libudev(3) — Linux manual page


LIBUDEV(3)                       libudev                      LIBUDEV(3)

NAME         top

       libudev - API for enumerating and introspecting local devices

SYNOPSIS         top

       #include <libudev.h>

       pkg-config --cflags --libs libudev

DESCRIPTION         top

       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's safe to allocate multiple independent objects and
       use each from a specific thread in parallel. However, it's 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 don't 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

       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).

SEE ALSO         top

       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),

COLOPHON         top

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systemd 257~devel                                             LIBUDEV(3)

Pages that refer to this page: sd-device(3)systemd.directives(7)systemd.index(7)