[#BIO_vsnprintf]
= BIO_vsnprintf
:mrdocs:

Format a string into `buf` like vsnprintf, using OpenSSL's portable formatter.

== Synopsis

Declared in `<openssl/bio.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
BIO_vsnprintf(
    char* buf,
    size_t n,
    char const* format,
    va_list args);
----

== Return Value

Length that would have been written excluding the NUL, or ‐1 on encoding error.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *buf*
| Destination buffer.
| *n*
| Capacity of `buf` in bytes (including the trailing NUL).
| *format*
| printf‐style format string.
| *args*
| Variable‐argument list for `format.`
|===


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