如何轮询 /sys 中的文件
我一直在读取 /sys/ 中的一个文件，其中包含诺基亚 N900 手机上环境光传感器的光强度（以勒克斯为单位）。
我尝试使用 pyinotify轮询文件，但这对我来说看起来有些错误，因为文件总是“process_IN_OPEN”、“process_IN_ACCESS”和“process_IN_CLOSE_NOWRITE”
我基本上想尽快获得更改，如果某些更改触发事件，则执行一个类。 这是我尝试过的代码，它有效，但没有达到我的
预期（我希望 process_IN_MODIFY 被触发）：
#!/usr/bin/env python
import os, time, pyinotify
import pyinotify
ambient_sensor = '/sys/class/i2c-adapter/i2c-2/2-0029/lux'
wm = pyinotify.WatchManager() # Watch Manager
mask = pyinotify.ALL_EVENTS
def action(self, the_event):
value = open(the_event.pathname, 'r').read().strip()
return value
class EventHandler(pyinotify.ProcessEvent):
...
def process_IN_MODIFY(self, event):
print "MODIFY event:", action(self, event)
...
#log.setLevel(10)
notifier = pyinotify.ThreadedNotifier(wm, EventHandler())
notifier.start()
wdd = wm.add_watch(ambient_sensor, mask)
wdd
time.sleep(5)
notifier.stop()
更新 1：
嗯，我想出的所有内容都没有任何线索。特殊的机制如下：
f = open('/sys/class/i2c-adapter/i2c-2/2-0029/lux')
while True:
value = f.read()
print value
f.seek(0)
这个包裹在自己的线程中，可以解决问题，但是有没有人有更聪明、更少占用 CPU 和更快的方法来获取最新值？
I am stuck reading a file in /sys/ which contains the light intensity in Lux of the ambient light sensor on my Nokia N900 phone.
See thread on talk.maemo.org here
I tried to use pyinotify to poll the file but this looks some kind of wrong to me since the file is alway "process_IN_OPEN", "process_IN_ACCESS" and "process_IN_CLOSE_NOWRITE"
I basically want to get the changes ASAP and if something changed trigger an event, execute a class...
Here's the code I tried, which works, but not as I expected (I was hoping for process_IN_MODIFY to be triggered):
#!/usr/bin/env python
import os, time, pyinotify
import pyinotify
ambient_sensor = '/sys/class/i2c-adapter/i2c-2/2-0029/lux'
wm = pyinotify.WatchManager() # Watch Manager
mask = pyinotify.ALL_EVENTS
def action(self, the_event):
value = open(the_event.pathname, 'r').read().strip()
return value
class EventHandler(pyinotify.ProcessEvent):
...
def process_IN_MODIFY(self, event):
print "MODIFY event:", action(self, event)
...
#log.setLevel(10)
notifier = pyinotify.ThreadedNotifier(wm, EventHandler())
notifier.start()
wdd = wm.add_watch(ambient_sensor, mask)
wdd
time.sleep(5)
notifier.stop()
Update 1:
Mmmh, all I came up without having a clue if there is a special mechanism is the following:
f = open('/sys/class/i2c-adapter/i2c-2/2-0029/lux')
while True:
value = f.read()
print value
f.seek(0)
This, wrapped in a own thread, could to the trick, but does anyone have a smarter, less CPU-hogging and faster way to get the latest value?
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评论（2）
由于 /sys/file 是一个伪文件，它仅呈现底层、易失性操作系统值的视图，因此永远不会引发修改事件是有道理的。由于该文件是从下面“修改”的，因此它不遵循常规文件系统语义。
如果从未引发修改事件，那么使用像 pinotify 这样的包不会有任何帮助。 '最好寻找特定于平台的机制。
对更新 1 的响应：
由于 N900 maemo 运行时支持 GFileMonitor，您最好检查它是否可以提供您想要的异步事件。
据我所知，忙碌的等待是一种浪费。在手机上，它确实会耗尽电池。你至少应该在忙碌的循环中睡觉。
Since the /sys/file is a pseudo-file which just presents a view on an underlying, volatile operating system value, it makes sense that there would never be a modify event raised. Since the file is "modified" from below it doesn't follow regular file-system semantics.
If a modify event is never raised, using a package like pinotify isn't going to get you anywhere. 'twould be better to look for a platform-specific mechanism.
Response to Update 1:
Since the N900 maemo runtime supports GFileMonitor, you'd do well to check if it can provide the asynchronous event that you desire.
Busy waiting - as I gather you know - is wasteful. On a phone it can really drain a battery. You should at least sleep in your busy loop.
嗯，我在不知道是否有特殊机制的情况下想到了以下内容：
这个包裹在自己的线程中，可以解决问题，但是有没有人有更聪明、更少占用 CPU 和更快的方法来获得最新值？
干杯
比约恩
Mmmh, all I came up without having a clue if there is a special mechanism is the following:
This, wrapped in a own thread, could to the trick, but does anyone have a smarter, less CPU-hogging and faster way to get the latest value?
Cheers
Bjoern