@EXPORT = qw( );
@EXPORT_OK = qw (usleep sleep ualarm alarm gettimeofday time tv_interval
- getitimer setitimer
+ getitimer setitimer nanosleep clock_gettime clock_getres
+ clock clock_nanosleep
+ CLOCK_HIGHRES CLOCK_MONOTONIC CLOCK_PROCESS_CPUTIME_ID
+ CLOCK_REALTIME CLOCK_SOFTTIME CLOCK_THREAD_CPUTIME_ID
+ CLOCK_TIMEOFDAY CLOCKS_PER_SEC
ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF ITIMER_REALPROF
+ TIMER_ABSTIME
d_usleep d_ualarm d_gettimeofday d_getitimer d_setitimer
- d_nanosleep);
+ d_nanosleep d_clock_gettime d_clock_getres
+ d_clock d_clock_nanosleep
+ stat
+ );
-$VERSION = '1.47';
+$VERSION = '1.9708';
$XS_VERSION = $VERSION;
$VERSION = eval $VERSION;
sub AUTOLOAD {
my $constname;
($constname = $AUTOLOAD) =~ s/.*:://;
+ # print "AUTOLOAD: constname = $constname ($AUTOLOAD)\n";
die "&Time::HiRes::constant not defined" if $constname eq 'constant';
my ($error, $val) = constant($constname);
- if ($error) { die $error; }
+ # print "AUTOLOAD: error = $error, val = $val\n";
+ if ($error) {
+ my (undef,$file,$line) = caller;
+ die "$error at $file line $line.\n";
+ }
{
no strict 'refs';
*$AUTOLOAD = sub { $val };
goto &$AUTOLOAD;
}
+sub import {
+ my $this = shift;
+ for my $i (@_) {
+ if (($i eq 'clock_getres' && !&d_clock_getres) ||
+ ($i eq 'clock_gettime' && !&d_clock_gettime) ||
+ ($i eq 'clock_nanosleep' && !&d_clock_nanosleep) ||
+ ($i eq 'clock' && !&d_clock) ||
+ ($i eq 'nanosleep' && !&d_nanosleep) ||
+ ($i eq 'usleep' && !&d_usleep) ||
+ ($i eq 'ualarm' && !&d_ualarm)) {
+ require Carp;
+ Carp::croak("Time::HiRes::$i(): unimplemented in this platform");
+ }
+ }
+ Time::HiRes->export_to_level(1, $this, @_);
+}
+
bootstrap Time::HiRes;
# Preloaded methods go here.
=head1 SYNOPSIS
- use Time::HiRes qw( usleep ualarm gettimeofday tv_interval );
+ use Time::HiRes qw( usleep ualarm gettimeofday tv_interval nanosleep
+ clock_gettime clock_getres clock_nanosleep clock
+ stat );
usleep ($microseconds);
+ nanosleep ($nanoseconds);
ualarm ($microseconds);
ualarm ($microseconds, $interval_microseconds);
alarm ($floating_seconds);
alarm ($floating_seconds, $floating_interval);
- use Time::HiRes qw( setitimer getitimer
- ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF ITIMER_REALPROF );
+ use Time::HiRes qw( setitimer getitimer );
setitimer ($which, $floating_seconds, $floating_interval );
getitimer ($which);
-=head1 DESCRIPTION
+ use Time::HiRes qw( clock_gettime clock_getres clock_nanosleep
+ ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF ITIMER_REALPROF );
+
+ $realtime = clock_gettime(CLOCK_REALTIME);
+ $resolution = clock_getres(CLOCK_REALTIME);
+
+ clock_nanosleep(CLOCK_REALTIME, 1.5e9);
+ clock_nanosleep(CLOCK_REALTIME, time()*1e9 + 10e9, TIMER_ABSTIME);
+
+ my $ticktock = clock();
-The Time::HiRes module implements a Perl interface to the usleep,
-ualarm, gettimeofday, and setitimer/getitimer system calls, in other
-words, high resolution time and timers. See the EXAMPLES section below
-and the test scripts for usage; see your system documentation for the
-description of the underlying nanosleep or usleep, ualarm,
-gettimeofday, and setitimer/getitimer calls.
+ use Time::HiRes qw( stat );
-If your system lacks gettimeofday() or an emulation of it you don't
-get gettimeofday() or the one-arg form of tv_interval(). If you don't
-have any of the nanosleep() or usleep() or select() you don't get
-Time::HiRes::usleep() or Time::HiRes::sleep(). If your system don't
-have either ualarm() or setitimer() you don't get
-Time::HiRes::ualarm() or Time::HiRes::alarm().
+ my @stat = stat("file");
+ my @stat = stat(FH);
+
+=head1 DESCRIPTION
+
+The C<Time::HiRes> module implements a Perl interface to the
+C<usleep>, C<nanosleep>, C<ualarm>, C<gettimeofday>, and
+C<setitimer>/C<getitimer> system calls, in other words, high
+resolution time and timers. See the L</EXAMPLES> section below and the
+test scripts for usage; see your system documentation for the
+description of the underlying C<nanosleep> or C<usleep>, C<ualarm>,
+C<gettimeofday>, and C<setitimer>/C<getitimer> calls.
+
+If your system lacks C<gettimeofday()> or an emulation of it you don't
+get C<gettimeofday()> or the one-argument form of C<tv_interval()>.
+If your system lacks all of C<nanosleep()>, C<usleep()>,
+C<select()>, and C<poll>, you don't get C<Time::HiRes::usleep()>,
+C<Time::HiRes::nanosleep()>, or C<Time::HiRes::sleep()>.
+If your system lacks both C<ualarm()> and C<setitimer()> you don't get
+C<Time::HiRes::ualarm()> or C<Time::HiRes::alarm()>.
If you try to import an unimplemented function in the C<use> statement
it will fail at compile time.
-If your subsecond sleeping is implemented with nanosleep() instead of
-usleep(), you can mix subsecond sleeping with signals since
-nanosleep() does not use signals. This however is unportable, and you
-should first check for the truth value of &Time::HiRes::d_nanosleep to
-see whether you have nanosleep, and then read carefully your
-nanosleep() C API documentation for any peculiarities. (There is no
-separate interface to call nanosleep(); just use Time::HiRes::sleep()
-or Time::HiRes::usleep() with small enough values.)
-
-Unless using nanosleep for mixing sleeping with signals, also give
-some thought to whether Perl is the tool you should be using for work
-requiring nanosecond accuracies.
+If your subsecond sleeping is implemented with C<nanosleep()> instead
+of C<usleep()>, you can mix subsecond sleeping with signals since
+C<nanosleep()> does not use signals. This, however, is not portable,
+and you should first check for the truth value of
+C<&Time::HiRes::d_nanosleep> to see whether you have nanosleep, and
+then carefully read your C<nanosleep()> C API documentation for any
+peculiarities.
+
+If you are using C<nanosleep> for something else than mixing sleeping
+with signals, give some thought to whether Perl is the tool you should
+be using for work requiring nanosecond accuracies.
+
+Remember that unless you are working on a I<hard realtime> system,
+any clocks and timers will be imprecise, especially so if you are working
+in a pre-emptive multiuser system. Understand the difference between
+I<wallclock time> and process time (in UNIX-like systems the sum of
+I<user> and I<system> times). Any attempt to sleep for X seconds will
+most probably end up sleeping B<more> than that, but don't be surpised
+if you end up sleeping slightly B<less>.
The following functions can be imported from this module.
No functions are exported by default.
In array context returns a two-element array with the seconds and
microseconds since the epoch. In scalar context returns floating
-seconds like Time::HiRes::time() (see below).
+seconds like C<Time::HiRes::time()> (see below).
=item usleep ( $useconds )
-Sleeps for the number of microseconds specified. Returns the number
-of microseconds actually slept. Can sleep for more than one second
-unlike the usleep system call. See also Time::HiRes::sleep() below.
+Sleeps for the number of microseconds (millionths of a second)
+specified. Returns the number of microseconds actually slept.
+Can sleep for more than one second, unlike the C<usleep> system call.
+Can also sleep for zero seconds, which often works like a I<thread yield>.
+See also C<Time::HiRes::usleep()>, C<Time::HiRes::sleep()>, and
+C<Time::HiRes::clock_nanosleep()>.
+
+Do not expect usleep() to be exact down to one microsecond.
+
+=item nanosleep ( $nanoseconds )
+
+Sleeps for the number of nanoseconds (1e9ths of a second) specified.
+Returns the number of nanoseconds actually slept (accurate only to
+microseconds, the nearest thousand of them). Can sleep for more than
+one second. Can also sleep for zero seconds, which often works like
+a I<thread yield>. See also C<Time::HiRes::sleep()>,
+C<Time::HiRes::usleep()>, and C<Time::HiRes::clock_nanosleep()>.
+
+Do not expect nanosleep() to be exact down to one nanosecond.
+Getting even accuracy of one thousand nanoseconds is good.
=item ualarm ( $useconds [, $interval_useconds ] )
-Issues a ualarm call; the $interval_useconds is optional and
-will be zero if unspecified, resulting in alarm-like behaviour.
+Issues a C<ualarm> call; the C<$interval_useconds> is optional and
+will be zero if unspecified, resulting in C<alarm>-like behaviour.
+
+ualarm(0) will cancel an outstanding ualarm().
+
+Note that the interaction between alarms and sleeps is unspecified.
=item tv_interval
tv_interval ( $ref_to_gettimeofday [, $ref_to_later_gettimeofday] )
Returns the floating seconds between the two times, which should have
-been returned by gettimeofday(). If the second argument is omitted,
+been returned by C<gettimeofday()>. If the second argument is omitted,
then the current time is used.
=item time ()
Returns a floating seconds since the epoch. This function can be
-imported, resulting in a nice drop-in replacement for the time
-provided with core Perl, see the EXAMPLES below.
-
-B<NOTE 1>: this higher resolution timer can return values either less
-or more than the core time(), depending on whether your platforms
-rounds the higher resolution timer values up, down, or to the nearest
-to get the core time(), but naturally the difference should be never
-more than half a second.
-
-B<NOTE 2>: Since Sunday, September 9th, 2001 at 01:46:40 AM GMT (when
-the time() seconds since epoch rolled over to 1_000_000_000), the
+imported, resulting in a nice drop-in replacement for the C<time>
+provided with core Perl; see the L</EXAMPLES> below.
+
+B<NOTE 1>: This higher resolution timer can return values either less
+or more than the core C<time()>, depending on whether your platform
+rounds the higher resolution timer values up, down, or to the nearest second
+to get the core C<time()>, but naturally the difference should be never
+more than half a second. See also L</clock_getres>, if available
+in your system.
+
+B<NOTE 2>: Since Sunday, September 9th, 2001 at 01:46:40 AM GMT, when
+the C<time()> seconds since epoch rolled over to 1_000_000_000, the
default floating point format of Perl and the seconds since epoch have
conspired to produce an apparent bug: if you print the value of
-Time::HiRes::time() you seem to be getting only five decimals, not six
-as promised (microseconds). Not to worry, the microseconds are there
-(assuming your platform supports such granularity in first place).
-What is going on is that the default floating point format of Perl
-only outputs 15 digits. In this case that means ten digits before the
-decimal separator and five after. To see the microseconds you can use
-either printf/sprintf with "%.6f", or the gettimeofday() function in
-list context, which will give you the seconds and microseconds as two
-separate values.
+C<Time::HiRes::time()> you seem to be getting only five decimals, not
+six as promised (microseconds). Not to worry, the microseconds are
+there (assuming your platform supports such granularity in the first
+place). What is going on is that the default floating point format of
+Perl only outputs 15 digits. In this case that means ten digits
+before the decimal separator and five after. To see the microseconds
+you can use either C<printf>/C<sprintf> with C<"%.6f">, or the
+C<gettimeofday()> function in list context, which will give you the
+seconds and microseconds as two separate values.
=item sleep ( $floating_seconds )
Sleeps for the specified amount of seconds. Returns the number of
-seconds actually slept (a floating point value). This function can be
-imported, resulting in a nice drop-in replacement for the sleep
-provided with perl, see the EXAMPLES below.
+seconds actually slept (a floating point value). This function can
+be imported, resulting in a nice drop-in replacement for the C<sleep>
+provided with perl, see the L</EXAMPLES> below.
+
+Note that the interaction between alarms and sleeps is unspecified.
=item alarm ( $floating_seconds [, $interval_floating_seconds ] )
-The SIGALRM signal is sent after the specified number of seconds.
-Implemented using ualarm(). The $interval_floating_seconds argument
-is optional and will be zero if unspecified, resulting in alarm()-like
+The C<SIGALRM> signal is sent after the specified number of seconds.
+Implemented using C<ualarm()>. The C<$interval_floating_seconds> argument
+is optional and will be zero if unspecified, resulting in C<alarm()>-like
behaviour. This function can be imported, resulting in a nice drop-in
-replacement for the alarm provided with perl, see the EXAMPLES below.
+replacement for the C<alarm> provided with perl, see the L</EXAMPLES> below.
-B<NOTE 1>: With some operating system and Perl release combinations
-select() gets restarted by SIGALRM, instead of dropping out of
-select(). This means that an alarm() followed by a select()
-may together take the sum of the times specified for the the
-alarm() and the select(), not just the time of the alarm().
+B<NOTE 1>: With some combinations of operating systems and Perl
+releases C<SIGALRM> restarts C<select()>, instead of interrupting it.
+This means that an C<alarm()> followed by a C<select()> may together
+take the sum of the times specified for the the C<alarm()> and the
+C<select()>, not just the time of the C<alarm()>.
-=item setitimer
+Note that the interaction between alarms and sleeps is unspecified.
-setitimer ( $which, $floating_seconds [, $interval_floating_seconds ] )
+=item setitimer ( $which, $floating_seconds [, $interval_floating_seconds ] )
-Start up an interval timer: after a certain time, a signal arrives,
-and more signals may keep arriving at certain intervals. To disable a
-timer, use $floating_seconds of zero. If the $interval_floating_seconds
-is set to zero (or unspecified), the timer is disabled B<after> the
-next delivered signal.
+Start up an interval timer: after a certain time, a signal ($which) arrives,
+and more signals may keep arriving at certain intervals. To disable
+an "itimer", use C<$floating_seconds> of zero. If the
+C<$interval_floating_seconds> is set to zero (or unspecified), the
+timer is disabled B<after> the next delivered signal.
-Use of interval timers may interfere with alarm(), sleep(),
-and usleep(). In standard-speak the "interaction is unspecified",
+Use of interval timers may interfere with C<alarm()>, C<sleep()>,
+and C<usleep()>. In standard-speak the "interaction is unspecified",
which means that I<anything> may happen: it may work, it may not.
In scalar context, the remaining time in the timer is returned.
In list context, both the remaining time and the interval are returned.
-There are usually three or four interval timers available: the $which
-can be ITIMER_REAL, ITIMER_VIRTUAL, ITIMER_PROF, or ITIMER_REALPROF.
-Note that which ones are available depends: true UNIX platforms have
-usually all first three, but for example Win32 and Cygwin only have
-ITIMER_REAL, and only Solaris seems to have ITIMER_REALPROF (which is
-used to profile multithreaded programs).
+There are usually three or four interval timers (signals) available: the
+C<$which> can be C<ITIMER_REAL>, C<ITIMER_VIRTUAL>, C<ITIMER_PROF>, or
+C<ITIMER_REALPROF>. Note that which ones are available depends: true
+UNIX platforms usually have the first three, but (for example) Win32
+and Cygwin have only C<ITIMER_REAL>, and only Solaris seems to have
+C<ITIMER_REALPROF> (which is used to profile multithreaded programs).
-ITIMER_REAL results in alarm()-like behavior. Time is counted in
-I<real time>, that is, wallclock time. SIGALRM is delivered when
+C<ITIMER_REAL> results in C<alarm()>-like behaviour. Time is counted in
+I<real time>; that is, wallclock time. C<SIGALRM> is delivered when
the timer expires.
-ITIMER_VIRTUAL counts time in (process) I<virtual time>, that is, only
-when the process is running. In multiprocessor/user/CPU systems this
-may be more or less than real or wallclock time. (This time is also
-known as the I<user time>.) SIGVTALRM is delivered when the timer expires.
+C<ITIMER_VIRTUAL> counts time in (process) I<virtual time>; that is,
+only when the process is running. In multiprocessor/user/CPU systems
+this may be more or less than real or wallclock time. (This time is
+also known as the I<user time>.) C<SIGVTALRM> is delivered when the
+timer expires.
-ITIMER_PROF counts time when either the process virtual time or when
+C<ITIMER_PROF> counts time when either the process virtual time or when
the operating system is running on behalf of the process (such as I/O).
(This time is also known as the I<system time>.) (The sum of user
-time and system time is known as the I<CPU time>.) SIGPROF is
-delivered when the timer expires. SIGPROF can interrupt system calls.
+time and system time is known as the I<CPU time>.) C<SIGPROF> is
+delivered when the timer expires. C<SIGPROF> can interrupt system calls.
The semantics of interval timers for multithreaded programs are
system-specific, and some systems may support additional interval
-timers. See your setitimer() documentation.
+timers. For example, it is unspecified which thread gets the signals.
+See your C<setitimer()> documentation.
=item getitimer ( $which )
-Return the remaining time in the interval timer specified by $which.
+Return the remaining time in the interval timer specified by C<$which>.
In scalar context, the remaining time is returned.
In list context, both the remaining time and the interval are returned.
-The interval is always what you put in using setitimer().
+The interval is always what you put in using C<setitimer()>.
+
+=item clock_gettime ( $which )
+
+Return as seconds the current value of the POSIX high resolution timer
+specified by C<$which>. All implementations that support POSIX high
+resolution timers are supposed to support at least the C<$which> value
+of C<CLOCK_REALTIME>, which is supposed to return results close to the
+results of C<gettimeofday>, or the number of seconds since 00:00:00:00
+January 1, 1970 Greenwich Mean Time (GMT). Do not assume that
+CLOCK_REALTIME is zero, it might be one, or something else.
+Another potentially useful (but not available everywhere) value is
+C<CLOCK_MONOTONIC>, which guarantees a monotonically increasing time
+value (unlike time(), which can be adjusted). See your system
+documentation for other possibly supported values.
+
+=item clock_getres ( $which )
+
+Return as seconds the resolution of the POSIX high resolution timer
+specified by C<$which>. All implementations that support POSIX high
+resolution timers are supposed to support at least the C<$which> value
+of C<CLOCK_REALTIME>, see L</clock_gettime>.
+
+=item clock_nanosleep ( $which, $nanoseconds, $flags = 0)
+
+Sleeps for the number of nanoseconds (1e9ths of a second) specified.
+Returns the number of nanoseconds actually slept. The $which is the
+"clock id", as with clock_gettime() and clock_getres(). The flags
+default to zero but C<TIMER_ABSTIME> can specified (must be exported
+explicitly) which means that C<$nanoseconds> is not a time interval
+(as is the default) but instead an absolute time. Can sleep for more
+than one second. Can also sleep for zero seconds, which often works
+like a I<thread yield>. See also C<Time::HiRes::sleep()>,
+C<Time::HiRes::usleep()>, and C<Time::HiRes::nanosleep()>.
+
+Do not expect clock_nanosleep() to be exact down to one nanosecond.
+Getting even accuracy of one thousand nanoseconds is good.
+
+=item clock()
+
+Return as seconds the I<process time> (user + system time) spent by
+the process since the first call to clock() (the definition is B<not>
+"since the start of the process", though if you are lucky these times
+may be quite close to each other, depending on the system). What this
+means is that you probably need to store the result of your first call
+to clock(), and subtract that value from the following results of clock().
+
+The time returned also includes the process times of the terminated
+child processes for which wait() has been executed. This value is
+somewhat like the second value returned by the times() of core Perl,
+but not necessarily identical. Note that due to backward
+compatibility limitations the returned value may wrap around at about
+2147 seconds or at about 36 minutes.
+
+=item stat
+
+=item stat FH
+
+=item stat EXPR
+
+As L<perlfunc/stat> but with the access/modify/change file timestamps
+in subsecond resolution, if the operating system and the filesystem
+both support such timestamps. To override the standard stat():
+
+ use Time::HiRes qw(stat);
+
+Test for the value of &Time::HiRes::d_hires_stat to find out whether
+the operating system supports subsecond file timestamps: a value
+larger than zero means yes. There are unfortunately no easy
+ways to find out whether the filesystem supports such timestamps.
+UNIX filesystems often do; NTFS does; FAT doesn't (FAT timestamp
+granularity is B<two> seconds).
+
+A zero return value of &Time::HiRes::d_hires_stat means that
+Time::HiRes::stat is a no-op passthrough for CORE::stat(),
+and therefore the timestamps will stay integers. The same
+thing will happen if the filesystem does not do subsecond timestamps,
+even if the &Time::HiRes::d_hires_stat is non-zero.
+
+In any case do not expect nanosecond resolution, or even a microsecond
+resolution. Also note that the modify/access timestamps might have
+different resolutions, and that they need not be synchronized, e.g.
+if the operations are
+
+ write
+ stat # t1
+ read
+ stat # t2
+
+the access time stamp from t2 need not be greater-than the modify
+time stamp from t1: it may be equal or I<less>.
=back
use Time::HiRes qw(usleep ualarm gettimeofday tv_interval);
$microseconds = 750_000;
- usleep $microseconds;
+ usleep($microseconds);
# signal alarm in 2.5s & every .1s thereafter
- ualarm 2_500_000, 100_000;
+ ualarm(2_500_000, 100_000);
+ # cancel that ualarm
+ ualarm(0);
# get seconds and microseconds since the epoch
- ($s, $usec) = gettimeofday;
+ ($s, $usec) = gettimeofday();
# measure elapsed time
# (could also do by subtracting 2 gettimeofday return values)
$SIG{VTALRM} = sub { print time, "\n" };
setitimer(ITIMER_VIRTUAL, 10, 2.5);
+ use Time::HiRes qw( clock_gettime clock_getres CLOCK_REALTIME );
+ # Read the POSIX high resolution timer.
+ my $high = clock_getres(CLOCK_REALTIME);
+ # But how accurate we can be, really?
+ my $reso = clock_getres(CLOCK_REALTIME);
+
+ use Time::HiRes qw( clock_nanosleep TIMER_ABSTIME );
+ clock_nanosleep(CLOCK_REALTIME, 1e6);
+ clock_nanosleep(CLOCK_REALTIME, 2e9, TIMER_ABSTIME);
+
+ use Time::HiRes qw( clock );
+ my $clock0 = clock();
+ ... # Do something.
+ my $clock1 = clock();
+ my $clockd = $clock1 - $clock0;
+
+ use Time::HiRes qw( stat );
+ my ($atime, $mtime, $ctime) = (stat("istics"))[8, 9, 10];
+
=head1 C API
In addition to the perl API described above, a C API is available for
name C prototype
--------------- ----------------------
Time::NVtime double (*)()
- Time::U2time void (*)(UV ret[2])
+ Time::U2time void (*)(pTHX_ UV ret[2])
-Both functions return equivalent information (like gettimeofday)
-but with different representations. The names NVtime and U2time
+Both functions return equivalent information (like C<gettimeofday>)
+but with different representations. The names C<NVtime> and C<U2time>
were selected mainly because they are operating system independent.
-(gettimeofday is Unix-centric, though some platforms like VMS have
-emulations for it.)
+(C<gettimeofday> is Unix-centric, though some platforms like Win32 and
+VMS have emulations for it.)
-Here is an example of using NVtime from C:
+Here is an example of using C<NVtime> from C:
- double (*myNVtime)();
+ double (*myNVtime)(); /* Returns -1 on failure. */
SV **svp = hv_fetch(PL_modglobal, "Time::NVtime", 12, 0);
if (!svp) croak("Time::HiRes is required");
if (!SvIOK(*svp)) croak("Time::NVtime isn't a function pointer");
myNVtime = INT2PTR(double(*)(), SvIV(*svp));
printf("The current time is: %f\n", (*myNVtime)());
+=head1 DIAGNOSTICS
+
+=head2 useconds or interval more than ...
+
+In ualarm() you tried to use number of microseconds or interval (also
+in microseconds) more than 1_000_000 and setitimer() is not available
+in your system to emulate that case.
+
+=head2 negative time not invented yet
+
+You tried to use a negative time argument.
+
+=head2 internal error: useconds < 0 (unsigned ... signed ...)
+
+Something went horribly wrong-- the number of microseconds that cannot
+become negative just became negative. Maybe your compiler is broken?
+
=head1 CAVEATS
-Notice that the core time() maybe rounding rather than truncating.
-What this means that the core time() may be giving time one second
-later than gettimeofday(), also known as Time::HiRes::time().
+Notice that the core C<time()> maybe rounding rather than truncating.
+What this means is that the core C<time()> may be reporting the time
+as one second later than C<gettimeofday()> and C<Time::HiRes::time()>.
+
+Adjusting the system clock (either manually or by services like ntp)
+may cause problems, especially for long running programs that assume
+a monotonously increasing time (note that all platforms do not adjust
+time as gracefully as UNIX ntp does). For example in Win32 (and derived
+platforms like Cygwin and MinGW) the Time::HiRes::time() may temporarily
+drift off from the system clock (and the original time()) by up to 0.5
+seconds. Time::HiRes will notice this eventually and recalibrate.
+Note that since Time::HiRes 1.77 the clock_gettime(CLOCK_MONOTONIC)
+might help in this (in case your system supports CLOCK_MONOTONIC).
+
+=head1 SEE ALSO
+
+Perl modules L<BSD::Resource>, L<Time::TAI64>.
+
+Your system documentation for C<clock>, C<clock_gettime>,
+C<clock_getres>, C<clock_nanosleep>, C<clock_settime>, C<getitimer>,
+C<gettimeofday>, C<setitimer>, C<sleep>, C<stat>, C<ualarm>.
=head1 AUTHORS
Copyright (c) 1996-2002 Douglas E. Wegscheid. All rights reserved.
-Copyright (c) 2002,2003 Jarkko Hietaniemi. All rights reserved.
+Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007 Jarkko Hietaniemi. All rights reserved.
This program is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.
https://perl5.git.perl.org / perl5.git / blobdiff