Terraform CLI environment variables reference

Terraform predefined and meta variables reference

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.

Example Usage:

output "workspace" {
  value = terraform.workspace
}
Code language: JavaScript (javascript)

output "current_path" {
  value = path.module
}
Code language: JavaScript (javascript)

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

Rajesh Kumar

I’m Rajesh Kumar, a DevOps, SRE, DevSecOps, Cloud, and Platform Engineering expert passionate about sharing practical knowledge, real-world experiences, and industry best practices. I have worked at Cotocus and regularly write about technology, travel, investing, health, product reviews, and digital marketing through my various platforms.

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