How to understand variable and variable's value in bash

Question

#!/bin/bash

list="one two three"
one=1
two=2 
three=3
for k in $list
do 
    echo $k
done

For the code above, output is:
one
two
three

But I always think it should output:
1
2
3
It's confusing. How to understand this?

Answer 1

The expansion $k just gives you the name of the variable as a string. If you want the value of the variable, you must use the parameter expansion syntax ${!k}. This is documented here.

#!/bin/bash

list="one two three"
one=1
two=2 
three=3
for k in $list
do 
        echo "${!k}"
done

Output

1
2
3