Okay well I pulled the calculation stuff from the procps (top) source code, and knowing absolutely no C at all
I'm not to certain that I interpreted it right, the code seems to work though, but feels like a cheap hack especially
with sleep(). So any suggestions on how to improve this would be greatly appreciated. 
#!/usr/bin/perl -w
use strict;

sub cpu_stat {
    my($cpu_user, $cpu_nice, $cpu_total, $cpu_idle);
    open STAT_FILE, "/proc/stat" or warn "Couldn't open /proc/stat: $!
+\n";
    while (<STAT_FILE>) {
        ($cpu_user, $cpu_nice, $cpu_total, $cpu_idle) = ($1,$2,$3,$4) 
+if /^cpu\s+(\d+)\ (\d+) (\d+) (\d+)/;
        last;
    }
    close STAT_FILE;
    return($cpu_user, $cpu_nice, $cpu_total, $cpu_idle);
}

my($cpu_user_old, $cpu_nice_old, $cpu_total_old, $cpu_idle_old) = cpu_
+stat();
sleep(1);  
my($cpu_user, $cpu_nice, $cpu_total, $cpu_idle) = cpu_stat();

my $ticks_past = ($cpu_user + $cpu_nice + $cpu_total + $cpu_idle) - ($
+cpu_user_old + $cpu_nice_old + $cpu_total_old + $cpu_idle_old);
my $scale = 100.0 / $ticks_past;

$cpu_user  = sprintf "%.0f", ($cpu_user - $cpu_user_old) * $scale;
$cpu_nice  = sprintf "%.0f", ($cpu_nice - $cpu_nice_old) * $scale;
$cpu_total = sprintf "%.0f", ($cpu_total - $cpu_total_old) * $scale;
$cpu_idle  = sprintf "%.0f", ($cpu_idle - $cpu_idle_old) * $scale;

print  "user: $cpu_user%, nice: $cpu_nice%, total: $cpu_total%, idle: 
+$cpu_idle%\n";

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Edit Masem 2001-11-04 - CODE tags

In reply to suggestions for improvement by rendler

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