Terraform Variables Programmers Quickie

With terraform we can use variables for example an integer which is defined as a number or a string or a list of strings and then we can reference these variables further down in the code in order to reuse them you can also output variables to the screen and we could also ask the customer to input interactively variable values into the console


In this session

- init plan apply destroy
- state file
- variables


- terraform pattern consistent
- resource keyword
- resource identifier "aws_vpc"
- our name "mypc"
- in curly braces the parametesrs like cidr_block = "10.0.0.0/16"


- `terraform init`
- i's like mvn install
- Download the plugins to use aws
- We can run this command after created main.tf
- pull down modules

- `terraform plan`
- will show what's its going to do
- checks state
- Get developer style diff before commit
- What already created which diff
- don't want to loose this state file

- `terraform apply`
- showing the diff
- click `yes` to continue
- resources created in aws!

- `terraform destroy`
- to delete all reources
- confirm

- `state file` `terraform.tfstate`
- we can see locally all that we created with terraform!
- this file will have ALL resources created by terraform
- visibility!
- we want this file to get missing
- json format
- .bak
- track changes we made
- used for diff


# Variables

- define variables
- folder `variables`
- `default` is like the value
- we have `type` and then `default` for default value
- `main.tf` create file in that folder
```json
variable "vpcname" {
type = string (or number boolean list(string) with values ["val1", "val2"] to access 1 [0])
default = "myvpc"
}

variable "mymap" {
type = map
default = {
key1 = "value1"
key2 = "value2"
}
}

variable "mytuple" {
type tuple([string, number, string])
default = ["mystr1", 45, "mystr2"]
}

variable "myobject" {
type = object({name = string, port = number})
default {
name = "myval1"
default = "232"
}
}
```
- cidr_range would get used multiple times so just put it in var

- use variables
- `var.myvarname` can also be done with string interpolation
- `var.mylist[0]`
- `var.mymap["Key1"]`

- interactive input variables
```json
variable "inputname" {
type = string
description = "please enter value for input name"
}
```

next use this
- `var.inputname` as usuall
- `terraform plan` will now ask to input the input vars values


# Outputs

```json
output "myoutput" {
value = aws_vpc.myvpc.id
}
```

so nw we can print the dynamic id we get when we run terraform.

run `terraform plan` will not print the id as it's created only after the apply is run and resources actually run.