Variable block

The variable block declares a value that the command line or an environment variable can override.

Example usage

# define config variable - the default value is used if not provided via --variable
variable config {
  description = "configuration to build"
  default = "Debug"
}

Argument reference

The following arguments are supported:

• description - (Optional) Description of the variable. This helps document what the variable is used for and appears in help text.
• default - (Optional) Default value for the variable if not provided via command line or environment. It must evaluate to a scalar value (string, number, boolean) if provided.

Variable override

Variables must be declared in the WORKSPACE file before they can be used.

Terrabuild supports variable overriding using the following precedence order (first match wins):

1. Environment variable: Use TB_VAR_xxx to override a variable (where xxx is the variable name). For example, TB_VAR_config=Release overrides the config variable. Note variable name is case insensitive.
2. Command line argument: Use the --variable or -v switch when building a target. For example, terrabuild run build --variable config=Release.
3. Default value: If neither of the above is provided, the default value from the variable declaration is used.