BIO_F_NULL(3)

💅 BIO_F_NULL(3) — the null filter, bestie ✨

okay so this one lives in the Library Functions Manual and it's from libcrypto, which you already know and love 🫶. It's a <pink>filter BIO</pink> page, and honestly? It's giving minimalist icon. Let's get into it.

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✨ SYNOPSIS ✨

library “libcrypto” #include <openssl/bio.h>

const BIO_METHOD *
BIO_f_null(void);

that's it. that's the whole vibe. 🎀

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🌸 DESCRIPTION 🌸

So BIO_f_null() hands you back the null filter BIO method. And what does a null filter BIO do? literally nothing 💀. That's the whole job. As may be apparent (their words, not mine, but I felt that), a null filter BIO is not particularly useful. It's the human equivalent of a group chat member who never types. iconic for existing, tbh.

Here's the cute part though: every single request you send to a null filter BIO gets passed through to the next BIO in the chain. So a BIO chain that contains a null filter BIO behaves exactly as though the BIO wasn't there at all. Ghost mode. 👻

⚠️ but bestie, listen — a chain containing a null filter BIO cannot be copied with BIO_dup_chain(3). Any attempt to do so fails and returns NULL. no cap. don't try it and then act surprised 😭

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👑 RETURN VALUES 👑

BIO_f_null() returns the null filter BIO method. slay, consistent.

And when you call stuff on an actual null filter BIO object:

• BIO_method_type(3) returns the constant BIO_TYPE_NULL_FILTER
• BIO_method_name(3) returns a pointer to the static string "NULL filter"

🙈 and here's the disclaimer they insisted on: that string is not to be confused with a NUL string nor with a NULL pointer. three very different things, bestie. do not mix them up, i'm begging. 💅

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🦋 SEE ALSO 🦋

• BIO_new(3)

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💖 HISTORY 💖

BIO_f_null() first appeared in SSLeay 0.8.0 and has been available since OpenBSD 2.4. an elder. a legend. main character since day one 🌈

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⭐ anyway, that's the null filter — does nothing, gets copied by no one, and somehow still has a whole manpage. we have no choice but to stan. ✨

mwah 💋 — this page was served up by Debian on June 8, 2025. go touch some grass now, bestie 🍓