[#BIO_set_callback_ex]
= BIO&lowbar;set&lowbar;callback&lowbar;ex
:mrdocs:

Install an extended pre&sol;post I&sol;O callback on a BIO&period;

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
void
BIO&lowbar;set&lowbar;callback&lowbar;ex(
    xref:BIO.adoc[BIO]* b,
    xref:BIO_callback_fn_ex.adoc[BIO&lowbar;callback&lowbar;fn&lowbar;ex] callback);
----

== Parameters

[cols="1,4"]
|===
| Name| Description
| *b*
| BIO whose callback is replaced&period;
| *callback*
| Extended callback function, or NULL to clear&period;
|===


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