Referencing the Terraform command used


I would like to write a custom script that will be called using the local exec resource. If I run a terraform apply it will run the script with a set of parameters and if I run terraform destroy it will run with different parameters to delete. Is it possible to reference a variable that might know which command I am using?

Hi @david10,

terraform destroy is largely just a shorthand for terraform apply -destroy, which creates a plan in the special “destroy mode” and then applies that plan. The destroy planning mode forces Terraform to propose a “delete” action for anything that is currently tracked, ignoring whether it exists in the configuration.

The specific command being run is not something you can program with directly – Terraform CLI and the Terraform language are two distinct parts of the system that work largely independently – but for provisioners in particular you can specify whether each one should run either during a create action or during a destroy action using the when argument in your provisioner block:

  provisioner "local-exec" {
    # with no "when" argument, the provisioner is
    # for create-time.

  provisioner "local-exec" {
    # Setting "when" to "destroy" makes this instead
    # run when the object is being destroyed.
    when = destroy

There’s more information on this in Destroy-time Provisioners.

Please note that provisioners are a last resort and so there might be another better way to solve your underlying problem, without using provisioner blocks at all.