Terraform Functions

Function in terraform help you transform data, build dynamic values, and write smarter infrastructure code.
Terraform supports only built in function. Here are some details -

📌 String Functions:

✅ lower() - lower("HELLO") → "hello"
✅ upper() - upper("hello") → "HELLO"
✅ replace() - replace("dev-app", "dev", "prod") → "prod-app"
✅ substr()
✅ trim() - trim(" hello ", " ") → "hello"
✅ split() - split(",", "a,b,c") → ["a", "b", "c"]
✅ join() - join(",", ["a", "b", "c"]) → "a,b,c"
✅ chomp() - chomp("hello\n") → "hello" hashtag#cuts off the last newline character from a string.

📌 Numeric Functions
✅ abs() - abs(-3) → 3 hashtag#Absolute value
✅ max() - max(10, 5, 8) → 10
✅ min() - min(10, 5, 8) → 5
✅ ceil() - ceil(4.2) → 5 hashtag#Round UP a number
✅ floor() - floor(4.8) → 4 hashtag#Round DOWN a number
✅ sum() - sum([1, 2, 3]) → 6

📌 Collection Functions
✅ length() - length([1,2,3]) → 3
✅ concat() - concat([1,2], [3,4]) → [1,2,3,4]
✅ merge() - merge({a=1}, {b=2}) → {a=1, b=2}
✅ reverse() - reverse([1, 2, 3, 4]) → [4, 3, 2, 1]
✅ toset() - toset(["a", "b", "a"]) → ["a", "b"]

1. Converts a list into a set.
2. A set has unique values (no duplicates) and order does not matter ✅ tolist() - tolist(toset(["a", "b", "a"])) → ["a", "b"]
3. Converts something (like a set or tuple) into a list.
4. A list keeps order and allows duplicates

📌 Type Conversion
✅ tonumber() - tonumber("10") → 10
✅ tostring() - tostring(100) → "100"
✅ tobool() -

1. tobool("true") → true
2. tobool(1) → true
3. tobool(0) → false

📌 File Functions
✅ file() - file("message.txt") → "Hello Nandan"

1. Reads a file from your system and returns the text inside it.
2. Use this when loading user-data scripts or config files. ✅ fileexists() - fileexists("config.yaml") → true/false ✅ dirname() - get folder / directory path ✅ basename() - get the filename inside the directory

📌 Date/Time Functions
✅ timestamp() - current date and time
✅ formatdate() - formatdate("YYYY-MM-DD", timestamp()) hashtag#changes a date/time into a different format.
✅ timeadd() - adds time (like days, hours, minutes) to a timestamp.

📌 Validation Functions

✅ can() - can(tolist("hello")) → false hashtag#cannot convert string "hello" to list

1. It tells you if an expression will run without error.
2. Use it to safely test something without breaking Terraform. ✅ regex() - regex("^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$", "[e-mail]") hashtag#Check if a value looks like an email
3. Checks if a string matches a regular expression pattern. ✅ contains() - contains(["dev", "prod"], "dev") → true
4. Returns true if an item exists inside a list. ✅ startswith() - startswith("dev-app", "dev") → true hashtag#Returns true if the string starts with the given text. ✅ endswith() - endswith("app-prod", "dev") → false hashtag#Returns true if the string ends with the given text.

📌 Lookup Functions

✅ lookup() - lookup({env = "dev", region = "us-east-1"}, "env", "default") → "dev"

1. It returns a value from a map (key–value pair).
2. If the key does NOT exist → it returns a default value.

✅ element() - element(["a", "b", "c"], 1) → "b" hashtag#returns the item at a specific index from a list.
✅ index() - index(["dev", "stage", "prod"], "stage") → 1 hashtag#Find the Position of a Value in a List.

Refer: https://lnkd.in/gNHnBNDe

hashtag#Devops hashtag#Terraform hashtag#AWS

Thanks to Piyush sachdeva The CloudOps Community