---
page_title: keys function reference
description: The `keys` function returns a list of keys in a given map. Learn how to use the `key` function in Packer templates.
---

# `keys` Function

`keys` takes a map and returns a list containing the keys from that map.

The keys are returned in lexicographical order, ensuring that the result will
be identical as long as the keys in the map don't change.

## Examples

```shell-session
> keys({a=1, c=2, d=3})
[
  "a",
  "c",
  "d",
]
```

## Related Functions

- [`values`](/packer/docs/templates/hcl_templates/functions/collection/values) returns a list of the _values_ from a map.
