#!/bin/bash

# input eg: /dev/sda1 or /dev/sda
# output: /dev/disk/by-id/model+serial, or if no link exists, the same as input

short_dev=$1 # i.e.

# devices are identified by model+serial num,
# and wwn. model+serial gives me more info, so use that.
shopt -s extglob
for id in /dev/disk/by-id/!(wwn*); do
    [[ -e $id ]] || break # if we matched nothing
    if [[ $(readlink -f $id) == "$short_dev" ]]; then
        printf '%s\n' "$id"
        exit
    fi
done
# a vm may not have a by-id link.
printf '%s\n' "$short_dev"