Swap two files in a naming scheme of "xx-yy" where xx is a number and yy a string

swap

#!/bin/bash

set -eu

a=$1
b=$2

mv "$a" "$a.backup"
mv "$b" "$b.backup"

numberA=$(echo $a | cut -d- -f1)
afterA=$(printf "%s" "${a#*-}")
numberB=$(echo $b | cut -d- -f1)
afterB=$(printf "%s" "${b#*-}")

mv "$a.backup" "$numberB-$afterA"
mv "$b.backup" "$numberA-$afterB"