# S.Chudley (www.chudley.me) : Script to fill up a drive, leaving a given number of bytes free
my $leave = $ARGV[0];
if ($leave eq "")
{
    print "Specify amount of space to leave (as bytes).\n";
    exit(1);
}

print "Filling buffer...\n";
$block_size = 1024 * 1024;
my $data_buffer = "";
for (my $i=0;$i!=$block_size;$i++) { $data_buffer .= " "; }

if ($leave >=  2000 * $block_size)
{
    print "Can't leave more than ".(2000 * $block_size / 1024)." kb free!\n";
    exit(1);
}

my $free_space = &get_free();
print "Drive has ".($free_space/1024)." kb free...\n";

if ($free_space >= 2097152000)
{
    print "Making a big file (2048 MB) called file.big...";
    &make_file("file.big", 2000 * $block_size);
    print " Done.\n";
}

$free_space = &get_free();
print "Drive now has ".($free_space/1024)." kb free...\n";

if ($free_space <= $leave)
{
    print "Arn't $leave bytes free anyway!\n";
    exit(1);
}

my $multi = int($free_space / (2000 * $block_size));
print "Spinning out $multi copies of this file (total ".(2000 * 1024 * $multi)." kb)...\n";

for (my $i=0;$i!=$multi;$i++)
{
    `copy file.big file.$i.big`;
    if ($? != 0)
    {
        print "Oops? File write failed?\n";
        exit(1);
    }
    my $pc = ($i / $multi) * 100;
    $pc = substr($pc, 0, 5);
    print "  Created ".($i + 1)." files [".$pc." %]\n";
}

$free_space = &get_free();
print "Drive now has ".($free_space/1024)." kb free...\n";

my $remains = $free_space - $leave;
print "Consuming up remaining ".($remains / 1024)." kbs... ";
&make_file("remaining.big", $remains);
print "Done\n";

$free_space = &get_free();
print "Drive now has ".($free_space/1024)." kb free...\n";
if ($free_space ne $leave)
{
    print "Erm? Something went wrong\n";
    exit(1);
}

exit(0);

sub make_file
{
   my ($name, $size) = @_;
   open(OUT,">$name") or die "Can't create file '$name'!\n";

   my $done = 0;
   my $blocks = int($size / $block_size);
   while ($done < ($blocks * $block_size)) { print OUT $data_buffer or die "Oops? Write failed in make_file()?"; $done += $block_size; }
   for (my $i=$done;$i!=$size;$i++) { print OUT " " or die "Oops? Write failed in make_file()?"; }
   close(OUT);
}


sub get_free
{
    my @free_txt = `dir /-C`;
    my $free = 0;
    foreach (@free_txt) { if ($_ =~ m/\s+([0-9,]+)\s+bytes\s+free/) { $free = $1; $free =~ s/,//g; } }
    return $free;
}