Is there a way to inject variables into a Terraform apply run from another process outside of Terraform?

[rhoboat]

Is there a way to inject variables into Terraform from another process outside of Terraform?

For example: I'm running an automated test where at some point I'm creating an AMI. I want to pass this AMI ID as a var in Terraform running in a CI / CD pipeline, so that I can have Terraform spin up that image.

[rhoboat]

Most likely you'll need to set a variable in Terraform using one of the standard ways of assigning values to root module variables. If you're using Terragrunt, you would write the value to a terragrunt.hcl file.

Some programmatic options:

• If you are doing this for testing, then we have terratest where you can use Go to dynamically generate variables and drive terraform apply. Examples of this are at terratest.gruntwork.io (Open source: no subscription needed)
• If you want to do a CI/CD workflow where you are updating variables to commit to git, then we have terraform-update-variable, which is a bash script that can update a tfvars or terragrunt.hcl file and commit the update to git: https://github.com/gruntwork-io/terraform-aws-ci/tree/master/modules/terraform-helpers (Subscriber only)
• If you want to dynamically update variables every time you run terraform, then Terragrunt offers the run_cmd function which can run arbitrary commands to render out to the Terraform variable every time terraform is called. Example is here: https://terragrunt.gruntwork.io/docs/reference/built-in-functions/#run_cmd (Open source: no subscription needed)