• Description:
  Terraform can run local shell commands during apply using a null_resource together with the local-exec provisioner. This is useful for small automation tasks (generating files, calling scripts, bootstrapping local tools) that you want to trigger as part of your Terraform workflow. The example below writes a message into script_output.txt on your machine.

•  Step 1 — Create project folder
   Open a terminal and run:

  mkdir terraform-script
  cd terraform-script
      

•  Step 2 — Create main.tf
   Create main.tf (edit with your editor) and paste:

  terraform {
    required_providers {
      null = {
        source  = "hashicorp/null"
        version = "3.2.2"
      }
    }
  }
  
  provider "null" {}
  
  resource "null_resource" "script" {
    provisioner "local-exec" {
      command = "echo 'Terraform executed this script!' > script_output.txt"
    }
  }
      

   Explanation:
   null_resource is a placeholder resource you can attach provisioners to.
   local-exec runs the given command on the machine that runs terraform apply.
•  Step 3 — Initialize Terraform
   Download provider plugins and initialize the working directory:

  terraform init
      

   Expected console output snippet:

  Terraform has been successfully initialized!
      

•  Step 4 — Validate configuration
   Check HCL syntax and config validity:

  terraform validate
      

   Expected:

  Success! The configuration is valid.
      

•  Step 5 — Preview
   You can preview what Terraform will do:

  terraform plan
      

   You’ll see that one resource (null_resource.script) will be created.
•  Step 6 — Apply to run the script
   Execute the plan (this runs the shell command):

  terraform apply
      

   When prompted, type yes and press Enter.
   What happens: Terraform creates the null_resource and runs the local-exec command, which writes to script_output.txt.
  
   Sample apply output snippet:

  null_resource.script: Creating...
  null_resource.script: Provisioning with 'local-exec'...
  null_resource.script: Creation complete after 0s [id=...]
      

•  Step 7 — Verify the output file
   Check the file created by the command:

  cat script_output.txt
      

   Expected file content:

  Terraform executed this script!
      

•  Step 8 — Cleanup (optional)
   Remove the resource and (optionally) the file via Terraform:

  terraform destroy
      

   Type yes when prompted. If script_output.txt remains (depending on how your command behaves), remove it manually:

  rm -f script_output.txt
      

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