=head1 NAME
-Time::HiRes - High resolution ualarm, usleep, and gettimeofday
+Time::HiRes - High resolution alarm, sleep, gettimeofday, interval timers
=head1 SYNOPSIS
=head1 DESCRIPTION
-The C<Time::HiRes> module implements a Perl interface to the usleep, ualarm,
-and gettimeofday system calls. See the EXAMPLES section below and the test
-scripts for usage; see your system documentation for the description of
-the underlying gettimeofday, usleep, and ualarm calls.
+The C<Time::HiRes> module implements a Perl interface to the usleep,
+ualarm, gettimeofday, and setitimer/getitimer system calls. See the
+EXAMPLES section below and the test scripts for usage; see your system
+documentation for the description of the underlying usleep, ualarm,
+gettimeofday, and setitimer/getitimer calls.
-If your system lacks gettimeofday(2) you don't get gettimeofday() or the
-one-arg form of tv_interval(). If you don't have usleep(3) or select(2)
-you don't get usleep() or sleep(). If your system don't have ualarm(3)
-or setitimer(2) you don't get ualarm() or alarm().
-If you try to import an unimplemented function in the C<use> statement
-it will fail at compile time.
+If your system lacks gettimeofday(2) or an emulation of it you don't
+get gettimeofday() or the one-arg form of tv_interval().
+If you don't have usleep(3) or select(2) you don't get usleep()
+or sleep(). If your system don't have ualarm(3) or setitimer(2) you
+don't get ualarm() or alarm(). If you try to import an unimplemented
+function in the C<use> statement it will fail at compile time.
The following functions can be imported from this module.
No functions are exported by default.
=item gettimeofday ()
-In array context it returns a 2 element array with the seconds and
-microseconds since the epoch. In scalar context it returns floating
+In array context returns a 2 element array with the seconds and
+microseconds since the epoch. In scalar context returns floating
seconds like Time::HiRes::time() (see below).
=item usleep ( $useconds )
-Issues a usleep for the number of microseconds specified. Returns the
-number of microseconds actually slept. The number of microseconds
-B<must> be between 0 and 1_000_0000 (inclusive): you B<cannot> sleep
-a minute by usleep(60_000_000). See also Time::HiRes::sleep() below.
+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.
=item ualarm ( $useconds [, $interval_useconds ] )
=item tv_interval
-S<tv_interval ( $ref_to_gettimeofday [, $ref_to_later_gettimeofday] )>
+C<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, then the
-current time is used.
+Returns the floating seconds between the two times, which should have
+been returned by 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 C<time> provided with perl,
-see the EXAMPLES below.
+Returns a floating seconds since the epoch. This function can be
+imported, resulting in a nice drop-in replacement for the C<time>
+provided with core Perl, see the EXAMPLES below.
-B<NOTE>: Since Sunday, September 9th, 2001 at 01:46:40 AM GMT
+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 default floating point format of Perl and the seconds since epoch
have conspired to produce an apparent bug: if you print the value of
=item sleep ( $floating_seconds )
-Converts $floating_seconds to microseconds and issues a usleep for the
-result. 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 C<sleep> provided with perl, see the
-EXAMPLES below.
+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 C<sleep>
+provided with perl, see the EXAMPLES below.
=item alarm ( $floating_seconds [, $interval_floating_seconds ] )
-Converts $floating_seconds and $interval_floating_seconds and issues
-a ualarm for the results. The $interval_floating_seconds argument
-is optional and will be 0 if unspecified, resulting in alarm-like
+The SIGALRM signal is sent after the specfified number of seconds.
+Implemented using ualarm(). The $interval_floating_seconds argument
+is optional and will be 0 if unspecified, resulting in alarm()-like
behaviour. This function can be imported, resulting in a nice drop-in
replacement for the C<alarm> provided with perl, see the EXAMPLES below.
=item setitimer
-S<setitimer ( $which, $floating_seconds [, $interval_floating_seconds ] )>
+C<setitimer ( $which, $floating_seconds [, $interval_floating_seconds ] )>
Start up an interval timer: after a certain time, a signal is arrives,
and more may keep arriving at certain intervals. To disable a timer,
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