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How can I measure time under a second?

by faq_monk (Initiate)
on Oct 08, 1999 at 00:29 UTC ( #722=perlfaq nodetype: print w/replies, xml ) Need Help??

Current Perl documentation can be found at perldoc.perl.org.

Here is our local, out-dated (pre-5.6) version:

In general, you may not be able to. The Time::HiRes module (available from CPAN) provides this functionality for some systems.

In general, you may not be able to. But if your system supports both the syscall() function in Perl as well as a system call like gettimeofday(2), then you may be able to do something like this:

    require 'sys/syscall.ph';

    $TIMEVAL_T = "LL";

    $done = $start = pack($TIMEVAL_T, ());

    syscall( &SYS_gettimeofday, $start, 0)) != -1
               or die "gettimeofday: $!";

       ##########################
       # DO YOUR OPERATION HERE #
       ##########################

    syscall( &SYS_gettimeofday, $done, 0) != -1
           or die "gettimeofday: $!";

    @start = unpack($TIMEVAL_T, $start);
    @done  = unpack($TIMEVAL_T, $done);

    # fix microseconds
    for ($done[1], $start[1]) { $_ /= 1_000_000 }

    $delta_time = sprintf "%.4f", ($done[0]  + $done[1]  )
                                            -
                                 ($start[0] + $start[1] );

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[stevieb]: interestingly enough, someone else got my Devel::Examine:: Subs distribution for their PRC, and I applaud the change. This dist is extremely complicated and mostly obfu, but the person doing it understood PPI enough to change...
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