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When I run a terminal command in python, it throws an error. Below is the code I run from a .py-file in terminal:

import time
import os
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BOARD)
GPIO.setup(12, GPIO.IN, pull_up_down = GPIO.PUD_UP)
GPIO.setup(16, GPIO.IN, pull_up_down = GPIO.PUD_UP)
GPIO.setup(18, GPIO.IN, pull_up_down = GPIO.PUD_UP)
while True:
   if(GPIO.input(12) == 0):
      os.system ('omxplayer /home/pi/Downloads/bell.mp3')
      print("DOOR BELL RINGING")
      os.system ("cd /home/pi/picam")
      os.system ("./picam --alsadev hw:1,0 -w 640 -h 360 -v 800000 -f 24 --tcpout $")
      time.sleep(1)

This code is for video streaming, but it doesn't work. The error message is:

sh: 1: ./picam: not found
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  • I have had trouble with calling bash-files (like your picam) as well. Usually it helps to insert "bash" in front of the command.. Would you mind posting your picam-file? Nov 28, 2016 at 11:26
  • 2
    ./picam: not found means it isn't in the directory or it is but doesn't have execute permissions.
    – joan
    Nov 28, 2016 at 11:38
  • Is picam in the directory where you are running the command from? You can verify this by doing ls -la from the command line and looking for the file in the output. Please edit your question and include the output of ls -la. is picam the entire file name or is it picam.sh? Nov 28, 2016 at 15:12

1 Answer 1

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Note that the two separate calls of os.system are exactly that - completely separate from each other. Whatever happens in the first call is lost and forgotten in the second (like tears in rain).

os.system ("cd /home/pi/picam")
os.system ("./picam --alsadev ...")

Changing to /home/pi/picam is of no relevance to the next call which leads to the expected result - the error that is thrown - not found. Simplest solution here: use the full path /home/pi/picam/picam --alsadev ... instead of ./picam --alsadev ....

From https://docs.python.org/3/library/os.html#os.system it is recommended to use subprocess over os.system:

The subprocess module provides more powerful facilities for spawning new processes and retrieving their results; using that module is preferable to using this function. See the Replacing Older Functions with the subprocess Module section in the subprocess documentation for some helpful recipes.

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  • In other words, when you run the script it should do the cd itself.
    – SDsolar
    Apr 21, 2017 at 17:18

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