Interpolation in Terraform

Variable Interpolation:

• ${var.variable_name}: Interpolates the value of a variable.

Resource Attribute Interpolation:

• ${resource_type.resource_name.attribute}: Interpolates the value of a specific attribute of a resource.

Data Attribute Interpolation:

• ${data.data_type.data_name.attribute}: Interpolates the value of a specific attribute of a data source.

Output Interpolation:

• ${output.output_name}: Interpolates the value of an output variable.

String Interpolation:

• "${expression}": Interpolates a string with an expression.

List Interpolation:

• [element1, element2, ...]: Interpolates a list of elements.

Map Interpolation:

• {key1 = value1, key2 = value2, ...}: Interpolates a map of key-value pairs.

Conditional Interpolation:

• condition ? true_val : false_val: Interpolates a value based on a condition.

Numeric Interpolation:

• Arithmetic operations: +, -, *, /, %: Interpolates the result of arithmetic operations on numbers.

Splat Expression Interpolation:

• ${resource_type.resource_name.*.attribute}: Interpolates a list of values for a specific attribute of multiple resources.

Count Interpolation:

• ${count.index}: Interpolates the current index value when using resource or module count.

Element Interpolation:

• ${list[index]}: Interpolates a specific element from a list based on the index.

Lookup Interpolation:

• ${lookup(map, key, default)}: Interpolates the value of a key in a map and provides a default value if the key doesn't exist.

File Interpolation:

• ${file(path)}: Interpolates the content of a file at the specified path.

Templatefile Interpolation:

• ${templatefile(path, vars)}: Interpolates the content of a template file at the specified path, replacing variables with values from the vars map.

Join Interpolation:

• ${join(delimiter, list)}: Interpolates a string by joining elements of a list with the specified delimiter.

Lower and Upper Case Interpolation:

• ${lower(string)}: Interpolates a lowercase version of the given string.

• ${upper(string)}: Interpolates an uppercase version of the given string.

Regex Replace Interpolation:

• ${replace(string, regex, replacement)}: Interpolates a string by replacing substrings matching a regex pattern with a specified replacement.

JSON Interpolation:

• ${jsonencode(data_structure)}: Interpolates a JSON-encoded string representation of a data structure.

Terraform Function Interpolation:

• ${function_name(arg1, arg2, ...)}: Interpolates the result of a Terraform function call with the specified arguments.