COMEDI_COMMAND(3)

💅 COMEDI_COMMAND 💅

okay bestie, welcome to the comedi_command page from the Comedi reference, section 3 of the manual. this is the one that makes your device start streaming, and no cap, it's kind of a big deal. 🎀

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✨ NAME ✨

comedi_command — start streaming input/output 🦋

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🌸 SYNOPSIS 🌸

#include <comedilib.h>

int comedi_command(comedi_t * device, comedi_cmd * command);

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💖 DESCRIPTION 💖

so. the function comedi_command starts a streaming input or output. yes, literally. it's the moment your acquisition goes from "sitting there" to "going off". ✨

the command structure that command points to is the whole vibe board here — it specifies all the settings for the acquisition. that's where you tell it what you want.

⚠️ but listen: the command must be able to pass comedi_command_test with a return value of 0. if it can't, comedi_command will fail. no passing go, no vibes. 💀

then, once it's streaming:

• for input subdevices, you read sample values using the function read on the device file descriptor 🫶
• for output subdevices, you write sample values using the function write 👑

iykyk. that's the whole loop. iconic behaviour fr fr.

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⭐ RETURN VALUE ⭐

• on success → 0 is returned 🎉
• on failure → -1 is returned 😭

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👑 AUTHORS 👑

the legends who made this happen, periodt:

• David Schleef <ds@schleef.org> — Author.
• Frank Mori Hess <fmhess@users.sourceforge.net> — Author.
• Herman Bruyninckx <Herman.Bruyninckx@mech.kuleuven.ac.be> — Author.
• Bernd Porr <tech@linux-usb-daq.co.uk> — Author.
• Ian Abbott <abbotti@mev.co.uk> — Author.
• Éric Piel <piel@delmic.com> — Author.

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🎀 COPYRIGHT 🎀

Copyright © 1998-2003 David Schleef Copyright © 2001-2003, 2005, 2008 Frank Mori Hess Copyright © 2002-2003 Herman Bruyninckx Copyright © 2012 Bernd Porr Copyright © 2012 Ian Abbott Copyright © 2012, 2015 Éric Piel

This document is part of Comedilib. In the context of this document, the term "source code" as defined by the license is interpreted as the XML source.

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, version 2.1 of the License.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.

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💜 ngl that license section is giving very much "read the whole thing" energy, but bestie you gotta respect the LGPL. it's the rules. 🌈

Comedi · 03/20/2026 · COMEDI_COMMAND(3)

and that's the page babes, go stream something ✨🦋💅