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(linux_command_line)-> Mico time measurement with perl submited by Russell Sun 20 Feb 05
Edited Thu 12 Jan 06
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Now if you only need to the seccond accuracy you can use this:
$start=time;
##  do something you want to measure.
$end=time;
$elapsed=$end-$start;
print "$elapsed seconds elapsed\n";
But, if you need better accuracy, you can use this:

My friend found this, it lets me mesure an event in fractions of a second:
    require 'sys/syscall.ph';
    $TIMEVAL_T = "LL";
    $done = $start = pack($TIMEVAL_T, ());
 
    syscall( &SYS_gettimeofday, $start, 0) != -1  or die "gettimeofday: $!";
### do something here you want to measure
    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] );

I don't know how accurate it is. I was just looking for fractions of a second 0.1 .. 0.9 .. but it returns 4 digiits , but that comes from the sprintf command, I don't know if that means it's only that accurate. (it might not even be that good )

Now this didn't work the first time for me (rhat 9.0) . perl died with a missing module,not syscal but rather asm:unistd.ph , my friend had found this file on his newer configuration, and on a lark I put his copy in what I figured should be the correct location /usr/lib/perl5/5.8.0/i386-linux-thread-multi/asm (I had to create 'asm') and to my suprise, it worked.

I have saved that copy of unistd.ph here


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