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Looping in Terraform

Hashicorp Language (HCL) supports the use of internal interations (loops).

We can loop in HCL by using either count or for_each.

Looping with count

This is one of the easiest ways to loop, as it just loops over a range of numbers.

If we need multiple identical VMs, this type of loop is perfect. 

resource "proxmox_vm_qemu" "vm" {
  count = 3
  name = "test-vm-${count.index + 1}"
  target_node = "home-pve"
  ...
}
At the top of the resource block, we specify a count of 3. This makes three copies of the VM resource.

When looping, we can tap into the current loop number with count.index, using the same notation as Bash (${...}).
Within these braces, we can do some basic operations (i.e., addition).

By default, HCL uses zero-based indexing for its loops, so we add 1 to get the desired number.

This will create:

  • test-vm-1
  • test-vm-2
  • test-vm-3

All with identical configurations.

Padding with Zeroes

Say we want our naming convention to use something like control-node01, control-node02, etc., but we don't want to hardcode the leading zero in. If the count gets to ten, we'd end up with control-node010. That's not what we want.

We can use the format() builtin function to pad the number with zero(es).

resource "example" "example-name" {
  count = 2
  name = format("control-node%02d", count.index + 1)
}
This format of %02d will pad the left side with zeroes, as long as the padding doesn't exceed 2 digits.

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