sudo 在 subprocess.run 中的什么位置? [英] Where to put sudo in subprocess.run?

问题描述

我正在尝试从我的 Python 应用程序调用 bash 命令，以更改触摸屏上的背景灯.python 应用程序将在我的 Raspberry Pi(Rasbian/stretch)上运行.

I am trying to invoke a bash command from my python application in order to change background light on my touch screen. The python application will run on my Raspberry Pi (Rasbian/stretch).

在终端中运行 bash 命令并不复杂:sudo sh -c "echo 80 >/sys/class/backlight/rpi_backlight/brightness" 肯定会使屏幕变暗(这是我想要的是).但是我如何在我的 python 应用程序中 sudo 脚本?(我知道有几个线程在谈论这个，例如这个 将 sudo 与 Python 脚本一起使用，但我不明白如何在实践中做到这一点?)

It's not complicated to run the bash command in a terminal: sudo sh -c "echo 80 > /sys/class/backlight/rpi_backlight/brightness" will certainly dim the screen (which is what I want). But how can I sudo scripts in my python application? (I know that there are several threads talking about this, for example this Using sudo with Python script, but I do not understand how to do it in practice?)

这是我的代码:

#!/usr/bin/env python3
import subprocess
import time
import sys

# read arguments from the run command: 
# idle time before dim (in seconds)
idleTimeBeforeDimMS = int( sys.argv[1] )*1000

# brightness when dimmed (between 0 and 255)
brightnessDimmed = int( sys.argv[2] )
brightnessFull = 255

def get(cmd):
    # just a helper function
    return subprocess.check_output(cmd).decode("utf-8").strip()

isIdle0 = False
stateChanged = False
timeIntervalToWatchChangesS = 100 / 1000

while True:
    time.sleep( timeIntervalToWatchChangesS )

    currentIdleTimeMS = int( get("xprintidle") )

    isIdle = currentIdleTimeMS > idleTimeBeforeDimMS
    stateChanged = isIdle0 != isIdle

    if isIdle and stateChanged:
        # idling
        bashCommand = "echo 50 > /sys/class/backlight/rpi_backlight/brightness"
        subprocess.run(['bash', '-c', bashCommand])
    elif not isIdle and stateChanged:
        # active
        bashCommand = "echo 255 > /sys/class/backlight/rpi_backlight/brightness"
        subprocess.run(['bash', '-c', bashCommand])

        # set current state as initial one for the next loop cycle
    isIdle0 = isIdle

如果我立即运行脚本，我的 bash 命令会出错:bash:/sys/class/backlight/rpi_backlight/brightness: Permission denied.没关系，我知道我缺少 sudo 部分，但是我应该把它放在哪里?

If I run the script right out of box, I get an error with my bash command: bash: /sys/class/backlight/rpi_backlight/brightness: Permission denied. That's ok, I understand that I am missing the sudo-part, but where should I put it?

推荐答案

把它放在 shell 前面，就像你交互一样:

Put it in front of the shell just like you do interactively:

subprocess.run(['sudo', 'bash', '-c', bashCommand])

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