#!/bin/bash

#This program is free software; you can redistribute it and/or modify
#it under the terms of the GNU General Public License version 2 as published by
#the Free Software Foundation.

#This program is distributed in the hope that it will be useful,
#but WITHOUT ANY WARRANTY; without even the implied warranty of
#MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#GNU General Public License for more details:
#http://www.gnu.org/copyleft/gpl.html

if [ $# != 1 ] || echo $1 | grep '[^0-9]' &> /dev/null
    then
    echo "Error. Arguments must consist of a single positive integer." 3>&1 1>&2 2>&3
    exit 1
fi

NUMCHARS=$1
NEWPASS=""
OK=false
while ! $OK
  do
  if [ ${#NEWPASS} -ge $NUMCHARS ]
      then
      OK=true
      echo $NEWPASS | cut -c -$NUMCHARS
      unset NEWPASS
  else
      NEWPASS=$NEWPASS`dd bs=$NUMCHARS count=1 if=/dev/urandom 2> /dev/null | perl -e 'my $input = <>; my @letters = split(//, $input); for my $go (@letters) {if ($go =~ /[a-zA-Z0-9]/) { print "$go" }};'`
  fi
done