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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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[marto]: so I have to work Saturday, which is good and bad. Bad in the sense that I have to be hear early :( Good in that I am here only as support for another client project, so I get to spend the day working on my personal 'ToDo' list, without the kids :P
[Corion]: marto: Ooof - but yes, being there as only second level support or third level support is good and if you have enough things that you can work on, it won't be a wasted (if paid) day
[marto]: I've opted for a day off later on, rather than pay. I only have to do about 45 mins work for the client, but do need to hang around

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