open(PS,"ps|");
while (my $thisLine = <PS>){
 #do something
}
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Maybe that is what you mean. If not, and your machine actually does have a /proc/PID/* directory, then this does not seem like a very portable manner of doing it. Perhaps you should rethink using ps, as it should be very portable.

If you really want to use the 'pure perl' method, then you will not reinvent the wheel. Look here at Proc::ProcessTable from... you guessed it CPAN. It will do everything you need.

Good luck.

Well.. actually this is for the Linux half of a Linux/Solaris library. I could use ps, but from years of using ps I tend not to entirely trust parsing the output.

And there are a couple problems with Proc::ProcessTable... 1) it is mostly C, 2) I can't seem to see a way to call for individual pids in it... maybe I am reading the docs wrong, but it looks like you can only get the whole processtable as a snapshot, basically...

                - Ant
                - Some of my best work - (1 2 3)

From /proc/$PID/stat, you can get the amount of cpu time a process has used in user and system mode (similar to times, but for other processes). If you examine this twice, with a few seconds of delay between them, you get the amount of time the cpu spent on it. You then divide this amount with the delay, and there you are. (Of course, on an smp machine you may or may not want to divide with the number of cpus, depending on what you mean by cpu-percent.)

There must be a faster wat though, as ps u can return the percent-cpu faster. As eXile has recommended, get procps from http://procps.sf.net/.

Update: fix to %CPU in printf per zentara.

A minor nitpick...Invalid conversion in printf: "%C" at ./cpu-usage

But what I really wanted to say, is I often use a similar script I wrote called MeM. It pops up a Tk window in the upper left corner of the screen, and constantly updates and reports memory usage of a pid( or the calling script). Anyways, you could easily modify the code, to report cpu usage. Here is the code, just change it to run your code, and name it accordingly.

package MeM;
use warnings;
use strict;

use vars qw(@ISA @EXPORT_OK);
@ISA = qw(Exporter);

# inherit the import() from Exporter.pm 
@EXPORT_OK = qw();

# list of things to export if asked to 

my $pid =$$;

if (fork() == 0) {
    require Tk;
    my $mw = new MainWindow;
    $mw->overrideredirect(1);
    my $t = $mw->Label(-text => '', -bg => 'black', -fg => 'yellow')->
+pack;
    $0 = 'MeM';
    my $id = Tk::After->new($mw, 1000, 'repeat', [ \&refresh, $pid ]);

    Tk::MainLoop();

    sub refresh {
        my $pid = shift;
        #asmutils version of cat 
        my @size = split "\n", `/home/zentara/perl5lib/cat /proc/$pid/
+status`;
        #my @size = split "\n", `cat /proc/$pid/status`; 

        (my $vmsize) = grep { /VmSize/ } @size;
        my (undef, $size) = split '   ', $vmsize;
        $t->configure(-text => "PID: $pid ->  $size");
        if ($size eq '') { exit }
    }
}

1;
[download]

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I'm not really a human, but I play one on earth. flash japh

Ahh.. that looks like it works.. thanks a lot!

                - Ant
                - Some of my best work - (1 2 3)