Name
udev_device_has_tag, udev_device_has_current_tag, 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, 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
#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
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).
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.
History
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.