The Terraform lookup function is one that falls under the built-in functions category. It retrieves a single value of an element in a map. This function takes the map name, key, and a default value as its arguments and looks for the key in the specified map.
Full Answer
How does the lookup function work in TerraForm?
Until Terraform 0.12.7, the lookup function is indeed restricted to only work with maps of primitive types. In Terraform 0.12.7 it was generalized to behave the same way as the index operator, but with the extra rule of returning the default value if the requested key isn't present.
Can terraform check if a map is a specific type?
If you just write "map" then that's a legacy shorthand for map (any), in which case Terraform can only check that it's a map of any single type, not specifically what the element type must be. I'd recommend always using exact type constraints in Terraform 0.12.0 or later.
What are the most used functions in TerraForm?
This has got to be one of the most used functions in Terraform. There are a ton of data sources that return a map of values you might want to parse through. AWS AMIs, Azure VMs, firewall rules, metadata tags.
Is it possible to use INDEX syntax in TerraForm?
You can also use the index syntax in Terraform v0.11 or earlier, but it must be wrapped in a template string because that is how we indicate to Terraform that we intend to use an expression in those older versions:
What is the use of lookup in terraform?
» lookup Function lookup retrieves the value of a single element from a map, given its key. If the given key does not exist, the given default value is returned instead.
What is flatten in terraform?
» flatten Function flatten takes a list and replaces any elements that are lists with a flattened sequence of the list contents.
What are the data types in terraform?
Terraform supports a number of types, including string, number, bool, list, map, set, object, tuple, and any....Primitive Typesstring: a sequence of characters representing some text, such as “hello”.number: a numeric value. ... bool: either true or false.
How do you use functions in terraform?
The templatefile function fills in a file with Terraform input variables and reads the file into your configuration.Review the template file.Add the templatefile function.Initialize and apply the Terraform configuration.Review the AMI variables.Review the main configuration.More items...
What is dynamic terraform?
Terraform dynamic blocks are used to create repeatable nested blocks inside an argument. These dynamic blocks represent separate objects that are related or embedded with the containing object. Dynamic blocks are a lot like the for expression except dynamic blocks iterate over complex values.
What is map type in terraform?
Terraform variable Map Type Explained!!! Maps are a collection of string keys and string values. These can be useful for selecting values based on predefined parameters such as the server configuration by the monthly price. We've replaced our sensitive strings with variables, but we still are hard-coding AMIs.
What is main TF in Terraform?
main.tf: This is our main configuration file where we are going to define our resource definition. variables.tf: This is the file where we are going to define our variables. outputs.tf: This file contains output definitions for our resources.
What is difference between data and resource in Terraform?
The main difference between Terraform data source, resource and variable is : Resource: Provisioning of resources/infra on our platform. Create, Update and delete! Variable Provides predefined values as variables on our IAC.
How do Terraform variables work?
Terraform variables can be defined within the infrastructure plan but are recommended to be stored in their own variables file. All files in your Terraform directory using the . tf file format will be automatically loaded during operations. Create a variables file, for example, variables.tf and open the file for edit.
What is module in Terraform?
A module is a container for multiple resources that are used together. Every Terraform configuration has at least one module, known as its root module, which consists of the resources defined in the . tf files in the main working directory.
What is data Terraform?
Data sources in Terraform are used to get information about resources external to Terraform, and use them to set up your Terraform resources. For example, a list of IP addresses a cloud provider exposes.
What language is Terraform written in?
GoTerraform / Programming languageGo is a statically typed, compiled programming language designed at Google by Robert Griesemer, Rob Pike, and Ken Thompson. It is syntactically similar to C, but with memory safety, garbage collection, structural typing, and CSP-style concurrency. Wikipedia
What is it?
Returns: Takes a map, a key, and an optional default value. Returns the value in the map that corresponds to the key if found. If not found, returns the optional default value or throws an error.
Why use it?
This has got to be one of the most used functions in Terraform. There are a ton of data sources that return a map of values you might want to parse through. AWS AMIs, Azure VMs, firewall rules, metadata tags. That’s just a few off the top of my head. If you’ve got a map of key pairs, lookup is your pal.
Lessons Learned
The documentation on the Terraform site states that the function will not work with nested maps, i.e. maps with maps as the value associated to a key. I tried using a nested map for funsies, and it didn’t throw an error. What I learned is that the function evaluates the presence of the key first.
