terraform/website/docs/configuration/functions/lookup.html.md

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---
layout: "functions"
page_title: "lookup - Functions - Configuration Language"
sidebar_current: "docs-funcs-collection-lookup"
description: |-
The lookup function retrieves an element value from a map given its key.
---
# `lookup` Function
`lookup` retrieves the value of a single element from a map, given its key.
If the given key does not exist, a the given default value is returned instead.
```
lookup(map, key, default)
```
-> For historical reasons, the `default` parameter is actually optional. However,
omitting `default` is deprecated since v0.7 because that would then be
equivalent to the native index syntax, `map[key]`.
## Examples
```
> lookup({a="ay", b="bee"}, "a", "what?")
ay
> lookup({a="ay", b="bee"}, "c", "what?")
what?
```
## Related Functions
* [`element`](./element.html) retrieves a value from a _list_ given its _index_.