> ## Documentation Index
> Fetch the complete documentation index at: https://docs.chronosphere.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Copy keys

export const entity_0 = "copy keys processing rule"

The copy keys [processing rule](/ingest/pipeline/processing-rules) copies the value of
a specified source key to the value of a specified destination key. This destination
can either be a new or existing key.

## Configuration parameters

Use the parameters in this section to configure the {entity_0}. The
Telemetry Pipeline web interface uses the items in the **Name** column to
describe these parameters. [Pipeline configuration files](/ingest/pipeline/v2/configure/config-files)
use the items in the **Key** column as YAML keys.

| Name                    | Key           | Description                                                                                                                                                                                                              | Default      |
| ----------------------- | ------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------ |
| **Source key**          | `src`         | Required. The key whose value to copy.                                                                                                                                                                                   | *none*       |
| **Destination key**     | `dst`         | Required. The key whose value is set to match the source key. If no matching key exists, this rule creates a new key and then set its value accordingly.                                                                 | *none*       |
| **Regex engine**        | `regexEngine` | Required. The [engine](/ingest/pipeline/processing-rules#regex-engines) to parse your regular expression. Accepted values: `GNU`, `Oniguruma`, `PCRE2`, `POSIX`, `TRE`.                                                  | `PCRE2`      |
| **Regex mode** checkbox | `regexMode`   | Indicates whether the values of the source key and destination key are regular expressions. If selected, **Source key** is treated as a regular expression and **Destination key** is treated as a substitution pattern. | Not selected |
| **Comment**             | `comment`     | A custom note or description of the rule's function. This text is displayed next to the rule's name in the **Actions** list in the processing rules interface.                                                           | *none*       |

## Example

Using the block keys rule lets you copy the same value across multiple keys or
create a new key with the same value as an existing key.

For example, given the following sample website log data:

```json theme={null}
{"timestamp":"2023-03-28T09:08:41.64283645Z","user_id":3,"page_id":30,"action":"purchase"}
{"timestamp":"2023-03-28T09:08:42.643343109Z","user_id":4,"page_id":10,"action":"purchase"}
{"timestamp":"2023-03-28T09:08:48.643600498Z","user_id":1,"page_id":50,"action":"click"}
{"timestamp":"2023-03-28T09:08:50.643773688Z","user_id":5,"page_id":40,"action":"purchase"}
{"timestamp":"2023-03-28T09:08:51.643932272Z","user_id":1,"page_id":30,"action":"purchase"}
{"timestamp":"2023-03-28T09:08:56.644080944Z","user_id":2,"page_id":40,"action":"click"}
{"timestamp":"2023-03-28T09:09:03.64425954Z","user_id":3,"page_id":30,"action":"click"}
{"timestamp":"2023-03-28T09:09:03.644317046Z","user_id":1,"page_id":20,"action":"view"}
{"timestamp":"2023-03-28T09:09:10.64447719Z","user_id":2,"page_id":50,"action":"purchase"}
{"timestamp":"2023-03-28T09:09:17.644810963Z","user_id":2,"page_id":10,"action":"view"}
{"timestamp":"2023-03-28T09:09:20.644994805Z","user_id":1,"page_id":50,"action":"view"}
```

A processing rule with the **Source key** value `page_id` and the
**Destination key** value `product_id` returns the following result:

```json theme={null}
{"user_id":3,"product_id":30,"page_id":30,"action":"purchase","timestamp":"2023-03-28T09:08:41.64283645Z"}
{"user_id":4,"product_id":10,"page_id":10,"action":"purchase","timestamp":"2023-03-28T09:08:42.643343109Z"}
{"user_id":1,"product_id":50,"page_id":50,"action":"click","timestamp":"2023-03-28T09:08:48.643600498Z"}
{"user_id":5,"product_id":40,"page_id":40,"action":"purchase","timestamp":"2023-03-28T09:08:50.643773688Z"}
{"user_id":1,"product_id":30,"page_id":30,"action":"purchase","timestamp":"2023-03-28T09:08:51.643932272Z"}
{"user_id":2,"product_id":40,"page_id":40,"action":"click","timestamp":"2023-03-28T09:08:56.644080944Z"}
{"user_id":3,"product_id":30,"page_id":30,"action":"click","timestamp":"2023-03-28T09:09:03.64425954Z"}
{"user_id":1,"product_id":20,"page_id":20,"action":"view","timestamp":"2023-03-28T09:09:03.644317046Z"}
{"user_id":2,"product_id":50,"page_id":50,"action":"purchase","timestamp":"2023-03-28T09:09:10.64447719Z"}
{"user_id":2,"product_id":10,"page_id":10,"action":"view","timestamp":"2023-03-28T09:09:17.644810963Z"}
{"user_id":1,"product_id":50,"page_id":50,"action":"view","timestamp":"2023-03-28T09:09:20.644994805Z"}
```

This rule copied the value of each log's `page_id` key to the value of a new key
called `product_id`.