Fixed Script

#!/bin/sh

version=4.05
vanillamd5="0e63d4223b01d9aba596259dc155a174"
modmd5="51a29ae081ef69e6d9856d22e42777c5"

infile="$1"
outfile="20XX ${version}.iso"
delta="20XX ${version} xdelta patch.xdelta"

# not doing checking, so make sure you have these binaries installed somewhere
xdelta=xdelta3
md5sum=md5sum


checkhash () {
    printf "    This will take a few moments...."
    filehash=$(${md5sum} -b "$1" |cut -d' ' -f1)
    if [ "$filehash" != "$2" ]; then
        printf "FAIL\n"
        printf "Hashes don't match. Continue? (y/n) "
        read cont;
        if [ "$cont" != "y" ]; then
            exit
        fi
    fi
    printf "SUCCESS\n"
}

build () {
    if [ -f "$outfile" ]; then
        printf "File $outfile already exists. Overwrite? (y/n) "
        read overwrite
        if [ "$overwrite" != "y" ]; then
            exit
        fi
    fi
    printf "Constructing 20XX ${version}.\n"
    printf "    Please stand by...."

    $xdelta -f -d -s "$infile" "$delta" "$outfile" 2>/dev/null && printf "SUCCESS\n" || printf "FAIL\n"
}

if [ "$infile" = "" ]; then
    printf "usage: 20XX-${version}-convert.sh FILE\n"
    exit
fi
printf "Verifying that the given file is a vanilla v1.02 copy of SSBM.\n"
checkhash "$infile" "$vanillamd5"
printf "The ISO has been verified!\n\n"

build
test $? -eq 0 || exit
printf "Conversion complete!\n\n"

printf "Would you like to check the hash of your new 20XX copy? (y/n): "
read check;
if [ "$check" = "y" ]; then
    checkhash "$outfile" "$modmd5"
fi