FAQ 8.17 How can I measure time under a second?

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8.17: How can I measure time under a second?

In general, you may not be able to. The Time::HiRes module (available
from CPAN, and starting from Perl 5.8 part of the standard distribution)
provides this functionality for some systems.

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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