This is not how to get, in bash, the value of a variable whose name is in another variable:
$ A=1
$ B=A
$ echo ${$B}
bash: ${$B}: bad substitution
This is how:
$ echo ${!B}
1
It however only works in bash. For more portable scripts, eval is needed:
$ eval echo \$$B
1
Thanks to Martin Krafft and Cyril Brulebois.