在 Python 应用程序中使用 Raspberry Pi 4B 终端命令

Question

I am currently working on a small Python Application which turns a Raspberry Pi 4B into a 48 Channel Audio-Recorder. Basics work, but during Recording, I need a log file which tells me when recording started, which ALSA warnings occurred and when recording stopped.

The recorder can be started with this terminal command:

pi@raspberrypi:~ $ rec -q -t caf --endian little --buffer 96000 -c 48 -b 24 /home/pi/myssd-one/Aufnahmen/test.caf 2>&1 | tee /home/pi/myssd-one/Aufnahmen/logging.log

this records audio in the test.caf file and writes ALSA warnings to logging.log So far so good.

The Python Program (which should run on a touchscreen with GUI so recording can easily started and stopped) takes care of variable audio-filenames (date-time-stamp) and controls an LED to show that recording is running.

This part of the code takes care of switching on and off:

#!/usr/bin/env python

from tkinter import *
import shlex
import os
import subprocess
import tkinter.font
import datetime
from gpiozero import LED
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setup(11, GPIO.OUT)

def ledToggle():
    if led.is_lit:
        led.off()
        my_env = os.environ.copy()
        my_env['AUDIODRIVER'] = 'alsa'
        my_env['AUDIODEV'] = 'hw:KTUSB,0'
        ledButton["text"] = "Turn Recorder on"
        print ("recorder stops")
        subprocess.Popen(['sudo', 'pkill', '-SIGINT', 'rec'],  env = my_env, shell = FALSE, stdout=subprocess.PIPE)
    else:
        led.on()
        my_env = os.environ.copy()
        my_env['AUDIODRIVER'] = 'alsa'
        my_env['AUDIODEV'] = 'hw:KTUSB,0'
        ledButton["text"] = "Turn Recorder off"
        print ("recorder starts")
        ##reference statement command line: "rec -q -t caf --endian little --buffer 96000 -c 48 -b 24 /home/pi/myssd-one/Aufnahmen/test.caf 2>&1 | tee /home/pi/myssd-one/Aufnahmen/logging.log"
        command_line = shlex.split("rec '-q' '-t' 'caf' '--buffer' '96000' '-c 48' '-b 24' '/home/pi/myssd-one/Aufnahmen/test.caf' '"2>&1 | tee"' '/home/pi/myssd-one/Aufnahmen/logging.log'")
        p1 = subprocess.Popen(command_line, env = my_env, shell = False, stdout=subprocess.PIPE)

I am trying to move the original command line statement into the subprocess.Popen command, to no success yet. The part where routing to the log file is done, fails. It looks as the initiating sox-application 'rec' tries to interpret it as part of its own parameter list, instead of interpreting it as a redirection of stdout and stderr to the log file. I appreciate some guidance in this issue. Variable Filenames for audio files is already done, but for simplicity taken out of this code snippet.

Answer 1

Thanks Mark, I dived into this command line along your hint that it only can run with shell=True and this implied that it had to be written as a full statement without separating commas and escape quotes. Now it works. Actually, the shlex.split() becomes obsolete.