Bash script - Need help getting match and substitution working

Question

I am trying to get parameter substitution working in my bash script ... I know I have gotten this all wrong ... I am trying to create a script that will rename a PART of a file.

#!/bin/bash
for i in *.hpp; do  mv -v "$3 ${$3/$1/$2}" ; done

The error I am getting is:

line 2: $3 ${$3/$1/$2}: bad substitution

Answer 1

${$3} will attempt to interpolate ${"CONTENTS OF $3"} into a variable. It is more likely that you want ${3} . It is even more likely that you want ${i} .