Terraform to detect OS and run local commands appropriately based on OS

windows_or_linux_external.tf

terraform {
  required_providers {
    external = {
      source = "hashicorp/external"
      version = "~> 2.3.3"
    }
  }
}

locals {
  # Windows paths will start with a drive letter (C:/), Linux paths will start with "/"
  os_family = startswith(abspath(path.module), "/") ? "linux" : "windows"
  username = local.os_family == "linux" ? data.external.user_linux[0].result.user : data.external.user_windows[0].result.user
}

data "external" "user_linux" {
  count = local.os_family == "linux" ? 1 : 0
  program = [
    "sh",
    "-c",
    <<-EOF
      echo "{\"user\":\"$USER\"}"
    EOF
  ]
}

data "external" "user_windows" {
  count = local.os_family == "windows" ? 1 : 0
  program = [
    "powershell",
    "-c",
    <<-EOF
      Write-Output "{`"user`":`"$env:USERNAME`"}"
    EOF
  ]
}

output "os_family" {
  value = local.os_family
}

output "username" {
  value = local.username
}