Bash array expansion using variable indirection expansion

Question

I am trying to expand all values in an array I get to through indirect expansion:

> my_array=(coconut banana)
> echo "${my_array[@]}" 
coconut banana
> my_array_name=my_array
> echo ${!my_array_name}
coconut
> echo "${!my_array_name[@]}"
0

I am erroneously using "List of array keys" in the last command because I don't know how to type the right command?

I would like to get:

coconut banana

possibly without resorting to some ugly eval hack.. Example of one suck hack:

> echo \${$my_array_name[@]}
${my_array[@]}
> eval echo \${$my_array_name[@]}
coconut banana

Note

my_array may contain values with spaces!

EDIT

In the function I am writing, my_array_name is set through "$1" so I cannot use that literally.

Similar to: https://unix.stackexchange.com/questions/20171/indirect-return-of-all-elements-in-an-array but I need to avoid using eval to protect from the nasty effects the script would have if the environment was "hacked" just at the right time...

Nahuel Fouilleul · Accepted Answer · 2012-10-02 14:01:58Z

4

This should work

my_array_name='my_array[@]'
echo "${!my_array_name}"

After comment : you have to create a string with the name of the array and '[@]', another example

my_array_name="$1"'[@]'
echo "${!my_array_name}"

After comment : test in a function

display_elem() {
  local arrname
  arrname="$1[@]"
  printf "%s\n" "${!arrname}"
}

display_elem my_array

edited Oct 2, 2012 at 14:01

answered Oct 2, 2012 at 13:33

Nahuel Fouilleul

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4 Comments

Nahuel Fouilleul Over a year ago

@Robottinosino the my_array comes from your example, you can replace by whatever else

Robottinosino Over a year ago

SMART and completely unexpected that bash would fall for that trick! Better than eval, I say!

p_strand Over a year ago

I second that! Great job, Nahuel!

user2350426 Over a year ago

Maybe this example will work for you: stackoverflow.com/a/30156747/2350426 It indeed does not use the ARRAY name in the function.

p_strand · Accepted Answer · 2012-10-02 13:32:30Z

1

The problem is my_array_name=my_array. You need to retrieve all values of my_array. Try this instead:

 my_array_name=${my_array[@]}
 echo "${my_array_name[@]}"

answered Oct 2, 2012 at 13:32

p_strand

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1 Comment

Robottinosino Over a year ago

I don't know that the name I should use is my_array when executing the code. That itself comes from $1, apologies I did not make that clear. Upvoting anyway, even if this is not a solution for me.

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