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About bash : Bash—variable-variables-duplicate

Question Detail

I have the variable $foo="something" and would like to use:

bar="foo"; echo $($bar)

to get “something” echoed.

Question Answer

In bash, you can use ${!variable} to use variable variables.

foo="something"
bar="foo"
echo "${!bar}"

# something

eval echo \"\$$bar\" would do it.

The accepted answer is great. However, @Edison asked how to do the same for arrays. The trick is that you want your variable holding the “[@]”, so that the array is expanded with the “!”. Check out this function to dump variables:

$ function dump_variables() {
    for var in "[email protected]"; do
        echo "$var=${!var}"
    done
}
$ STRING="Hello World"
$ ARRAY=("ab" "cd")
$ dump_variables STRING ARRAY ARRAY[@]

This outputs:

STRING=Hello World
ARRAY=ab
ARRAY[@]=ab cd

When given as just ARRAY, the first element is shown as that’s what’s expanded by the !. By giving the ARRAY[@] format, you get the array and all its values expanded.

To make it more clear how to do it with arrays:

arr=( 'a' 'b' 'c' )
# construct a var assigning the string representation 
# of the variable (array) as its value:
var=arr[@]         
echo "${!var}"

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