help find possible order of unorder base64 fragment

find-base64-fragment-order.sh

#!/bin/sh
# this script help find possible order of base64 fragment.
#
# like "hello world" is aGVsbG8gd29ybGQ= ,
# it would help find "hello world" from "G8g Vsb d2 9yb GQ= aG"
#
# usage: sh find-base64-fragment-order.sh $known_start $frag1 $frag2 ...
# unknown init base:
#    sh find-base64-fragment-order.sh '' G8g Vsb d2 9yb GQ= aG
# know start with h, which is `a` in base64, so first is `aG`
#    sh find-base64-fragment-order.sh aG G8g Vsb d2 9yb GQ=
#
# just pick the longest match pattern,
# because wrong base64 code # often cause
# mojibake (like not printable text)
#
# need: base64 awk grep


nth() {
    echo $list | awk "{print \$$1}"
}

debase64() {
    echo $1 | base64 -d 2>/dev/null
}

all_match() {
    for next in $list
    do
        debase64 "$base$next"
        echo
    done
}

filter_out() {
    match=$1
    echo $list | sed 's/ /\n/g' | grep --invert-match "^$match\$"
}

base=$1
shift
list="$*"

while [ -n "$list" ]
do
    echo
    echo base: $base
    echo list: $list
    echo possible match:
    all_match "$base" $list | nl
    echo -n 'which one most possible? '
    read n
    match_frag=$(nth $n $list)
    base="$base$match_frag"
    list=$(filter_out $match_frag $list)
done

debase64 $base