[Python库] pyudev

pyudev是什么

pyudev是libudev的python版本，而libudev是linux的设备和硬件管理库。

pyudev支持libudev的所有功能，可以通过官方提供的接口枚举设备、查找设备属性或者监听设备状态，包括异步监听。

资料：
- pyudev github
- https://pyudev.readthedocs.io/en/latest/api/pyudev.html

如何枚举设备

from pyudev import Context
context = Context() # 创建设备数据库连接对象
devices_list = context.list_devices() # 列出所有可用的设备，类型是pyudev.Enumerator 可迭代设备的对象
for device in devices_list:print(device)
----------------------------------
Device('/sys/devices/virtual/tty/tty48')
Device('/sys/devices/virtual/tty/tty49')
Device('/sys/devices/virtual/tty/tty5')
Device('/sys/devices/virtual/tty/tty50')
...

在Context()中，默认定义了下面几个可以获取到设备的地址：

sys_path: /sys
device_path: /dev
run_path: /run

如何查找设备

官方提供了几种查找设备的方法

from_path(*context, path* )

根据设备路径查找设备

from pyudev import Context, Devices
Device.from_path(context, '/devices/platform')
---------------------------------
Device(u'/sys/devices/platform')

from_sys_path(*context, sys_path* )

根据系统设备路径查找设备

from pyudev import Context, Devices
Device.from_sys_path(context, '/sys//devices/platform')
---------------------------------
Device(u'/sys/devices/platform')

from_name(*context, subsystem, sys_name* )

根据设备标识符查找设备

from pyudev import Context, Devices
context = Context()
sda = Devices.from_name(context, 'block', 'sda')
------------------------------------------------
Device(u'/sys/devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda')

from_device_number(*context, typ, number* )

根据设备号查找设备

from pyudev import Context, Devices
context = Context()
major, minor = 8, 0
device = Devices.from_device_number(context, 'block', os.makedev(major, minor))
-------------------------------
Device(u'/sys/devices/pci0000:00/0000:00:11.0/host0/target0:0:0/0:0:0:0/block/sda')

from_device_file(*context, filename* )

根据设备文件查找设备

from pyudev import Context, Devices
context = Context()
device = Devices.from_device_file(context, '/dev/sda')
------------------------------
Device(u'/sys/devices/pci0000:00/0000:00:0d.0/host2/target2:0:0/2:0:0:0/block/sda')

如何监听设备

pyudev提供了现成的监听接口，可以识别目前市面上所有类型的设备。
```
context = Context() 
monitor = Monitor.from_netlink(context) 
monitor.filter_by(subsystem='block')
for device in iter(monitor.poll, None):print('{0.action} on {0.device_path}'.format(device))
```
上面代码块的意思是，当插入、拔出、挂载、卸载存储设备时，会输出设备的行为以及设备地址。

获取到设备后获取设备属性

下面列出一部分属性，具体看文档。想更全面的获取设备属性，不但要去了解pyudev的用法，更要学习udev的底层知识。

Device 类

udev 中文手册

https://blog.csdn.net/u013253075/article/details/122703980

from pyudev import Context, Device, Devices
context = Context()
device = Devices.from_name(context, "block", "sda")
print(device)
print(f"device.get('ID_MODEL'): {device.get('ID_MODEL')}")
print(f"device.context: {device.context}")
print(f"device.sys_path: {device.sys_path}")
print(f"device.sys_name: {device.sys_name}")
print(f"device.sys_number: {device.sys_number}")
print(f"device.device_path: {device.device_path}")
print(f"device.device.tags: {list(device.tags)}")
print(f"device.subsystem: {device.subsystem}")
print(f"device.driver: {device.driver}")
print(f"device.device_type: {device.device_type}")
print(f"device.device_node: {device.device_node}")
print(f"device.device_number: {device.device_number}")
print(f"device.device_links: {device.device_links}")
print(f"device.device_links: {device.device_links}")
-------------------------------------
Device('/sys/devices/pci0000:00/0000:00:0d.0/usb2/2-1/2-1:1.0/host0/target0:0:0/0:0:0:0/block/sda')
device.get('ID_MODEL'): Extreme_55AE
device.context: <pyudev.core.Context object at 0x7ef3d978c310>
device.sys_path: /sys/devices/pci0000:00/0000:00:0d.0/usb2/2-1/2-1:1.0/host0/target0:0:0/0:0:0:0/block/sda
device.sys_name: sda
device.sys_number: None
device.device_path: /devices/pci0000:00/0000:00:0d.0/usb2/2-1/2-1:1.0/host0/target0:0:0/0:0:0:0/block/sda
device.device.tags: ['systemd']
device.subsystem: block
device.driver: None
device.device_type: disk
device.device_node: /dev/sda
device.device_number: 2048
device.device_links: <generator object Device.device_links at 0x7ef3d96ff920>