TF conditional provisioner

main.tf

variable "switch" {
  default = true
}

locals {
  prov_cmd = var.switch ? "echo 'YES'" : "echo 'NO'"
}

resource "null_resource" "test" {
  provisioner "local-exec" {
    command = local.prov_cmd
  }
}

no.sh

$ TF_VAR_switch=false terraform apply --auto-approve

Terraform used the selected providers to generate the following execution plan. Resource actions are indicated with the following symbols:
  + create

Terraform will perform the following actions:

  # null_resource.test will be created
  + resource "null_resource" "test" {
      + id = (known after apply)
    }

Plan: 1 to add, 0 to change, 0 to destroy.
null_resource.test: Creating...
null_resource.test: Provisioning with 'local-exec'...
null_resource.test (local-exec): Executing: ["/bin/sh" "-c" "echo 'NO'"]
null_resource.test (local-exec): NO
null_resource.test: Creation complete after 0s [id=8525017274064731153]

yes.sh

$ terraform apply --auto-approve

Terraform used the selected providers to generate the following execution plan. Resource actions are indicated with the following symbols:
  + create

Terraform will perform the following actions:

  # null_resource.test will be created
  + resource "null_resource" "test" {
      + id = (known after apply)
    }

Plan: 1 to add, 0 to change, 0 to destroy.
null_resource.test: Creating...
null_resource.test: Provisioning with 'local-exec'...
null_resource.test (local-exec): Executing: ["/bin/sh" "-c" "echo 'YES'"]
null_resource.test (local-exec): YES
null_resource.test: Creation complete after 0s [id=1591540309584719601]