How to do substitution within substituion in Bash

Question

Example:

X=TEST
TEST_VAR=123

eval echo ${${X}_VAR}

This gives the error:

${${X}_VAR}: bad substitution

How can I achieve what I'm looking to do?

Answer 1

Or avoid eval altogether with a nameref (created with declare -n), e.g.

#!/bin/bash

X=TEST
TEST_VAR=123

declare -n foo=${X}_VAR

echo $foo

Example Use/Output

$ ./myscript
123

Answer 2

Just escape the dollar sign:

eval echo \$${X}_VAR