[#BIO_get_callback]
= BIO&lowbar;get&lowbar;callback
:mrdocs:

Return the legacy BIO callback previously set with BIO&lowbar;set&lowbar;callback() (deprecated)&period;

== Synopsis

Declared in `&lt;openssl&sol;bio&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
&lsqb;&lsqb;deprecated&rsqb;&rsqb;
xref:BIO_callback_fn.adoc[BIO&lowbar;callback&lowbar;fn]
BIO&lowbar;get&lowbar;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&period;

== Parameters

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


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