use Fcntl;

#----------------------------(  promptUser  )-----------------------------#
#                                                                         #
#  FUNCTION:	promptUser                                                #
#                                                                         #
#  PURPOSE:	Prompt the user for some type of input, and return the    #
#		input back to the calling program.                        #
#                                                                         #
#  ARGS:	$promptString - what you want to prompt the user with     #
#		$defaultValue - (optional) a default value for the prompt #
#                                                                         #
#-------------------------------------------------------------------------#

sub promptUser {

   #-------------------------------------------------------------------#
   #  two possible input arguments - $promptString, and $defaultValue  #
   #  make the input arguments local variables.                        #
   #-------------------------------------------------------------------#

   local($promptString,$defaultValue) = @_;

   #-------------------------------------------------------------------#
   #  if there is a default value, use the first print statement; if   #
   #  no default is provided, print the second string.                 #
   #-------------------------------------------------------------------#

   if ($defaultValue) {
      print $promptString, "[", $defaultValue, "]: ";
   } else {
      print $promptString, ": ";
   }

   $| = 1;               # force a flush after our print
   $_ = <STDIN>;         # get the input from STDIN (presumably the keyboard)


   #------------------------------------------------------------------#
   # remove the newline character from the end of the input the user  #
   # gave us.                                                         #
   #------------------------------------------------------------------#

   chomp;

   #-----------------------------------------------------------------#
   #  if we had a $default value, and the user gave us input, then   #
   #  return the input; if we had a default, and they gave us no     #
   #  no input, return the $defaultValue.                            #
   #                                                                 # 
   #  if we did not have a default value, then just return whatever  #
   #  the user gave us.  if they just hit the <enter> key,           #
   #  the calling routine will have to deal with that.               #
   #-----------------------------------------------------------------#

   if (defined($defaultValue) && "$defaultValue") {
      return $_ ? $_ : $defaultValue;    # return $_ if it has a value
   } else {
      return $_;
   }
}

#$path = "x.txt";
$path = promptUser("File to shred - ");

$n = 2000000;
$abc = "qwertyuiopadsfghjklzxcvbnm";
sysopen(FH, $path, O_RDWR) || die $!;

$ok = "";
while (1) {
$ok = promptUser("Shall I shred $path? ", "no");
	exit if $ok eq "no" || $ok eq "n" || $ok eq "N";
	last if ($ok eq "y" || $ok eq "Y" || $ok eq "yes");
}

($x,$x,$x,$x,$x,$x,$x,$x) = stat(FH);
print "$x bytes\n";
$n = $x;
for ($i=0; $i<20; $i++) {
	$x = "";

	$j = 0;
	for ($j = 0 ; $j <$n; $j++) {


		$x = substr($abc, rand(length($abc)), 1);
		#$x |= 0xffff if rand(10) > 5;
		sysseek(FH,$j,0) || die "$!";
		syswrite(FH, $x, 1) || die "$!" ;
	}
}