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NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COLOPHON |
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LIBUDEV(3) libudev LIBUDEV(3)
libudev - API for enumerating and introspecting local devices
#include <libudev.h>
pkg-config --cflags --libs libudev
libudev.h provides an API to introspect and enumerate devices on
the local system. This library is supported, but should not be
used in new projects. Please see sd-device(3) for an equivalent
replacement with a more modern API.
All functions require a libudev context to operate. This context
can be created via udev_new(3). It is used to track library state
and link objects together. No global state is used by libudev,
everything is always linked to a udev context.
All functions listed here are thread-agnostic and only a single
specific thread may operate on a given object during its entire
lifetime. It is safe to allocate multiple independent objects and
use each from a specific thread in parallel. However, it is not
safe to allocate such an object in one thread, and operate or free
it from any other, even if locking is used to ensure these threads
do not operate on it at the very same time.
The code described here uses getenv(3), which is declared to be
not multi-thread-safe. This means that the code calling the
functions described here must not call setenv(3) from a parallel
thread. It is recommended to only do calls to setenv() from an
early phase of the program when no other threads have been
started.
To introspect a local device on a system, a udev device object can
be created via udev_device_new_from_syspath(3) and friends. The
device object allows one to query current state, read and write
attributes and lookup properties of the device in question.
To enumerate local devices on the system, an enumeration object
can be created via udev_enumerate_new(3).
To monitor the local system for hotplugged or unplugged devices, a
monitor can be created via udev_monitor_new_from_netlink(3).
Whenever libudev returns a list of objects, the udev_list_entry(3)
API should be used to iterate, access and modify those lists.
Furthermore, libudev also exports legacy APIs that should not be
used by new software (and as such are not documented as part of
this manual). This includes the hardware database known as
udev_hwdb (please use the new sd-hwdb(3) API instead) and the
udev_queue object to query the udev daemon (which should not be
used by new software at all).
udev_new(3), udev_device_new_from_syspath(3),
udev_enumerate_new(3), udev_monitor_new_from_netlink(3),
udev_list_entry(3), systemd(1), sd-device(3), sd-hwdb(3),
pkg-config(1)
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a
bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 258~rc2 LIBUDEV(3)
Pages that refer to this page: libsystemd(3), sd-device(3), systemd.directives(7), systemd.index(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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