{"id":12951,"date":"2023-08-18T06:21:46","date_gmt":"2023-08-18T06:21:46","guid":{"rendered":"https:\/\/www.devopsschool.com\/blog\/?p=12951"},"modified":"2023-08-18T06:24:37","modified_gmt":"2023-08-18T06:24:37","slug":"introdcution-of-built-in-functions-in-terraform","status":"publish","type":"post","link":"https:\/\/www.devopsschool.com\/blog\/introdcution-of-built-in-functions-in-terraform\/","title":{"rendered":"Terraform Tutorials: Functions in terraform"},"content":{"rendered":"\n
\"\"<\/figure>\n\n\n\n

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:<\/p>\n\n\n\n

max(5, 12, 9)<\/p>\n\n\n\n

The Terraform language does not support user-defined functions<\/strong>, and so only the functions built in to the language are available for use.<\/p>\n\n\n\n

You can experiment with the behavior of Terraform’s built-in functions from the Terraform expression console, by running the terraform console<\/strong> command:<\/p>\n\n\n\n

max(5, 12, 9)
12<\/p>\n\n\n\n

List of category of terraform Built-in Functions<\/strong><\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

List of top 20 terraform Function<\/h2>\n\n\n\n

Here are the top 20 Terraform functions with one-liner explanations:<\/p>\n\n\n\n

    \n
  1. concat<\/code>: Concatenates two or more lists together.<\/li>\n\n\n\n
  2. element<\/code>: Selects a specific element from a list.<\/li>\n\n\n\n
  3. join<\/code>: Joins a list of strings into a single string.<\/li>\n\n\n\n
  4. map<\/code>: Creates a map from a list of keys and values.<\/li>\n\n\n\n
  5. slice<\/code>: Extracts a slice of a list.<\/li>\n\n\n\n
  6. format<\/code>: Formats a string with placeholders for variables.<\/li>\n\n\n\n
  7. file<\/code>: Reads the contents of a file.<\/li>\n\n\n\n
  8. lookup<\/code>: Looks up a value in a map based on a key.<\/li>\n\n\n\n
  9. replace<\/code>: Replaces parts of a string with other values.<\/li>\n\n\n\n
  10. setproduct<\/code>: Generates all combinations of elements from multiple sets.<\/li>\n\n\n\n
  11. sort<\/code>: Sorts a list of values.<\/li>\n\n\n\n
  12. toset<\/code>: Converts a list to a set, removing any duplicates.<\/li>\n\n\n\n
  13. transpose<\/code>: Transposes a matrix.<\/li>\n\n\n\n
  14. uuid<\/code>: Generates a unique ID.<\/li>\n\n\n\n
  15. abs<\/code>: Returns the absolute value of a number.<\/li>\n\n\n\n
  16. ceil<\/code>: Rounds up to the nearest integer.<\/li>\n\n\n\n
  17. floor<\/code>: Rounds down to the nearest integer.<\/li>\n\n\n\n
  18. max<\/code>: Returns the maximum value from a list.<\/li>\n\n\n\n
  19. min<\/code>: Returns the minimum value from a list.<\/li>\n\n\n\n
  20. timeadd<\/code>: Adds a duration to a timestamp.<\/li>\n<\/ol>\n\n\n\n

    These functions can be used to manipulate and transform data within your Terraform configurations, and can help you to write more flexible and dynamic infrastructure as code.<\/p>\n\n\n\n

    Top terraform function with example usecase with aws provider<\/h2>\n\n\n\n
      \n
    1. count<\/code>: The count<\/code> function allows you to create multiple instances of a resource based on a variable value. For example, you can use count<\/code> to create multiple EC2 instances.<\/strong><\/li>\n<\/ol>\n\n\n
      resource \"aws_instance\"<\/span> \"example\"<\/span> {\n  count = var<\/span>.instance_count\n  ami = \"ami-0c55b159cbfafe1f0\"<\/span>\n  instance_type = \"t2.micro\"<\/span>\n}\n<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
        \n
      1. element<\/code>: The element<\/code> function allows you to select a specific element from a list. For example, you can use element<\/code> to select a specific subnet in a list of subnets.<\/strong><\/li>\n<\/ol>\n\n\n
        resource \"aws_instance\"<\/span> \"example\"<\/span> {\n  subnet_id = element(var<\/span>.subnet_ids, 0<\/span>)\n  ami = \"ami-0c55b159cbfafe1f0\"<\/span>\n  instance_type = \"t2.micro\"<\/span>\n}\n<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
          \n
        1. join<\/code>: The join<\/code> function allows you to join a list of strings into a single string. For example, you can use join<\/code> to create a comma-separated list of security group IDs.<\/strong><\/li>\n<\/ol>\n\n\n
          resource \"aws_security_group_rule\"<\/span> \"example\"<\/span> {\n  security_group_id = aws_security_group.example.id\n  type = \"ingress\"<\/span>\n  from_port = 0<\/span>\n  to_port = 65535<\/span>\n  protocol = \"tcp\"<\/span>\n  cidr_blocks = [join(\",\"<\/span>, aws_security_group.allow_all_sg.*.id)]\n}\n<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
            \n
          1. merge<\/code>: The merge<\/code> function allows you to merge multiple maps into a single map. For example, you can use merge<\/code> to merge multiple tags into a single map.<\/strong><\/li>\n<\/ol>\n\n\n
            resource \"aws_instance\"<\/span> \"example\"<\/span> {\n  ami = \"ami-0c55b159cbfafe1f0\"<\/span>\n  instance_type = \"t2.micro\"<\/span>\n  tags = merge(\n    {\n      \"Name\"<\/span> = \"example-instance\"<\/span>\n    },\n    var<\/span>.extra_tags\n  )\n}\n<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
            List 20 of terraform functions command example on terraform console<\/h2>\n\n\n\n
            Here are 20 examples of Terraform functions that you can try out in the Terraform console:<\/p>\n\n\n\n
              \n
            1. abs(-5)<\/code> – Returns the absolute value of a number.<\/li>\n\n\n\n
            2. basename(\"path\/to\/file.txt\")<\/code> – Returns the basename of a file path.<\/li>\n\n\n\n
            3. ceil(3.14159)<\/code> – Returns the smallest integer greater than or equal to a number.<\/li>\n\n\n\n
            4. coalesce(null, \"default\")<\/code> – Returns the first non-null argument.<\/li>\n\n\n\n
            5. compact([\"a\", \"\", \"b\", null])<\/code> – Returns a list with all empty and null values removed.<\/li>\n\n\n\n
            6. element([\"a\", \"b\", \"c\"], 1)<\/code> – Returns the element at a specific index of a list.<\/li>\n\n\n\n
            7. file(\"path\/to\/file.txt\")<\/code> – Returns the contents of a file.<\/li>\n\n\n\n
            8. format(\"Hello, %s!\", \"Terraform\")<\/code> – Returns a formatted string.<\/li>\n\n\n\n
            9. index([\"a\", \"b\", \"c\"], \"b\")<\/code> – Returns the index of an element in a list.<\/li>\n\n\n\n
            10. join(\", \", [\"a\", \"b\", \"c\"])<\/code> – Returns a string with the elements of a list joined together with a delimiter.<\/li>\n\n\n\n
            11. jsonencode({\"key\": \"value\"})<\/code> – Returns a JSON-encoded string.<\/li>\n\n\n\n
            12. length(\"hello\")<\/code> – Returns the length of a string.<\/li>\n\n\n\n
            13. list(\"a\", \"b\", \"c\")<\/code> – Returns a list.<\/li>\n\n\n\n
            14. lower(\"HELLO\")<\/code> – Returns a string with all characters in lowercase.<\/li>\n\n\n\n
            15. map(\"key\", \"value\")<\/code> – Returns a map.<\/li>\n\n\n\n
            16. merge({\"a\": 1}, {\"b\": 2})<\/code> – Returns a map with two maps merged together.<\/li>\n\n\n\n
            17. range(1, 5)<\/code> – Returns a list of numbers between two values.<\/li>\n\n\n\n
            18. regex(\"hello\", \"^h\")<\/code> – Returns a boolean indicating whether a string matches a regular expression.<\/li>\n\n\n\n
            19. reverse([\"a\", \"b\", \"c\"])<\/code> – Returns a list with the elements in reverse order.<\/li>\n\n\n\n
            20. timeadd(\"2022-02-15T00:00:00Z\", \"24h\")<\/code> – Returns a string representing a time that is a specified duration after a given time.<\/li>\n<\/ol>\n\n\n\n
              You can try these functions out in the Terraform console by running terraform console<\/code> in your terminal and typing in the function call. For example, to try out lower(\"HELLO\")<\/code>, you would type lower(\"HELLO\")<\/code> into the console and hit enter.<\/p>\n\n\n\n
              Example Program<\/h2>\n\n\n\n
              \n\n\n
              variable \"instance_count1\"<\/span> {\n  type = number\n  default<\/span> = 1<\/span>\n}\n\nvariable \"instance_count2\"<\/span> {\n  type = number\n  default<\/span> = 2<\/span>\n}\n\nresource \"aws_instance\"<\/span> \"web\"<\/span> {\n  ami           = \"ami-053b0d53c279acc90\"<\/span>\n  instance_type = \"t3.micro\"<\/span>\n  count = sum([var<\/span>.instance_count1,var<\/span>.instance_count2])\n  tags = {\n    Name = \"RajeshKumar\"<\/span>\n  }\n}<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
              \n\n\n
              variable \"plans\"<\/span> {\n    type = map\n    default<\/span> = {\n        \"5USD\"<\/span>  = \"1xCPU-1GB\"<\/span>\n        \"10USD\"<\/span> = \"1xCPU-2GB\"<\/span>\n        \"20USD\"<\/span> = \"2xCPU-4GB\"<\/span>\n    }\n}\n\nvariable \"storage_sizes\"<\/span> {\n    type = map\n    default<\/span> = {\n        \"1xCPU-1GB\"<\/span>  = \"25\"<\/span>\n        \"1xCPU-2GB\"<\/span>  = \"50\"<\/span>\n        \"2xCPU-4GB\"<\/span>  = \"80\"<\/span>\n    }\n}\n\nresource \"aws_ebs_volume\"<\/span> \"example\"<\/span> {\n  availability_zone = \"us-east-1a\"<\/span>       \n  size              = lookup(var<\/span>.storage_sizes, var<\/span>.plans[\"5USD\"<\/span>])                \n\n  tags = {\n    Name = \"example-ebs-volume\"<\/span>\n  }\n}\n\n<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
              \n\n\n
              resource \"aws_key_pair\"<\/span> \"example\"<\/span> {\n  key_name   = \"examplekey\"<\/span>\n  public_key = file(\"~\/.ssh\/terraform.pub\"<\/span>)\n}<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
              \n\n\n
              resource \"aws_instance\"<\/span> \"example\"<\/span> {\n  key_name      = aws_key_pair.example.key_name\n  ami           = \"ami-04590e7389a6e577c\"<\/span>\n  instance_type = \"t2.micro\"<\/span>\n\n  connection {\n    type        = \"ssh\"<\/span>\n    user        = \"ec2-user\"<\/span>\n    private_key = file(\"rajesh.pem\"<\/span>)\n    host        = self<\/span>.public_ip\n  }\n\n  provisioner \"remote-exec\"<\/span> {\n    inline = [\n      \"sudo amazon-linux-extras enable nginx1.12\"<\/span>,\n      \"sudo yum -y install nginx\"<\/span>,\n      \"sudo systemctl start nginx\"<\/span>\n    ]\n  }\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
              \n\n\n