---
title: "echo_struct"
url: "https://docs.adyen.com/point-of-sale/classic-library-deprecation/classic-library-integrations/c-library-integration/structs/echo_struct"
source_url: "https://docs.adyen.com/point-of-sale/classic-library-deprecation/classic-library-integrations/c-library-integration/structs/echo_struct.md"
canonical: "https://docs.adyen.com/point-of-sale/classic-library-deprecation/classic-library-integrations/c-library-integration/structs/echo_struct"
last_modified: "2026-05-24T12:54:31+02:00"
language: "en"
---

# echo\_struct

[View source](/point-of-sale/classic-library-deprecation/classic-library-integrations/c-library-integration/structs/echo_struct.md)

A user-defined struct that is echoed back in the callback. Use this to share a data struct between the call to the library and the callback from the library. You can add any pointer to `echo_struct`, and this will be returned on its specific callback.