how to use data external scripts in terraform

main.js

console.log(
  JSON.stringify({
    result: "hello world",
    json: JSON.stringify({
      hello: "world",
    }),
  }),
);

main.tf

data "external" "hello_world" {
  program = ["node", "main.js"]
}

output "result" {
    value = data.external.hello_world.result["result"]
}

output "json" {
    value = jsondecode(data.external.hello_world.result["json"])
}

output.txt

$ tofu apply
data.external.hello_world: Reading...
data.external.hello_world: Read complete after 0s [id=-]

No changes. Your infrastructure matches the configuration.

OpenTofu has compared your real infrastructure against your configuration and found no differences, so no changes are needed.

Apply complete! Resources: 0 added, 0 changed, 0 destroyed.

Outputs:

json = {
  "hello" = "world"
}
result = "hello world"