Terraform meta argument: count

• https://www.terraform.io/docs/language/meta-arguments/count.html

• count = length(var.subnet_ids)
• count = var.vpc_cidr_block != null ? 1 : 0

count = var.istest == true ? 3 : 0

Terraform does not allow to use count inside module block.

resource "aws_instance" "dev" {
   ami = "ami-082b5a644766e0e6f"
   instance_type = "t2.micro"
   count = var.istest == true ? 3 : 0
}

See also

• Terraform functions, Terraform collection functions: tolist, toset, length, sum, file, join, depends_on, zipmap, replace, lookup, read files, concat, merge, templatefile, for_each, format, element, slice, try, filebase64, upper, filemd5, coalesce, formatlist, flatten
• Terraform, OpenTofu, Terrakube.org, Installation, Terraform AWS, Terraform GCP, Terraform commands, Terraform Cloud, Terraform Enterprise (TFE), HCL, HIL, meta-arguments, providers, modules, resource, provisioners, data sources, backends: remote backends, examples, configuration files, state files, variables, types, Terraform Registry, conditionals: depends_on, functions, Blocks, dynamic blocks, errors, Terragrunt, Terraformer, Terratest, Terraform certifications, Terraform map type, Terraform Associate, Terraform: list type, TF_VAR_, TF_LOG, Terraform provider versioning, Terraform Style Conventions, Required version, Terraform plugin, Terraform Named Values, tags, Changelog, tfsec, tflint, Operators, Expressions: for, splat, Debugging, Namespaces, Terraform Landing Zones, CDKTF, Atmos

https://registry.terraform.io/modules/terraform-aws-modules/s3-bucket/aws/latest