# Using Functions and Variables

> Markdown source of <https://docs.calebsargeant.com/computing/terraform/getting-started/using-functions-and-variables/>.

## Working with Variables

- Name, type, default
- Multiple sources
  - File, environment variable, var option
- Overriding variables and precedence
  - Environment, file, command line
- Select values based on environment
- Split Terraform configuration file

### Variable Examples

``` text
#Specify default variable and type
variable "environment_name" {
type = string
defualt = "development"
}
#Specify variable in file
environment_name = "uat"

#Specify variable in-file
terraform plan -var 'environment_name=production'

#Create variable map
variable "cidr" {
  type = map(string)
  default = {
    development = "10.0.0.0/16"
    uat = "10.1.0.0/16"
    production = "10.2.0.0/16"
  }
}

#Use map based on environment
cidr_block = lookup(var.cidr, var.environment_name)
```

### Updating the Configuration Variables

[variables.tf](https://github.com/CalebSargeant/Getting-Started-Terraform/blob/master/m7/variables.tf)

[terraform.tfvars.example](https://github.com/CalebSargeant/Getting-Started-Terraform/blob/master/m7/terraform.tfvars.example)

## Multiple Environments

- Commonality and differences
- Abstractiosn and ruse
- Production access
- Using workspaces

### Multiple Environment Decisions

- State management
- Variables data
- Credentials management
- Complexity and overhead

### State File Example

**Main** - main.config.tf - common.tfvars

**Dev** - dev.state - dev.tfvars -`terraform plan -state="./dev/dev.state" -var-file="common.tfvars" -var-file="./dev/dev.tfvars"`

**UAT** - uat.state - uat.tfvars - `terraform plan -state="./uat/uat.state" -var-file="common.tfvars" -var-file="./uat/uat.tfvars"`

**Prod** - prod.state - prod.tfvars - `terraform plan -state="./prod/prod.state" -var-file="common.tfvars" -var-file="./prod/prod.tfvars"`

### Workspaces Example

- main.config.tf
- terraform.tfvars
- terraform.tfstate.d (folder)

``` text
terraform workspace new dev
terraform plan
```

## Managing Secrets

- Variables file
- Environment variable
- Secrets management

### Environment Variables

``` text
#AWS Environment Variables
AWS_ACCESSS_KEY_ID
AWS_SECRET_ACCESS_KEY
AWS_SHARED_CREDENTIALS_FILE
AWS_PROFILE
#Powershell
$env:AWS_ACCESS_KEY_ID="AASAS9283708FDKJ"

#Linux
export AWS_ACCESS_KEY_ID="AASAS9283708FDKJ"
```