terraform/website/source/docs/configuration/environment-variables.html.md

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docs	Environment Variables	docs-config-environment-variables	Terraform uses different environment variables that can be used to configure various aspects of how Terraform behaves. this section documents those variables, their potential values, and how to use them.

Environment Variables

TF_LOG

If set to any value, enables detailed logs to appear on stderr which is useful for debugging. For example:

export TF_LOG=TRACE

To disable, either unset it or set it to empty. When unset, logging will default to stderr. For example:

export TF_LOG=

For more on debugging Terraform, check out the section on Debugging.

TF_LOG_PATH

This specifies where the log should persist its output to. Note that even when TF_LOG_PATH is set, TF_LOG must be set in order for any logging to be enabled. For example, to always write the log to the directory you're currently running terraform from:

export TF_LOG_PATH=./terraform.log

For more on debugging Terraform, check out the section on Debugging.

TF_INPUT

If set to "false" or "0", causes terraform commands to behave as if the -input=false flag was specified. This is used when you want to disable prompts for variables that haven't had their values specified. For example:

export TF_INPUT=0

TF_MODULE_DEPTH

When given a value, causes terraform commands to behave as if the -module=depth=VALUE flag was specified. By setting this to 0, for example, you enable commands such as plan and graph to display more compressed information.

export TF_MODULE_DEPTH=0

For more information regarding modules, check out the section on Using Modules.

TF_VAR_name

Environment variables can be used to set variables. The environment variables must be in the format TF_VAR_name and this will be checked last for a value. For example:

export TF_VAR_region=us-west-1
export TF_VAR_ami=ami-049d8641

For more on how to use TF_VAR_name in context, check out the section on Variable Configuration.

TF_SKIP_REMOTE_TESTS

This can be set prior to running the unit tests to opt-out of any tests requiring remote network connectivity. The unit tests make an attempt to automatically detect when connectivity is unavailable and skip the relevant tests, but by setting this variable you can force these tests to be skipped.

export TF_SKIP_REMOTE_TESTS=1
make test