How to Use the Join Function in Terraform: Simple Guide
In Terraform, the
join function combines elements of a list into one string, separated by a specified delimiter. Use it like join(",", ["a", "b", "c"]) to get "a,b,c". This helps create strings from lists for resource configuration.Syntax
The join function takes two arguments: a separator string and a list of strings. It returns a single string where list elements are joined by the separator.
- separator: The string placed between each list element.
- list: The list of strings to join.
terraform
join(separator, list_of_strings)Example
This example shows how to join a list of words with a comma and space to form a sentence.
terraform
output "joined_string" { value = join(", ", ["apple", "banana", "cherry"]) }
Output
joined_string = "apple, banana, cherry"
Common Pitfalls
Common mistakes include using join on non-list values or lists containing non-string elements, which causes errors. Also, forgetting to provide a separator or using an empty string separator can lead to unexpected results.
Wrong usage example:
join(",", "not-a-list")Correct usage:
join(",", ["one", "two", "three"])Quick Reference
| Function | Description | Example | Result |
|---|---|---|---|
| join(separator, list) | Joins list elements with separator | join(",", ["a", "b"]) | "a,b" |
| join("-", ["x", "y", "z"]) | Joins with dash | join("-", ["x", "y", "z"]) | "x-y-z" |
| join("", ["1", "2", "3"]) | Joins without separator | join("", ["1", "2", "3"]) | "123" |
Key Takeaways
Use join(separator, list) to combine list elements into one string with a separator.
The separator can be any string, including empty for no space.
Ensure the second argument is a list of strings to avoid errors.
join is useful for creating strings from lists in resource configurations.