udev_device_has_tag(3) — Linux manual page


UDEV_DEVICE_HAS_TAG(3)     udev_device_has_tag    UDEV_DEVICE_HAS_TAG(3)

NAME         top

       udev_device_has_tag, udev_device_has_current_tag,
       udev_device_get_property_value, udev_device_get_sysattr_value,
       udev_device_set_sysattr_value - Retrieve or set device attributes

SYNOPSIS         top

       #include <libudev.h>

       int udev_device_has_tag(struct udev_device *udev_device,
                               const char *tag);

       int udev_device_has_current_tag(struct udev_device *udev_device,
                                       const char *tag);

       struct udev_list_entry
                                                                   *udev_device_get_devlinks_list_entry(struct udev_device *udev_device);

       struct udev_list_entry
                                                                     *udev_device_get_properties_list_entry(struct udev_device *udev_device);

       struct udev_list_entry
                                                               *udev_device_get_tags_list_entry(struct udev_device *udev_device);

       struct udev_list_entry
                                                                       *udev_device_get_current_tags_list_entry(struct udev_device *udev_device);

       struct udev_list_entry
                                                                  *udev_device_get_sysattr_list_entry(struct udev_device *udev_device);

       const char
                                                  *udev_device_get_property_value(struct udev_device *udev_device,
                                                  const char *key);

       const char
                                                 *udev_device_get_sysattr_value(struct udev_device *udev_device,
                                                 const char *sysattr);

                                         udev_device_set_sysattr_value(struct udev_device *udev_device,
                                         const char *sysattr,
                                         const char *value);

DESCRIPTION         top

       udev_device_has_tag() returns a valuer larger than zero if the
       specified device object has the indicated tag assigned to it, and
       zero otherwise. See udev(7) for details on the tags concept.
       udev_device_has_current_tag() executes a similar check, however
       only determines whether the indicated tag was set as result of
       the most recent event seen for the device. Tags are "sticky",
       i.e. once set for a device they remain on the device until the
       device is unplugged, even if the rules run for later events of
       the same device do not set them anymore. Any tag for which
       udev_device_has_current_tag() returns true will hence also return
       true when passed to udev_device_has_tag(), but the opposite might
       not be true, in case a tag is no longer configured by the rules
       applied to the most recent device even.

       udev_device_get_tags_list_entry() returns a udev_list_entry
       object, encapsulating a list of tags set for the specified
       device. Similar, udev_device_get_current_tags_list_entry()
       returns a list of tags set for the specified device as effect of
       the most recent device event seen (see above for details on the

RETURN VALUE         top

       On success, udev_device_has_tag() and
       udev_device_has_current_tag() return positive or 0, depending on
       whether the device has the given tag or not. On failure, a
       negative error code is returned.

       On success, udev_device_get_devlinks_list_entry(),
       udev_device_get_current_tags_list_entry() and
       udev_device_get_sysattr_list_entry() return a pointer to the
       first entry of the retrieved list. If that list is empty, or if
       an error occurred, NULL is returned.

       On success, udev_device_get_property_value() and
       udev_device_get_sysattr_value() return a pointer to a constant
       string of the requested value. On error, NULL is returned.
       Attributes that may contain NUL bytes should not be retrieved
       with udev_device_get_sysattr_value(); instead, read them directly
       from the files within the device's syspath.

       On success, udev_device_set_sysattr_value() returns an integer
       greater than, or equal to, 0. On failure, a negative error code
       is returned. Values that contain NUL bytes should not be set with
       this function; instead, write them directly to the files within
       the device's syspath.

HISTORY         top

       udev_device_get_property_value(), udev_device_has_tag(),
       udev_device_get_sysattr_value(), and
       udev_device_set_sysattr_value() were added in version 221.

       udev_device_has_current_tag() and
       udev_device_get_current_tags_list_entry() were added in version

SEE ALSO         top

       udev(7), udev_new(3), udev_device_new_from_syspath(3),
       udev_device_get_syspath(3), udev_enumerate_new(3),
       udev_monitor_new_from_netlink(3), udev_list_entry(3), systemd(1),

COLOPHON         top

       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
       This page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2023-12-22.  (At that
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       problems in this HTML version of the page, or you believe there
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       (which is not part of the original manual page), send a mail to

systemd 255                                       UDEV_DEVICE_HAS_TAG(3)

Pages that refer to this page: udev_device_get_syspath(3)udev_device_new_from_syspath(3)systemd.directives(7)systemd.index(7)