Shell script to optimize a given pdf file on Linux

optpdf.sh

#!/bin/bash
# 
# 1. Install ghostscript
#   sudo apt-get update
#   sudo apt-get install ghostscript
# 2. Use this shell script to optimize the given pdf
#   sh optpdf.sh <filename>.pdf

file="$1"
filebase="$(basename "$file" .pdf)"
optfile="./${filebase}_opt.pdf"
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.5 -dNOPAUSE -dQUIET -dBATCH -dPrinted=false -sOutputFile="${optfile}" "${file}"

if [ $? -eq '0' ]; then
    optsize=$(stat -c "%s" "${optfile}")
    orgsize=$(stat -c "%s" "${file}")
    if [ "${optsize}" -eq 0 ]; then
        echo "No output!  Keeping original file."
        rm -f "${optfile}"
        exit;
    fi
    if [ ${optsize} -ge ${orgsize} ]; then
        echo "Didn't make it smaller! Keeping original file."
        rm -f "${optfile}"
        exit;
    fi
    bytesSaved=$(expr $orgsize - $optsize)
    percent=$(expr $optsize '*' 100 / $orgsize)
    echo Saving $bytesSaved bytes \(now ${percent}% of old\)
    rm "${file}"
    mv "${optfile}" "${file}"
fi