udev_device_has_tag - Man Page

#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);

udev_device_has_tag() returns a value 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 difference)​.

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_properties_list_entry(), udev_device_get_tags_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​.

udev_device_get_devlinks_list_entry(), udev_device_get_properties_list_entry(), udev_device_get_tags_list_entry(), udev_device_get_sysattr_list_entry(), 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 247​.

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)

systemd.directives(7), systemd.index(7), udev_device_get_syspath(3), udev_device_new_from_syspath(3).

The man pages udev_device_get_current_tags_list_entry(3), udev_device_get_devlinks_list_entry(3), udev_device_get_properties_list_entry(3), udev_device_get_property_value(3), udev_device_get_sysattr_list_entry(3), udev_device_get_sysattr_value(3), udev_device_get_tags_list_entry(3), udev_device_has_current_tag(3) and udev_device_set_sysattr_value(3) are aliases of udev_device_has_tag(3).