Current File : //usr/lib/python2.7/site-packages/pyudev/device.py
# -*- coding: utf-8 -*-
# Copyright (C) 2011, 2012 Sebastian Wiesner <lunaryorn@googlemail.com>
# This library is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by the
# Free Software Foundation; either version 2.1 of the License, or (at your
# option) any later version.
# This library is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
# for more details.
# You should have received a copy of the GNU Lesser General Public License
# along with this library; if not, write to the Free Software Foundation,
# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
"""
pyudev.device
=============
Device class implementation of :mod:`pyudev`.
.. moduleauthor:: Sebastian Wiesner <lunaryorn@googlemail.com>
"""
from __future__ import (print_function, division, unicode_literals,
absolute_import)
import os
from collections import Mapping, Container, Iterable
from datetime import timedelta
from pyudev._util import (ensure_byte_string, ensure_unicode_string,
udev_list_iterate, string_to_bool,
get_device_type)
__all__ = ['Device', 'Attributes', 'Tags',
'DeviceNotFoundError', 'DeviceNotFoundAtPathError',
'DeviceNotFoundByNameError', 'DeviceNotFoundByNumberError',
'DeviceNotFoundInEnvironmentError']
class DeviceNotFoundError(LookupError):
"""
An error indicating that no :class:`Device` was found.
.. versionchanged:: 0.5
Renamed from ``NoSuchDeviceError`` to its current name.
"""
class DeviceNotFoundAtPathError(DeviceNotFoundError):
"""
A :exc:`DeviceNotFoundError` indicating that no :class:`Device` was
found at a given path.
"""
def __init__(self, sys_path):
DeviceNotFoundError.__init__(self, sys_path)
@property
def sys_path(self):
"""
The path that caused this error as string.
"""
return self.args[0]
def __str__(self):
return 'No device at {0!r}'.format(self.sys_path)
class DeviceNotFoundByNameError(DeviceNotFoundError):
"""
A :exc:`DeviceNotFoundError` indicating that no :class:`Device` was
found with a given name.
"""
def __init__(self, subsystem, sys_name):
DeviceNotFoundError.__init__(self, subsystem, sys_name)
@property
def subsystem(self):
"""
The subsystem that caused this error as string.
"""
return self.args[0]
@property
def sys_name(self):
"""
The sys name that caused this error as string.
"""
return self.args[1]
def __str__(self):
return 'No device {0.sys_name!r} in {0.subsystem!r}'.format(self)
class DeviceNotFoundByNumberError(DeviceNotFoundError):
"""
A :exc:`DeviceNotFoundError` indicating, that no :class:`Device` was found
for a given device number.
"""
def __init__(self, type, number):
DeviceNotFoundError.__init__(self, type, number)
@property
def device_type(self):
"""
The device type causing this error as string. Either ``'char'`` or
``'block'``.
"""
return self.args[0]
@property
def device_number(self):
"""
The device number causing this error as integer.
"""
return self.args[1]
def __str__(self):
return ('No {0.device_type} device with number '
'{0.device_number}'.format(self))
class DeviceNotFoundInEnvironmentError(DeviceNotFoundError):
"""
A :exc:`DeviceNotFoundError` indicating, that no :class:`Device` could
be constructed from the process environment.
"""
def __str__(self):
return 'No device found in environment'
class Device(Mapping):
"""
A single device with attached attributes and properties.
This class subclasses the ``Mapping`` ABC, providing a read-only
dictionary mapping property names to the corresponding values.
Therefore all well-known dicitionary methods and operators
(e.g. ``.keys()``, ``.items()``, ``in``) are available to access device
properties.
Aside of the properties, a device also has a set of udev-specific
attributes like the path inside ``sysfs``.
:class:`Device` objects compare equal and unequal to other devices and
to strings (based on :attr:`device_path`). However, there is no
ordering on :class:`Device` objects, and the corresponding operators
``>``, ``<``, ``<=`` and ``>=`` raise :exc:`~exceptions.TypeError`.
.. warning::
Do **never** use object identity (``is`` operator) to compare
:class:`Device` objects. :mod:`pyudev` may create multiple
:class:`Device` objects for the same device. Instead simply compare
devices by value using ``==`` or ``!=``.
:class:`Device` objects are hashable and can therefore be used as keys
in dictionaries and sets.
They can also be given directly as ``udev_device *`` to functions wrapped
through :mod:`ctypes`.
"""
@classmethod
def from_path(cls, context, path):
"""
Create a device from a device ``path``. The ``path`` may or may not
start with the ``sysfs`` mount point:
>>> context = pyudev.Context()
>>> Device.from_path(context, '/devices/platform')
Device(u'/sys/devices/platform')
>>> Device.from_path(context, '/sys/devices/platform')
Device(u'/sys/devices/platform')
``context`` is the :class:`Context` in which to search the device.
``path`` is a device path as unicode or byte string.
Return a :class:`Device` object for the device. Raise
:exc:`DeviceNotFoundAtPathError`, if no device was found for ``path``.
.. versionadded:: 0.4
"""
if not path.startswith(context.sys_path):
path = os.path.join(context.sys_path, path.lstrip(os.sep))
return cls.from_sys_path(context, path)
@classmethod
def from_sys_path(cls, context, sys_path):
"""
Create a new device from a given ``sys_path``:
>>> context = pyudev.Context()
>>> Device.from_path(context, '/sys/devices/platform')
Device(u'/sys/devices/platform')
``context`` is the :class:`Context` in which to search the device.
``sys_path`` is a unicode or byte string containing the path of the
device inside ``sysfs`` with the mount point included.
Return a :class:`Device` object for the device. Raise
:exc:`DeviceNotFoundAtPathError`, if no device was found for
``sys_path``.
.. versionchanged:: 0.4
Raise :exc:`NoSuchDeviceError` instead of returning ``None``, if
no device was found for ``sys_path``
.. versionchanged:: 0.5
Raise :exc:`DeviceNotFoundAtPathError` instead of
:exc:`NoSuchDeviceError`
"""
device = context._libudev.udev_device_new_from_syspath(
context, ensure_byte_string(sys_path))
if not device:
raise DeviceNotFoundAtPathError(sys_path)
return cls(context, device)
@classmethod
def from_name(cls, context, subsystem, sys_name):
"""
Create a new device from a given ``subsystem`` and a given
``sys_name``:
>>> context = pyudev.Context()
>>> sda = pyudev.Device.from_name(context, 'block', 'sda')
>>> sda
Device(u'/sys/devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda')
>>> sda == pyudev.Device.from_path(context, '/block/sda')
``context`` is the :class:`Context` in which to search the device.
``subsystem`` and ``sys_name`` are byte or unicode strings, which
denote the subsystem and the name of the device to create.
Return a :class:`Device` object for the device. Raise
:exc:`DeviceNotFoundByNameError`, if no device was found with the given
name.
.. versionadded:: 0.5
"""
device = context._libudev.udev_device_new_from_subsystem_sysname(
context, ensure_byte_string(subsystem),
ensure_byte_string(sys_name))
if not device:
raise DeviceNotFoundByNameError(subsystem, sys_name)
return cls(context, device)
@classmethod
def from_device_number(cls, context, type, number):
"""
Create a new device from a device ``number`` with the given device
``type``:
>>> import os
>>> ctx = Context()
>>> major, minor = 8, 0
>>> device = Device.from_device_number(context, 'block',
... os.makedev(major, minor))
>>> device
Device(u'/sys/devices/pci0000:00/0000:00:11.0/host0/target0:0:0/0:0:0:0/block/sda')
>>> os.major(device.device_number), os.minor(device.device_number)
(8, 0)
Use :func:`os.makedev` to construct a device number from a major and a
minor device number, as shown in the example above.
.. note::
Device numbers are not unique across different device types.
Passing a correct number with a wrong type may silently yield a
wrong device object, so make sure to pass the correct device type.
``context`` is the :class:`Context`, in which to search the device.
``type`` is either ``'char'`` or ``'block'``, according to whether the
device is a character or block device. ``number`` is the device number
as integer.
Return a :class:`Device` object for the device with the given device
``number``. Raise :exc:`DeviceNotFoundByNumberError`, if no device was
found with the given device type and number. Raise
:exc:`~exceptions.ValueError`, if ``type`` is any other string than
``'char'`` or ``'block'``.
.. versionadded:: 0.11
"""
if type not in ('char', 'block'):
raise ValueError('Invalid type: {0!r}. Must be one of "char" '
'or "block".'.format(type))
device = context._libudev.udev_device_new_from_devnum(
context, ensure_byte_string(type[0]), number)
if not device:
raise DeviceNotFoundByNumberError(type, number)
return cls(context, device)
@classmethod
def from_device_file(cls, context, filename):
"""
Create a new device from the given device file:
>>> context = Context()
>>> device = Device.from_device_file(context, '/dev/sda')
>>> device
Device(u'/sys/devices/pci0000:00/0000:00:0d.0/host2/target2:0:0/2:0:0:0/block/sda')
>>> device.device_node
u'/dev/sda'
.. warning::
Though the example seems to suggest that ``device.device_node ==
filename`` holds with ``device = Device.from_device_file(context,
filename)``, this is only true in a majority of cases. There *can*
be devices, for which this relation is actually false! Thus, do
*not* expect :attr:`~Device.device_node` to be equal to the given
``filename`` for the returned :class:`Device`. Especially, use
:attr:`~Device.device_node` if you need the device file of a
:class:`Device` created with this method afterwards.
``context`` is the :class:`Context` in which to search the device.
``filename`` is a string containing the path of a device file.
Return a :class:`Device` representing the given device file. Raise
:exc:`~exceptions.ValueError` if ``filename`` is no device file at all.
Raise :exc:`~exceptions.EnvironmentError` if ``filename`` does not
exist or if its metadata was inaccessible.
.. versionadded:: 0.15
"""
device_type = get_device_type(filename)
device_number = os.stat(filename).st_rdev
return cls.from_device_number(context, device_type, device_number)
@classmethod
def from_environment(cls, context):
"""
Create a new device from the process environment (as in
:data:`os.environ`).
This only works reliable, if the current process is called from an
udev rule, and is usually used for tools executed from ``IMPORT=``
rules. Use this method to create device objects in Python scripts
called from udev rules.
``context`` is the library :class:`Context`.
Return a :class:`Device` object constructed from the environment.
Raise :exc:`DeviceNotFoundInEnvironmentError`, if no device could be
created from the environment.
.. udevversion:: 152
.. versionadded:: 0.6
"""
device = context._libudev.udev_device_new_from_environment(context)
if not device:
raise DeviceNotFoundInEnvironmentError()
return cls(context, device)
def __init__(self, context, _device):
self.context = context
self._as_parameter_ = _device
self._libudev = context._libudev
def __del__(self):
self._libudev.udev_device_unref(self)
def __repr__(self):
return 'Device({0.sys_path!r})'.format(self)
@property
def parent(self):
"""
The parent :class:`Device` or ``None``, if there is no parent
device.
"""
parent = self._libudev.udev_device_get_parent(self)
if not parent:
return None
# the parent device is not referenced, thus forcibly acquire a
# reference
return Device(self.context, self._libudev.udev_device_ref(parent))
@property
def children(self):
"""
Yield all direct children of this device.
.. note::
As the underlying library does not provide any means to directly
query the children of a device, this property performs a linear
search through all devices.
Return an iterable yielding a :class:`Device` object for each direct
child of this device.
.. udevversion:: 172
.. versionchanged:: 0.13
Requires udev version 172 now.
"""
for device in self.context.list_devices().match_parent(self):
if device != self:
yield device
def find_parent(self, subsystem, device_type=None):
"""
Find the parent device with the given ``subsystem`` and
``device_type``.
``subsystem`` is a byte or unicode string containing the name of the
subsystem, in which to search for the parent. ``device_type`` is a
byte or unicode string holding the expected device type of the parent.
It can be ``None`` (the default), which means, that no specific device
type is expected.
Return a parent :class:`Device` within the given ``subsystem`` and – if
``device_type`` is not ``None`` – with the given ``device_type``, or
``None``, if this device has no parent device matching these
constraints.
.. versionadded:: 0.9
"""
subsystem = ensure_byte_string(subsystem)
if device_type is not None:
device_type = ensure_byte_string(device_type)
parent = self._libudev.udev_device_get_parent_with_subsystem_devtype(
self, subsystem, device_type)
if not parent:
return None
# parent device is not referenced, thus forcibly acquire a reference
return Device(self.context, self._libudev.udev_device_ref(parent))
def traverse(self):
"""
Traverse all parent devices of this device from bottom to top.
Return an iterable yielding all parent devices as :class:`Device`
objects, *not* including the current device. The last yielded
:class:`Device` is the top of the device hierarchy.
"""
parent = self.parent
while parent:
yield parent
parent = parent.parent
@property
def sys_path(self):
"""
Absolute path of this device in ``sysfs`` including the ``sysfs``
mount point as unicode string.
"""
return ensure_unicode_string(
self._libudev.udev_device_get_syspath(self))
@property
def device_path(self):
"""
Kernel device path as unicode string. This path uniquely identifies
a single device.
Unlike :attr:`sys_path`, this path does not contain the ``sysfs``
mount point. However, the path is absolute and starts with a slash
``'/'``.
"""
return ensure_unicode_string(
self._libudev.udev_device_get_devpath(self))
@property
def subsystem(self):
"""
Name of the subsystem this device is part of as unicode string.
"""
return ensure_unicode_string(
self._libudev.udev_device_get_subsystem(self))
@property
def sys_name(self):
"""
Device file name inside ``sysfs`` as unicode string.
"""
return ensure_unicode_string(
self._libudev.udev_device_get_sysname(self))
@property
def sys_number(self):
"""
The trailing number of the :attr:`sys_name` as unicode string, or
``None``, if the device has no trailing number in its name.
.. note::
The number is returned as unicode string to preserve the exact
format of the number, especially any leading zeros:
>>> device = pyudev.Device.from_path(ctx, '/sys/devices/LNXSYSTM:00')
>>> device.sys_number
u'00'
To work with numbers, explicitly convert them to ints:
>>> int(device.sys_number)
0
.. versionadded:: 0.11
"""
number = self._libudev.udev_device_get_sysnum(self)
if number is not None:
return ensure_unicode_string(number)
@property
def device_type(self):
"""
Device type as unicode string, or ``None``, if the device type is
unknown.
>>> context = Context()
>>> for device in context.list_devices(subsystem='net'):
... '{0} - {1}'.format(device.sys_name, device.device_type or 'ethernet')
...
u'eth0 - ethernet'
u'wlan0 - wlan'
u'lo - ethernet'
u'vboxnet0 - ethernet'
.. versionadded:: 0.10
"""
device_type = self._libudev.udev_device_get_devtype(self)
if device_type is not None:
return ensure_unicode_string(device_type)
@property
def driver(self):
"""
The driver name as unicode string, or ``None``, if there is no
driver for this device.
.. versionadded:: 0.5
"""
driver = self._libudev.udev_device_get_driver(self)
if driver:
return ensure_unicode_string(driver)
@property
def device_node(self):
"""
Absolute path to the device node of this device as unicode string or
``None``, if this device doesn't have a device node. The path
includes the device directory (see :attr:`Context.device_path`).
This path always points to the actual device node associated with
this device, and never to any symbolic links to this device node.
See :attr:`device_links` to get a list of symbolic links to this
device node.
.. warning::
For devices created with :meth:`from_device_file()`, the value of
this property is not necessary equal to the ``filename`` given to
:meth:`from_device_file()`.
"""
node = self._libudev.udev_device_get_devnode(self)
if node:
return ensure_unicode_string(node)
@property
def device_number(self):
"""
The device number of the associated device as integer, or ``0``, if no
device number is associated.
Use :func:`os.major` and :func:`os.minor` to decompose the device
number into its major and minor number:
>>> context = Context()
>>> sda = Device.from_name(context, 'block', 'sda')
>>> sda.device_number
2048L
>>> (os.major(sda.device_number), os.minor(sda.device_number))
(8, 0)
For devices with an associated :attr:`device_node`, this is the same as
the ``st_rdev`` field of the stat result of the :attr:`device_node`:
>>> os.stat(sda.device_node).st_rdev
2048
.. versionadded:: 0.11
"""
return self._libudev.udev_device_get_devnum(self)
@property
def is_initialized(self):
"""
``True``, if the device is initialized, ``False`` otherwise.
A device is initialized, if udev has already handled this device and
has set up device node permissions and context, or renamed a network
device.
Consequently, this property is only implemented for devices with a
device node or for network devices. On all other devices this property
is always ``True``.
It is *not* recommended, that you use uninitialized devices.
.. seealso:: :attr:`time_since_initialized`
.. udevversion:: 165
.. versionadded:: 0.8
"""
return bool(self._libudev.udev_device_get_is_initialized(self))
@property
def time_since_initialized(self):
"""
The time elapsed since initialization as :class:`~datetime.timedelta`.
This property is only implemented on devices, which need to store
properties in the udev database. On all other devices this property is
simply zero :class:`~datetime.timedelta`.
.. seealso:: :attr:`is_initialized`
.. udevversion:: 165
.. versionadded:: 0.8
"""
microseconds = self._libudev.udev_device_get_usec_since_initialized(
self)
return timedelta(microseconds=microseconds)
@property
def device_links(self):
"""
An iterator, which yields the absolute paths (including the device
directory, see :attr:`Context.device_path`) of all symbolic links
pointing to the :attr:`device_node` of this device. The paths are
unicode strings.
UDev can create symlinks to the original device node (see
:attr:`device_node`) inside the device directory. This is often
used to assign a constant, fixed device node to devices like
removeable media, which technically do not have a constant device
node, or to map a single device into multiple device hierarchies.
The property provides access to all such symbolic links, which were
created by UDev for this device.
"""
devlinks = self._libudev.udev_device_get_devlinks_list_entry(self)
for name, _ in udev_list_iterate(self._libudev, devlinks):
yield ensure_unicode_string(name)
@property
def attributes(self):
"""
The system attributes of this device as read-only
:class:`Attributes` mapping.
System attributes are basically normal files inside the the device
directory. These files contain all sorts of information about the
device, which may not be reflected by properties. These attributes
are commonly used for matching in udev rules, and can be printed
using ``udevadm info --attribute-walk``.
The values of these attributes are not always proper strings, and
can contain arbitrary bytes.
.. versionadded:: 0.5
"""
# do *not* cache the created object in an attribute of this class.
# Doing so creates an uncollectable reference cycle between Device and
# Attributes, because Attributes refers to this object through
# Attributes.device.
return Attributes(self)
@property
def tags(self):
"""
A :class:`Tags` object representing the tags attached to this device.
The :class:`Tags` object supports a test for a single tag as well as
iteration over all tags:
>>> 'systemd' in device.tags
True
>>> list(device.tags)
[u'systemd', u'seat']
Tags are arbitrary classifiers that can be attached to devices by udev
scripts and daemons. For instance, systemd_ uses tags for multi-seat_
support.
.. _systemd: http://freedesktop.org/wiki/Software/systemd
.. _multi-seat: http://www.freedesktop.org/wiki/Software/systemd/multiseat
.. udevversion:: 154
.. versionadded:: 0.6
.. versionchanged:: 0.13
Return a :class:`Tags` object now.
"""
return Tags(self)
def __iter__(self):
"""
Iterate over the names of all properties defined for this device.
Return a generator yielding the names of all properties of this
device as unicode strings.
"""
properties = self._libudev.udev_device_get_properties_list_entry(self)
for name, _ in udev_list_iterate(self._libudev, properties):
yield ensure_unicode_string(name)
def __len__(self):
"""
Return the amount of properties defined for this device as integer.
"""
properties = self._libudev.udev_device_get_properties_list_entry(self)
return sum(1 for _ in udev_list_iterate(self._libudev, properties))
def __getitem__(self, property):
"""
Get the given ``property`` from this device.
``property`` is a unicode or byte string containing the name of the
property.
Return the property value as unicode string, or raise a
:exc:`~exceptions.KeyError`, if the given property is not defined
for this device.
"""
value = self._libudev.udev_device_get_property_value(
self, ensure_byte_string(property))
if value is None:
raise KeyError(property)
return ensure_unicode_string(value)
def asint(self, property):
"""
Get the given ``property`` from this device as integer.
``property`` is a unicode or byte string containing the name of the
property.
Return the property value as integer. Raise a
:exc:`~exceptions.KeyError`, if the given property is not defined
for this device, or a :exc:`~exceptions.ValueError`, if the property
value cannot be converted to an integer.
"""
return int(self[property])
def asbool(self, property):
"""
Get the given ``property`` from this device as boolean.
A boolean property has either a value of ``'1'`` or of ``'0'``,
where ``'1'`` stands for ``True``, and ``'0'`` for ``False``. Any
other value causes a :exc:`~exceptions.ValueError` to be raised.
``property`` is a unicode or byte string containing the name of the
property.
Return ``True``, if the property value is ``'1'`` and ``False``, if
the property value is ``'0'``. Any other value raises a
:exc:`~exceptions.ValueError`. Raise a :exc:`~exceptions.KeyError`,
if the given property is not defined for this device.
"""
return string_to_bool(self[property])
def __hash__(self):
return hash(self.device_path)
def __eq__(self, other):
if isinstance(other, Device):
return self.device_path == other.device_path
else:
return self.device_path == other
def __ne__(self, other):
if isinstance(other, Device):
return self.device_path != other.device_path
else:
return self.device_path != other
def __gt__(self, other):
raise TypeError('Device not orderable')
def __lt__(self, other):
raise TypeError('Device not orderable')
def __le__(self, other):
raise TypeError('Device not orderable')
def __ge__(self, other):
raise TypeError('Device not orderable')
class Tags(Iterable, Container):
"""
A iterable over :class:`Device` tags.
Subclasses the ``Container`` and the ``Iterable`` ABC.
"""
def __init__(self, device):
self.device = device
def _has_tag(self, tag):
if hasattr(self._libudev, 'udev_device_has_tag'):
return bool(self._libudev.udev_device_has_tag(
self.device, ensure_byte_string(tag)))
else:
return any(t == tag for t in self)
@property
def _libudev(self):
return self.device._libudev
def __contains__(self, tag):
"""
Check for existence of ``tag``.
``tag`` is a tag as unicode string.
Return ``True``, if ``tag`` is attached to the device, ``False``
otherwise.
"""
return self._has_tag(tag)
def __iter__(self):
"""
Iterate over all tags.
Yield each tag as unicode string.
"""
tags = self._libudev.udev_device_get_tags_list_entry(self.device)
for tag, _ in udev_list_iterate(self._libudev, tags):
yield ensure_unicode_string(tag)
def _is_attribute_file(filepath):
"""
Check, if ``filepath`` points to a valid udev attribute filename.
Implementation is stolen from udev source code, ``print_all_attributes``
in ``udev/udevadm-info.c``. It excludes hidden files (starting with a
dot), the special files ``dev`` and ``uevent`` and links.
Return ``True``, if ``filepath`` refers to an attribute, ``False``
otherwise.
"""
filename = os.path.basename(filepath)
return not (filename.startswith('.') or
filename in ('dev', 'uevent') or
os.path.islink(filepath))
class Attributes(Mapping):
"""
A mapping which holds udev attributes for :class:`Device` objects.
This class subclasses the ``Mapping`` ABC, providing a read-only
dictionary mapping attribute names to the corresponding values.
Therefore all well-known dicitionary methods and operators
(e.g. ``.keys()``, ``.items()``, ``in``) are available to access device
attributes.
.. versionadded:: 0.5
"""
def __init__(self, device):
self.device = device
self._libudev = device._libudev
def _get_attributes(self):
if hasattr(self._libudev, 'udev_device_get_sysattr_list_entry'):
attrs = self._libudev.udev_device_get_sysattr_list_entry(
self.device)
for attribute, _ in udev_list_iterate(self._libudev, attrs):
yield ensure_unicode_string(attribute)
else:
sys_path = self.device.sys_path
for filename in os.listdir(sys_path):
filepath = os.path.join(sys_path, filename)
if _is_attribute_file(filepath):
yield filename
def __len__(self):
"""
Return the amount of attributes defined.
"""
return sum(1 for _ in self._get_attributes())
def __iter__(self):
"""
Iterate over all attributes defined.
Yield each attribute name as unicode string.
"""
return self._get_attributes()
def __contains__(self, attribute):
value = self._libudev.udev_device_get_sysattr_value(
self.device, ensure_byte_string(attribute))
return value is not None
def __getitem__(self, attribute):
"""
Get the given system ``attribute`` for the device.
``attribute`` is a unicode or byte string containing the name of the
system attribute.
Return the attribute value as byte string, or raise a
:exc:`~exceptions.KeyError`, if the given attribute is not defined
for this device.
"""
value = self._libudev.udev_device_get_sysattr_value(
self.device, ensure_byte_string(attribute))
if value is None:
raise KeyError(attribute)
return value
def asstring(self, attribute):
"""
Get the given ``atribute`` for the device as unicode string.
Depending on the content of the attribute, this may or may not work.
Be prepared to catch :exc:`~exceptions.UnicodeDecodeError`.
``attribute`` is a unicode or byte string containing the name of the
attribute.
Return the attribute value as byte string. Raise a
:exc:`~exceptions.KeyError`, if the given attribute is not defined
for this device, or :exc:`~exceptions.UnicodeDecodeError`, if the
content of the attribute cannot be decoded into a unicode string.
"""
return ensure_unicode_string(self[attribute])
def asint(self, attribute):
"""
Get the given ``attribute`` as integer.
``attribute`` is a unicode or byte string containing the name of the
attribute.
Return the attribute value as integer. Raise a
:exc:`~exceptions.KeyError`, if the given attribute is not defined
for this device, or a :exc:`~exceptions.ValueError`, if the
attribute value cannot be converted to an integer.
"""
return int(self.asstring(attribute))
def asbool(self, attribute):
"""
Get the given ``attribute`` from this device as boolean.
A boolean attribute has either a value of ``'1'`` or of ``'0'``,
where ``'1'`` stands for ``True``, and ``'0'`` for ``False``. Any
other value causes a :exc:`~exceptions.ValueError` to be raised.
``attribute`` is a unicode or byte string containing the name of the
attribute.
Return ``True``, if the attribute value is ``'1'`` and ``False``, if
the attribute value is ``'0'``. Any other value raises a
:exc:`~exceptions.ValueError`. Raise a :exc:`~exceptions.KeyError`,
if the given attribute is not defined for this device.
"""
return string_to_bool(self.asstring(attribute))
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