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

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docs	Environment Variables	docs-config-environment-variables	Something on Environment Variables!

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=1

To disable, either unset it or set it to empty. 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. Modules are treated like a black box and terraform commands do not show what resources within the module will be created. By setting this to -1, for example, you enable commands such as plan and graph to display more detailed information.

export TF_MODULE_DEPTH=-1

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.