Hands-on: Try the Perform Dynamic Operations with Functions tutorial.
The Terraform language includes a number of built-in functions that you can call from within expressions to transform and combine values. The general syntax for function calls is a function name followed by comma-separated arguments in parentheses:
max(5, 12, 9)
For more details on syntax, see Function Calls in the Expressions section.
The Terraform language does not support user-defined functions, and so only the functions built in to the language are available for use. The documentation includes a page for all of the available built-in functions.
You can experiment with the behavior of Terraform's built-in functions from
the Terraform expression console, by running
terraform console command:
> max(5, 12, 9) 12
The examples in the documentation for each function use console output to illustrate the result of calling the function with different parameters.