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I have made a simple script that uses when_pressed and when_released to read the value of a GPIO pin and writes it to file. It works as expected when run from terminal, but not when run from rc.local. (I have a couple other python scripts in rc.local that run fine.) I have tried to catch an error by running it like: python3 /home/user/myfile.py > /home/user/errors.txt 2>&1 & but nothing gets written to the file. (If I force an error, it does show up in errors.txt)

The code is as follows:

from gpiozero import Button from signal import pause pin = Button("BOARD7",pull_up=None,active_state=True) def write_0(): with open('/home/user/file.txt', 'w+') as f: f.write('%s\n' %0) f.close() def write_1(): with open('/home/user/file.txt', 'w+') as f: f.write('%s\n' %1) f.close() while True: pin.when_released = write_0 pin.when_pressed = write_1 pause()

Replacing the code in the while loop with:

 pin.wait_for_press() write_1() pin.wait_for_release() write_0()

also doesn't work.

Now, I know that the script is run because I can replace the code in the while loop with:

 if pin.is_pressed: write_1() else: write_0()

and the file gets updated according to the value of the pin correctly. However, it writes constantly and I would rather it not do that. (sleep is not the solution)

What's causing this? I have not tried running it via the systemd method, mainly because I can't get anything to run...

I did find discussion #1153 on gpiozero's github page. I added os.chdir() before every call to gpiozero, but A - I don't know what directory to set B - it didn't help when I set it to home directory

Operating system: Debian 12 Bookworm Python version: 3.11.2 Pi model: Pi 3 Model B Rev 1.2 GPIO Zero version: 2.0.1 Pin factory used: LGPIO

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    I believe rc.local runs as root user. What happens if you run your code from terminal with sudo? Commented Jul 31 at 21:20
  • It runs just fine, sudo or not. Commented Aug 1 at 11:12
  • This is terrible code; you create callbacks in a loop - you should run ONCE only. As you also have a pause in the loop it is unclear what exactly is happening. See gpiozero.readthedocs.io/en/latest/recipes.html#button for examples of how it should be used. You have no debounce so code will be called multiple times for each press! You write files in a callback; callbacks should do minimal processing. I suggest you fix this first. Commented Aug 2 at 1:28
  • See gpiozero.readthedocs.io/en/latest/api_input.html Commented Aug 2 at 1:44
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    The while loop was added when I was testing out the other options and I forgot to remove it when I switched to using when_released / when_pressed. Removing the while loop did not fix the issue of the script not running when started from rc.local. I do not have a debounce because I do not need it. I am not reading a physical button. Commented Aug 2 at 12:00

1 Answer 1

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I added a 10s sleep after importing all modules, but before assigning the button.

from gpiozero import Button from signal import pause from time import sleep sleep(10) pin = Button("BOARD7",pull_up=None,active_state=True) . . .

And the script now works when started from rc.local. So, I guess, it might be a boot order issue.

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