Script for validating a Linux password. Method SHA-512 (Type ID 6 - first shadow col) expected.

valpwd.sh

#!/bin/bash

L1=`grep $1 /etc/shadow|cut -d ":" -f 2`
if [ $L1 ]; then
	SALT=`echo $L1|cut -d "$" -f 3`
	L2=`mkpasswd --salt=$SALT --method=sha-512 $2`
	if [ "$L1" == "$L2" ]; then
		exit 0
	else
		exit 1
	fi
else
	exit 2
fi