nbdkit_debug(3)

📦
version 1.48.1 · 10 versions
, in fedora 44

💖 nbdkit_debug 💖

okay bestie, welcome to the nbdkit_debug(3) page, aka the nbdkit manual's little corner for yelling debug stuff into the void ✨

🌸 NAME 🌸

nbdkit_debug, nbdkit_vdebug — print debugging messages for nbdkit 🫶

✨ SYNOPSIS ✨

#include <nbdkit-plugin.h>

void nbdkit_debug (const char *fs, ...);
void nbdkit_vdebug (const char *fs, va_list args);

🎀 DESCRIPTION 🎀

so like, when you're building a plugin or a filter and you wanna peek at what's going on, you reach for nbdkit_debug or nbdkit_vdebug to print debug messages. that's the whole vibe 💅

these functions ship the debug message straight to stderr. and here's the tea: debug messages are only emitted when the server is in verbose mode, i.e. the nbdkit -v option. no -v, no messages, no cap 🧚

nbdkit_debug works like printf(3). nbdkit_vdebug works like vprintf(3). classic behavior, iconic pairing.

and for convenience, both of these functions preserve the value of errno — so your error handling doesn't get wrecked mid-debug 🫶 — and they also support the glibc extension where a single %m in a format string expands to strerror(errno), even on platforms that don't support that natively. lowkey a lifesaver fr fr.

one thing though: nbdkit_debug does not timestamp messages. if you want timestamps you gotta go see nbdkit_timestamp(3). it's giving "do it yourself era" 😭

🌈 LANGUAGE BINDINGS 🌈

in nbdkit-golang-plugin(3):

import "libguestfs.org/nbdkit"
nbdkit.Debug(msg)

in nbdkit-ocaml-plugin(3):

NBDKit.debug : ('a, unit, string, unit) format4 -> 'a

in nbdkit-perl-plugin(3):

Nbdkit::debug ($msg);

in nbdkit-python-plugin(3):

import nbdkit
nbdkit.debug(str)

in nbdkit-rust-plugin(3):

use nbdkit::*;
debug!(fs, ...);

🦋 HISTORY 🦋

nbdkit_debug was present in nbdkit 0.1.0. it's been here since the beginning, main character energy from day one 👑

⭐ SEE ALSO ⭐

👑 AUTHORS 👑

Richard W.M. Jones

Copyright Red Hat

📜 LICENSE 📜

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
  • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
  • Neither the name of Red Hat nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

okay that's the whole page bestie, you ate it up 🍓 this was nbdkit version nbdkit-1.48.1, dated 2026-08-29, and yeah that's the nbdkit_debug(3) moment. mwah 💋 bye pookie 🦋✨

📦 where this page comes from