For more information on the meaning and behavior of these different types, as well as detailed information about automatic conversion of complex types, see Type Constraints. The keyword any may be used to indicate that any type is acceptable.

Type constraints are created from a mixture of type keywords and type constructors. While type constraints are optional, we recommend specifying them they serve as easy reminders for users of the module, and allow Terraform to return a helpful error message if the wrong type is used. If no type constraint is set then a value of any type is accepted. The type argument in a variable block allows you to restrict the type of value that will be accepted as the value for a variable. The value assigned to a variable can be accessed only from expressions within the module where it was declared. Within the module that declared a variable, its value can be accessed from within expressions as var. The default argument requires a literal value and cannot reference other objects in the configuration. If present, the variable is considered to be optional and the default value will be used if no value is set when calling the module or running Terraform. The variable declaration can also include a default argument. The variable declaration can optionally include a type argument to specify what value types are accepted for the variable, as described in the following section. These names are reserved for meta-arguments in module configuration blocksand cannot be declared as variable names. The name of a variable can be any valid identifier except the following. This name is used to assign a value to the variable from outside and to reference the variable's value from within the module. The label after the variable keyword is a name for the variable, which must be unique among all variables in the same module. Other kinds of variables in Terraform include environment variables set by the shell where Terraform runs and expression variables used to indirectly represent a value in an expression. Note: For brevity, input variables are often referred to as just 'variables' or 'Terraform variables' when it is clear from context what sort of variable is being discussed. Input variable usage is introduced in the Getting Started guide section Input Variables. When you declare them in child modulesthe calling module should pass values in the module block. When you declare variables in the root module of your configuration, you can set their values using CLI options and environment variables. Input variables serve as parameters for a Terraform module, allowing aspects of the module to be customized without altering the module's own source code, and allowing modules to be shared between different configurations. Learn the Learn how Terraform fits into the.

Terraform module source