[#BIO_read]
= BIO&lowbar;read
:mrdocs:

Read up to `dlen` bytes from BIO `b` into `data&period;`

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
BIO&lowbar;read(
    xref:BIO.adoc[BIO]* b,
    void* data,
    int dlen);
----

== Return Value

Number of bytes read, 0 on EOF&sol;no data, or a negative value on error (see BIO&lowbar;should&lowbar;retry)&period;

== Parameters

[cols="1,4"]
|===
| Name| Description
| *b*
| Source BIO&period;
| *data*
| Destination buffer&period;
| *dlen*
| Maximum number of bytes to read (must be non&hyphen;negative and fit in int)&period;
|===


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