Terraform CLI environment variables reference

Environment Variable	Description	Example Usage
TF_LOG	Controls logging verbosity. Values: TRACE, DEBUG, INFO, WARN, ERROR, OFF.	export TF_LOG=DEBUG
TF_LOG_PATH	Specifies log file path to store logs.	export TF_LOG_PATH=./terraform.log
TF_INPUT	Determines if Terraform prompts for user input. Set to false to disable.	export TF_INPUT=false
TF_VAR_name	Sets Terraform input variables from the environment. Example: TF_VAR_region.	export TF_VAR_region=us-west-1
TF_CLI_ARGS and TF_CLI_ARGS_name	Defines default CLI arguments for Terraform commands. Example: TF_CLI_ARGS_plan.	export TF_CLI_ARGS=’-input=false’
TF_DATA_DIR	Changes Terraform data directory from the default `.terraform`.	export TF_DATA_DIR=/custom/data/dir
TF_WORKSPACE	Specifies the workspace to use in Terraform.	export TF_WORKSPACE=production
TF_IN_AUTOMATION	Indicates if Terraform is running in an automated environment (CI/CD).	export TF_IN_AUTOMATION=true
TF_REGISTRY_DISCOVERY_RETRY	Number of retries for Terraform Registry discovery.	export TF_REGISTRY_DISCOVERY_RETRY=5
TF_REGISTRY_CLIENT_TIMEOUT	Sets timeout duration for Terraform Registry client operations.	export TF_REGISTRY_CLIENT_TIMEOUT=30
TF_STATE_PERSIST_INTERVAL	Defines how frequently Terraform writes its state file.	export TF_STATE_PERSIST_INTERVAL=10
TF_CLI_CONFIG_FILE	Specifies custom path for Terraform CLI configuration file.	export TF_CLI_CONFIG_FILE=$HOME/.terraformrc
TF_PLUGIN_CACHE_DIR	Specifies the directory for Terraform plugin cache.	export TF_PLUGIN_CACHE_DIR=$HOME/.terraform.d/plugin-cache
TF_IGNORE	Defines patterns for files and directories that Terraform should ignore.	export TF_IGNORE=’*.bak’

Terraform predefined and meta variables reference

Built-in Variable	Description

terraform.workspace

Returns the current workspace name.

path.module

Returns the current module path.

path.root

Returns the root module path.

path.cwd

Returns the current working directory.

count.index

Current index in a count loop.

each.key, each.value

Current key-value in a for_each loop.

var.<variable_name>

References an input variable.

local.<local_variable>

References a local variable.

module.<module_name>.<output>

Retrieves an output from a child module.

self	Refers to current resource instance.

depends_on

Explicitly sets dependencies between resources.

env.<ENV_VAR>

Retrieves environment variables from the shell.

Comprehensive Guide: Terraform CLI Environment Variables & Predefined Variables

1. Terraform CLI Environment Variables Reference

Terraform allows configuring its behavior using various environment variables. These variables control logging, input handling, workspace management, and registry discovery settings. Below is a detailed guide with use cases and examples.

1.1 Logging & Debugging

TF_LOG

• Description: Controls Terraform logging verbosity.
• Possible Values: TRACE, DEBUG, INFO, WARN, ERROR, OFF
• Use Case: Useful for debugging Terraform execution.
• Example: export TF_LOG=DEBUG terraform apply

TF_LOG_PATH

• Description: Specifies a log file path to store logs.
• Use Case: Useful when debugging Terraform automation pipelines.
• Example: export TF_LOG_PATH=./terraform.log terraform apply

---

1.2 Input Handling

TF_INPUT

• Description: Determines if Terraform prompts for user input. Set to false to disable interactive prompts.
• Use Case: Useful in CI/CD environments.
• Example: export TF_INPUT=false terraform apply

---

1.3 Variable Handling

TF_VAR_name

• Description: Sets Terraform input variables from the environment.
• Use Case: Allows dynamic configuration of Terraform variables without modifying the .tf file.
• Example: export TF_VAR_region=us-west-1 terraform apply

TF_CLI_ARGS and TF_CLI_ARGS_name

• Description: Defines default CLI arguments for Terraform commands.
• Use Case: Ensures that Terraform always runs with specific flags.
• Example: export TF_CLI_ARGS='-input=false' terraform apply export TF_CLI_ARGS_plan='-refresh=false' terraform plan

---

1.4 Terraform State & Data Management

TF_DATA_DIR

• Description: Changes Terraform data directory from the default .terraform.
• Use Case: Useful when running multiple Terraform executions in parallel.
• Example: export TF_DATA_DIR=/custom/data/dir terraform init

TF_WORKSPACE

• Description: Specifies the workspace to use in Terraform.
• Use Case: Automate Terraform workspace switching.
• Example: export TF_WORKSPACE=production terraform apply

TF_IN_AUTOMATION

• Description: Indicates if Terraform is running in an automated environment (CI/CD).
• Use Case: Helps Terraform suppress interactive prompts.
• Example: export TF_IN_AUTOMATION=true terraform apply

---

1.5 Terraform Registry & Plugin Management

TF_REGISTRY_DISCOVERY_RETRY

• Description: Number of retries for Terraform Registry discovery.
• Use Case: Useful when working in unstable network environments.
• Example: export TF_REGISTRY_DISCOVERY_RETRY=5

TF_REGISTRY_CLIENT_TIMEOUT

• Description: Sets timeout duration for Terraform Registry client operations.
• Use Case: Useful in slow networks.
• Example: export TF_REGISTRY_CLIENT_TIMEOUT=30

TF_PLUGIN_CACHE_DIR

• Description: Specifies the directory for Terraform plugin cache.
• Use Case: Helps speed up Terraform runs by avoiding plugin downloads.
• Example: export TF_PLUGIN_CACHE_DIR=$HOME/.terraform.d/plugin-cache

---

1.6 Miscellaneous Terraform Configurations

TF_STATE_PERSIST_INTERVAL

• Description: Defines how frequently Terraform writes its state file.
• Example: export TF_STATE_PERSIST_INTERVAL=10

TF_CLI_CONFIG_FILE

• Description: Specifies a custom path for the Terraform CLI configuration file.
• Example: export TF_CLI_CONFIG_FILE=$HOME/.terraformrc

TF_IGNORE

• Description: Defines patterns for files and directories that Terraform should ignore.
• Example: export TF_IGNORE='*.bak'

---

2. Terraform Predefined and Meta Variables Reference

Terraform provides a set of predefined variables that allow access to system metadata.

Built-in Variable	Description
terraform.workspace	Returns the current workspace name.
path.module	Returns the current module path.
path.root	Returns the root module path.
path.cwd	Returns the current working directory.
count.index	Current index in a count loop.
each.key, each.value	Current key-value in a for_each loop.
var.<variable_name>	References an input variable.
local.<local_variable>	References a local variable.
module.<module_name>.<output>	Retrieves an output from a child module.
self	Refers to the current resource instance.
depends_on	Explicitly sets dependencies between resources.
env.<ENV_VAR>	Retrieves environment variables from the shell.

Example Usage:

output "workspace" {
  value = terraform.workspace
}

output "current_path" {
  value = path.module
}

By understanding and utilizing these Terraform environment variables and predefined expressions, users can optimize their infrastructure as code (IaC) workflows efficiently.