#!/usr/bin/perl -s

# filetrack {-h | -H} file

$p = 1024;
if ($H) { $h = 1; $p = 1000 }

$| = 1;                 # this forces a flush after every print
$f = $ARGV[0];          # this is the name of the file
$s = ( stat $f )[7];    # this is the size of the file
$t = time;              # this is the time

defined $f || die "filetrack: no file name provided\n";

while ( sleep 1 ) {

  # we're going to print the following information
  printf "\r$f %s bytes at %.2f Kb/s",

    # the size the file is occupying now
    $_ = h( ( stat $f )[7] ),

    # and the rate at which it has been increasing (sort of)
    ( $_ - h($s) ) / $p / ( time - $t );
}

sub h {
  $h || return $_[0];
  my $n = $_[0];
  my $m;
  for ( 'k', 'M', 'G', 'T' ) {
    $n > $p || last;
    $m = $_;
    $n = int( $n / $p );
  }
  return "$n$m";
}