Linux /dev/input/event* 的格式
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Format of /dev/input/event*
提问by jldupont
What is the "format" of the character devices located in /dev/input/event*?
位于的字符设备的“格式”是/dev/input/event*什么？
In other words, how can I decode the character stream? A Python example would be greatly appreciated.
换句话说，我如何解码字符流？一个 Python 示例将不胜感激。
采纳答案by Keith
回答by Jeremiah Willcock
The data is in the form of input_eventstructures; see http://www.thelinuxdaily.com/2010/05/grab-raw-keyboard-input-from-event-device-node-devinputevent/for a C example. The struct definition is at (for example) http://www.cs.fsu.edu/~baker/devices/lxr/http/source/linux/include/linux/input.h?v=2.6.11.8. Note that you will need to use a bunch of ioctlcalls to get information on the device before reading from it.
数据采用input_event结构形式；有关 C 示例，请参见http://www.thelinuxdaily.com/2010/05/grab-raw-keyboard-input-from-event-device-node-devinputevent/。结构体定义位于（例如）http://www.cs.fsu.edu/~baker/devices/lxr/http/source/linux/include/linux/input.h?v=2.6.11.8。请注意，ioctl在读取设备信息之前，您需要使用一堆调用来获取设备上的信息。
回答by nelhage
The format is described in the Documentation/input/input.txtfile in the Linux source. Basically, you read structs of the following form from the file:
该格式Documentation/input/input.txt在 Linux 源文件中的文件中有所描述。基本上，您从文件中读取以下形式的结构：
struct input_event {
struct timeval time;
unsigned short type;
unsigned short code;
unsigned int value;
};
typeand codeare values defined in linux/input.h. For example,
type might be EV_RELfor relative moment of a mouse, or EV_KEYfor
a keypress, and codeis the keycode, or REL_Xor ABS_Xfor a
mouse.
type和code中定义的值linux/input.h。例如，类型可能是EV_REL相对时刻鼠标，或EV_KEY用于一个按键，并且code是的键码，或者REL_X或ABS_X为鼠标。
回答by gvalkov
The python-evdevpackage provides bindings to the event device interface. A short usage example would be:
的蟒-了evdev包提供绑定到事件设备接口。一个简短的使用示例是：
from evdev import InputDevice
from select import select
dev = InputDevice('/dev/input/event1')
while True:
r,w,x = select([dev], [], [])
for event in dev.read():
print(event)
# event at 1337427573.061822, code 01, type 02, val 01
# event at 1337427573.061846, code 00, type 00, val 00
Keep in mind that, unlike the very convenient, purely Pythonic modules mentioned so far, evdevcontains C extensions. Building them requires having your Python development and kernel headers installed.
请记住，与目前提到的非常方便的纯 Pythonic 模块不同，evdev包含 C 扩展。构建它们需要安装 Python 开发和内核头文件。
回答by Trevi?o
A simple and raw reader can be just done using:
一个简单而原始的阅读器可以使用：
#!/usr/bin/python
import struct
import time
import sys
infile_path = "/dev/input/event" + (sys.argv[1] if len(sys.argv) > 1 else "0")
"""
FORMAT represents the format used by linux kernel input event struct
See https://github.com/torvalds/linux/blob/v5.5-rc5/include/uapi/linux/input.h#L28
Stands for: long int, long int, unsigned short, unsigned short, unsigned int
"""
FORMAT = 'llHHI'
EVENT_SIZE = struct.calcsize(FORMAT)
#open file in binary mode
in_file = open(infile_path, "rb")
event = in_file.read(EVENT_SIZE)
while event:
(tv_sec, tv_usec, type, code, value) = struct.unpack(FORMAT, event)
if type != 0 or code != 0 or value != 0:
print("Event type %u, code %u, value %u at %d.%d" % \
(type, code, value, tv_sec, tv_usec))
else:
# Events with code, type and value == 0 are "separator" events
print("===========================================")
event = in_file.read(EVENT_SIZE)
in_file.close()
