All functions require a libudev context to operate. This context can be create 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. Furthermore, multiple different udev contexts can be used in parallel by multiple threads. However, a single context must not be accessed by multiple threads in parallel. The caller is responsible for providing suitable locking if they intend to use it from multiple threads.

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 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).