Terraform template_file issue with a bash script

Question

I am using template_file to pass a list from tfvars to my shell script, I do escape "$" in my tpl.sh script but then my script ends-up ignoring the values of my variables, how to go around this?

In below, the script ignores the values of $${i} and $${device_names[i]} because of the two dollar signs

for i in `seq 0 6`; do
    block_device="/dev/nvme$${i}n1"
        if [ -e  $block_device ]; then
            mapping_device="$${device_names[i]}"

I did attempt with eval and got an error in terraform

for i in `seq 0 6`; do
    block_device="/dev/nvme" eval "${i}n1"
        if [ -e  $block_device ]; then
            mapping_device=eval "${device_names[i]}"

It turns out that the above issue is that I was not calling the template correctly

But now I am trying to call the template in user_data but getting the below error, can someone pls advice?

locals {
  cloud_config_config = <<-END
    #cloud-config
    ${jsonencode({
      write_files = [
        {
          path        = "/usr/tmp/myscript.sh.tpl"
          permissions = "0744"
          owner       = "root:root"
          encoding    = "b64"
          #content     = "${data.template_file.init.*.rendered}"
        },
      ]
    })}
  END
  myvars = ["var1","var2","var3"]
}

# Template_file
data "template_file" "init" {
  template = "${file("${path.module}/script.sh.tpl")}"
  vars = {
    myvariables = join(" ", local.myvars)
  }
}

# cloud-init to copy myscript to the instance "/usr/tmp/myscript.sh.tpl"
# I am not really sure how to move my rendered template into my instance
data "cloudinit_config" "userdata" {
  gzip          = false
  base64_encode = false

  part {
    content_type = "text/cloud-config"
    filename     = "cloud-config.yaml"
    content      = local.cloud_config_config
  }
  depends_on = [ data.template_file.init ]
}


# User Data
user_data = data.cloudinit_config.userdata.rendered

This configuration throws this error and not really sure why

│ Error: Incorrect attribute value type │ │ on main.tf line 31, in data "cloudinit_config" "userdata": │ 31: content = data.template_file.init.*.rendered
│ ├──────────────── │ │ data.template_file.init is object with 5 attributes
│ │ Inappropriate value for attribute "content": string required.