Implementing a 'for loop' within user_data provisioner file - amazon-web-services

Question

I am currently using a template_file to provision user_data into an aws_launch_configuration, like so:
resource "aws_launch_configuration" "launch_config" {
...
user_data = "${data.template_file.init.rendered}"
}
data "template_file" "init" {
template = "${file("router-init.sh.tpl")}"
vars {
hub_ip_addresses = "${join(",", aws_instance.gridHub.*.private_ip)}"
}
}
I am feeding in a variable (i.e. hub_ip_addresses) into the router-init.sh.tpl file, and in this file I am making use of the argument like so:
`#!/bin/sh
...
IFS=',' read -r -a array <<< "$hub_ip_addresses"
for element in "${array[#]}"
do
#do stuff with $element
done
Basically, I am splitting the string based on a delimiter, and then looping through each ip address in the array.
This bash script works fine when I run it on my local machine -- however, when terraform executes it, it throws a error:
* data.template_file.init: data.template_file.init: failed to render : parse error at 13:25: expected expression but found invalid sequence "#"
I'm supposing the '#' symbol is causing an issue. Is there a reason why this is so? Do I need to escape it with a '\' ?
EDIT: Not sure if related to this issue, but in the preceeding line in the bash script, IFS=',' read -r -a array <<< "$hub_ip_addresses", the <<< seems to be causing everything else that follows to look as if they are inside a comment (i.e. greyed out as if it was within a quotation mark ').)

Answer 1

You need to escape the $ characters in your template by doubling them up or Terraform will attempt to interpolate them as the input variables to the template.
The template docs cover this briefly although the example given is for inline templates rather than for all templates, including those that are loaded with the file() function.
So something like:
#!/bin/sh
...
IFS=',' read -r -a array <<< "$hub_ip_addresses"
for element in "$${array[#]}"
do
#do stuff with $$element
done