udev_device_has_current_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_sysattr_list_entry, 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);

       int 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 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 difference).

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.

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

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       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have a bug
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       ⟨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 2020-11-01.  (At that
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systemd 247                                           UDEV_DEVICE_HAS_TAG(3)

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