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Store arrays in variables

Freshabout 22 hours ago
Mar 14, 20260 views
Confidence Score89%
89%

Problem

I have lists of security groups and or lists of ec2 instances that i would like to to keep in arrays ( separated by files which are auto loaded by *.tf ) so i know when i change things in one place, it gets changed in another. Right now vars can only hold strings or key value maps, but not arrays (if i am reading the docs and error messages correctly)

Error Output

error messages correctly)

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1 Fix

Canonical Fix
Unverified Fix
New Fix – Awaiting Verification

Implement Array Variables in Terraform using Lists

Medium Risk

Terraform's variable system traditionally supports strings and maps, but it also allows for lists (arrays) when defined correctly. The issue arises when users attempt to declare variables without the proper syntax or type, leading to confusion and errors.

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  1. 1

    Define Variables as Lists

    In your Terraform variable files (e.g., variables.tf), define your security groups and EC2 instances as lists. This allows you to store multiple values in a single variable.

    hcl
    variable "security_groups" {
  type = list(string)
  default = ["sg-12345678", "sg-87654321"]
}
  2. 2

    Reference List Variables

    When you need to reference these variables in your Terraform configuration files, use the syntax `var.security_groups` to access the entire list or `var.security_groups[index]` to access a specific element.

    hcl
    resource "aws_security_group" "example" {
  count = length(var.security_groups)
  name  = var.security_groups[count.index]
}
  3. 3

    Load Variables from Separate Files

    Create separate `.tfvars` files for each environment or configuration. Use the `terraform apply -var-file` option to load these variables automatically, ensuring changes in one file reflect across your infrastructure.

    bash
    terraform apply -var-file="production.tfvars"
  4. 4

    Validate Configuration

    Run `terraform validate` to ensure that your configuration is correct and that the list variables are being recognized properly. This will help catch any syntax errors or misconfigurations.

    bash
    terraform validate

Validation

After implementing the changes, run `terraform plan` and check the output to confirm that the security groups and EC2 instances are being referenced correctly. Ensure that any changes made in the variable files are reflected in the plan output.

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Environment

Submitted by

AC

Alex Chen

2450 rep

Tags

terraformiacawsenhancementcore