#!/bin/bash

export PATH=/bin:/usr/bin

if [ ! -e /usr/bin/openssl ]; then
	echo $0: requires /usr/bin/openssl, please install openssl tools
	exit 1
fi

if [ "$#" -lt 1 ]; then
	echo $0: Usage: $0 '<input>' '[output]'
	exit 1
fi

if [ ! -r "$1" ]; then
	echo $0: $1 does not exist or is not readable.
	exit 1
fi

outpath=`echo "$1" | sed 's/[.]aes$//'`
if [ "$#" -ge 2 ]; then
	outpath="$2"
fi

if [ -f "$outpath" ]; then
	echo $0: $outpath already exists, delete or rename first.
	exit 1
fi

openssl aes-256-cbc -d -salt -in "$1" -out "$outpath"

echo $0: wrote "$outpath"