[#OSSL_trace_begin]
= OSSL&lowbar;trace&lowbar;begin
:mrdocs:

Begin a locked trace output group for `category` and return its BIO channel&period;

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:BIO.adoc[BIO]*
OSSL&lowbar;trace&lowbar;begin(int category);
----

== Description

Pair with OSSL&lowbar;trace&lowbar;end() using the same category and returned BIO&period;

== Return Value

Trace BIO to write to, or NULL if tracing is disabled for `category&period;`

== Parameters

[cols="1,4"]
|===
| Name| Description
| *category*
| OSSL&lowbar;TRACE&lowbar;CATEGORY&lowbar;&ast; value selecting the channel&period;
|===


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