BASH using double variable $ - bad substitution [duplicate]

Question

From my code below, how to make the value of 'zz' become 500 after replacing 'critical_' with x on variable 'yy'

xab123=500

yy="critical_ab123"
zz=${"${yy//critical_/x}"}

echo $zz

instead the result, there is an error:

line 8: ${"${yy//critical_/x}"}: bad substitution

thanks adi

Answer 1

May be like this:

xab123=500
yy="critical_ab123"
zz="${yy//critical_/x}"
echo ${!zz}
500