[#BIO_get_callback]
= BIO_get_callback
:mrdocs:

Return the legacy BIO callback previously set with BIO_set_callback() (deprecated).

== Synopsis

Declared in `<openssl/bio.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
[[deprecated]]
xref:BIO_callback_fn.adoc[BIO_callback_fn]
BIO_get_callback(xref:BIO.adoc[BIO] const* b);
----

[WARNING]
====
https://en.cppreference.com/cpp/language/attributes/deprecated[Deprecated^]. Use of this entity is allowed but discouraged.
====
== Return Value

Callback function pointer, or NULL if unset.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *b*
| BIO to query.
|===


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