tfenv

Command line utility to transform environment variables for use with Terraform. (e.g. HOSTNAME → TF_VAR_hostname)

It can also intelligently map environment variables to terraform command line arguments (e.g. TF_CLI_INIT_BACKEND_CONFIG_BUCKET=example → TF_CLI_ARGS_init=-backend-config=bucket=example).

NOTE: tfenv is not a terraform version manager. It strictly manages environment variables much like env or direnv.

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This project is part of our comprehensive "SweetOps" approach towards DevOps.

It's 100% Open Source and licensed under the APACHE2.

Introduction

If you answer "yes" to any of these questions, then look no further!

• Have you ever wished you could easily pass environment variables to terraform without adding the TF_VAR_ prefix?
• Do you use chamber and get annoyed when it transforms environment variables to uppercase?
• Would you like to use common environment variables names with terraform? (e.g. USER or AWS_REGION)
• Is there some argument to terraform init you want to specify with an environment variable? (e.g. a -backend-config property)

Yes? Great! Then this utility is for you.

The tfenv utility will perform the following transformations:

1. Lowercase all envs (Terraform convention)
2. Strip leading or trailing underscores (_)
3. Replace consecutive underscores with a single underscore (_)
4. Prepend prefix (TF_VAR_)

NOTE: tfenv will preserve the existing environment and add the new environment variables with TF_VAR_. This is because some terraform providers expect non-TF_VAR_* prefixed environment variables. Additionally, when using the local-exec provisioner, it's convenient to use regular environment variables. See our terraform-null-smtp-mail module for an example of using this pattern.

But wait, there's more!

With tfenv we can surgically assign a value to any terraform argument using per-argument environment variables.

History

Why is this project called tfenv?

This tfenv project borrows its naming convention from popular tools like env, direnv, and autoenv. These tools provide various ways to export variables in the environment.

The env command has been around since the early 90s, while environment variables were first conceived of in 1979. On the other hand there are tools like rbenv Et al., which are "version managers" that were conceived of sometime around 2010.

Usage

NOTE: The utility supports a number of configuration settings which can be passed via environment variables.

• TFENV_PREFIX - Prefix used for all normalized environment variables (default is TF_VAR_, but you could do something like TF_VAR_app_)
• TFENV_WHITELIST - Whitelist of allowed environment variables. Processed after blacklist. Regular expression should match wanted environment variables (by default .*)
• TFENV_BLACKLIST - Blacklist of excluded environment variables. Processed before whitelist. Regular expression should exclude unwanted/dangerous environment variables (e.g. AWS credentials)

The basic usage looks like this. We're going to run some command and pass it arg1 ... argN:

tfenv command arg1 arg2 arg3 ... argN

So for example, we can pass our current environment to terraform by simply running:

tfenv terraform plan

Direnv

You can use tfenv with direnv very easily. Running tfenv without any arguments will emit export statements.

Example .envrc:

# Export terraform environment
source <(tfenv)

or...

# Export terraform environment
eval "$(tfenv)"

Bash

Load the terraform environment into your shell.

Just add the following into your shell script:

source <(tfenv)

Terraform Args

With tfenv we can populate the TF_CLI_ARGS and TF_CLI_ARGS_* environment variables automatically. This makes it easy to toggle settings.

For example, if you want to pass -backend-config=bucket=terraform-state-bucket to terraform init, then you would do the following:

export TF_CLI_INIT_BACKEND_CONFIG_BUCKET=terraform-state-bucket

Running tfenv will populate the TF_CLI_ARGS_init=-backend-config=bucket=terraform-state-bucket

Multiple arguments can be specified and they will be properly concatenated.

Initializing Modules

Terraform has the built-in capability to initialize "root modules" from a remote sources by passing the -from-module argument to terraform init.

We can turn this into a 12-factor style invocation using tfenv.

export TF_CLI_INIT_FROM_MODULE=git::https://github.com/cloudposse/terraform-root-modules.git//aws/tfstate-backend?ref=tags/x.y.z
source <(tfenv)
terraform init

Learn more about TF_CLI_ARGS and TF_CLI_ARGS_* in the official documentation.

Examples

Compiling the Binary

make go/build

Use with Chamber

chamber exec foobar -- tfenv terraform plan

Use with Terragrunt

tfenv terragrunt plan

Print Environment

tfenv printenv

Use with Direnv

You can easily integrate tfenv with direnv so that your environment is automatically setup for Terraform.

Add the following to your .envrc:

source <(tfenv)

Example Output

direnv: loading .envrc
direnv: export +TF_VAR_aws_profile +TF_VAR_aws_vault_backend +TF_VAR_colorterm +TF_VAR_dbus_session_bus_address +TF_VAR_desktop_session +TF_VAR_direnv_diff +TF_VAR_direnv_in_envrc +TF_VAR_direnv_watches +TF_VAR_display +TF_VAR_fzf_orig_completion_git +TF_VAR_github_token +TF_VAR_gtk_overlay_scrolling +TF_VAR_histcontrol +TF_VAR_histsize +TF_VAR_home +TF_VAR_hostname +TF_VAR_lang +TF_VAR_lessopen +TF_VAR_logname +TF_VAR_ls_colors +TF_VAR_mail +TF_VAR_mate_desktop_session_id +TF_VAR_okta_user +TF_VAR_oldpwd +TF_VAR_path +TF_VAR_pwd +TF_VAR_qt_auto_screen_scale_factor +TF_VAR_qt_scale_factor +TF_VAR_session_manager +TF_VAR_sessiontype +TF_VAR_shell +TF_VAR_shlvl +TF_VAR_ssh_auth_sock +TF_VAR_term +TF_VAR_user +TF_VAR_vte_version +TF_VAR_windowid +TF_VAR_xauthority +TF_VAR_xdg_current_desktop +TF_VAR_xdg_runtime_dir +TF_VAR_xdg_seat +TF_VAR_xdg_session_id +TF_VAR_xdg_vtnr

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Related Projects

Check out these related projects.

• Packages - Cloud Posse installer and distribution of native apps
• build-harness - Collection of Makefiles to facilitate building Golang projects, Dockerfiles, Helm charts, and more
• geodesic - Geodesic is the fastest way to get up and running with a rock solid, production grade cloud platform built on strictly Open Source tools.
• direnv - Unclutter your .profile with an environment switcher for the shell
• env - Used to either print a list of environment variables or run another utility in an altered environment without having to modify the currently existing environment.

References

For additional context, refer to some of these links.

• Terraform Without Wrappers is AWESOME! - Reddit discussion regarding this project.

Help

Got a question?

File a GitHub issue, send us an email or join our Slack Community.

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Contributing

Bug Reports & Feature Requests

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Developing

If you are interested in being a contributor and want to get involved in developing this project or help out with our other projects, we would love to hear from you! Shoot us an email.

In general, PRs are welcome. We follow the typical "fork-and-pull" Git workflow.

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5. Submit a Pull Request so that we can review your changes

NOTE: Be sure to merge the latest changes from "upstream" before making a pull request!

Copyright

Copyright © 2017-2019 Cloud Posse, LLC

License

See LICENSE for full details.

Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

  https://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.

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Contributors

Erik Osterman