#!/usr/pkg/bin/bash
function die {
 echo $@ >&2
 exit 1
}
function find_delta {
 shift # drop username
 delta=`expr $@` # calculate the delta in days
}
[ "$EUID" == "0" ] || die "Must be root to do this!"
[ "$1" -a "$2" ] || die "Must specify username to expire and expiration date"
now=`date +%s` # seconds since the epoch
today=`expr $now / 86400` # divide by seconds in a day
expiration=`awk -F : "\\$1 ~ \"$1\" {print \\$8}" /etc/shadow`
yesterday=$((today - 1)) # prevent login by setting expiry to yesterday
find_delta
echo new delta: $((yesterday + delta))