udev_device_has_tag - Man Page

Retrieve or set device attributes


#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 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 difference).

Return Value

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.

See Also

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),

Referenced By

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).

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