#!/bin/bash

aantalTeControleren=5

if [ $1 == "-b" ]; then
        if [[ ! $2 =~ [0-9]+ ]]; then
                echo "gebruik: $0 [-b bytes] file1 file2 [file3 [...]]"
                exit -1
        fi
        aantalTeControleren=$2
        shift 2
fi
if [ $# -lt 2 ]; then
        echo "gebruik: $0 [-b bytes] file1 file2 [file3 [...]]"
        exit -1
fi

for file in "$@"; do
        if [ ! -f $file ]; then
                echo "$file is geen file"
                exit -1
        fi
done


byte=""

# args: bestand, positie
getbyte() {
        byte=`dd if=$1 bs=1 count=1 skip=$2 2> /dev/null`
}

for (( p=0; p<$aantalTeControleren; p++)); do
        getbyte $1 $p
        eerste=$byte

        #echo eerste : $eerste

        #true = 0, false = 1

        isZelfde=0

        for file in "$@"; do
                getbyte $file $p

                #echo byte: $byte

                if [ $byte != $eerste ]; then
                        isZelfde=1
                        break
                fi

                #echo isZelde: $isZelfde 1=F
        done
        if [ $isZelfde == 0 ]; then
                echo $p: $byte
        fi

        #echo
done