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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | HISTORY | SEE ALSO | COLOPHON |
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UDEV_DEV..._SYSPATH(3) udev_device_new_from_syspathUDEV_DEV..._SYSPATH(3)
udev_device_new_from_syspath, udev_device_new_from_devnum,
udev_device_new_from_subsystem_sysname,
udev_device_new_from_device_id, udev_device_new_from_environment,
udev_device_ref, udev_device_unref - Create, acquire and release a
udev device object
#include <libudev.h>
struct udev_device
*udev_device_new_from_syspath(struct udev *udev,
const char *syspath);
struct udev_device *udev_device_new_from_devnum(struct udev *udev,
char type,
dev_t devnum);
struct udev_device
*udev_device_new_from_subsystem_sysname(struct udev *udev,
const char *subsystem,
const char *sysname);
struct udev_device
*udev_device_new_from_device_id(struct udev *udev,
const char *id);
struct udev_device
*udev_device_new_from_environment(struct udev *udev);
struct udev_device
*udev_device_ref(struct udev_device *udev_device);
struct udev_device
*udev_device_unref(struct udev_device *udev_device);
udev_device_new_from_syspath(), udev_device_new_from_devnum(),
udev_device_new_from_subsystem_sysname(),
udev_device_new_from_device_id(), and
udev_device_new_from_environment() allocate a new udev device
object and returns a pointer to it. This object is opaque and must
not be accessed by the caller via different means than functions
provided by libudev. Initially, the reference count of the device
is 1. You can acquire further references, and drop gained
references via udev_device_ref() and udev_device_unref(). Once the
reference count hits 0, the device object is destroyed and freed.
udev_device_new_from_syspath(), udev_device_new_from_devnum(),
udev_device_new_from_subsystem_sysname(), and
udev_device_new_from_device_id() create the device object based on
information found in /sys/, annotated with properties from the
udev-internal device database. A syspath is any subdirectory of
/sys/, with the restriction that a subdirectory of /sys/devices
(or a symlink to one) represents a real device and as such must
contain a uevent file. udev_device_new_from_devnum() takes a
device type, which can be b for block devices or c for character
devices, as well as a devnum (see makedev(3)).
udev_device_new_from_subsystem_sysname() looks up devices based on
the provided subsystem and sysname (see
udev_device_get_subsystem(3) and udev_device_get_sysname(3)) and
udev_device_new_from_device_id() looks up devices based on the
provided device ID, which is a special string in one of the
following four forms:
Table 1. Device ID strings
┌───────────────┬──────────────────────────┐
│ Example │ Explanation │
├───────────────┼──────────────────────────┤
│ b8:2 │ block device major:minor │
├───────────────┼──────────────────────────┤
│ c128:1 │ char device major:minor │
├───────────────┼──────────────────────────┤
│ n3 │ network device ifindex │
├───────────────┼──────────────────────────┤
│ +sound:card29 │ kernel driver core │
│ │ subsystem:device name │
└───────────────┴──────────────────────────┘
udev_device_new_from_environment() creates a device from the
current environment (see environ(7)). Each key-value pair is
interpreted in the same way as if it was received in an uevent
(see udev_monitor_receive_device(3)). The keys DEVPATH, SUBSYSTEM,
ACTION, and SEQNUM are mandatory.
On success, udev_device_new_from_syspath(),
udev_device_new_from_devnum(),
udev_device_new_from_subsystem_sysname(),
udev_device_new_from_device_id() and
udev_device_new_from_environment() return a pointer to the
allocated udev device. On failure, NULL is returned, and errno is
set appropriately. udev_device_ref() returns the argument that it
was passed, unmodified. udev_device_unref() always returns NULL.
udev_device_new_from_syspath(), udev_device_new_from_devnum(),
udev_device_new_from_subsystem_sysname(),
udev_device_new_from_device_id(),
udev_device_new_from_environment(), udev_device_ref(), and
udev_device_unref() were added in version 221.
udev_new(3), udev_device_get_syspath(3), udev_device_has_tag(3),
udev_enumerate_new(3), udev_monitor_new_from_netlink(3),
udev_list_entry(3), systemd(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
man-pages@man7.org
systemd 258~rc2 UDEV_DEV..._SYSPATH(3)
Pages that refer to this page: libudev(3), udev_device_get_syspath(3), udev_device_has_tag(3), udev_enumerate_add_match_subsystem(3), udev_enumerate_new(3), udev_enumerate_scan_devices(3), udev_list_entry(3), udev_monitor_filter_update(3), udev_monitor_new_from_netlink(3), udev_monitor_receive_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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