---
title: "Terraforming Christmas Cards"
url: "https://www.bekk.christmas/post/2019/20/terraforming-christmas-cards"
authors: ["Stefan Magnus Landrø"]
published: "2019-12-20"
updated: "2024-11-07T13:05:28Z"
language: "en-US"
type: "article"
tags: ["Sky"]
---

# Terraforming Christmas Cards

So like every year, Christmas is approaching too fast, and like every year I’m late at writing Christmas cards! Like all other complex problems in life, also this can be tackled by using the open source infrastructure as code tool Terraform!

Now from last year, I had the list of friends and their respective addresses in a CSV file that looks like this:

```csv
name,street,zip,city,country
Julenissen,Julenissens postkontor,1440,Drøbak,Norway
Santa Claus,Santa Claus's Main Post Office,96930,Napapiiri,Finland
Father Christmas,Santa's Grotto,XM4 5HQ,Reindeerland,United Kingdom
An den Weihnachtsmann,Weihnachtspostfiliale,16798,Himmelpfort,Germany
```

I then quickly put together a Christmas card template file that looks like the following:

```
${name}
${street}
%{ if country == "United Kingdom" }${city} ${zip}%{ else }${zip} ${city}%{ endif }
${country}


Dear ${name},

Merry Christmas and a Happy New Year!
```

The Brits are a bit peculiar about [how they address mail](https://www.postoffice.co.uk/mail/how-to-address-mail) compared to the rest of us, and I therefore had to add an [if directive](https://www.terraform.io/docs/configuration/expressions.html#string-templates) in the template.

In order to actually generate some Christmas cards, I decided to write all the cards to disk using the [local_file](https://www.terraform.io/docs/providers/local/r/file.html) resource in Terraform in combination with the new [for_each](https://www.terraform.io/docs/configuration/resources.html#for_each-multiple-resource-instances-defined-by-a-map-or-set-of-strings) resource meta-argument and the new [for](https://www.terraform.io/docs/configuration/expressions.html#for-expressions) expression (these features were added to Terraform in version 0.12.0 and 0.12.6 respectively). Combine all that with the [templatefile](https://www.terraform.io/docs/configuration/functions/templatefile.html) expression, and you end up with this Terraform "one-liner":

```hcl
resource "local_file" "christmascard" {
  for_each = { for address in csvdecode(file("${path.module}/addresses.csv")) : address.country => address }
  content  = templatefile("${path.module}/card.tmpl", each.value)
  filename = "${path.module}/cards/${each.key}.txt"
}
```

Whys is this cool you might ask? Well, there a lots of features in Terraform that allow you to do stuff that you can't do with any of the other infrastructure as code tools out there. Here's a brief list of features that come in handy on a regular basis when working with Terraform:

- [Built-in functions](https://www.terraform.io/docs/configuration/functions.html) that let you do anything from math to crypto
- [Miscellaneous Providers](https://www.terraform.io/docs/providers/type/misc-index.html) that let you do anything from generating TLS certificates to random passwords. These are all non-cloud related resources really.

## Source code

If you're keen on running this example on your laptop, do the following:

```shell
git clone https://github.com/landro/terraform-christmas-postcards
cd terraform-christmas-postcards
terraform init
terraform apply
```

## Relevant resources recommended by the author

- [Terraform](https://www.terraform.io/)
- [Sourcecode](https://github.com/landro/terraform-christmas-postcards)

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