Exclude a given string from the given list in terraform

Question

I would like to exclude a given string from the list of string in terraform

example: I have following data source as a variable

region_list = data.oci_identity_region_subscriptions.region_subscriptions.region_subscriptions.*.region_name

Now, I would like to exclude a region from it. Region "us-ashburn-1"

exclude ("us-ashburn-1") form region_list. Any thoughts on how to do that?

Answer 1

Easiest way to get rid of a set of values in another set is to use setsubtract():

locals {
  regions = ["us-west-2", "us-west-1", "us-east-2", "us-ashburn-1"]
}

output "excluded" {
  value = setsubtract(local.regions, ["us-ashburn-1"])
}

outputs:

excluded = [
  "us-east-2",
  "us-west-1",
  "us-west-2",
]

if you want to keep the order or duplicates in a list, then using a for expression as already mentioned in another answer is preferred.

Answer 2

You can do this by using for loop and if condition in terraform.

Example terraform configuration,

variable "regions" {
  type    = list
  default = ["us-west-2", "us-west-1", "us-east-2", "us-east-1"]
}

output "excluded" {
  value = [for region in var.regions : region if region != "us-east-1"]
}

The above config will output all the region except us-east-1.

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

Outputs:

excluded = [
  "us-west-2",
  "us-west-1",
  "us-east-2",
]