| 271 | |
| 272 | There are usually three or four interval timers available: the |
| 273 | C<$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). |
| 278 | |
| 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 |
| 281 | the timer expires. |
| 282 | |
| 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 |
| 287 | timer expires. |
| 288 | |
| 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. |
| 294 | |
| 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. |
| 298 | |
| 299 | =item getitimer ( $which ) |
| 300 | |
| 301 | Return the remaining time in the interval timer specified by C<$which>. |
| 302 | |
| 303 | In scalar context, the remaining time is returned. |
| 304 | |
| 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()>. |
| 307 | |
| 308 | =item clock_gettime ( $which ) |
| 309 | |
| 310 | Return as seconds the current value of the POSIX high resolution timer |
| 311 | specified by C<$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. |
| 321 | |
| 322 | =item clock_getres ( $which ) |
| 323 | |
| 324 | Return as seconds the resolution of the POSIX high resolution timer |
| 325 | specified by C<$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>. |
| 328 | |
| 329 | =item clock_nanosleep ( $which, $seconds, $flags = 0) |
| 330 | |
| 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()>. |
| 340 | |
| 341 | Do not expect clock_nanosleep() to be exact down to one nanosecond. |
| 342 | Getting even accuracy of one thousand nanoseconds is good. |
| 343 | |
| 344 | =item clock() |
| 345 | |
| 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(). |
| 352 | |
| 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. |
| 359 | |
| 360 | =back |
| 361 | |
| 362 | =head1 EXAMPLES |
| 363 | |
| 364 | use Time::HiRes qw(usleep ualarm gettimeofday tv_interval); |
| 365 | |
| 366 | $microseconds = 750_000; |
| 367 | usleep($microseconds); |
| 368 | |
| 369 | # signal alarm in 2.5s & every .1s thereafter |
| 370 | ualarm(2_500_000, 100_000); |
| 371 | |
| 372 | # get seconds and microseconds since the epoch |
| 373 | ($s, $usec) = gettimeofday(); |
| 374 | |
| 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]; |
| 380 | # do more stuff here |
| 381 | $t0_t1 = tv_interval $t0, $t1; |
| 382 | |
| 383 | $elapsed = tv_interval ($t0, [gettimeofday]); |
| 384 | $elapsed = tv_interval ($t0); # equivalent code |
| 385 | |
| 386 | # |
| 387 | # replacements for time, alarm and sleep that know about |
| 388 | # floating seconds |
| 389 | # |
| 390 | use Time::HiRes; |
| 391 | $now_fractions = Time::HiRes::time; |
| 392 | Time::HiRes::sleep (2.5); |
| 393 | Time::HiRes::alarm (10.6666666); |
| 394 | |
| 395 | use Time::HiRes qw ( time alarm sleep ); |
| 396 | $now_fractions = time; |
| 397 | sleep (2.5); |
| 398 | alarm (10.6666666); |
| 399 | |
| 400 | # Arm an interval timer to go off first at 10 seconds and |
| 401 | # after that every 2.5 seconds, in process virtual time |
| 402 | |
| 403 | use Time::HiRes qw ( setitimer ITIMER_VIRTUAL time ); |
| 404 | |
| 405 | $SIG{VTALRM} = sub { print time, "\n" }; |
| 406 | setitimer(ITIMER_VIRTUAL, 10, 2.5); |
| 407 | |
| 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); |
| 413 | |
| 414 | use Time::HiRes qw( clock_nanosleep TIMER_ABSTIME ); |
| 415 | clock_nanosleep(CLOCK_REALTIME, 1e6); |
| 416 | clock_nanosleep(CLOCK_REALTIME, 2e9, TIMER_ABSTIME); |
| 417 | |
| 418 | use Time::HiRes qw( clock ); |
| 419 | my $clock0 = clock(); |
| 420 | ... # Do something. |
| 421 | my $clock1 = clock(); |
| 422 | my $clockd = $clock1 - $clock0; |
| 423 | |
| 424 | =head1 C API |
| 425 | |
| 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 |
| 428 | modglobal hash: |
| 429 | |
| 430 | name C prototype |
| 431 | --------------- ---------------------- |
| 432 | Time::NVtime double (*)() |
| 433 | Time::U2time void (*)(pTHX_ UV ret[2]) |
| 434 | |
| 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.) |
| 440 | |
| 441 | Here is an example of using C<NVtime> from C: |
| 442 | |
| 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)()); |
| 449 | |
| 450 | =head1 DIAGNOSTICS |
| 451 | |
| 452 | =head2 negative time not invented yet |
| 453 | |
| 454 | You tried to use a negative time argument. |
| 455 | |
| 456 | =head2 internal error: useconds < 0 (unsigned ... signed ...) |
| 457 | |
| 458 | Something went horribly wrong-- the number of microseconds that cannot |
| 459 | become negative just became negative. Maybe your compiler is broken? |
| 460 | |
| 461 | =head1 CAVEATS |
| 462 | |
| 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()>. |
| 466 | |
| 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). |
| 476 | |
| 477 | =head1 SEE ALSO |
| 478 | |
| 479 | Perl modules L<BSD::Resource>, L<Time::TAI64>. |
| 480 | |
| 481 | Your system documentation for C<clock_gettime>, C<clock_settime>, |
| 482 | C<gettimeofday>, C<getitimer>, C<setitimer>, C<ualarm>. |
| 483 | |
| 484 | =head1 AUTHORS |
| 485 | |
| 486 | D. Wegscheid <wegscd@whirlpool.com> |
| 487 | R. Schertler <roderick@argon.org> |
| 488 | J. Hietaniemi <jhi@iki.fi> |
| 489 | G. Aas <gisle@aas.no> |
| 490 | |
| 491 | =head1 COPYRIGHT AND LICENSE |
| 492 | |
| 493 | Copyright (c) 1996-2002 Douglas E. Wegscheid. All rights reserved. |
| 494 | |
| 495 | Copyright (c) 2002, 2003, 2004, 2005 Jarkko Hietaniemi. All rights reserved. |
| 496 | |
| 497 | This program is free software; you can redistribute it and/or modify |
| 498 | it under the same terms as Perl itself. |
| 499 | |
| 500 | =cut |