linux - Replace hyphens with underscores in bash script

Trying to write a bash script and in one part of it I need to take whatever parameter was passed to it and replace the hyphens with underscores if they exist.

Tried to do the following

#!/usr/bin/env bash
string=$1
string=${string//-/_}
echo $string;

It's telling me that this line string=${string//-/_} fails due to "Bad substitution" but it looks like it should do it? Am I missing something?

Answer

There is nothing wrong with your script, and it should work in modern versions of Bash.

But just in case you can simplify that to :

#!/bin/bash

echo "$1" | tr '-' '_'

This is in case that parameter substitution does not work ( which seems to be your case ).

Regards!