watch

#!/usr/bin/perl

# $Id: watch,v 1.1 2005/11/12 03:36:09 jonathan Exp $

use strict;
use Getopt::Std;
use Statistics::Descriptive;

# Written by Jonathan Ledlie
# jonathan@eecs.harvard.edu

##################################################

my $usage = "Usage: tail -f file | watch -f frequency -k column -w [keyword column] > result\n";

my %para = ();
getopts('f:k:w:', \%para);

my $frequency = 0;
if (defined($para{'f'})) {
    $frequency = $para{'f'};
} else {
    die ("Frequency required");
}

my @items = ();
my $count = 0;

while (my $line = <>) {

    if (defined ($para{'w'})) {
	if ($line =~ /$para{'w'}\s(\d+\.?\d*)/) {
	    my $item = $1;
	    $items[$#items+1] = $item;
	    #print "$line $item\n";
	} else {
	    #print "no match $line\n";
	}
    } elsif (defined ($para{'k'})) {
	my (@i) = split (/\s/,$line);
	if (defined ($i[$para{'k'}-1])) {
	    $items[$#items+1] = $i[$para{'k'}-1];
	}
    }

    $count++;

    if ($count >= $frequency) {
	my $stat = Statistics::Descriptive::Full->new();
	$stat->add_data(@items);
	my $out = printf ("%.3f %.3f %.3f",
		$stat->mean(), $stat->standard_deviation(),
		$stat->max());
	print "$out\n";
	$count = 0;
	@items = ();
    }

}