Using variable value as variable name in bash

问题

I've seen this question asked before but I can't seem to get the grasp of it.

I have this variable that I get from user input read column_number

and then I join it with the "col" prefix to form the name of my variable

selected_column="col"$column_number

But when I try to evaluate it to get the result, I keep getting the (standard_in) 1: syntax error

sum=$(round $sum+"echo ${!selected_column}", 2)

full code:

回答1:

column_number=5
selected_column=col$column_number
col5=42
sum=17
echo $(($sum+${!selected_column}))

Output:

59

---

sum=$(round $(($sum+${!selected_column})) 2)

来源：https://stackoverflow.com/questions/33981637/using-variable-value-as-variable-name-in-bash