Using Terraform list of strings as an array in Shell template script

Question

So, basically I want to be able to iterate in my Bash script template file over the array, that I initialise in Terraform.

The template file is used as user_data for AWS instance:

resource "aws_instance" "my_instance" {
    
...

  user_data = templatefile("${path.module}/${var.template_file}",
    {
      my_array    = ["item1", "item2"]
  })

...

}

Here is my template file:

#!/usr/bin/env bash

printf "%s\n" "$${my_array[@]}" > my_array.txt

And when I execute cat my_array.txt it gives me no content.

I can know that workaround might be to define my_array as a string and after that parse it in Bash to an array, but I curios whether is it possible to avoid that and get kinda native variable interpolation here.

Any help or hints will be appreciated. Thanks!

Serhii Povísenko · Accepted Answer · 2020-06-30 13:39:26Z

5

Hmmmm. Seems like it's impossible yet. The shortest solution would be to pass the array as a string in the following way:

my_array    = join(",",["item1", "item2"])

and use that source to init required array:

IFS=',' read -r -a bash_array <<< "${my_array}"
printf "%s\n" "$${my_array[@]}" > my_array.txt

now your array's items should be listed in the file.

edited Jun 30, 2020 at 13:39

answered Jun 29, 2020 at 16:35

Serhii Povísenko

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