Looping in Terraform, Ansible and Bash

Looping in Terraform, Ansible and Bash

Looping is quite an important mechanism in coding. (Thanks @Andreas for the word coding, a mix of scripting and programming.)

Looping allows you to write a piece of logic once, and reuse it as many times are required.

Looping is difficult to understand for new people new to coding. It’s sometimes difficult for me to. This article will probably help me a bit too!

A sequence

The simplest loop I know is repeating a piece of logic for a set of number or letters, like this:

• 1 2 3

First off, here is how to generate a sequence:

bash	ansible	terraform
seq 1 3	with_sequence: start=1 end=3	range(1, 3)
{1..3}

For all languages, this returns a list of numbers.

bash	ansible	terraform
1 2 3	item: 1, item: 2, item: 3	[ 1, 2, 3, ]

So, a more complete example for the three languages:

Bash

for number in {1..3} ; do
  echo "number: ${number}
done

The above script returns:

1
2
3

Ansible

- name: show something
  debug:
    msg: "number: "
  with_sequence:
    start=1
    end=3

Note: See that = sign, I was expecting a : so made an issue.

The above script returns:

ok: [localhost] => (item=1) => {
    "msg": "1"
}
ok: [localhost] => (item=2) => {
    "msg": "2"
}
ok: [localhost] => (item=3) => {
    "msg": "3"
}

Terraform

locals {
  numbers = range(1,4)
}

output "number" {
  value = local.numbers
}

The above script returns:

number = tolist([
  1,
  2,
  3,
])