packer/website/content/docs/templates/hcl_templates/functions/collection/index-fn.mdx

---
page_title: index function reference
description: The `index` function finds the element index for a given value in a list. Learn how to use the `index` function in Packer templates.
---

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> [!IMPORTANT]  
> **Documentation Update:** Product documentation previously located in `/website` has moved to the [`hashicorp/web-unified-docs`](https://github.com/hashicorp/web-unified-docs) repository, where all product documentation is now centralized. Please make contributions directly to `web-unified-docs`, since changes to `/website` in this repository will not appear on developer.hashicorp.com.
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# `index` Function

`index` finds the element index for a given value in a list.

```hcl
index(list, value)
```

The returned index is zero-based. This function produces an error if the given
value is not present in the list.

## Examples

```shell-session
> index(["a", "b", "c"], "b")
1
```

## Related Functions

- [`element`](/packer/docs/templates/hcl_templates/functions/collection/element) retrieves a particular element from a list given
  its index.