[#BIO_ctrl]
= BIO&lowbar;ctrl
:mrdocs:

Invoke a type&hyphen;specific control operation on a BIO&period;

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
long
BIO&lowbar;ctrl(
    xref:BIO.adoc[BIO]* bp,
    int cmd,
    long larg,
    void* parg);
----

== Return Value

Command&hyphen;specific long result&semi; often 1 for success and 0&sol;negative for failure&period;

== Parameters

[cols="1,4"]
|===
| Name| Description
| *bp*
| BIO to control&period;
| *cmd*
| BIO&lowbar;CTRL&lowbar;&ast; (or type&hyphen;specific) command code&period;
| *larg*
| Integer&sol;long argument for `cmd&period;`
| *parg*
| Pointer argument for `cmd,` or NULL&period;
|===


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