bashrc, the program works fine, but it launches another instance of the program everytime I open another terminal session - not what I want. I know that it has something to do with subprocess.Popen - if I comment out the subprocess.Popen() and assume what the response would be, the program works fine.Īlso if I start the program from. I put some logging code in the program and I can tell that the program sees the GPIO pin go LOW, but the xmessage never comes up. However, if I try to run the program from /etc/rc.local or from crontab to have it start at bootup, it doesn't work - I never get the xmessage. If I run the program from a terminal session using sudo python3 mypgm.py &, it works perfectly. If the optional argument type is async, the process is started in the background and the process ID of the. Nasser Al-Wohaibi at 11:08 Could someone explain why you couldn't just set stdout to sys.stdout instead of subprocess. sets the xmessage info into a variable 'cmd' Execute a shell command specified by string. 1 (Coming from google) all PIPEs will deadlock when one of the PIPEs' buffer gets filled up and not read. The program uses GPIO.wait_for_edge(pin, GPIO.FALLING) to wait. When the pin goes LOW, the program uses xmessage to display a message and looks for a response.

I have a Python program that runs in the background and watches a GPIO pin.

Subprocess pipe in background python