Bash - How to get the value of a var with name from another var

Question

Sorry if it's a dumb q, but I couldn't find the answer! if I have var 1:

STR="hello"

var 2:

letter="T"

I want:

echo ${S${letter}R}

to get "hello", but instead I get bad substitution, what am I doing wrong? Thank you

Answer 1

STR="hello"
letter="T"
x="S${letter}R"   # concat string in new variable
echo "${!x}"

Output:

hello

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See: What is indirect expansion? What does ${!var*} mean?