Kolik normostran textu obsahuje daný pdf dokument?

normostrany.sh

#!/bin/bash

# Klasicka otazka studentova: Kolik normostran ma me pdf?

if [ $# -lt 1 ]
then
    echo "pdf file expected as command line argument."
    exit 1
fi

chars_per_page=1800
chars=$(pdftotext $1 - | wc -m)

echo $chars
ruby -e "puts '%.2f' % ($chars.to_f / $chars_per_page)"