#!/bin/bash

IFS=$'\n'
if [ -z "$1" ]
then echo rename files in current folder replacing arg1 with arg2.
     exit
fi

for file in $( ls | grep "$1" )
do echo "$file" '->' "$( echo $file | sed s/"$1"/"$2"/g )"
done
echo 'sure?'
read i
for file in $( ls | grep "$1" )
do mv -iv -- "$file" "$( echo $file | sed s/"$1"/"$2"/g )"
done